Merge remote-tracking branch 'vfio/next'

[deliverable/linux.git] / drivers / gpu / drm / drm_fb_helper.c

/*
 * Copyright (c) 2006-2009 Red Hat Inc.
 * Copyright (c) 2006-2008 Intel Corporation
 * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
 *
 * DRM framebuffer helper functions
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 *
 * Authors:
 *      Dave Airlie <airlied@linux.ie>
 *      Jesse Barnes <jesse.barnes@intel.com>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/console.h>
#include <linux/kernel.h>
#include <linux/sysrq.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <drm/drmP.h>
#include <drm/drm_crtc.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>

static bool drm_fbdev_emulation = true;
module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
MODULE_PARM_DESC(fbdev_emulation,
                 "Enable legacy fbdev emulation [default=true]");

static LIST_HEAD(kernel_fb_helper_list);

/**
 * DOC: fbdev helpers
 *
 * The fb helper functions are useful to provide an fbdev on top of a drm kernel
 * mode setting driver. They can be used mostly independently from the crtc
 * helper functions used by many drivers to implement the kernel mode setting
 * interfaces.
 *
 * Initialization is done as a four-step process with drm_fb_helper_prepare(),
 * drm_fb_helper_init(), drm_fb_helper_single_add_all_connectors() and
 * drm_fb_helper_initial_config(). Drivers with fancier requirements than the
 * default behaviour can override the third step with their own code.
 * Teardown is done with drm_fb_helper_fini().
 *
 * At runtime drivers should restore the fbdev console by calling
 * drm_fb_helper_restore_fbdev_mode_unlocked() from their ->lastclose callback.
 * They should also notify the fb helper code from updates to the output
 * configuration by calling drm_fb_helper_hotplug_event(). For easier
 * integration with the output polling code in drm_crtc_helper.c the modeset
 * code provides a ->output_poll_changed callback.
 *
 * All other functions exported by the fb helper library can be used to
 * implement the fbdev driver interface by the driver.
 *
 * It is possible, though perhaps somewhat tricky, to implement race-free
 * hotplug detection using the fbdev helpers. The drm_fb_helper_prepare()
 * helper must be called first to initialize the minimum required to make
 * hotplug detection work. Drivers also need to make sure to properly set up
 * the dev->mode_config.funcs member. After calling drm_kms_helper_poll_init()
 * it is safe to enable interrupts and start processing hotplug events. At the
 * same time, drivers should initialize all modeset objects such as CRTCs,
 * encoders and connectors. To finish up the fbdev helper initialization, the
 * drm_fb_helper_init() function is called. To probe for all attached displays
 * and set up an initial configuration using the detected hardware, drivers
 * should call drm_fb_helper_single_add_all_connectors() followed by
 * drm_fb_helper_initial_config().
 *
 * If &drm_framebuffer_funcs ->dirty is set, the
 * drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions will
 * accumulate changes and schedule &drm_fb_helper ->dirty_work to run right
 * away. This worker then calls the dirty() function ensuring that it will
 * always run in process context since the fb_*() function could be running in
 * atomic context. If drm_fb_helper_deferred_io() is used as the deferred_io
 * callback it will also schedule dirty_work with the damage collected from the
 * mmap page writes.
 */

/**
 * drm_fb_helper_single_add_all_connectors() - add all connectors to fbdev
 *                                             emulation helper
 * @fb_helper: fbdev initialized with drm_fb_helper_init
 *
 * This functions adds all the available connectors for use with the given
 * fb_helper. This is a separate step to allow drivers to freely assign
 * connectors to the fbdev, e.g. if some are reserved for special purposes or
 * not adequate to be used for the fbcon.
 *
 * This function is protected against concurrent connector hotadds/removals
 * using drm_fb_helper_add_one_connector() and
 * drm_fb_helper_remove_one_connector().
 */
int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        struct drm_connector *connector;
        int i, ret;

        if (!drm_fbdev_emulation)
                return 0;

        mutex_lock(&dev->mode_config.mutex);
        drm_for_each_connector(connector, dev) {
                ret = drm_fb_helper_add_one_connector(fb_helper, connector);

                if (ret)
                        goto fail;
        }
        mutex_unlock(&dev->mode_config.mutex);
        return 0;
fail:
        for (i = 0; i < fb_helper->connector_count; i++) {
                kfree(fb_helper->connector_info[i]);
                fb_helper->connector_info[i] = NULL;
        }
        fb_helper->connector_count = 0;
        mutex_unlock(&dev->mode_config.mutex);

        return ret;
}
EXPORT_SYMBOL(drm_fb_helper_single_add_all_connectors);

int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_connector *connector)
{
        struct drm_fb_helper_connector **temp;
        struct drm_fb_helper_connector *fb_helper_connector;

        if (!drm_fbdev_emulation)
                return 0;

        WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));
        if (fb_helper->connector_count + 1 > fb_helper->connector_info_alloc_count) {
                temp = krealloc(fb_helper->connector_info, sizeof(struct drm_fb_helper_connector *) * (fb_helper->connector_count + 1), GFP_KERNEL);
                if (!temp)
                        return -ENOMEM;

                fb_helper->connector_info_alloc_count = fb_helper->connector_count + 1;
                fb_helper->connector_info = temp;
        }


        fb_helper_connector = kzalloc(sizeof(struct drm_fb_helper_connector), GFP_KERNEL);
        if (!fb_helper_connector)
                return -ENOMEM;

        drm_connector_reference(connector);
        fb_helper_connector->connector = connector;
        fb_helper->connector_info[fb_helper->connector_count++] = fb_helper_connector;
        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_add_one_connector);

int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
                                       struct drm_connector *connector)
{
        struct drm_fb_helper_connector *fb_helper_connector;
        int i, j;

        if (!drm_fbdev_emulation)
                return 0;

        WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));

        for (i = 0; i < fb_helper->connector_count; i++) {
                if (fb_helper->connector_info[i]->connector == connector)
                        break;
        }

        if (i == fb_helper->connector_count)
                return -EINVAL;
        fb_helper_connector = fb_helper->connector_info[i];
        drm_connector_unreference(fb_helper_connector->connector);

        for (j = i + 1; j < fb_helper->connector_count; j++) {
                fb_helper->connector_info[j - 1] = fb_helper->connector_info[j];
        }
        fb_helper->connector_count--;
        kfree(fb_helper_connector);

        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_remove_one_connector);

static void drm_fb_helper_save_lut_atomic(struct drm_crtc *crtc, struct drm_fb_helper *helper)
{
        uint16_t *r_base, *g_base, *b_base;
        int i;

        if (helper->funcs->gamma_get == NULL)
                return;

        r_base = crtc->gamma_store;
        g_base = r_base + crtc->gamma_size;
        b_base = g_base + crtc->gamma_size;

        for (i = 0; i < crtc->gamma_size; i++)
                helper->funcs->gamma_get(crtc, &r_base[i], &g_base[i], &b_base[i], i);
}

static void drm_fb_helper_restore_lut_atomic(struct drm_crtc *crtc)
{
        uint16_t *r_base, *g_base, *b_base;

        if (crtc->funcs->gamma_set == NULL)
                return;

        r_base = crtc->gamma_store;
        g_base = r_base + crtc->gamma_size;
        b_base = g_base + crtc->gamma_size;

        crtc->funcs->gamma_set(crtc, r_base, g_base, b_base, crtc->gamma_size);
}

/**
 * drm_fb_helper_debug_enter - implementation for ->fb_debug_enter
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_debug_enter(struct fb_info *info)
{
        struct drm_fb_helper *helper = info->par;
        const struct drm_crtc_helper_funcs *funcs;
        int i;

        list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
                for (i = 0; i < helper->crtc_count; i++) {
                        struct drm_mode_set *mode_set =
                                &helper->crtc_info[i].mode_set;

                        if (!mode_set->crtc->enabled)
                                continue;

                        funcs = mode_set->crtc->helper_private;
                        drm_fb_helper_save_lut_atomic(mode_set->crtc, helper);
                        funcs->mode_set_base_atomic(mode_set->crtc,
                                                    mode_set->fb,
                                                    mode_set->x,
                                                    mode_set->y,
                                                    ENTER_ATOMIC_MODE_SET);
                }
        }

        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_debug_enter);

/* Find the real fb for a given fb helper CRTC */
static struct drm_framebuffer *drm_mode_config_fb(struct drm_crtc *crtc)
{
        struct drm_device *dev = crtc->dev;
        struct drm_crtc *c;

        drm_for_each_crtc(c, dev) {
                if (crtc->base.id == c->base.id)
                        return c->primary->fb;
        }

        return NULL;
}

/**
 * drm_fb_helper_debug_leave - implementation for ->fb_debug_leave
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_debug_leave(struct fb_info *info)
{
        struct drm_fb_helper *helper = info->par;
        struct drm_crtc *crtc;
        const struct drm_crtc_helper_funcs *funcs;
        struct drm_framebuffer *fb;
        int i;

        for (i = 0; i < helper->crtc_count; i++) {
                struct drm_mode_set *mode_set = &helper->crtc_info[i].mode_set;
                crtc = mode_set->crtc;
                funcs = crtc->helper_private;
                fb = drm_mode_config_fb(crtc);

                if (!crtc->enabled)
                        continue;

                if (!fb) {
                        DRM_ERROR("no fb to restore??\n");
                        continue;
                }

                drm_fb_helper_restore_lut_atomic(mode_set->crtc);
                funcs->mode_set_base_atomic(mode_set->crtc, fb, crtc->x,
                                            crtc->y, LEAVE_ATOMIC_MODE_SET);
        }

        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_debug_leave);

static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        struct drm_plane *plane;
        struct drm_atomic_state *state;
        int i, ret;
        unsigned plane_mask;

        state = drm_atomic_state_alloc(dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = dev->mode_config.acquire_ctx;
retry:
        plane_mask = 0;
        drm_for_each_plane(plane, dev) {
                struct drm_plane_state *plane_state;

                plane_state = drm_atomic_get_plane_state(state, plane);
                if (IS_ERR(plane_state)) {
                        ret = PTR_ERR(plane_state);
                        goto fail;
                }

                plane_state->rotation = DRM_ROTATE_0;

                plane->old_fb = plane->fb;
                plane_mask |= 1 << drm_plane_index(plane);

                /* disable non-primary: */
                if (plane->type == DRM_PLANE_TYPE_PRIMARY)
                        continue;

                ret = __drm_atomic_helper_disable_plane(plane, plane_state);
                if (ret != 0)
                        goto fail;
        }

        for(i = 0; i < fb_helper->crtc_count; i++) {
                struct drm_mode_set *mode_set = &fb_helper->crtc_info[i].mode_set;

                ret = __drm_atomic_helper_set_config(mode_set, state);
                if (ret != 0)
                        goto fail;
        }

        ret = drm_atomic_commit(state);

fail:
        drm_atomic_clean_old_fb(dev, plane_mask, ret);

        if (ret == -EDEADLK)
                goto backoff;

        if (ret != 0)
                drm_atomic_state_free(state);

        return ret;

backoff:
        drm_atomic_state_clear(state);
        drm_atomic_legacy_backoff(state);

        goto retry;
}

static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        struct drm_plane *plane;
        int i;

        drm_warn_on_modeset_not_all_locked(dev);

        if (dev->mode_config.funcs->atomic_commit)
                return restore_fbdev_mode_atomic(fb_helper);

        drm_for_each_plane(plane, dev) {
                if (plane->type != DRM_PLANE_TYPE_PRIMARY)
                        drm_plane_force_disable(plane);

                if (dev->mode_config.rotation_property) {
                        drm_mode_plane_set_obj_prop(plane,
                                                    dev->mode_config.rotation_property,
                                                    DRM_ROTATE_0);
                }
        }

        for (i = 0; i < fb_helper->crtc_count; i++) {
                struct drm_mode_set *mode_set = &fb_helper->crtc_info[i].mode_set;
                struct drm_crtc *crtc = mode_set->crtc;
                int ret;

                if (crtc->funcs->cursor_set2) {
                        ret = crtc->funcs->cursor_set2(crtc, NULL, 0, 0, 0, 0, 0);
                        if (ret)
                                return ret;
                } else if (crtc->funcs->cursor_set) {
                        ret = crtc->funcs->cursor_set(crtc, NULL, 0, 0, 0);
                        if (ret)
                                return ret;
                }

                ret = drm_mode_set_config_internal(mode_set);
                if (ret)
                        return ret;
        }

        return 0;
}

/**
 * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration
 * @fb_helper: fbcon to restore
 *
 * This should be called from driver's drm ->lastclose callback
 * when implementing an fbcon on top of kms using this helper. This ensures that
 * the user isn't greeted with a black screen when e.g. X dies.
 *
 * RETURNS:
 * Zero if everything went ok, negative error code otherwise.
 */
int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        bool do_delayed;
        int ret;

        if (!drm_fbdev_emulation)
                return -ENODEV;

        drm_modeset_lock_all(dev);
        ret = restore_fbdev_mode(fb_helper);

        do_delayed = fb_helper->delayed_hotplug;
        if (do_delayed)
                fb_helper->delayed_hotplug = false;
        drm_modeset_unlock_all(dev);

        if (do_delayed)
                drm_fb_helper_hotplug_event(fb_helper);
        return ret;
}
EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);

static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        struct drm_crtc *crtc;
        int bound = 0, crtcs_bound = 0;

        /* Sometimes user space wants everything disabled, so don't steal the
         * display if there's a master. */
        if (READ_ONCE(dev->master))
                return false;

        drm_for_each_crtc(crtc, dev) {
                if (crtc->primary->fb)
                        crtcs_bound++;
                if (crtc->primary->fb == fb_helper->fb)
                        bound++;
        }

        if (bound < crtcs_bound)
                return false;

        return true;
}

#ifdef CONFIG_MAGIC_SYSRQ
/*
 * restore fbcon display for all kms driver's using this helper, used for sysrq
 * and panic handling.
 */
static bool drm_fb_helper_force_kernel_mode(void)
{
        bool ret, error = false;
        struct drm_fb_helper *helper;

        if (list_empty(&kernel_fb_helper_list))
                return false;

        list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
                struct drm_device *dev = helper->dev;

                if (dev->switch_power_state == DRM_SWITCH_POWER_OFF)
                        continue;

                drm_modeset_lock_all(dev);
                ret = restore_fbdev_mode(helper);
                if (ret)
                        error = true;
                drm_modeset_unlock_all(dev);
        }
        return error;
}

static void drm_fb_helper_restore_work_fn(struct work_struct *ignored)
{
        bool ret;
        ret = drm_fb_helper_force_kernel_mode();
        if (ret == true)
                DRM_ERROR("Failed to restore crtc configuration\n");
}
static DECLARE_WORK(drm_fb_helper_restore_work, drm_fb_helper_restore_work_fn);

static void drm_fb_helper_sysrq(int dummy1)
{
        schedule_work(&drm_fb_helper_restore_work);
}

static struct sysrq_key_op sysrq_drm_fb_helper_restore_op = {
        .handler = drm_fb_helper_sysrq,
        .help_msg = "force-fb(V)",
        .action_msg = "Restore framebuffer console",
};
#else
static struct sysrq_key_op sysrq_drm_fb_helper_restore_op = { };
#endif

static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_device *dev = fb_helper->dev;
        struct drm_crtc *crtc;
        struct drm_connector *connector;
        int i, j;

        /*
         * For each CRTC in this fb, turn the connectors on/off.
         */
        drm_modeset_lock_all(dev);
        if (!drm_fb_helper_is_bound(fb_helper)) {
                drm_modeset_unlock_all(dev);
                return;
        }

        for (i = 0; i < fb_helper->crtc_count; i++) {
                crtc = fb_helper->crtc_info[i].mode_set.crtc;

                if (!crtc->enabled)
                        continue;

                /* Walk the connectors & encoders on this fb turning them on/off */
                for (j = 0; j < fb_helper->connector_count; j++) {
                        connector = fb_helper->connector_info[j]->connector;
                        connector->funcs->dpms(connector, dpms_mode);
                        drm_object_property_set_value(&connector->base,
                                dev->mode_config.dpms_property, dpms_mode);
                }
        }
        drm_modeset_unlock_all(dev);
}

/**
 * drm_fb_helper_blank - implementation for ->fb_blank
 * @blank: desired blanking state
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_blank(int blank, struct fb_info *info)
{
        if (oops_in_progress)
                return -EBUSY;

        switch (blank) {
        /* Display: On; HSync: On, VSync: On */
        case FB_BLANK_UNBLANK:
                drm_fb_helper_dpms(info, DRM_MODE_DPMS_ON);
                break;
        /* Display: Off; HSync: On, VSync: On */
        case FB_BLANK_NORMAL:
                drm_fb_helper_dpms(info, DRM_MODE_DPMS_STANDBY);
                break;
        /* Display: Off; HSync: Off, VSync: On */
        case FB_BLANK_HSYNC_SUSPEND:
                drm_fb_helper_dpms(info, DRM_MODE_DPMS_STANDBY);
                break;
        /* Display: Off; HSync: On, VSync: Off */
        case FB_BLANK_VSYNC_SUSPEND:
                drm_fb_helper_dpms(info, DRM_MODE_DPMS_SUSPEND);
                break;
        /* Display: Off; HSync: Off, VSync: Off */
        case FB_BLANK_POWERDOWN:
                drm_fb_helper_dpms(info, DRM_MODE_DPMS_OFF);
                break;
        }
        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_blank);

static void drm_fb_helper_crtc_free(struct drm_fb_helper *helper)
{
        int i;

        for (i = 0; i < helper->connector_count; i++) {
                drm_connector_unreference(helper->connector_info[i]->connector);
                kfree(helper->connector_info[i]);
        }
        kfree(helper->connector_info);
        for (i = 0; i < helper->crtc_count; i++) {
                kfree(helper->crtc_info[i].mode_set.connectors);
                if (helper->crtc_info[i].mode_set.mode)
                        drm_mode_destroy(helper->dev, helper->crtc_info[i].mode_set.mode);
        }
        kfree(helper->crtc_info);
}

static void drm_fb_helper_resume_worker(struct work_struct *work)
{
        struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
                                                    resume_work);

        console_lock();
        fb_set_suspend(helper->fbdev, 0);
        console_unlock();
}

static void drm_fb_helper_dirty_work(struct work_struct *work)
{
        struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
                                                    dirty_work);
        struct drm_clip_rect *clip = &helper->dirty_clip;
        struct drm_clip_rect clip_copy;
        unsigned long flags;

        spin_lock_irqsave(&helper->dirty_lock, flags);
        clip_copy = *clip;
        clip->x1 = clip->y1 = ~0;
        clip->x2 = clip->y2 = 0;
        spin_unlock_irqrestore(&helper->dirty_lock, flags);

        helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
}

/**
 * drm_fb_helper_prepare - setup a drm_fb_helper structure
 * @dev: DRM device
 * @helper: driver-allocated fbdev helper structure to set up
 * @funcs: pointer to structure of functions associate with this helper
 *
 * Sets up the bare minimum to make the framebuffer helper usable. This is
 * useful to implement race-free initialization of the polling helpers.
 */
void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
                           const struct drm_fb_helper_funcs *funcs)
{
        INIT_LIST_HEAD(&helper->kernel_fb_list);
        spin_lock_init(&helper->dirty_lock);
        INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker);
        INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
        helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
        helper->funcs = funcs;
        helper->dev = dev;
}
EXPORT_SYMBOL(drm_fb_helper_prepare);

/**
 * drm_fb_helper_init - initialize a drm_fb_helper structure
 * @dev: drm device
 * @fb_helper: driver-allocated fbdev helper structure to initialize
 * @crtc_count: maximum number of crtcs to support in this fbdev emulation
 * @max_conn_count: max connector count
 *
 * This allocates the structures for the fbdev helper with the given limits.
 * Note that this won't yet touch the hardware (through the driver interfaces)
 * nor register the fbdev. This is only done in drm_fb_helper_initial_config()
 * to allow driver writes more control over the exact init sequence.
 *
 * Drivers must call drm_fb_helper_prepare() before calling this function.
 *
 * RETURNS:
 * Zero if everything went ok, nonzero otherwise.
 */
int drm_fb_helper_init(struct drm_device *dev,
                       struct drm_fb_helper *fb_helper,
                       int crtc_count, int max_conn_count)
{
        struct drm_crtc *crtc;
        int i;

        if (!drm_fbdev_emulation)
                return 0;

        if (!max_conn_count)
                return -EINVAL;

        fb_helper->crtc_info = kcalloc(crtc_count, sizeof(struct drm_fb_helper_crtc), GFP_KERNEL);
        if (!fb_helper->crtc_info)
                return -ENOMEM;

        fb_helper->crtc_count = crtc_count;
        fb_helper->connector_info = kcalloc(dev->mode_config.num_connector, sizeof(struct drm_fb_helper_connector *), GFP_KERNEL);
        if (!fb_helper->connector_info) {
                kfree(fb_helper->crtc_info);
                return -ENOMEM;
        }
        fb_helper->connector_info_alloc_count = dev->mode_config.num_connector;
        fb_helper->connector_count = 0;

        for (i = 0; i < crtc_count; i++) {
                fb_helper->crtc_info[i].mode_set.connectors =
                        kcalloc(max_conn_count,
                                sizeof(struct drm_connector *),
                                GFP_KERNEL);

                if (!fb_helper->crtc_info[i].mode_set.connectors)
                        goto out_free;
                fb_helper->crtc_info[i].mode_set.num_connectors = 0;
        }

        i = 0;
        drm_for_each_crtc(crtc, dev) {
                fb_helper->crtc_info[i].mode_set.crtc = crtc;
                i++;
        }

        return 0;
out_free:
        drm_fb_helper_crtc_free(fb_helper);
        return -ENOMEM;
}
EXPORT_SYMBOL(drm_fb_helper_init);

/**
 * drm_fb_helper_alloc_fbi - allocate fb_info and some of its members
 * @fb_helper: driver-allocated fbdev helper
 *
 * A helper to alloc fb_info and the members cmap and apertures. Called
 * by the driver within the fb_probe fb_helper callback function.
 *
 * RETURNS:
 * fb_info pointer if things went okay, pointer containing error code
 * otherwise
 */
struct fb_info *drm_fb_helper_alloc_fbi(struct drm_fb_helper *fb_helper)
{
        struct device *dev = fb_helper->dev->dev;
        struct fb_info *info;
        int ret;

        info = framebuffer_alloc(0, dev);
        if (!info)
                return ERR_PTR(-ENOMEM);

        ret = fb_alloc_cmap(&info->cmap, 256, 0);
        if (ret)
                goto err_release;

        info->apertures = alloc_apertures(1);
        if (!info->apertures) {
                ret = -ENOMEM;
                goto err_free_cmap;
        }

        fb_helper->fbdev = info;

        return info;

err_free_cmap:
        fb_dealloc_cmap(&info->cmap);
err_release:
        framebuffer_release(info);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL(drm_fb_helper_alloc_fbi);

/**
 * drm_fb_helper_unregister_fbi - unregister fb_info framebuffer device
 * @fb_helper: driver-allocated fbdev helper
 *
 * A wrapper around unregister_framebuffer, to release the fb_info
 * framebuffer device
 */
void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper)
{
        if (fb_helper && fb_helper->fbdev)
                unregister_framebuffer(fb_helper->fbdev);
}
EXPORT_SYMBOL(drm_fb_helper_unregister_fbi);

/**
 * drm_fb_helper_release_fbi - dealloc fb_info and its members
 * @fb_helper: driver-allocated fbdev helper
 *
 * A helper to free memory taken by fb_info and the members cmap and
 * apertures
 */
void drm_fb_helper_release_fbi(struct drm_fb_helper *fb_helper)
{
        if (fb_helper) {
                struct fb_info *info = fb_helper->fbdev;

                if (info) {
                        if (info->cmap.len)
                                fb_dealloc_cmap(&info->cmap);
                        framebuffer_release(info);
                }

                fb_helper->fbdev = NULL;
        }
}
EXPORT_SYMBOL(drm_fb_helper_release_fbi);

void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
{
        if (!drm_fbdev_emulation)
                return;

        if (!list_empty(&fb_helper->kernel_fb_list)) {
                list_del(&fb_helper->kernel_fb_list);
                if (list_empty(&kernel_fb_helper_list)) {
                        unregister_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
                }
        }

        drm_fb_helper_crtc_free(fb_helper);

}
EXPORT_SYMBOL(drm_fb_helper_fini);

/**
 * drm_fb_helper_unlink_fbi - wrapper around unlink_framebuffer
 * @fb_helper: driver-allocated fbdev helper
 *
 * A wrapper around unlink_framebuffer implemented by fbdev core
 */
void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
{
        if (fb_helper && fb_helper->fbdev)
                unlink_framebuffer(fb_helper->fbdev);
}
EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);

static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
                                u32 width, u32 height)
{
        struct drm_fb_helper *helper = info->par;
        struct drm_clip_rect *clip = &helper->dirty_clip;
        unsigned long flags;

        if (!helper->fb->funcs->dirty)
                return;

        spin_lock_irqsave(&helper->dirty_lock, flags);
        clip->x1 = min_t(u32, clip->x1, x);
        clip->y1 = min_t(u32, clip->y1, y);
        clip->x2 = max_t(u32, clip->x2, x + width);
        clip->y2 = max_t(u32, clip->y2, y + height);
        spin_unlock_irqrestore(&helper->dirty_lock, flags);

        schedule_work(&helper->dirty_work);
}

/**
 * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
 * @info: fb_info struct pointer
 * @pagelist: list of dirty mmap framebuffer pages
 *
 * This function is used as the &fb_deferred_io ->deferred_io
 * callback function for flushing the fbdev mmap writes.
 */
void drm_fb_helper_deferred_io(struct fb_info *info,
                               struct list_head *pagelist)
{
        unsigned long start, end, min, max;
        struct page *page;
        u32 y1, y2;

        min = ULONG_MAX;
        max = 0;
        list_for_each_entry(page, pagelist, lru) {
                start = page->index << PAGE_SHIFT;
                end = start + PAGE_SIZE - 1;
                min = min(min, start);
                max = max(max, end);
        }

        if (min < max) {
                y1 = min / info->fix.line_length;
                y2 = min_t(u32, DIV_ROUND_UP(max, info->fix.line_length),
                           info->var.yres);
                drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
        }
}
EXPORT_SYMBOL(drm_fb_helper_deferred_io);

/**
 * drm_fb_helper_sys_read - wrapper around fb_sys_read
 * @info: fb_info struct pointer
 * @buf: userspace buffer to read from framebuffer memory
 * @count: number of bytes to read from framebuffer memory
 * @ppos: read offset within framebuffer memory
 *
 * A wrapper around fb_sys_read implemented by fbdev core
 */
ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
                               size_t count, loff_t *ppos)
{
        return fb_sys_read(info, buf, count, ppos);
}
EXPORT_SYMBOL(drm_fb_helper_sys_read);

/**
 * drm_fb_helper_sys_write - wrapper around fb_sys_write
 * @info: fb_info struct pointer
 * @buf: userspace buffer to write to framebuffer memory
 * @count: number of bytes to write to framebuffer memory
 * @ppos: write offset within framebuffer memory
 *
 * A wrapper around fb_sys_write implemented by fbdev core
 */
ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
                                size_t count, loff_t *ppos)
{
        ssize_t ret;

        ret = fb_sys_write(info, buf, count, ppos);
        if (ret > 0)
                drm_fb_helper_dirty(info, 0, 0, info->var.xres,
                                    info->var.yres);

        return ret;
}
EXPORT_SYMBOL(drm_fb_helper_sys_write);

/**
 * drm_fb_helper_sys_fillrect - wrapper around sys_fillrect
 * @info: fbdev registered by the helper
 * @rect: info about rectangle to fill
 *
 * A wrapper around sys_fillrect implemented by fbdev core
 */
void drm_fb_helper_sys_fillrect(struct fb_info *info,
                                const struct fb_fillrect *rect)
{
        sys_fillrect(info, rect);
        drm_fb_helper_dirty(info, rect->dx, rect->dy,
                            rect->width, rect->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);

/**
 * drm_fb_helper_sys_copyarea - wrapper around sys_copyarea
 * @info: fbdev registered by the helper
 * @area: info about area to copy
 *
 * A wrapper around sys_copyarea implemented by fbdev core
 */
void drm_fb_helper_sys_copyarea(struct fb_info *info,
                                const struct fb_copyarea *area)
{
        sys_copyarea(info, area);
        drm_fb_helper_dirty(info, area->dx, area->dy,
                            area->width, area->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);

/**
 * drm_fb_helper_sys_imageblit - wrapper around sys_imageblit
 * @info: fbdev registered by the helper
 * @image: info about image to blit
 *
 * A wrapper around sys_imageblit implemented by fbdev core
 */
void drm_fb_helper_sys_imageblit(struct fb_info *info,
                                 const struct fb_image *image)
{
        sys_imageblit(info, image);
        drm_fb_helper_dirty(info, image->dx, image->dy,
                            image->width, image->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);

/**
 * drm_fb_helper_cfb_fillrect - wrapper around cfb_fillrect
 * @info: fbdev registered by the helper
 * @rect: info about rectangle to fill
 *
 * A wrapper around cfb_imageblit implemented by fbdev core
 */
void drm_fb_helper_cfb_fillrect(struct fb_info *info,
                                const struct fb_fillrect *rect)
{
        cfb_fillrect(info, rect);
        drm_fb_helper_dirty(info, rect->dx, rect->dy,
                            rect->width, rect->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);

/**
 * drm_fb_helper_cfb_copyarea - wrapper around cfb_copyarea
 * @info: fbdev registered by the helper
 * @area: info about area to copy
 *
 * A wrapper around cfb_copyarea implemented by fbdev core
 */
void drm_fb_helper_cfb_copyarea(struct fb_info *info,
                                const struct fb_copyarea *area)
{
        cfb_copyarea(info, area);
        drm_fb_helper_dirty(info, area->dx, area->dy,
                            area->width, area->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);

/**
 * drm_fb_helper_cfb_imageblit - wrapper around cfb_imageblit
 * @info: fbdev registered by the helper
 * @image: info about image to blit
 *
 * A wrapper around cfb_imageblit implemented by fbdev core
 */
void drm_fb_helper_cfb_imageblit(struct fb_info *info,
                                 const struct fb_image *image)
{
        cfb_imageblit(info, image);
        drm_fb_helper_dirty(info, image->dx, image->dy,
                            image->width, image->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);

/**
 * drm_fb_helper_set_suspend - wrapper around fb_set_suspend
 * @fb_helper: driver-allocated fbdev helper
 * @suspend: whether to suspend or resume
 *
 * A wrapper around fb_set_suspend implemented by fbdev core.
 * Use drm_fb_helper_set_suspend_unlocked() if you don't need to take
 * the lock yourself
 */
void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper, bool suspend)
{
        if (fb_helper && fb_helper->fbdev)
                fb_set_suspend(fb_helper->fbdev, suspend);
}
EXPORT_SYMBOL(drm_fb_helper_set_suspend);

/**
 * drm_fb_helper_set_suspend_unlocked - wrapper around fb_set_suspend that also
 *                                      takes the console lock
 * @fb_helper: driver-allocated fbdev helper
 * @suspend: whether to suspend or resume
 *
 * A wrapper around fb_set_suspend() that takes the console lock. If the lock
 * isn't available on resume, a worker is tasked with waiting for the lock
 * to become available. The console lock can be pretty contented on resume
 * due to all the printk activity.
 *
 * This function can be called multiple times with the same state since
 * &fb_info->state is checked to see if fbdev is running or not before locking.
 *
 * Use drm_fb_helper_set_suspend() if you need to take the lock yourself.
 */
void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
                                        bool suspend)
{
        if (!fb_helper || !fb_helper->fbdev)
                return;

        /* make sure there's no pending/ongoing resume */
        flush_work(&fb_helper->resume_work);

        if (suspend) {
                if (fb_helper->fbdev->state != FBINFO_STATE_RUNNING)
                        return;

                console_lock();

        } else {
                if (fb_helper->fbdev->state == FBINFO_STATE_RUNNING)
                        return;

                if (!console_trylock()) {
                        schedule_work(&fb_helper->resume_work);
                        return;
                }
        }

        fb_set_suspend(fb_helper->fbdev, suspend);
        console_unlock();
}
EXPORT_SYMBOL(drm_fb_helper_set_suspend_unlocked);

static int setcolreg(struct drm_crtc *crtc, u16 red, u16 green,
                     u16 blue, u16 regno, struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_framebuffer *fb = fb_helper->fb;

        if (info->fix.visual == FB_VISUAL_TRUECOLOR) {
                u32 *palette;
                u32 value;
                /* place color in psuedopalette */
                if (regno > 16)
                        return -EINVAL;
                palette = (u32 *)info->pseudo_palette;
                red >>= (16 - info->var.red.length);
                green >>= (16 - info->var.green.length);
                blue >>= (16 - info->var.blue.length);
                value = (red << info->var.red.offset) |
                        (green << info->var.green.offset) |
                        (blue << info->var.blue.offset);
                if (info->var.transp.length > 0) {
                        u32 mask = (1 << info->var.transp.length) - 1;
                        mask <<= info->var.transp.offset;
                        value |= mask;
                }
                palette[regno] = value;
                return 0;
        }

        /*
         * The driver really shouldn't advertise pseudo/directcolor
         * visuals if it can't deal with the palette.
         */
        if (WARN_ON(!fb_helper->funcs->gamma_set ||
                    !fb_helper->funcs->gamma_get))
                return -EINVAL;

        WARN_ON(fb->bits_per_pixel != 8);

        fb_helper->funcs->gamma_set(crtc, red, green, blue, regno);

        return 0;
}

/**
 * drm_fb_helper_setcmap - implementation for ->fb_setcmap
 * @cmap: cmap to set
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_device *dev = fb_helper->dev;
        const struct drm_crtc_helper_funcs *crtc_funcs;
        u16 *red, *green, *blue, *transp;
        struct drm_crtc *crtc;
        int i, j, rc = 0;
        int start;

        if (oops_in_progress)
                return -EBUSY;

        drm_modeset_lock_all(dev);
        if (!drm_fb_helper_is_bound(fb_helper)) {
                drm_modeset_unlock_all(dev);
                return -EBUSY;
        }

        for (i = 0; i < fb_helper->crtc_count; i++) {
                crtc = fb_helper->crtc_info[i].mode_set.crtc;
                crtc_funcs = crtc->helper_private;

                red = cmap->red;
                green = cmap->green;
                blue = cmap->blue;
                transp = cmap->transp;
                start = cmap->start;

                for (j = 0; j < cmap->len; j++) {
                        u16 hred, hgreen, hblue, htransp = 0xffff;

                        hred = *red++;
                        hgreen = *green++;
                        hblue = *blue++;

                        if (transp)
                                htransp = *transp++;

                        rc = setcolreg(crtc, hred, hgreen, hblue, start++, info);
                        if (rc)
                                goto out;
                }
                if (crtc_funcs->load_lut)
                        crtc_funcs->load_lut(crtc);
        }
 out:
        drm_modeset_unlock_all(dev);
        return rc;
}
EXPORT_SYMBOL(drm_fb_helper_setcmap);

/**
 * drm_fb_helper_check_var - implementation for ->fb_check_var
 * @var: screeninfo to check
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
                            struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_framebuffer *fb = fb_helper->fb;
        int depth;

        if (var->pixclock != 0 || in_dbg_master())
                return -EINVAL;

        /* Need to resize the fb object !!! */
        if (var->bits_per_pixel > fb->bits_per_pixel ||
            var->xres > fb->width || var->yres > fb->height ||
            var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
                DRM_DEBUG("fb userspace requested width/height/bpp is greater than current fb "
                          "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
                          var->xres, var->yres, var->bits_per_pixel,
                          var->xres_virtual, var->yres_virtual,
                          fb->width, fb->height, fb->bits_per_pixel);
                return -EINVAL;
        }

        switch (var->bits_per_pixel) {
        case 16:
                depth = (var->green.length == 6) ? 16 : 15;
                break;
        case 32:
                depth = (var->transp.length > 0) ? 32 : 24;
                break;
        default:
                depth = var->bits_per_pixel;
                break;
        }

        switch (depth) {
        case 8:
                var->red.offset = 0;
                var->green.offset = 0;
                var->blue.offset = 0;
                var->red.length = 8;
                var->green.length = 8;
                var->blue.length = 8;
                var->transp.length = 0;
                var->transp.offset = 0;
                break;
        case 15:
                var->red.offset = 10;
                var->green.offset = 5;
                var->blue.offset = 0;
                var->red.length = 5;
                var->green.length = 5;
                var->blue.length = 5;
                var->transp.length = 1;
                var->transp.offset = 15;
                break;
        case 16:
                var->red.offset = 11;
                var->green.offset = 5;
                var->blue.offset = 0;
                var->red.length = 5;
                var->green.length = 6;
                var->blue.length = 5;
                var->transp.length = 0;
                var->transp.offset = 0;
                break;
        case 24:
                var->red.offset = 16;
                var->green.offset = 8;
                var->blue.offset = 0;
                var->red.length = 8;
                var->green.length = 8;
                var->blue.length = 8;
                var->transp.length = 0;
                var->transp.offset = 0;
                break;
        case 32:
                var->red.offset = 16;
                var->green.offset = 8;
                var->blue.offset = 0;
                var->red.length = 8;
                var->green.length = 8;
                var->blue.length = 8;
                var->transp.length = 8;
                var->transp.offset = 24;
                break;
        default:
                return -EINVAL;
        }
        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_check_var);

/**
 * drm_fb_helper_set_par - implementation for ->fb_set_par
 * @info: fbdev registered by the helper
 *
 * This will let fbcon do the mode init and is called at initialization time by
 * the fbdev core when registering the driver, and later on through the hotplug
 * callback.
 */
int drm_fb_helper_set_par(struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct fb_var_screeninfo *var = &info->var;

        if (oops_in_progress)
                return -EBUSY;

        if (var->pixclock != 0) {
                DRM_ERROR("PIXEL CLOCK SET\n");
                return -EINVAL;
        }

        drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper);

        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_set_par);

static int pan_display_atomic(struct fb_var_screeninfo *var,
                              struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_device *dev = fb_helper->dev;
        struct drm_atomic_state *state;
        struct drm_plane *plane;
        int i, ret;
        unsigned plane_mask;

        state = drm_atomic_state_alloc(dev);
        if (!state)
                return -ENOMEM;

        state->acquire_ctx = dev->mode_config.acquire_ctx;
retry:
        plane_mask = 0;
        for(i = 0; i < fb_helper->crtc_count; i++) {
                struct drm_mode_set *mode_set;

                mode_set = &fb_helper->crtc_info[i].mode_set;

                mode_set->x = var->xoffset;
                mode_set->y = var->yoffset;

                ret = __drm_atomic_helper_set_config(mode_set, state);
                if (ret != 0)
                        goto fail;

                plane = mode_set->crtc->primary;
                plane_mask |= (1 << drm_plane_index(plane));
                plane->old_fb = plane->fb;
        }

        ret = drm_atomic_commit(state);
        if (ret != 0)
                goto fail;

        info->var.xoffset = var->xoffset;
        info->var.yoffset = var->yoffset;


fail:
        drm_atomic_clean_old_fb(dev, plane_mask, ret);

        if (ret == -EDEADLK)
                goto backoff;

        if (ret != 0)
                drm_atomic_state_free(state);

        return ret;

backoff:
        drm_atomic_state_clear(state);
        drm_atomic_legacy_backoff(state);

        goto retry;
}

/**
 * drm_fb_helper_pan_display - implementation for ->fb_pan_display
 * @var: updated screen information
 * @info: fbdev registered by the helper
 */
int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
                              struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_device *dev = fb_helper->dev;
        struct drm_mode_set *modeset;
        int ret = 0;
        int i;

        if (oops_in_progress)
                return -EBUSY;

        drm_modeset_lock_all(dev);
        if (!drm_fb_helper_is_bound(fb_helper)) {
                drm_modeset_unlock_all(dev);
                return -EBUSY;
        }

        if (dev->mode_config.funcs->atomic_commit) {
                ret = pan_display_atomic(var, info);
                goto unlock;
        }

        for (i = 0; i < fb_helper->crtc_count; i++) {
                modeset = &fb_helper->crtc_info[i].mode_set;

                modeset->x = var->xoffset;
                modeset->y = var->yoffset;

                if (modeset->num_connectors) {
                        ret = drm_mode_set_config_internal(modeset);
                        if (!ret) {
                                info->var.xoffset = var->xoffset;
                                info->var.yoffset = var->yoffset;
                        }
                }
        }
unlock:
        drm_modeset_unlock_all(dev);
        return ret;
}
EXPORT_SYMBOL(drm_fb_helper_pan_display);

/*
 * Allocates the backing storage and sets up the fbdev info structure through
 * the ->fb_probe callback and then registers the fbdev and sets up the panic
 * notifier.
 */
static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
                                         int preferred_bpp)
{
        int ret = 0;
        int crtc_count = 0;
        int i;
        struct fb_info *info;
        struct drm_fb_helper_surface_size sizes;
        int gamma_size = 0;

        memset(&sizes, 0, sizeof(struct drm_fb_helper_surface_size));
        sizes.surface_depth = 24;
        sizes.surface_bpp = 32;
        sizes.fb_width = (unsigned)-1;
        sizes.fb_height = (unsigned)-1;

        /* if driver picks 8 or 16 by default use that
           for both depth/bpp */
        if (preferred_bpp != sizes.surface_bpp)
                sizes.surface_depth = sizes.surface_bpp = preferred_bpp;

        /* first up get a count of crtcs now in use and new min/maxes width/heights */
        for (i = 0; i < fb_helper->connector_count; i++) {
                struct drm_fb_helper_connector *fb_helper_conn = fb_helper->connector_info[i];
                struct drm_cmdline_mode *cmdline_mode;

                cmdline_mode = &fb_helper_conn->connector->cmdline_mode;

                if (cmdline_mode->bpp_specified) {
                        switch (cmdline_mode->bpp) {
                        case 8:
                                sizes.surface_depth = sizes.surface_bpp = 8;
                                break;
                        case 15:
                                sizes.surface_depth = 15;
                                sizes.surface_bpp = 16;
                                break;
                        case 16:
                                sizes.surface_depth = sizes.surface_bpp = 16;
                                break;
                        case 24:
                                sizes.surface_depth = sizes.surface_bpp = 24;
                                break;
                        case 32:
                                sizes.surface_depth = 24;
                                sizes.surface_bpp = 32;
                                break;
                        }
                        break;
                }
        }

        crtc_count = 0;
        for (i = 0; i < fb_helper->crtc_count; i++) {
                struct drm_display_mode *desired_mode;
                struct drm_mode_set *mode_set;
                int x, y, j;
                /* in case of tile group, are we the last tile vert or horiz?
                 * If no tile group you are always the last one both vertically
                 * and horizontally
                 */
                bool lastv = true, lasth = true;

                desired_mode = fb_helper->crtc_info[i].desired_mode;
                mode_set = &fb_helper->crtc_info[i].mode_set;

                if (!desired_mode)
                        continue;

                crtc_count++;

                x = fb_helper->crtc_info[i].x;
                y = fb_helper->crtc_info[i].y;

                if (gamma_size == 0)
                        gamma_size = fb_helper->crtc_info[i].mode_set.crtc->gamma_size;

                sizes.surface_width  = max_t(u32, desired_mode->hdisplay + x, sizes.surface_width);
                sizes.surface_height = max_t(u32, desired_mode->vdisplay + y, sizes.surface_height);

                for (j = 0; j < mode_set->num_connectors; j++) {
                        struct drm_connector *connector = mode_set->connectors[j];
                        if (connector->has_tile) {
                                lasth = (connector->tile_h_loc == (connector->num_h_tile - 1));
                                lastv = (connector->tile_v_loc == (connector->num_v_tile - 1));
                                /* cloning to multiple tiles is just crazy-talk, so: */
                                break;
                        }
                }

                if (lasth)
                        sizes.fb_width  = min_t(u32, desired_mode->hdisplay + x, sizes.fb_width);
                if (lastv)
                        sizes.fb_height = min_t(u32, desired_mode->vdisplay + y, sizes.fb_height);
        }

        if (crtc_count == 0 || sizes.fb_width == -1 || sizes.fb_height == -1) {
                /* hmm everyone went away - assume VGA cable just fell out
                   and will come back later. */
                DRM_INFO("Cannot find any crtc or sizes - going 1024x768\n");
                sizes.fb_width = sizes.surface_width = 1024;
                sizes.fb_height = sizes.surface_height = 768;
        }

        /* push down into drivers */
        ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);
        if (ret < 0)
                return ret;

        info = fb_helper->fbdev;

        /*
         * Set the fb pointer - usually drm_setup_crtcs does this for hotplug
         * events, but at init time drm_setup_crtcs needs to be called before
         * the fb is allocated (since we need to figure out the desired size of
         * the fb before we can allocate it ...). Hence we need to fix things up
         * here again.
         */
        for (i = 0; i < fb_helper->crtc_count; i++)
                if (fb_helper->crtc_info[i].mode_set.num_connectors)
                        fb_helper->crtc_info[i].mode_set.fb = fb_helper->fb;


        info->var.pixclock = 0;
        if (register_framebuffer(info) < 0)
                return -EINVAL;

        dev_info(fb_helper->dev->dev, "fb%d: %s frame buffer device\n",
                        info->node, info->fix.id);

        if (list_empty(&kernel_fb_helper_list)) {
                register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
        }

        list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list);

        return 0;
}

/**
 * drm_fb_helper_fill_fix - initializes fixed fbdev information
 * @info: fbdev registered by the helper
 * @pitch: desired pitch
 * @depth: desired depth
 *
 * Helper to fill in the fixed fbdev information useful for a non-accelerated
 * fbdev emulations. Drivers which support acceleration methods which impose
 * additional constraints need to set up their own limits.
 *
 * Drivers should call this (or their equivalent setup code) from their
 * ->fb_probe callback.
 */
void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
                            uint32_t depth)
{
        info->fix.type = FB_TYPE_PACKED_PIXELS;
        info->fix.visual = depth == 8 ? FB_VISUAL_PSEUDOCOLOR :
                FB_VISUAL_TRUECOLOR;
        info->fix.mmio_start = 0;
        info->fix.mmio_len = 0;
        info->fix.type_aux = 0;
        info->fix.xpanstep = 1; /* doing it in hw */
        info->fix.ypanstep = 1; /* doing it in hw */
        info->fix.ywrapstep = 0;
        info->fix.accel = FB_ACCEL_NONE;

        info->fix.line_length = pitch;
        return;
}
EXPORT_SYMBOL(drm_fb_helper_fill_fix);

/**
 * drm_fb_helper_fill_var - initalizes variable fbdev information
 * @info: fbdev instance to set up
 * @fb_helper: fb helper instance to use as template
 * @fb_width: desired fb width
 * @fb_height: desired fb height
 *
 * Sets up the variable fbdev metainformation from the given fb helper instance
 * and the drm framebuffer allocated in fb_helper->fb.
 *
 * Drivers should call this (or their equivalent setup code) from their
 * ->fb_probe callback after having allocated the fbdev backing
 * storage framebuffer.
 */
void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
                            uint32_t fb_width, uint32_t fb_height)
{
        struct drm_framebuffer *fb = fb_helper->fb;
        info->pseudo_palette = fb_helper->pseudo_palette;
        info->var.xres_virtual = fb->width;
        info->var.yres_virtual = fb->height;
        info->var.bits_per_pixel = fb->bits_per_pixel;
        info->var.accel_flags = FB_ACCELF_TEXT;
        info->var.xoffset = 0;
        info->var.yoffset = 0;
        info->var.activate = FB_ACTIVATE_NOW;
        info->var.height = -1;
        info->var.width = -1;

        switch (fb->depth) {
        case 8:
                info->var.red.offset = 0;
                info->var.green.offset = 0;
                info->var.blue.offset = 0;
                info->var.red.length = 8; /* 8bit DAC */
                info->var.green.length = 8;
                info->var.blue.length = 8;
                info->var.transp.offset = 0;
                info->var.transp.length = 0;
                break;
        case 15:
                info->var.red.offset = 10;
                info->var.green.offset = 5;
                info->var.blue.offset = 0;
                info->var.red.length = 5;
                info->var.green.length = 5;
                info->var.blue.length = 5;
                info->var.transp.offset = 15;
                info->var.transp.length = 1;
                break;
        case 16:
                info->var.red.offset = 11;
                info->var.green.offset = 5;
                info->var.blue.offset = 0;
                info->var.red.length = 5;
                info->var.green.length = 6;
                info->var.blue.length = 5;
                info->var.transp.offset = 0;
                break;
        case 24:
                info->var.red.offset = 16;
                info->var.green.offset = 8;
                info->var.blue.offset = 0;
                info->var.red.length = 8;
                info->var.green.length = 8;
                info->var.blue.length = 8;
                info->var.transp.offset = 0;
                info->var.transp.length = 0;
                break;
        case 32:
                info->var.red.offset = 16;
                info->var.green.offset = 8;
                info->var.blue.offset = 0;
                info->var.red.length = 8;
                info->var.green.length = 8;
                info->var.blue.length = 8;
                info->var.transp.offset = 24;
                info->var.transp.length = 8;
                break;
        default:
                break;
        }

        info->var.xres = fb_width;
        info->var.yres = fb_height;
}
EXPORT_SYMBOL(drm_fb_helper_fill_var);

static int drm_fb_helper_probe_connector_modes(struct drm_fb_helper *fb_helper,
                                               uint32_t maxX,
                                               uint32_t maxY)
{
        struct drm_connector *connector;
        int count = 0;
        int i;

        for (i = 0; i < fb_helper->connector_count; i++) {
                connector = fb_helper->connector_info[i]->connector;
                count += connector->funcs->fill_modes(connector, maxX, maxY);
        }

        return count;
}

struct drm_display_mode *drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector, int width, int height)
{
        struct drm_display_mode *mode;

        list_for_each_entry(mode, &fb_connector->connector->modes, head) {
                if (mode->hdisplay > width ||
                    mode->vdisplay > height)
                        continue;
                if (mode->type & DRM_MODE_TYPE_PREFERRED)
                        return mode;
        }
        return NULL;
}
EXPORT_SYMBOL(drm_has_preferred_mode);

static bool drm_has_cmdline_mode(struct drm_fb_helper_connector *fb_connector)
{
        return fb_connector->connector->cmdline_mode.specified;
}

struct drm_display_mode *drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
                                                      int width, int height)
{
        struct drm_cmdline_mode *cmdline_mode;
        struct drm_display_mode *mode;
        bool prefer_non_interlace;

        cmdline_mode = &fb_helper_conn->connector->cmdline_mode;
        if (cmdline_mode->specified == false)
                return NULL;

        /* attempt to find a matching mode in the list of modes
         *  we have gotten so far, if not add a CVT mode that conforms
         */
        if (cmdline_mode->rb || cmdline_mode->margins)
                goto create_mode;

        prefer_non_interlace = !cmdline_mode->interlace;
again:
        list_for_each_entry(mode, &fb_helper_conn->connector->modes, head) {
                /* check width/height */
                if (mode->hdisplay != cmdline_mode->xres ||
                    mode->vdisplay != cmdline_mode->yres)
                        continue;

                if (cmdline_mode->refresh_specified) {
                        if (mode->vrefresh != cmdline_mode->refresh)
                                continue;
                }

                if (cmdline_mode->interlace) {
                        if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
                                continue;
                } else if (prefer_non_interlace) {
                        if (mode->flags & DRM_MODE_FLAG_INTERLACE)
                                continue;
                }
                return mode;
        }

        if (prefer_non_interlace) {
                prefer_non_interlace = false;
                goto again;
        }

create_mode:
        mode = drm_mode_create_from_cmdline_mode(fb_helper_conn->connector->dev,
                                                 cmdline_mode);
        list_add(&mode->head, &fb_helper_conn->connector->modes);
        return mode;
}
EXPORT_SYMBOL(drm_pick_cmdline_mode);

static bool drm_connector_enabled(struct drm_connector *connector, bool strict)
{
        bool enable;

        if (strict)
                enable = connector->status == connector_status_connected;
        else
                enable = connector->status != connector_status_disconnected;

        return enable;
}

static void drm_enable_connectors(struct drm_fb_helper *fb_helper,
                                  bool *enabled)
{
        bool any_enabled = false;
        struct drm_connector *connector;
        int i = 0;

        for (i = 0; i < fb_helper->connector_count; i++) {
                connector = fb_helper->connector_info[i]->connector;
                enabled[i] = drm_connector_enabled(connector, true);
                DRM_DEBUG_KMS("connector %d enabled? %s\n", connector->base.id,
                          enabled[i] ? "yes" : "no");
                any_enabled |= enabled[i];
        }

        if (any_enabled)
                return;

        for (i = 0; i < fb_helper->connector_count; i++) {
                connector = fb_helper->connector_info[i]->connector;
                enabled[i] = drm_connector_enabled(connector, false);
        }
}

static bool drm_target_cloned(struct drm_fb_helper *fb_helper,
                              struct drm_display_mode **modes,
                              struct drm_fb_offset *offsets,
                              bool *enabled, int width, int height)
{
        int count, i, j;
        bool can_clone = false;
        struct drm_fb_helper_connector *fb_helper_conn;
        struct drm_display_mode *dmt_mode, *mode;

        /* only contemplate cloning in the single crtc case */
        if (fb_helper->crtc_count > 1)
                return false;

        count = 0;
        for (i = 0; i < fb_helper->connector_count; i++) {
                if (enabled[i])
                        count++;
        }

        /* only contemplate cloning if more than one connector is enabled */
        if (count <= 1)
                return false;

        /* check the command line or if nothing common pick 1024x768 */
        can_clone = true;
        for (i = 0; i < fb_helper->connector_count; i++) {
                if (!enabled[i])
                        continue;
                fb_helper_conn = fb_helper->connector_info[i];
                modes[i] = drm_pick_cmdline_mode(fb_helper_conn, width, height);
                if (!modes[i]) {
                        can_clone = false;
                        break;
                }
                for (j = 0; j < i; j++) {
                        if (!enabled[j])
                                continue;
                        if (!drm_mode_equal(modes[j], modes[i]))
                                can_clone = false;
                }
        }

        if (can_clone) {
                DRM_DEBUG_KMS("can clone using command line\n");
                return true;
        }

        /* try and find a 1024x768 mode on each connector */
        can_clone = true;
        dmt_mode = drm_mode_find_dmt(fb_helper->dev, 1024, 768, 60, false);

        for (i = 0; i < fb_helper->connector_count; i++) {

                if (!enabled[i])
                        continue;

                fb_helper_conn = fb_helper->connector_info[i];
                list_for_each_entry(mode, &fb_helper_conn->connector->modes, head) {
                        if (drm_mode_equal(mode, dmt_mode))
                                modes[i] = mode;
                }
                if (!modes[i])
                        can_clone = false;
        }

        if (can_clone) {
                DRM_DEBUG_KMS("can clone using 1024x768\n");
                return true;
        }
        DRM_INFO("kms: can't enable cloning when we probably wanted to.\n");
        return false;
}

static int drm_get_tile_offsets(struct drm_fb_helper *fb_helper,
                                struct drm_display_mode **modes,
                                struct drm_fb_offset *offsets,
                                int idx,
                                int h_idx, int v_idx)
{
        struct drm_fb_helper_connector *fb_helper_conn;
        int i;
        int hoffset = 0, voffset = 0;

        for (i = 0; i < fb_helper->connector_count; i++) {
                fb_helper_conn = fb_helper->connector_info[i];
                if (!fb_helper_conn->connector->has_tile)
                        continue;

                if (!modes[i] && (h_idx || v_idx)) {
                        DRM_DEBUG_KMS("no modes for connector tiled %d %d\n", i,
                                      fb_helper_conn->connector->base.id);
                        continue;
                }
                if (fb_helper_conn->connector->tile_h_loc < h_idx)
                        hoffset += modes[i]->hdisplay;

                if (fb_helper_conn->connector->tile_v_loc < v_idx)
                        voffset += modes[i]->vdisplay;
        }
        offsets[idx].x = hoffset;
        offsets[idx].y = voffset;
        DRM_DEBUG_KMS("returned %d %d for %d %d\n", hoffset, voffset, h_idx, v_idx);
        return 0;
}

static bool drm_target_preferred(struct drm_fb_helper *fb_helper,
                                 struct drm_display_mode **modes,
                                 struct drm_fb_offset *offsets,
                                 bool *enabled, int width, int height)
{
        struct drm_fb_helper_connector *fb_helper_conn;
        int i;
        uint64_t conn_configured = 0, mask;
        int tile_pass = 0;
        mask = (1 << fb_helper->connector_count) - 1;
retry:
        for (i = 0; i < fb_helper->connector_count; i++) {
                fb_helper_conn = fb_helper->connector_info[i];

                if (conn_configured & (1 << i))
                        continue;

                if (enabled[i] == false) {
                        conn_configured |= (1 << i);
                        continue;
                }

                /* first pass over all the untiled connectors */
                if (tile_pass == 0 && fb_helper_conn->connector->has_tile)
                        continue;

                if (tile_pass == 1) {
                        if (fb_helper_conn->connector->tile_h_loc != 0 ||
                            fb_helper_conn->connector->tile_v_loc != 0)
                                continue;

                } else {
                        if (fb_helper_conn->connector->tile_h_loc != tile_pass -1 &&
                            fb_helper_conn->connector->tile_v_loc != tile_pass - 1)
                        /* if this tile_pass doesn't cover any of the tiles - keep going */
                                continue;

                        /* find the tile offsets for this pass - need
                           to find all tiles left and above */
                        drm_get_tile_offsets(fb_helper, modes, offsets,
                                             i, fb_helper_conn->connector->tile_h_loc, fb_helper_conn->connector->tile_v_loc);
                }
                DRM_DEBUG_KMS("looking for cmdline mode on connector %d\n",
                              fb_helper_conn->connector->base.id);

                /* got for command line mode first */
                modes[i] = drm_pick_cmdline_mode(fb_helper_conn, width, height);
                if (!modes[i]) {
                        DRM_DEBUG_KMS("looking for preferred mode on connector %d %d\n",
                                      fb_helper_conn->connector->base.id, fb_helper_conn->connector->tile_group ? fb_helper_conn->connector->tile_group->id : 0);
                        modes[i] = drm_has_preferred_mode(fb_helper_conn, width, height);
                }
                /* No preferred modes, pick one off the list */
                if (!modes[i] && !list_empty(&fb_helper_conn->connector->modes)) {
                        list_for_each_entry(modes[i], &fb_helper_conn->connector->modes, head)
                                break;
                }
                DRM_DEBUG_KMS("found mode %s\n", modes[i] ? modes[i]->name :
                          "none");
                conn_configured |= (1 << i);
        }

        if ((conn_configured & mask) != mask) {
                tile_pass++;
                goto retry;
        }
        return true;
}

static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
                          struct drm_fb_helper_crtc **best_crtcs,
                          struct drm_display_mode **modes,
                          int n, int width, int height)
{
        int c, o;
        struct drm_connector *connector;
        const struct drm_connector_helper_funcs *connector_funcs;
        struct drm_encoder *encoder;
        int my_score, best_score, score;
        struct drm_fb_helper_crtc **crtcs, *crtc;
        struct drm_fb_helper_connector *fb_helper_conn;

        if (n == fb_helper->connector_count)
                return 0;

        fb_helper_conn = fb_helper->connector_info[n];
        connector = fb_helper_conn->connector;

        best_crtcs[n] = NULL;
        best_score = drm_pick_crtcs(fb_helper, best_crtcs, modes, n+1, width, height);
        if (modes[n] == NULL)
                return best_score;

        crtcs = kzalloc(fb_helper->connector_count *
                        sizeof(struct drm_fb_helper_crtc *), GFP_KERNEL);
        if (!crtcs)
                return best_score;

        my_score = 1;
        if (connector->status == connector_status_connected)
                my_score++;
        if (drm_has_cmdline_mode(fb_helper_conn))
                my_score++;
        if (drm_has_preferred_mode(fb_helper_conn, width, height))
                my_score++;

        connector_funcs = connector->helper_private;

        /*
         * If the DRM device implements atomic hooks and ->best_encoder() is
         * NULL we fallback to the default drm_atomic_helper_best_encoder()
         * helper.
         */
        if (fb_helper->dev->mode_config.funcs->atomic_commit &&
            !connector_funcs->best_encoder)
                encoder = drm_atomic_helper_best_encoder(connector);
        else
                encoder = connector_funcs->best_encoder(connector);

        if (!encoder)
                goto out;

        /* select a crtc for this connector and then attempt to configure
           remaining connectors */
        for (c = 0; c < fb_helper->crtc_count; c++) {
                crtc = &fb_helper->crtc_info[c];

                if ((encoder->possible_crtcs & (1 << c)) == 0)
                        continue;

                for (o = 0; o < n; o++)
                        if (best_crtcs[o] == crtc)
                                break;

                if (o < n) {
                        /* ignore cloning unless only a single crtc */
                        if (fb_helper->crtc_count > 1)
                                continue;

                        if (!drm_mode_equal(modes[o], modes[n]))
                                continue;
                }

                crtcs[n] = crtc;
                memcpy(crtcs, best_crtcs, n * sizeof(struct drm_fb_helper_crtc *));
                score = my_score + drm_pick_crtcs(fb_helper, crtcs, modes, n + 1,
                                                  width, height);
                if (score > best_score) {
                        best_score = score;
                        memcpy(best_crtcs, crtcs,
                               fb_helper->connector_count *
                               sizeof(struct drm_fb_helper_crtc *));
                }
        }
out:
        kfree(crtcs);
        return best_score;
}

static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        struct drm_fb_helper_crtc **crtcs;
        struct drm_display_mode **modes;
        struct drm_fb_offset *offsets;
        struct drm_mode_set *modeset;
        bool *enabled;
        int width, height;
        int i;

        DRM_DEBUG_KMS("\n");

        width = dev->mode_config.max_width;
        height = dev->mode_config.max_height;

        crtcs = kcalloc(fb_helper->connector_count,
                        sizeof(struct drm_fb_helper_crtc *), GFP_KERNEL);
        modes = kcalloc(fb_helper->connector_count,
                        sizeof(struct drm_display_mode *), GFP_KERNEL);
        offsets = kcalloc(fb_helper->connector_count,
                          sizeof(struct drm_fb_offset), GFP_KERNEL);
        enabled = kcalloc(fb_helper->connector_count,
                          sizeof(bool), GFP_KERNEL);
        if (!crtcs || !modes || !enabled || !offsets) {
                DRM_ERROR("Memory allocation failed\n");
                goto out;
        }


        drm_enable_connectors(fb_helper, enabled);

        if (!(fb_helper->funcs->initial_config &&
              fb_helper->funcs->initial_config(fb_helper, crtcs, modes,
                                               offsets,
                                               enabled, width, height))) {
                memset(modes, 0, fb_helper->connector_count*sizeof(modes[0]));
                memset(crtcs, 0, fb_helper->connector_count*sizeof(crtcs[0]));
                memset(offsets, 0, fb_helper->connector_count*sizeof(offsets[0]));

                if (!drm_target_cloned(fb_helper, modes, offsets,
                                       enabled, width, height) &&
                    !drm_target_preferred(fb_helper, modes, offsets,
                                          enabled, width, height))
                        DRM_ERROR("Unable to find initial modes\n");

                DRM_DEBUG_KMS("picking CRTCs for %dx%d config\n",
                              width, height);

                drm_pick_crtcs(fb_helper, crtcs, modes, 0, width, height);
        }

        /* need to set the modesets up here for use later */
        /* fill out the connector<->crtc mappings into the modesets */
        for (i = 0; i < fb_helper->crtc_count; i++) {
                modeset = &fb_helper->crtc_info[i].mode_set;
                modeset->num_connectors = 0;
                modeset->fb = NULL;
        }

        for (i = 0; i < fb_helper->connector_count; i++) {
                struct drm_display_mode *mode = modes[i];
                struct drm_fb_helper_crtc *fb_crtc = crtcs[i];
                struct drm_fb_offset *offset = &offsets[i];
                modeset = &fb_crtc->mode_set;

                if (mode && fb_crtc) {
                        DRM_DEBUG_KMS("desired mode %s set on crtc %d (%d,%d)\n",
                                      mode->name, fb_crtc->mode_set.crtc->base.id, offset->x, offset->y);
                        fb_crtc->desired_mode = mode;
                        fb_crtc->x = offset->x;
                        fb_crtc->y = offset->y;
                        if (modeset->mode)
                                drm_mode_destroy(dev, modeset->mode);
                        modeset->mode = drm_mode_duplicate(dev,
                                                           fb_crtc->desired_mode);
                        modeset->connectors[modeset->num_connectors++] = fb_helper->connector_info[i]->connector;
                        modeset->fb = fb_helper->fb;
                        modeset->x = offset->x;
                        modeset->y = offset->y;
                }
        }

        /* Clear out any old modes if there are no more connected outputs. */
        for (i = 0; i < fb_helper->crtc_count; i++) {
                modeset = &fb_helper->crtc_info[i].mode_set;
                if (modeset->num_connectors == 0) {
                        BUG_ON(modeset->fb);
                        if (modeset->mode)
                                drm_mode_destroy(dev, modeset->mode);
                        modeset->mode = NULL;
                }
        }
out:
        kfree(crtcs);
        kfree(modes);
        kfree(offsets);
        kfree(enabled);
}

/**
 * drm_fb_helper_initial_config - setup a sane initial connector configuration
 * @fb_helper: fb_helper device struct
 * @bpp_sel: bpp value to use for the framebuffer configuration
 *
 * Scans the CRTCs and connectors and tries to put together an initial setup.
 * At the moment, this is a cloned configuration across all heads with
 * a new framebuffer object as the backing store.
 *
 * Note that this also registers the fbdev and so allows userspace to call into
 * the driver through the fbdev interfaces.
 *
 * This function will call down into the ->fb_probe callback to let
 * the driver allocate and initialize the fbdev info structure and the drm
 * framebuffer used to back the fbdev. drm_fb_helper_fill_var() and
 * drm_fb_helper_fill_fix() are provided as helpers to setup simple default
 * values for the fbdev info structure.
 *
 * HANG DEBUGGING:
 *
 * When you have fbcon support built-in or already loaded, this function will do
 * a full modeset to setup the fbdev console. Due to locking misdesign in the
 * VT/fbdev subsystem that entire modeset sequence has to be done while holding
 * console_lock. Until console_unlock is called no dmesg lines will be sent out
 * to consoles, not even serial console. This means when your driver crashes,
 * you will see absolutely nothing else but a system stuck in this function,
 * with no further output. Any kind of printk() you place within your own driver
 * or in the drm core modeset code will also never show up.
 *
 * Standard debug practice is to run the fbcon setup without taking the
 * console_lock as a hack, to be able to see backtraces and crashes on the
 * serial line. This can be done by setting the fb.lockless_register_fb=1 kernel
 * cmdline option.
 *
 * The other option is to just disable fbdev emulation since very likely the
 * first modeset from userspace will crash in the same way, and is even easier
 * to debug. This can be done by setting the drm_kms_helper.fbdev_emulation=0
 * kernel cmdline option.
 *
 * RETURNS:
 * Zero if everything went ok, nonzero otherwise.
 */
int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel)
{
        struct drm_device *dev = fb_helper->dev;
        int count = 0;

        if (!drm_fbdev_emulation)
                return 0;

        mutex_lock(&dev->mode_config.mutex);
        count = drm_fb_helper_probe_connector_modes(fb_helper,
                                                    dev->mode_config.max_width,
                                                    dev->mode_config.max_height);
        mutex_unlock(&dev->mode_config.mutex);
        /*
         * we shouldn't end up with no modes here.
         */
        if (count == 0)
                dev_info(fb_helper->dev->dev, "No connectors reported connected with modes\n");

        drm_setup_crtcs(fb_helper);

        return drm_fb_helper_single_fb_probe(fb_helper, bpp_sel);
}
EXPORT_SYMBOL(drm_fb_helper_initial_config);

/**
 * drm_fb_helper_hotplug_event - respond to a hotplug notification by
 *                               probing all the outputs attached to the fb
 * @fb_helper: the drm_fb_helper
 *
 * Scan the connectors attached to the fb_helper and try to put together a
 * setup after notification of a change in output configuration.
 *
 * Called at runtime, takes the mode config locks to be able to check/change the
 * modeset configuration. Must be run from process context (which usually means
 * either the output polling work or a work item launched from the driver's
 * hotplug interrupt).
 *
 * Note that drivers may call this even before calling
 * drm_fb_helper_initial_config but only after drm_fb_helper_init. This allows
 * for a race-free fbcon setup and will make sure that the fbdev emulation will
 * not miss any hotplug events.
 *
 * RETURNS:
 * 0 on success and a non-zero error code otherwise.
 */
int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
{
        struct drm_device *dev = fb_helper->dev;
        u32 max_width, max_height;

        if (!drm_fbdev_emulation)
                return 0;

        mutex_lock(&fb_helper->dev->mode_config.mutex);
        if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
                fb_helper->delayed_hotplug = true;
                mutex_unlock(&fb_helper->dev->mode_config.mutex);
                return 0;
        }
        DRM_DEBUG_KMS("\n");

        max_width = fb_helper->fb->width;
        max_height = fb_helper->fb->height;

        drm_fb_helper_probe_connector_modes(fb_helper, max_width, max_height);
        mutex_unlock(&fb_helper->dev->mode_config.mutex);

        drm_modeset_lock_all(dev);
        drm_setup_crtcs(fb_helper);
        drm_modeset_unlock_all(dev);
        drm_fb_helper_set_par(fb_helper->fbdev);

        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_hotplug_event);

/* The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EXPERT)
 * but the module doesn't depend on any fb console symbols.  At least
 * attempt to load fbcon to avoid leaving the system without a usable console.
 */
int __init drm_fb_helper_modinit(void)
{
#if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && !defined(CONFIG_EXPERT)
        const char *name = "fbcon";
        struct module *fbcon;

        mutex_lock(&module_mutex);
        fbcon = find_module(name);
        mutex_unlock(&module_mutex);

        if (!fbcon)
                request_module_nowait(name);
#endif
        return 0;
}
EXPORT_SYMBOL(drm_fb_helper_modinit);