drivers/char/virtio_console.c

   1 /*
   2  * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  */
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/virtio.h>
  21 #include <linux/virtio_console.h>
  22 #include "hvc_console.h"
  23
  24 struct port_buffer {
  25         char *buf;
  26
  27         /* size of the buffer in *buf above */
  28         size_t size;
  29
  30         /* used length of the buffer */
  31         size_t len;
  32         /* offset in the buf from which to consume data */
  33         size_t offset;
  34 };
  35
  36 struct port {
  37         struct virtqueue *in_vq, *out_vq;
  38         struct virtio_device *vdev;
  39
  40         /* The current buffer from which data has to be fed to readers */
  41         struct port_buffer *inbuf;
  42
  43         /* The hvc device */
  44         struct hvc_struct *hvc;
  45 };
  46
  47 /* We have one port ready to go immediately, for a console. */
  48 static struct port console;
  49
  50 /* This is the very early arch-specified put chars function. */
  51 static int (*early_put_chars)(u32, const char *, int);
  52
  53 static void free_buf(struct port_buffer *buf)
  54 {
  55         kfree(buf->buf);
  56         kfree(buf);
  57 }
  58
  59 static struct port_buffer *alloc_buf(size_t buf_size)
  60 {
  61         struct port_buffer *buf;
  62
  63         buf = kmalloc(sizeof(*buf), GFP_KERNEL);
  64         if (!buf)
  65                 goto fail;
  66         buf->buf = kzalloc(buf_size, GFP_KERNEL);
  67         if (!buf->buf)
  68                 goto free_buf;
  69         buf->len = 0;
  70         buf->offset = 0;
  71         buf->size = buf_size;
  72         return buf;
  73
  74 free_buf:
  75         kfree(buf);
  76 fail:
  77         return NULL;
  78 }
  79
  80 /*
  81  * Create a scatter-gather list representing our input buffer and put
  82  * it in the queue.
  83  *
  84  * Callers should take appropriate locks.
  85  */
  86 static void add_inbuf(struct virtqueue *vq, struct port_buffer *buf)
  87 {
  88         struct scatterlist sg[1];
  89         sg_init_one(sg, buf->buf, buf->size);
  90
  91         if (vq->vq_ops->add_buf(vq, sg, 0, 1, buf) < 0)
  92                 BUG();
  93         vq->vq_ops->kick(vq);
  94 }
  95
  96 /*
  97  * The put_chars() callback is pretty straightforward.
  98  *
  99  * We turn the characters into a scatter-gather list, add it to the
 100  * output queue and then kick the Host.  Then we sit here waiting for
 101  * it to finish: inefficient in theory, but in practice
 102  * implementations will do it immediately (lguest's Launcher does).
 103  */
 104 static int put_chars(u32 vtermno, const char *buf, int count)
 105 {
 106         struct scatterlist sg[1];
 107         unsigned int len;
 108         struct port *port;
 109
 110         if (unlikely(early_put_chars))
 111                 return early_put_chars(vtermno, buf, count);
 112
 113         port = &console;
 114
 115         /* This is a convenient routine to initialize a single-elem sg list */
 116         sg_init_one(sg, buf, count);
 117
 118         /* This shouldn't fail: if it does, we lose chars. */
 119         if (port->out_vq->vq_ops->add_buf(port->out_vq, sg, 1, 0, port) >= 0) {
 120                 /* Tell Host to go! */
 121                 port->out_vq->vq_ops->kick(port->out_vq);
 122                 while (!port->out_vq->vq_ops->get_buf(port->out_vq, &len))
 123                         cpu_relax();
 124         }
 125
 126         /* We're expected to return the amount of data we wrote: all of it. */
 127         return count;
 128 }
 129
 130 /*
 131  * get_chars() is the callback from the hvc_console infrastructure
 132  * when an interrupt is received.
 133  *
 134  * Most of the code deals with the fact that the hvc_console()
 135  * infrastructure only asks us for 16 bytes at a time.  We keep
 136  * in_offset and in_used fields for partially-filled buffers.
 137  */
 138 static int get_chars(u32 vtermno, char *buf, int count)
 139 {
 140         struct port *port;
 141         unsigned int len;
 142
 143         port = &console;
 144
 145         /* If we don't have an input queue yet, we can't get input. */
 146         BUG_ON(!port->in_vq);
 147
 148         /* No more in buffer?  See if they've (re)used it. */
 149         if (port->inbuf->offset == port->inbuf->len) {
 150                 if (!port->in_vq->vq_ops->get_buf(port->in_vq, &len))
 151                         return 0;
 152                 port->inbuf->offset = 0;
 153                 port->inbuf->len = len;
 154         }
 155
 156         /* You want more than we have to give?  Well, try wanting less! */
 157         if (port->inbuf->offset + count > port->inbuf->len)
 158                 count = port->inbuf->len - port->inbuf->offset;
 159
 160         /* Copy across to their buffer and increment offset. */
 161         memcpy(buf, port->inbuf->buf + port->inbuf->offset, count);
 162         port->inbuf->offset += count;
 163
 164         /* Finished?  Re-register buffer so Host will use it again. */
 165         if (port->inbuf->offset == port->inbuf->len)
 166                 add_inbuf(port->in_vq, port->inbuf);
 167
 168         return count;
 169 }
 170
 171 /*
 172  * virtio console configuration. This supports:
 173  * - console resize
 174  */
 175 static void virtcons_apply_config(struct virtio_device *dev)
 176 {
 177         struct winsize ws;
 178
 179         if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
 180                 dev->config->get(dev,
 181                                  offsetof(struct virtio_console_config, cols),
 182                                  &ws.ws_col, sizeof(u16));
 183                 dev->config->get(dev,
 184                                  offsetof(struct virtio_console_config, rows),
 185                                  &ws.ws_row, sizeof(u16));
 186                 hvc_resize(console.hvc, ws);
 187         }
 188 }
 189
 190 /*
 191  * we support only one console, the hvc struct is a global var We set
 192  * the configuration at this point, since we now have a tty
 193  */
 194 static int notifier_add_vio(struct hvc_struct *hp, int data)
 195 {
 196         hp->irq_requested = 1;
 197         virtcons_apply_config(console.vdev);
 198
 199         return 0;
 200 }
 201
 202 static void notifier_del_vio(struct hvc_struct *hp, int data)
 203 {
 204         hp->irq_requested = 0;
 205 }
 206
 207 static void hvc_handle_input(struct virtqueue *vq)
 208 {
 209         if (hvc_poll(console.hvc))
 210                 hvc_kick();
 211 }
 212
 213 /* The operations for the console. */
 214 static const struct hv_ops hv_ops = {
 215         .get_chars = get_chars,
 216         .put_chars = put_chars,
 217         .notifier_add = notifier_add_vio,
 218         .notifier_del = notifier_del_vio,
 219         .notifier_hangup = notifier_del_vio,
 220 };
 221
 222 /*
 223  * Console drivers are initialized very early so boot messages can go
 224  * out, so we do things slightly differently from the generic virtio
 225  * initialization of the net and block drivers.
 226  *
 227  * At this stage, the console is output-only.  It's too early to set
 228  * up a virtqueue, so we let the drivers do some boutique early-output
 229  * thing.
 230  */
 231 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
 232 {
 233         early_put_chars = put_chars;
 234         return hvc_instantiate(0, 0, &hv_ops);
 235 }
 236
 237 /*
 238  * Once we're further in boot, we get probed like any other virtio
 239  * device.  At this stage we set up the output virtqueue.
 240  *
 241  * To set up and manage our virtual console, we call hvc_alloc().
 242  * Since we never remove the console device we never need this pointer
 243  * again.
 244  *
 245  * Finally we put our input buffer in the input queue, ready to
 246  * receive.
 247  */
 248 static int __devinit virtcons_probe(struct virtio_device *vdev)
 249 {
 250         vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
 251         const char *names[] = { "input", "output" };
 252         struct virtqueue *vqs[2];
 253         struct port *port;
 254         int err;
 255
 256         port = &console;
 257         if (port->vdev) {
 258                 dev_warn(&port->vdev->dev,
 259                          "Multiple virtio-console devices not supported yet\n");
 260                 return -EEXIST;
 261         }
 262         port->vdev = vdev;
 263
 264         /* This is the scratch page we use to receive console input */
 265         port->inbuf = alloc_buf(PAGE_SIZE);
 266         if (!port->inbuf) {
 267                 err = -ENOMEM;
 268                 goto fail;
 269         }
 270
 271         /* Find the queues. */
 272         err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
 273         if (err)
 274                 goto free;
 275
 276         port->in_vq = vqs[0];
 277         port->out_vq = vqs[1];
 278
 279         /*
 280          * The first argument of hvc_alloc() is the virtual console
 281          * number, so we use zero.  The second argument is the
 282          * parameter for the notification mechanism (like irq
 283          * number). We currently leave this as zero, virtqueues have
 284          * implicit notifications.
 285          *
 286          * The third argument is a "struct hv_ops" containing the
 287          * put_chars(), get_chars(), notifier_add() and notifier_del()
 288          * pointers.  The final argument is the output buffer size: we
 289          * can do any size, so we put PAGE_SIZE here.
 290          */
 291         port->hvc = hvc_alloc(0, 0, &hv_ops, PAGE_SIZE);
 292         if (IS_ERR(port->hvc)) {
 293                 err = PTR_ERR(port->hvc);
 294                 goto free_vqs;
 295         }
 296
 297         /* Register the input buffer the first time. */
 298         add_inbuf(port->in_vq, port->inbuf);
 299
 300         /* Start using the new console output. */
 301         early_put_chars = NULL;
 302         return 0;
 303
 304 free_vqs:
 305         vdev->config->del_vqs(vdev);
 306 free:
 307         free_buf(port->inbuf);
 308 fail:
 309         return err;
 310 }
 311
 312 static struct virtio_device_id id_table[] = {
 313         { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
 314         { 0 },
 315 };
 316
 317 static unsigned int features[] = {
 318         VIRTIO_CONSOLE_F_SIZE,
 319 };
 320
 321 static struct virtio_driver virtio_console = {
 322         .feature_table = features,
 323         .feature_table_size = ARRAY_SIZE(features),
 324         .driver.name =  KBUILD_MODNAME,
 325         .driver.owner = THIS_MODULE,
 326         .id_table =     id_table,
 327         .probe =        virtcons_probe,
 328         .config_changed = virtcons_apply_config,
 329 };
 330
 331 static int __init init(void)
 332 {
 333         return register_virtio_driver(&virtio_console);
 334 }
 335 module_init(init);
 336
 337 MODULE_DEVICE_TABLE(virtio, id_table);
 338 MODULE_DESCRIPTION("Virtio console driver");
 339 MODULE_LICENSE("GPL");