1 /*P:050 Lguest guests use a very simple bus for devices. It's a simple array
2 * of device descriptors contained just above the top of normal memory. The
3 * lguest bus is 80% tedious boilerplate code. :*/
4 #include <linux/init.h>
5 #include <linux/bootmem.h>
6 #include <linux/lguest_bus.h>
9 static ssize_t
type_show(struct device
*_dev
,
10 struct device_attribute
*attr
, char *buf
)
12 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
13 return sprintf(buf
, "%hu", lguest_devices
[dev
->index
].type
);
15 static ssize_t
features_show(struct device
*_dev
,
16 struct device_attribute
*attr
, char *buf
)
18 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
19 return sprintf(buf
, "%hx", lguest_devices
[dev
->index
].features
);
21 static ssize_t
pfn_show(struct device
*_dev
,
22 struct device_attribute
*attr
, char *buf
)
24 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
25 return sprintf(buf
, "%u", lguest_devices
[dev
->index
].pfn
);
27 static ssize_t
status_show(struct device
*_dev
,
28 struct device_attribute
*attr
, char *buf
)
30 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
31 return sprintf(buf
, "%hx", lguest_devices
[dev
->index
].status
);
33 static ssize_t
status_store(struct device
*_dev
, struct device_attribute
*attr
,
34 const char *buf
, size_t count
)
36 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
37 if (sscanf(buf
, "%hi", &lguest_devices
[dev
->index
].status
) != 1)
41 static struct device_attribute lguest_dev_attrs
[] = {
45 __ATTR(status
, 0644, status_show
, status_store
),
49 /*D:130 The generic bus infrastructure requires a function which says whether a
50 * device matches a driver. For us, it is simple: "struct lguest_driver"
51 * contains a "device_type" field which indicates what type of device it can
52 * handle, so we just cast the args and compare: */
53 static int lguest_dev_match(struct device
*_dev
, struct device_driver
*_drv
)
55 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
56 struct lguest_driver
*drv
= container_of(_drv
,struct lguest_driver
,drv
);
58 return (drv
->device_type
== lguest_devices
[dev
->index
].type
);
67 static struct lguest_bus lguest_bus
= {
70 .match
= lguest_dev_match
,
71 .dev_attrs
= lguest_dev_attrs
,
79 /*D:140 This is the callback which occurs once the bus infrastructure matches
80 * up a device and driver, ie. in response to add_lguest_device() calling
81 * device_register(), or register_lguest_driver() calling driver_register().
83 * At the moment it's always the latter: the devices are added first, since
84 * scan_devices() is called from a "core_initcall", and the drivers themselves
85 * called later as a normal "initcall". But it would work the other way too.
87 * So now we have the happy couple, we add the status bit to indicate that we
88 * found a driver. If the driver truly loves the device, it will return
89 * happiness from its probe function (ok, perhaps this wasn't my greatest
90 * analogy), and we set the final "driver ok" bit so the Host sees it's all
92 static int lguest_dev_probe(struct device
*_dev
)
95 struct lguest_device
*dev
= container_of(_dev
,struct lguest_device
,dev
);
96 struct lguest_driver
*drv
= container_of(dev
->dev
.driver
,
97 struct lguest_driver
, drv
);
99 lguest_devices
[dev
->index
].status
|= LGUEST_DEVICE_S_DRIVER
;
100 ret
= drv
->probe(dev
);
102 lguest_devices
[dev
->index
].status
|= LGUEST_DEVICE_S_DRIVER_OK
;
106 /* The last part of the bus infrastructure is the function lguest drivers use
107 * to register themselves. Firstly, we do nothing if there's no lguest bus
108 * (ie. this is not a Guest), otherwise we fill in the embedded generic "struct
109 * driver" fields and call the generic driver_register(). */
110 int register_lguest_driver(struct lguest_driver
*drv
)
115 drv
->drv
.bus
= &lguest_bus
.bus
;
116 drv
->drv
.name
= drv
->name
;
117 drv
->drv
.owner
= drv
->owner
;
118 drv
->drv
.probe
= lguest_dev_probe
;
120 return driver_register(&drv
->drv
);
123 /* At the moment we build all the drivers into the kernel because they're so
124 * simple: 8144 bytes for all three of them as I type this. And as the console
125 * really needs to be built in, it's actually only 3527 bytes for the network
128 * If they get complex it will make sense for them to be modularized, so we
129 * need to explicitly export the symbol.
131 * I don't think non-GPL modules make sense, so it's a GPL-only export.
133 EXPORT_SYMBOL_GPL(register_lguest_driver
);
135 /*D:120 This is the core of the lguest bus: actually adding a new device.
136 * It's a separate function because it's neater that way, and because an
137 * earlier version of the code supported hotplug and unplug. They were removed
138 * early on because they were never used.
140 * As Andrew Tridgell says, "Untested code is buggy code".
142 * It's worth reading this carefully: we start with an index into the array of
143 * "struct lguest_device_desc"s indicating the device which is new: */
144 static void add_lguest_device(unsigned int index
)
146 struct lguest_device
*new;
148 /* Each "struct lguest_device_desc" has a "status" field, which the
149 * Guest updates as the device is probed. In the worst case, the Host
150 * can look at these bits to tell what part of device setup failed,
151 * even if the console isn't available. */
152 lguest_devices
[index
].status
|= LGUEST_DEVICE_S_ACKNOWLEDGE
;
153 new = kmalloc(sizeof(struct lguest_device
), GFP_KERNEL
);
155 printk(KERN_EMERG
"Cannot allocate lguest device %u\n", index
);
156 lguest_devices
[index
].status
|= LGUEST_DEVICE_S_FAILED
;
160 /* The "struct lguest_device" setup is pretty straight-forward example
164 memset(&new->dev
, 0, sizeof(new->dev
));
165 new->dev
.parent
= &lguest_bus
.dev
;
166 new->dev
.bus
= &lguest_bus
.bus
;
167 sprintf(new->dev
.bus_id
, "%u", index
);
169 /* device_register() causes the bus infrastructure to look for a
170 * matching driver. */
171 if (device_register(&new->dev
) != 0) {
172 printk(KERN_EMERG
"Cannot register lguest device %u\n", index
);
173 lguest_devices
[index
].status
|= LGUEST_DEVICE_S_FAILED
;
178 /*D:110 scan_devices() simply iterates through the device array. The type 0
179 * is reserved to mean "no device", and anything else means we have found a
181 static void scan_devices(void)
185 for (i
= 0; i
< LGUEST_MAX_DEVICES
; i
++)
186 if (lguest_devices
[i
].type
)
187 add_lguest_device(i
);
190 /*D:100 Fairly early in boot, lguest_bus_init() is called to set up the lguest
191 * bus. We check that we are a Guest by checking paravirt_ops.name: there are
192 * other ways of checking, but this seems most obvious to me.
194 * So we can access the array of "struct lguest_device_desc"s easily, we map
195 * that memory and store the pointer in the global "lguest_devices". Then we
196 * register the bus with the core. Doing two registrations seems clunky to me,
197 * but it seems to be the correct sysfs incantation.
199 * Finally we call scan_devices() which adds all the devices found in the
200 * "struct lguest_device_desc" array. */
201 static int __init
lguest_bus_init(void)
203 if (strcmp(paravirt_ops
.name
, "lguest") != 0)
206 /* Devices are in a single page above top of "normal" mem */
207 lguest_devices
= lguest_map(max_pfn
<<PAGE_SHIFT
, 1);
209 if (bus_register(&lguest_bus
.bus
) != 0
210 || device_register(&lguest_bus
.dev
) != 0)
211 panic("lguest bus registration failed");
216 /* Do this after core stuff, before devices. */
217 postcore_initcall(lguest_bus_init
);