1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
|
/*P:050 Lguest guests use a very simple bus for devices. It's a simple array
* of device descriptors contained just above the top of normal memory. The
* lguest bus is 80% tedious boilerplate code. :*/
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/lguest_bus.h>
#include <asm/io.h>
#include <asm/paravirt.h>
struct lguest_device_desc *lguest_devices;
static ssize_t type_show(struct device *_dev,
struct device_attribute *attr, char *buf)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
return sprintf(buf, "%hu", lguest_devices[dev->index].type);
}
static ssize_t features_show(struct device *_dev,
struct device_attribute *attr, char *buf)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
return sprintf(buf, "%hx", lguest_devices[dev->index].features);
}
static ssize_t pfn_show(struct device *_dev,
struct device_attribute *attr, char *buf)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
return sprintf(buf, "%u", lguest_devices[dev->index].pfn);
}
static ssize_t status_show(struct device *_dev,
struct device_attribute *attr, char *buf)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
return sprintf(buf, "%hx", lguest_devices[dev->index].status);
}
static ssize_t status_store(struct device *_dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
if (sscanf(buf, "%hi", &lguest_devices[dev->index].status) != 1)
return -EINVAL;
return count;
}
static struct device_attribute lguest_dev_attrs[] = {
__ATTR_RO(type),
__ATTR_RO(features),
__ATTR_RO(pfn),
__ATTR(status, 0644, status_show, status_store),
__ATTR_NULL
};
/*D:130 The generic bus infrastructure requires a function which says whether a
* device matches a driver. For us, it is simple: "struct lguest_driver"
* contains a "device_type" field which indicates what type of device it can
* handle, so we just cast the args and compare: */
static int lguest_dev_match(struct device *_dev, struct device_driver *_drv)
{
struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
struct lguest_driver *drv = container_of(_drv,struct lguest_driver,drv);
return (drv->device_type == lguest_devices[dev->index].type);
}
/*:*/
struct lguest_bus {
struct bus_type bus;
struct device dev;
};
static struct lguest_bus lguest_bus = {
.bus = {
.name = "lguest",
.match = lguest_dev_match,
.dev_attrs = lguest_dev_attrs,
},
.dev = {
.parent = NULL,
.bus_id = "lguest",
}
};
/*D:140 This is the callback which occurs once the bus infrastructure matches
* up a device and driver, ie. in response to add_lguest_device() calling
* device_register(), or register_lguest_driver() calling driver_register().
*
* At the moment it's always the latter: the devices are added first, since
* scan_devices() is called from a "core_initcall", and the drivers themselves
* called later as a normal "initcall". But it would work the other way too.
*
* So now we have the happy couple, we add the status bit to indicate that we
* found a driver. If the driver truly loves the device, it will return
* happiness from its probe function (ok, perhaps this wasn't my greatest
* analogy), and we set the final "driver ok" bit so the Host sees it's all
* green. */
static int lguest_dev_probe(struct device *_dev)
{
int ret;
struct lguest_device*dev = container_of(_dev,struct lguest_device,dev);
struct lguest_driver*drv = container_of(dev->dev.driver,
struct lguest_driver, drv);
lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER;
ret = drv->probe(dev);
if (ret == 0)
lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER_OK;
return ret;
}
/* The last part of the bus infrastructure is the function lguest drivers use
* to register themselves. Firstly, we do nothing if there's no lguest bus
* (ie. this is not a Guest), otherwise we fill in the embedded generic "struct
* driver" fields and call the generic driver_register(). */
int register_lguest_driver(struct lguest_driver *drv)
{
if (!lguest_devices)
return 0;
drv->drv.bus = &lguest_bus.bus;
drv->drv.name = drv->name;
drv->drv.owner = drv->owner;
drv->drv.probe = lguest_dev_probe;
return driver_register(&drv->drv);
}
/* At the moment we build all the drivers into the kernel because they're so
* simple: 8144 bytes for all three of them as I type this. And as the console
* really needs to be built in, it's actually only 3527 bytes for the network
* and block drivers.
*
* If they get complex it will make sense for them to be modularized, so we
* need to explicitly export the symbol.
*
* I don't think non-GPL modules make sense, so it's a GPL-only export.
*/
EXPORT_SYMBOL_GPL(register_lguest_driver);
/*D:120 This is the core of the lguest bus: actually adding a new device.
* It's a separate function because it's neater that way, and because an
* earlier version of the code supported hotplug and unplug. They were removed
* early on because they were never used.
*
* As Andrew Tridgell says, "Untested code is buggy code".
*
* It's worth reading this carefully: we start with an index into the array of
* "struct lguest_device_desc"s indicating the device which is new: */
static void add_lguest_device(unsigned int index)
{
struct lguest_device *new;
/* Each "struct lguest_device_desc" has a "status" field, which the
* Guest updates as the device is probed. In the worst case, the Host
* can look at these bits to tell what part of device setup failed,
* even if the console isn't available. */
lguest_devices[index].status |= LGUEST_DEVICE_S_ACKNOWLEDGE;
new = kmalloc(sizeof(struct lguest_device), GFP_KERNEL);
if (!new) {
printk(KERN_EMERG "Cannot allocate lguest device %u\n", index);
lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED;
return;
}
/* The "struct lguest_device" setup is pretty straight-forward example
* code. */
new->index = index;
new->private = NULL;
memset(&new->dev, 0, sizeof(new->dev));
new->dev.parent = &lguest_bus.dev;
new->dev.bus = &lguest_bus.bus;
sprintf(new->dev.bus_id, "%u", index);
/* device_register() causes the bus infrastructure to look for a
* matching driver. */
if (device_register(&new->dev) != 0) {
printk(KERN_EMERG "Cannot register lguest device %u\n", index);
lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED;
kfree(new);
}
}
/*D:110 scan_devices() simply iterates through the device array. The type 0
* is reserved to mean "no device", and anything else means we have found a
* device: add it. */
static void scan_devices(void)
{
unsigned int i;
for (i = 0; i < LGUEST_MAX_DEVICES; i++)
if (lguest_devices[i].type)
add_lguest_device(i);
}
/*D:100 Fairly early in boot, lguest_bus_init() is called to set up the lguest
* bus. We check that we are a Guest by checking paravirt_ops.name: there are
* other ways of checking, but this seems most obvious to me.
*
* So we can access the array of "struct lguest_device_desc"s easily, we map
* that memory and store the pointer in the global "lguest_devices". Then we
* register the bus with the core. Doing two registrations seems clunky to me,
* but it seems to be the correct sysfs incantation.
*
* Finally we call scan_devices() which adds all the devices found in the
* "struct lguest_device_desc" array. */
static int __init lguest_bus_init(void)
{
if (strcmp(pv_info.name, "lguest") != 0)
return 0;
/* Devices are in a single page above top of "normal" mem */
lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1);
if (bus_register(&lguest_bus.bus) != 0
|| device_register(&lguest_bus.dev) != 0)
panic("lguest bus registration failed");
scan_devices();
return 0;
}
/* Do this after core stuff, before devices. */
postcore_initcall(lguest_bus_init);
|
