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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/driver-model/device.txt
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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1
2The Basic Device Structure
3~~~~~~~~~~~~~~~~~~~~~~~~~~
4
5struct device {
6 struct list_head g_list;
7 struct list_head node;
8 struct list_head bus_list;
9 struct list_head driver_list;
10 struct list_head intf_list;
11 struct list_head children;
12 struct device * parent;
13
14 char name[DEVICE_NAME_SIZE];
15 char bus_id[BUS_ID_SIZE];
16
17 spinlock_t lock;
18 atomic_t refcount;
19
20 struct bus_type * bus;
21 struct driver_dir_entry dir;
22
23 u32 class_num;
24
25 struct device_driver *driver;
26 void *driver_data;
27 void *platform_data;
28
29 u32 current_state;
30 unsigned char *saved_state;
31
32 void (*release)(struct device * dev);
33};
34
35Fields
36~~~~~~
37g_list: Node in the global device list.
38
39node: Node in device's parent's children list.
40
41bus_list: Node in device's bus's devices list.
42
43driver_list: Node in device's driver's devices list.
44
45intf_list: List of intf_data. There is one structure allocated for
46 each interface that the device supports.
47
48children: List of child devices.
49
50parent: *** FIXME ***
51
52name: ASCII description of device.
53 Example: " 3Com Corporation 3c905 100BaseTX [Boomerang]"
54
55bus_id: ASCII representation of device's bus position. This
56 field should be a name unique across all devices on the
57 bus type the device belongs to.
58
59 Example: PCI bus_ids are in the form of
60 <bus number>:<slot number>.<function number>
61 This name is unique across all PCI devices in the system.
62
63lock: Spinlock for the device.
64
65refcount: Reference count on the device.
66
67bus: Pointer to struct bus_type that device belongs to.
68
69dir: Device's sysfs directory.
70
71class_num: Class-enumerated value of the device.
72
73driver: Pointer to struct device_driver that controls the device.
74
75driver_data: Driver-specific data.
76
77platform_data: Platform data specific to the device.
78
79current_state: Current power state of the device.
80
81saved_state: Pointer to saved state of the device. This is usable by
82 the device driver controlling the device.
83
84release: Callback to free the device after all references have
85 gone away. This should be set by the allocator of the
86 device (i.e. the bus driver that discovered the device).
87
88
89Programming Interface
90~~~~~~~~~~~~~~~~~~~~~
91The bus driver that discovers the device uses this to register the
92device with the core:
93
94int device_register(struct device * dev);
95
96The bus should initialize the following fields:
97
98 - parent
99 - name
100 - bus_id
101 - bus
102
103A device is removed from the core when its reference count goes to
1040. The reference count can be adjusted using:
105
106struct device * get_device(struct device * dev);
107void put_device(struct device * dev);
108
109get_device() will return a pointer to the struct device passed to it
110if the reference is not already 0 (if it's in the process of being
111removed already).
112
113A driver can access the lock in the device structure using:
114
115void lock_device(struct device * dev);
116void unlock_device(struct device * dev);
117
118
119Attributes
120~~~~~~~~~~
121struct device_attribute {
122 struct attribute attr;
123 ssize_t (*show)(struct device * dev, char * buf, size_t count, loff_t off);
124 ssize_t (*store)(struct device * dev, const char * buf, size_t count, loff_t off);
125};
126
127Attributes of devices can be exported via drivers using a simple
128procfs-like interface.
129
130Please see Documentation/filesystems/sysfs.txt for more information
131on how sysfs works.
132
133Attributes are declared using a macro called DEVICE_ATTR:
134
135#define DEVICE_ATTR(name,mode,show,store)
136
137Example:
138
139DEVICE_ATTR(power,0644,show_power,store_power);
140
141This declares a structure of type struct device_attribute named
142'dev_attr_power'. This can then be added and removed to the device's
143directory using:
144
145int device_create_file(struct device *device, struct device_attribute * entry);
146void device_remove_file(struct device * dev, struct device_attribute * attr);
147
148Example:
149
150device_create_file(dev,&dev_attr_power);
151device_remove_file(dev,&dev_attr_power);
152
153The file name will be 'power' with a mode of 0644 (-rw-r--r--).
154