1 =================================
2 Linux Plug and Play Documentation
3 =================================
4
5 :Author: Adam Belay <ambx1@neo.rr.com>
6 :Last updated: Oct. 16, 2002
7
8
9 Overview
10 --------
11
12 Plug and Play provides a means of detecting and setting resources for legacy or
13 otherwise unconfigurable devices. The Linux Plug and Play Layer provides these
14 services to compatible drivers.
15
16
17 The User Interface
18 ------------------
19
20 The Linux Plug and Play user interface provides a means to activate PnP devices
21 for legacy and user level drivers that do not support Linux Plug and Play. The
22 user interface is integrated into sysfs.
23
24 In addition to the standard sysfs file the following are created in each
25 device's directory:
26 - id - displays a list of support EISA IDs
27 - options - displays possible resource configurations
28 - resources - displays currently allocated resources and allows resource changes
29
30 activating a device
31 ^^^^^^^^^^^^^^^^^^^
32
33 ::
34
35 # echo "auto" > resources
36
37 this will invoke the automatic resource config system to activate the device
38
39 manually activating a device
40 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
41
42 ::
43
44 # echo "manual <depnum> <mode>" > resources
45
46 <depnum> - the configuration number
47 <mode> - static or dynamic
48 static = for next boot
49 dynamic = now
50
51 disabling a device
52 ^^^^^^^^^^^^^^^^^^
53
54 ::
55
56 # echo "disable" > resources
57
58
59 EXAMPLE:
60
61 Suppose you need to activate the floppy disk controller.
62
63 1. change to the proper directory, in my case it is
64 /driver/bus/pnp/devices/00:0f::
65
66 # cd /driver/bus/pnp/devices/00:0f
67 # cat name
68 PC standard floppy disk controller
69
70 2. check if the device is already active::
71
72 # cat resources
73 DISABLED
74
75 - Notice the string "DISABLED". This means the device is not active.
76
77 3. check the device's possible configurations (optional)::
78
79 # cat options
80 Dependent: 01 - Priority acceptable
81 port 0x3f0-0x3f0, align 0x7, size 0x6, 16-bit address decoding
82 port 0x3f7-0x3f7, align 0x0, size 0x1, 16-bit address decoding
83 irq 6
84 dma 2 8-bit compatible
85 Dependent: 02 - Priority acceptable
86 port 0x370-0x370, align 0x7, size 0x6, 16-bit address decoding
87 port 0x377-0x377, align 0x0, size 0x1, 16-bit address decoding
88 irq 6
89 dma 2 8-bit compatible
90
91 4. now activate the device::
92
93 # echo "auto" > resources
94
95 5. finally check if the device is active::
96
97 # cat resources
98 io 0x3f0-0x3f5
99 io 0x3f7-0x3f7
100 irq 6
101 dma 2
102
103 also there are a series of kernel parameters::
104
105 pnp_reserve_irq=irq1[,irq2] ....
106 pnp_reserve_dma=dma1[,dma2] ....
107 pnp_reserve_io=io1,size1[,io2,size2] ....
108 pnp_reserve_mem=mem1,size1[,mem2,size2] ....
109
110
111
112 The Unified Plug and Play Layer
113 -------------------------------
114
115 All Plug and Play drivers, protocols, and services meet at a central location
116 called the Plug and Play Layer. This layer is responsible for the exchange of
117 information between PnP drivers and PnP protocols. Thus it automatically
118 forwards commands to the proper protocol. This makes writing PnP drivers
119 significantly easier.
120
121 The following functions are available from the Plug and Play Layer:
122
123 pnp_get_protocol
124 increments the number of uses by one
125
126 pnp_put_protocol
127 deincrements the number of uses by one
128
129 pnp_register_protocol
130 use this to register a new PnP protocol
131
132 pnp_unregister_protocol
133 use this function to remove a PnP protocol from the Plug and Play Layer
134
135 pnp_register_driver
136 adds a PnP driver to the Plug and Play Layer
137
138 this includes driver model integration
139 returns zero for success or a negative error number for failure; count
140 calls to the .add() method if you need to know how many devices bind to
141 the driver
142
143 pnp_unregister_driver
144 removes a PnP driver from the Plug and Play Layer
145
146
147
148 Plug and Play Protocols
149 -----------------------
150
151 This section contains information for PnP protocol developers.
152
153 The following Protocols are currently available in the computing world:
154
155 - PNPBIOS:
156 used for system devices such as serial and parallel ports.
157 - ISAPNP:
158 provides PnP support for the ISA bus
159 - ACPI:
160 among its many uses, ACPI provides information about system level
161 devices.
162
163 It is meant to replace the PNPBIOS. It is not currently supported by Linux
164 Plug and Play but it is planned to be in the near future.
165
166
167 Requirements for a Linux PnP protocol:
168 1. the protocol must use EISA IDs
169 2. the protocol must inform the PnP Layer of a device's current configuration
170
171 - the ability to set resources is optional but preferred.
172
173 The following are PnP protocol related functions:
174
175 pnp_add_device
176 use this function to add a PnP device to the PnP layer
177
178 only call this function when all wanted values are set in the pnp_dev
179 structure
180
181 pnp_init_device
182 call this to initialize the PnP structure
183
184 pnp_remove_device
185 call this to remove a device from the Plug and Play Layer.
186 it will fail if the device is still in use.
187 automatically will free mem used by the device and related structures
188
189 pnp_add_id
190 adds an EISA ID to the list of supported IDs for the specified device
191
192 For more information consult the source of a protocol such as
193 /drivers/pnp/pnpbios/core.c.
194
195
196
197 Linux Plug and Play Drivers
198 ---------------------------
199
200 This section contains information for Linux PnP driver developers.
201
202 The New Way
203 ^^^^^^^^^^^
204
205 1. first make a list of supported EISA IDS
206
207 ex::
208
209 static const struct pnp_id pnp_dev_table[] = {
210 /* Standard LPT Printer Port */
211 {.id = "PNP0400", .driver_data = 0},
212 /* ECP Printer Port */
213 {.id = "PNP0401", .driver_data = 0},
214 {.id = ""}
215 };
216
217 Please note that the character 'X' can be used as a wild card in the function
218 portion (last four characters).
219
220 ex::
221
222 /* Unknown PnP modems */
223 { "PNPCXXX", UNKNOWN_DEV },
224
225 Supported PnP card IDs can optionally be defined.
226 ex::
227
228 static const struct pnp_id pnp_card_table[] = {
229 { "ANYDEVS", 0 },
230 { "", 0 }
231 };
232
233 2. Optionally define probe and remove functions. It may make sense not to
234 define these functions if the driver already has a reliable method of detecting
235 the resources, such as the parport_pc driver.
236
237 ex::
238
239 static int
240 serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const
241 struct pnp_id *dev_id)
242 {
243 . . .
244
245 ex::
246
247 static void serial_pnp_remove(struct pnp_dev * dev)
248 {
249 . . .
250
251 consult /drivers/serial/8250_pnp.c for more information.
252
253 3. create a driver structure
254
255 ex::
256
257 static struct pnp_driver serial_pnp_driver = {
258 .name = "serial",
259 .card_id_table = pnp_card_table,
260 .id_table = pnp_dev_table,
261 .probe = serial_pnp_probe,
262 .remove = serial_pnp_remove,
263 };
264
265 * name and id_table cannot be NULL.
266
267 4. register the driver
268
269 ex::
270
271 static int __init serial8250_pnp_init(void)
272 {
273 return pnp_register_driver(&serial_pnp_driver);
274 }
275
276 The Old Way
277 ^^^^^^^^^^^
278
279 A series of compatibility functions have been created to make it easy to convert
280 ISAPNP drivers. They should serve as a temporary solution only.
281
282 They are as follows::
283
284 struct pnp_dev *pnp_find_dev(struct pnp_card *card,
285 unsigned short vendor,
286 unsigned short function,
287 struct pnp_dev *from)
288
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