Root/Documentation/pnp.txt

1Linux Plug and Play Documentation
2by Adam Belay <ambx1@neo.rr.com>
3last updated: Oct. 16, 2002
4---------------------------------------------------------------------------------------
5
6
7
8Overview
9--------
10    Plug and Play provides a means of detecting and setting resources for legacy or
11otherwise unconfigurable devices. The Linux Plug and Play Layer provides these
12services to compatible drivers.
13
14
15
16The User Interface
17------------------
18    The Linux Plug and Play user interface provides a means to activate PnP devices
19for legacy and user level drivers that do not support Linux Plug and Play. The
20user interface is integrated into sysfs.
21
22In addition to the standard sysfs file the following are created in each
23device's directory:
24id - displays a list of support EISA IDs
25options - displays possible resource configurations
26resources - displays currently allocated resources and allows resource changes
27
28-activating a device
29
30#echo "auto" > resources
31
32this will invoke the automatic resource config system to activate the device
33
34-manually activating a device
35
36#echo "manual <depnum> <mode>" > resources
37<depnum> - the configuration number
38<mode> - static or dynamic
39        static = for next boot
40        dynamic = now
41
42-disabling a device
43
44#echo "disable" > resources
45
46
47EXAMPLE:
48
49Suppose you need to activate the floppy disk controller.
501.) change to the proper directory, in my case it is
51/driver/bus/pnp/devices/00:0f
52# cd /driver/bus/pnp/devices/00:0f
53# cat name
54PC standard floppy disk controller
55
562.) check if the device is already active
57# cat resources
58DISABLED
59
60- Notice the string "DISABLED". This means the device is not active.
61
623.) check the device's possible configurations (optional)
63# cat options
64Dependent: 01 - Priority acceptable
65    port 0x3f0-0x3f0, align 0x7, size 0x6, 16-bit address decoding
66    port 0x3f7-0x3f7, align 0x0, size 0x1, 16-bit address decoding
67    irq 6
68    dma 2 8-bit compatible
69Dependent: 02 - Priority acceptable
70    port 0x370-0x370, align 0x7, size 0x6, 16-bit address decoding
71    port 0x377-0x377, align 0x0, size 0x1, 16-bit address decoding
72    irq 6
73    dma 2 8-bit compatible
74
754.) now activate the device
76# echo "auto" > resources
77
785.) finally check if the device is active
79# cat resources
80io 0x3f0-0x3f5
81io 0x3f7-0x3f7
82irq 6
83dma 2
84
85also there are a series of kernel parameters:
86pnp_reserve_irq=irq1[,irq2] ....
87pnp_reserve_dma=dma1[,dma2] ....
88pnp_reserve_io=io1,size1[,io2,size2] ....
89pnp_reserve_mem=mem1,size1[,mem2,size2] ....
90
91
92
93The Unified Plug and Play Layer
94-------------------------------
95    All Plug and Play drivers, protocols, and services meet at a central location
96called the Plug and Play Layer. This layer is responsible for the exchange of
97information between PnP drivers and PnP protocols. Thus it automatically
98forwards commands to the proper protocol. This makes writing PnP drivers
99significantly easier.
100
101The following functions are available from the Plug and Play Layer:
102
103pnp_get_protocol
104- increments the number of uses by one
105
106pnp_put_protocol
107- deincrements the number of uses by one
108
109pnp_register_protocol
110- use this to register a new PnP protocol
111
112pnp_unregister_protocol
113- use this function to remove a PnP protocol from the Plug and Play Layer
114
115pnp_register_driver
116- adds a PnP driver to the Plug and Play Layer
117- this includes driver model integration
118- returns zero for success or a negative error number for failure; count
119  calls to the .add() method if you need to know how many devices bind to
120  the driver
121
122pnp_unregister_driver
123- removes a PnP driver from the Plug and Play Layer
124
125
126
127Plug and Play Protocols
128-----------------------
129    This section contains information for PnP protocol developers.
130
131The following Protocols are currently available in the computing world:
132- PNPBIOS: used for system devices such as serial and parallel ports.
133- ISAPNP: provides PnP support for the ISA bus
134- ACPI: among its many uses, ACPI provides information about system level
135devices.
136It is meant to replace the PNPBIOS. It is not currently supported by Linux
137Plug and Play but it is planned to be in the near future.
138
139
140Requirements for a Linux PnP protocol:
1411.) the protocol must use EISA IDs
1422.) the protocol must inform the PnP Layer of a device's current configuration
143- the ability to set resources is optional but preferred.
144
145The following are PnP protocol related functions:
146
147pnp_add_device
148- use this function to add a PnP device to the PnP layer
149- only call this function when all wanted values are set in the pnp_dev
150structure
151
152pnp_init_device
153- call this to initialize the PnP structure
154
155pnp_remove_device
156- call this to remove a device from the Plug and Play Layer.
157- it will fail if the device is still in use.
158- automatically will free mem used by the device and related structures
159
160pnp_add_id
161- adds an EISA ID to the list of supported IDs for the specified device
162
163For more information consult the source of a protocol such as
164/drivers/pnp/pnpbios/core.c.
165
166
167
168Linux Plug and Play Drivers
169---------------------------
170    This section contains information for Linux PnP driver developers.
171
172The New Way
173...........
1741.) first make a list of supported EISA IDS
175ex:
176static const struct pnp_id pnp_dev_table[] = {
177    /* Standard LPT Printer Port */
178    {.id = "PNP0400", .driver_data = 0},
179    /* ECP Printer Port */
180    {.id = "PNP0401", .driver_data = 0},
181    {.id = ""}
182};
183
184Please note that the character 'X' can be used as a wild card in the function
185portion (last four characters).
186ex:
187    /* Unknown PnP modems */
188    { "PNPCXXX", UNKNOWN_DEV },
189
190Supported PnP card IDs can optionally be defined.
191ex:
192static const struct pnp_id pnp_card_table[] = {
193    { "ANYDEVS", 0 },
194    { "", 0 }
195};
196
1972.) Optionally define probe and remove functions. It may make sense not to
198define these functions if the driver already has a reliable method of detecting
199the resources, such as the parport_pc driver.
200ex:
201static int
202serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const
203                 struct pnp_id *dev_id)
204{
205. . .
206
207ex:
208static void serial_pnp_remove(struct pnp_dev * dev)
209{
210. . .
211
212consult /drivers/serial/8250_pnp.c for more information.
213
2143.) create a driver structure
215ex:
216
217static struct pnp_driver serial_pnp_driver = {
218    .name = "serial",
219    .card_id_table = pnp_card_table,
220    .id_table = pnp_dev_table,
221    .probe = serial_pnp_probe,
222    .remove = serial_pnp_remove,
223};
224
225* name and id_table cannot be NULL.
226
2274.) register the driver
228ex:
229
230static int __init serial8250_pnp_init(void)
231{
232    return pnp_register_driver(&serial_pnp_driver);
233}
234
235The Old Way
236...........
237
238A series of compatibility functions have been created to make it easy to convert
239ISAPNP drivers. They should serve as a temporary solution only.
240
241They are as follows:
242
243struct pnp_card *pnp_find_card(unsigned short vendor,
244                 unsigned short device,
245                 struct pnp_card *from)
246
247struct pnp_dev *pnp_find_dev(struct pnp_card *card,
248                unsigned short vendor,
249                unsigned short function,
250                struct pnp_dev *from)
251
252

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