1
Linux Plug and Play Documentation
2
by Adam Belay <ambx1@neo.rr.com>
3
last updated: Oct. 16, 2002
4
---------------------------------------------------------------------------------------
10
Plug and Play provides a means of detecting and setting resources for legacy or
11
otherwise unconfigurable devices. The Linux Plug and Play Layer provides these
12
services to compatible drivers.
18
The Linux Plug and Play user interface provides a means to activate PnP devices
19
for legacy and user level drivers that do not support Linux Plug and Play. The
20
user interface is integrated into sysfs.
22
In addition to the standard sysfs file the following are created in each
24
id - displays a list of support EISA IDs
25
options - displays possible resource configurations
26
resources - displays currently allocated resources and allows resource changes
30
#echo "auto" > resources
32
this will invoke the automatic resource config system to activate the device
34
-manually activating a device
36
#echo "manual <depnum> <mode>" > resources
37
<depnum> - the configuration number
38
<mode> - static or dynamic
39
static = for next boot
44
#echo "disable" > resources
49
Suppose you need to activate the floppy disk controller.
50
1.) 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
54
PC standard floppy disk controller
56
2.) check if the device is already active
60
- Notice the string "DISABLED". This means the device is not active.
62
3.) check the device's possible configurations (optional)
64
Dependent: 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
68
dma 2 8-bit compatible
69
Dependent: 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
73
dma 2 8-bit compatible
75
4.) now activate the device
76
# echo "auto" > resources
78
5.) finally check if the device is active
85
also there are a series of kernel parameters:
86
pnp_reserve_irq=irq1[,irq2] ....
87
pnp_reserve_dma=dma1[,dma2] ....
88
pnp_reserve_io=io1,size1[,io2,size2] ....
89
pnp_reserve_mem=mem1,size1[,mem2,size2] ....
93
The Unified Plug and Play Layer
94
-------------------------------
95
All Plug and Play drivers, protocols, and services meet at a central location
96
called the Plug and Play Layer. This layer is responsible for the exchange of
97
information between PnP drivers and PnP protocols. Thus it automatically
98
forwards commands to the proper protocol. This makes writing PnP drivers
101
The following functions are available from the Plug and Play Layer:
104
- increments the number of uses by one
107
- deincrements the number of uses by one
109
pnp_register_protocol
110
- use this to register a new PnP protocol
112
pnp_unregister_protocol
113
- use this function to remove a PnP protocol from the Plug and Play Layer
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
122
pnp_unregister_driver
123
- removes a PnP driver from the Plug and Play Layer
127
Plug and Play Protocols
128
-----------------------
129
This section contains information for PnP protocol developers.
131
The 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
136
It is meant to replace the PNPBIOS. It is not currently supported by Linux
137
Plug and Play but it is planned to be in the near future.
140
Requirements for a Linux PnP protocol:
141
1.) the protocol must use EISA IDs
142
2.) the protocol must inform the PnP Layer of a device's current configuration
143
- the ability to set resources is optional but preferred.
145
The following are PnP protocol related functions:
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
153
- call this to initialize the PnP structure
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
161
- adds an EISA ID to the list of supported IDs for the specified device
163
For more information consult the source of a protocol such as
164
/drivers/pnp/pnpbios/core.c.
168
Linux Plug and Play Drivers
169
---------------------------
170
This section contains information for Linux PnP driver developers.
174
1.) first make a list of supported EISA IDS
176
static 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},
184
Please note that the character 'X' can be used as a wild card in the function
185
portion (last four characters).
187
/* Unknown PnP modems */
188
{ "PNPCXXX", UNKNOWN_DEV },
190
Supported PnP card IDs can optionally be defined.
192
static const struct pnp_id pnp_card_table[] = {
197
2.) Optionally define probe and remove functions. It may make sense not to
198
define these functions if the driver already has a reliable method of detecting
199
the resources, such as the parport_pc driver.
202
serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const
203
struct pnp_id *dev_id)
208
static void serial_pnp_remove(struct pnp_dev * dev)
212
consult /drivers/serial/8250_pnp.c for more information.
214
3.) create a driver structure
217
static struct pnp_driver serial_pnp_driver = {
219
.card_id_table = pnp_card_table,
220
.id_table = pnp_dev_table,
221
.probe = serial_pnp_probe,
222
.remove = serial_pnp_remove,
225
* name and id_table cannot be NULL.
227
4.) register the driver
230
static int __init serial8250_pnp_init(void)
232
return pnp_register_driver(&serial_pnp_driver);
238
A series of compatibility functions have been created to make it easy to convert
239
ISAPNP drivers. They should serve as a temporary solution only.
243
struct pnp_card *pnp_find_card(unsigned short vendor,
244
unsigned short device,
245
struct pnp_card *from)
247
struct pnp_dev *pnp_find_dev(struct pnp_card *card,
248
unsigned short vendor,
249
unsigned short function,
250
struct pnp_dev *from)