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1 | Linux Plug and Play Documentation |
2 | by Adam Belay <ambx1@neo.rr.com> |
3 | last updated: Oct. 16, 2002 |
4 | --------------------------------------------------------------------------------------- |
5 | |
6 | |
7 | |
8 | Overview |
9 | -------- |
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. |
13 | |
14 | |
15 | |
16 | The User Interface |
17 | ------------------ |
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. |
21 | |
22 | In addition to the standard sysfs file the following are created in each |
23 | device's directory: |
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 |
27 | |
28 | -activating a device |
29 | |
30 | #echo "auto" > resources |
31 | |
32 | this 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 | |
47 | EXAMPLE: |
48 | |
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 |
53 | # cat name |
54 | PC standard floppy disk controller |
55 | |
56 | 2.) check if the device is already active |
57 | # cat resources |
58 | DISABLED |
59 | |
60 | - Notice the string "DISABLED". This means the device is not active. |
61 | |
62 | 3.) check the device's possible configurations (optional) |
63 | # cat options |
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 |
67 | irq 6 |
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 |
72 | irq 6 |
73 | dma 2 8-bit compatible |
74 | |
75 | 4.) now activate the device |
76 | # echo "auto" > resources |
77 | |
78 | 5.) finally check if the device is active |
79 | # cat resources |
80 | io 0x3f0-0x3f5 |
81 | io 0x3f7-0x3f7 |
82 | irq 6 |
83 | dma 2 |
84 | |
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] .... |
90 | |
91 | |
92 | |
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 |
99 | significantly easier. |
100 | |
101 | The following functions are available from the Plug and Play Layer: |
102 | |
103 | pnp_get_protocol |
104 | - increments the number of uses by one |
105 | |
106 | pnp_put_protocol |
107 | - deincrements the number of uses by one |
108 | |
109 | pnp_register_protocol |
110 | - use this to register a new PnP protocol |
111 | |
112 | pnp_unregister_protocol |
113 | - use this function to remove a PnP protocol from the Plug and Play Layer |
114 | |
115 | pnp_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 | |
122 | pnp_unregister_driver |
123 | - removes a PnP driver from the Plug and Play Layer |
124 | |
125 | |
126 | |
127 | Plug and Play Protocols |
128 | ----------------------- |
129 | This section contains information for PnP protocol developers. |
130 | |
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 |
135 | devices. |
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. |
138 | |
139 | |
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. |
144 | |
145 | The following are PnP protocol related functions: |
146 | |
147 | pnp_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 |
150 | structure |
151 | |
152 | pnp_init_device |
153 | - call this to initialize the PnP structure |
154 | |
155 | pnp_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 | |
160 | pnp_add_id |
161 | - adds an EISA ID to the list of supported IDs for the specified device |
162 | |
163 | For more information consult the source of a protocol such as |
164 | /drivers/pnp/pnpbios/core.c. |
165 | |
166 | |
167 | |
168 | Linux Plug and Play Drivers |
169 | --------------------------- |
170 | This section contains information for Linux PnP driver developers. |
171 | |
172 | The New Way |
173 | ........... |
174 | 1.) first make a list of supported EISA IDS |
175 | ex: |
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}, |
181 | {.id = ""} |
182 | }; |
183 | |
184 | Please note that the character 'X' can be used as a wild card in the function |
185 | portion (last four characters). |
186 | ex: |
187 | /* Unknown PnP modems */ |
188 | { "PNPCXXX", UNKNOWN_DEV }, |
189 | |
190 | Supported PnP card IDs can optionally be defined. |
191 | ex: |
192 | static const struct pnp_id pnp_card_table[] = { |
193 | { "ANYDEVS", 0 }, |
194 | { "", 0 } |
195 | }; |
196 | |
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. |
200 | ex: |
201 | static int |
202 | serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const |
203 | struct pnp_id *dev_id) |
204 | { |
205 | . . . |
206 | |
207 | ex: |
208 | static void serial_pnp_remove(struct pnp_dev * dev) |
209 | { |
210 | . . . |
211 | |
212 | consult /drivers/serial/8250_pnp.c for more information. |
213 | |
214 | 3.) create a driver structure |
215 | ex: |
216 | |
217 | static 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 | |
227 | 4.) register the driver |
228 | ex: |
229 | |
230 | static int __init serial8250_pnp_init(void) |
231 | { |
232 | return pnp_register_driver(&serial_pnp_driver); |
233 | } |
234 | |
235 | The Old Way |
236 | ........... |
237 | |
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. |
240 | |
241 | They are as follows: |
242 | |
243 | struct pnp_card *pnp_find_card(unsigned short vendor, |
244 | unsigned short device, |
245 | struct pnp_card *from) |
246 | |
247 | struct 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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