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Linux/Documentation/pnp.txt

  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 

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