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 devices 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 a 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
 240 ISAPNP drivers.  They should serve as a temporary solution only.
 241
 242 they are as follows:
 243
 244 struct pnp_card *pnp_find_card(unsigned short vendor,
 245                                  unsigned short device,
 246                                  struct pnp_card *from)
 247
 248 struct pnp_dev *pnp_find_dev(struct pnp_card *card,
 249                                 unsigned short vendor,
 250                                 unsigned short function,
 251                                 struct pnp_dev *from)
 252