Documentation/pnp.txt

   1 =================================
   2 Linux Plug and Play Documentation
   3 =================================
   4
   5 :Author: Adam Belay <ambx1@neo.rr.com>
   6 :Last updated: Oct. 16, 2002
   7
   8
   9 Overview
  10 --------
  11
  12 Plug and Play provides a means of detecting and setting resources for legacy or
  13 otherwise unconfigurable devices.  The Linux Plug and Play Layer provides these
  14 services to compatible drivers.
  15
  16
  17 The User Interface
  18 ------------------
  19
  20 The Linux Plug and Play user interface provides a means to activate PnP devices
  21 for legacy and user level drivers that do not support Linux Plug and Play.  The
  22 user interface is integrated into sysfs.
  23
  24 In addition to the standard sysfs file the following are created in each
  25 device's directory:
  26 - id - displays a list of support EISA IDs
  27 - options - displays possible resource configurations
  28 - resources - displays currently allocated resources and allows resource changes
  29
  30 activating a device
  31 ^^^^^^^^^^^^^^^^^^^
  32
  33 ::
  34
  35         # echo "auto" > resources
  36
  37 this will invoke the automatic resource config system to activate the device
  38
  39 manually activating a device
  40 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  41
  42 ::
  43
  44         # echo "manual <depnum> <mode>" > resources
  45
  46         <depnum> - the configuration number
  47         <mode> - static or dynamic
  48                  static = for next boot
  49                  dynamic = now
  50
  51 disabling a device
  52 ^^^^^^^^^^^^^^^^^^
  53
  54 ::
  55
  56         # echo "disable" > resources
  57
  58
  59 EXAMPLE:
  60
  61 Suppose you need to activate the floppy disk controller.
  62
  63 1. change to the proper directory, in my case it is
  64    /driver/bus/pnp/devices/00:0f::
  65
  66         # cd /driver/bus/pnp/devices/00:0f
  67         # cat name
  68         PC standard floppy disk controller
  69
  70 2. check if the device is already active::
  71
  72         # cat resources
  73         DISABLED
  74
  75   - Notice the string "DISABLED".  This means the device is not active.
  76
  77 3. check the device's possible configurations (optional)::
  78
  79         # cat options
  80         Dependent: 01 - Priority acceptable
  81             port 0x3f0-0x3f0, align 0x7, size 0x6, 16-bit address decoding
  82             port 0x3f7-0x3f7, align 0x0, size 0x1, 16-bit address decoding
  83             irq 6
  84             dma 2 8-bit compatible
  85         Dependent: 02 - Priority acceptable
  86             port 0x370-0x370, align 0x7, size 0x6, 16-bit address decoding
  87             port 0x377-0x377, align 0x0, size 0x1, 16-bit address decoding
  88             irq 6
  89             dma 2 8-bit compatible
  90
  91 4. now activate the device::
  92
  93         # echo "auto" > resources
  94
  95 5. finally check if the device is active::
  96
  97         # cat resources
  98         io 0x3f0-0x3f5
  99         io 0x3f7-0x3f7
 100         irq 6
 101         dma 2
 102
 103 also there are a series of kernel parameters::
 104
 105         pnp_reserve_irq=irq1[,irq2] ....
 106         pnp_reserve_dma=dma1[,dma2] ....
 107         pnp_reserve_io=io1,size1[,io2,size2] ....
 108         pnp_reserve_mem=mem1,size1[,mem2,size2] ....
 109
 110
 111
 112 The Unified Plug and Play Layer
 113 -------------------------------
 114
 115 All Plug and Play drivers, protocols, and services meet at a central location
 116 called the Plug and Play Layer.  This layer is responsible for the exchange of
 117 information between PnP drivers and PnP protocols.  Thus it automatically
 118 forwards commands to the proper protocol.  This makes writing PnP drivers
 119 significantly easier.
 120
 121 The following functions are available from the Plug and Play Layer:
 122
 123 pnp_get_protocol
 124   increments the number of uses by one
 125
 126 pnp_put_protocol
 127   deincrements the number of uses by one
 128
 129 pnp_register_protocol
 130   use this to register a new PnP protocol
 131
 132 pnp_unregister_protocol
 133   use this function to remove a PnP protocol from the Plug and Play Layer
 134
 135 pnp_register_driver
 136   adds a PnP driver to the Plug and Play Layer
 137
 138   this includes driver model integration
 139   returns zero for success or a negative error number for failure; count
 140   calls to the .add() method if you need to know how many devices bind to
 141   the driver
 142
 143 pnp_unregister_driver
 144   removes a PnP driver from the Plug and Play Layer
 145
 146
 147
 148 Plug and Play Protocols
 149 -----------------------
 150
 151 This section contains information for PnP protocol developers.
 152
 153 The following Protocols are currently available in the computing world:
 154
 155 - PNPBIOS:
 156     used for system devices such as serial and parallel ports.
 157 - ISAPNP:
 158     provides PnP support for the ISA bus
 159 - ACPI:
 160     among its many uses, ACPI provides information about system level
 161     devices.
 162
 163 It is meant to replace the PNPBIOS.  It is not currently supported by Linux
 164 Plug and Play but it is planned to be in the near future.
 165
 166
 167 Requirements for a Linux PnP protocol:
 168 1. the protocol must use EISA IDs
 169 2. the protocol must inform the PnP Layer of a device's current configuration
 170
 171 - the ability to set resources is optional but preferred.
 172
 173 The following are PnP protocol related functions:
 174
 175 pnp_add_device
 176   use this function to add a PnP device to the PnP layer
 177
 178   only call this function when all wanted values are set in the pnp_dev
 179   structure
 180
 181 pnp_init_device
 182   call this to initialize the PnP structure
 183
 184 pnp_remove_device
 185   call this to remove a device from the Plug and Play Layer.
 186   it will fail if the device is still in use.
 187   automatically will free mem used by the device and related structures
 188
 189 pnp_add_id
 190   adds an EISA ID to the list of supported IDs for the specified device
 191
 192 For more information consult the source of a protocol such as
 193 /drivers/pnp/pnpbios/core.c.
 194
 195
 196
 197 Linux Plug and Play Drivers
 198 ---------------------------
 199
 200 This section contains information for Linux PnP driver developers.
 201
 202 The New Way
 203 ^^^^^^^^^^^
 204
 205 1. first make a list of supported EISA IDS
 206
 207    ex::
 208
 209         static const struct pnp_id pnp_dev_table[] = {
 210                 /* Standard LPT Printer Port */
 211                 {.id = "PNP0400", .driver_data = 0},
 212                 /* ECP Printer Port */
 213                 {.id = "PNP0401", .driver_data = 0},
 214                 {.id = ""}
 215         };
 216
 217    Please note that the character 'X' can be used as a wild card in the function
 218    portion (last four characters).
 219
 220    ex::
 221
 222         /* Unknown PnP modems */
 223         {       "PNPCXXX",              UNKNOWN_DEV     },
 224
 225    Supported PnP card IDs can optionally be defined.
 226    ex::
 227
 228         static const struct pnp_id pnp_card_table[] = {
 229                 {       "ANYDEVS",              0       },
 230                 {       "",                     0       }
 231         };
 232
 233 2. Optionally define probe and remove functions.  It may make sense not to
 234    define these functions if the driver already has a reliable method of detecting
 235    the resources, such as the parport_pc driver.
 236
 237    ex::
 238
 239         static int
 240         serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const
 241                         struct pnp_id *dev_id)
 242         {
 243         . . .
 244
 245    ex::
 246
 247         static void serial_pnp_remove(struct pnp_dev * dev)
 248         {
 249         . . .
 250
 251    consult /drivers/serial/8250_pnp.c for more information.
 252
 253 3. create a driver structure
 254
 255    ex::
 256
 257         static struct pnp_driver serial_pnp_driver = {
 258                 .name           = "serial",
 259                 .card_id_table  = pnp_card_table,
 260                 .id_table       = pnp_dev_table,
 261                 .probe          = serial_pnp_probe,
 262                 .remove         = serial_pnp_remove,
 263         };
 264
 265    * name and id_table cannot be NULL.
 266
 267 4. register the driver
 268
 269    ex::
 270
 271         static int __init serial8250_pnp_init(void)
 272         {
 273                 return pnp_register_driver(&serial_pnp_driver);
 274         }
 275
 276 The Old Way
 277 ^^^^^^^^^^^
 278
 279 A series of compatibility functions have been created to make it easy to convert
 280 ISAPNP drivers.  They should serve as a temporary solution only.
 281
 282 They are as follows::
 283
 284         struct pnp_card *pnp_find_card(unsigned short vendor,
 285                                        unsigned short device,
 286                                        struct pnp_card *from)
 287
 288         struct pnp_dev *pnp_find_dev(struct pnp_card *card,
 289                                      unsigned short vendor,
 290                                      unsigned short function,
 291                                      struct pnp_dev *from)
 292