1Linux Plug and Play Documentation 2by Adam Belay <ambx1@neo.rr.com> 3last updated: Oct. 16, 2002 4--------------------------------------------------------------------------------------- 5 6 7 8Overview 9-------- 10 Plug and Play provides a means of detecting and setting resources for legacy or 11otherwise unconfigurable devices. The Linux Plug and Play Layer provides these 12services to compatible drivers. 13 14 15 16The User Interface 17------------------ 18 The Linux Plug and Play user interface provides a means to activate PnP devices 19for legacy and user level drivers that do not support Linux Plug and Play. The 20user interface is integrated into sysfs. 21 22In addition to the standard sysfs file the following are created in each 23device's directory: 24id - displays a list of support EISA IDs 25options - displays possible resource configurations 26resources - displays currently allocated resources and allows resource changes 27 28-activating a device 29 30#echo "auto" > resources 31 32this 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 47EXAMPLE: 48 49Suppose you need to activate the floppy disk controller. 501.) 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 54PC standard floppy disk controller 55 562.) check if the device is already active 57# cat resources 58DISABLED 59 60- Notice the string "DISABLED". This means the device is not active. 61 623.) check the device's possible configurations (optional) 63# cat options 64Dependent: 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 69Dependent: 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 74 754.) now activate the device 76# echo "auto" > resources 77 785.) finally check if the device is active 79# cat resources 80io 0x3f0-0x3f5 81io 0x3f7-0x3f7 82irq 6 83dma 2 84 85also there are a series of kernel parameters: 86pnp_reserve_irq=irq1[,irq2] .... 87pnp_reserve_dma=dma1[,dma2] .... 88pnp_reserve_io=io1,size1[,io2,size2] .... 89pnp_reserve_mem=mem1,size1[,mem2,size2] .... 90 91 92 93The Unified Plug and Play Layer 94------------------------------- 95 All Plug and Play drivers, protocols, and services meet at a central location 96called the Plug and Play Layer. This layer is responsible for the exchange of 97information between PnP drivers and PnP protocols. Thus it automatically 98forwards commands to the proper protocol. This makes writing PnP drivers 99significantly easier. 100 101The following functions are available from the Plug and Play Layer: 102 103pnp_get_protocol 104- increments the number of uses by one 105 106pnp_put_protocol 107- deincrements the number of uses by one 108 109pnp_register_protocol 110- use this to register a new PnP protocol 111 112pnp_unregister_protocol 113- use this function to remove a PnP protocol from the Plug and Play Layer 114 115pnp_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 122pnp_unregister_driver 123- removes a PnP driver from the Plug and Play Layer 124 125 126 127Plug and Play Protocols 128----------------------- 129 This section contains information for PnP protocol developers. 130 131The 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 135devices. 136It is meant to replace the PNPBIOS. It is not currently supported by Linux 137Plug and Play but it is planned to be in the near future. 138 139 140Requirements for a Linux PnP protocol: 1411.) the protocol must use EISA IDs 1422.) the protocol must inform the PnP Layer of a device's current configuration 143- the ability to set resources is optional but preferred. 144 145The following are PnP protocol related functions: 146 147pnp_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 150structure 151 152pnp_init_device 153- call this to initialize the PnP structure 154 155pnp_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 160pnp_add_id 161- adds an EISA ID to the list of supported IDs for the specified device 162 163For more information consult the source of a protocol such as 164/drivers/pnp/pnpbios/core.c. 165 166 167 168Linux Plug and Play Drivers 169--------------------------- 170 This section contains information for Linux PnP driver developers. 171 172The New Way 173........... 1741.) first make a list of supported EISA IDS 175ex: 176static 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 184Please note that the character 'X' can be used as a wild card in the function 185portion (last four characters). 186ex: 187 /* Unknown PnP modems */ 188 { "PNPCXXX", UNKNOWN_DEV }, 189 190Supported PnP card IDs can optionally be defined. 191ex: 192static const struct pnp_id pnp_card_table[] = { 193 { "ANYDEVS", 0 }, 194 { "", 0 } 195}; 196 1972.) Optionally define probe and remove functions. It may make sense not to 198define these functions if the driver already has a reliable method of detecting 199the resources, such as the parport_pc driver. 200ex: 201static int 202serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const 203 struct pnp_id *dev_id) 204{ 205. . . 206 207ex: 208static void serial_pnp_remove(struct pnp_dev * dev) 209{ 210. . . 211 212consult /drivers/serial/8250_pnp.c for more information. 213 2143.) create a driver structure 215ex: 216 217static 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 2274.) register the driver 228ex: 229 230static int __init serial8250_pnp_init(void) 231{ 232 return pnp_register_driver(&serial_pnp_driver); 233} 234 235The Old Way 236........... 237 238A series of compatibility functions have been created to make it easy to convert 239ISAPNP drivers. They should serve as a temporary solution only. 240 241They are as follows: 242 243struct pnp_card *pnp_find_card(unsigned short vendor, 244 unsigned short device, 245 struct pnp_card *from) 246 247struct pnp_dev *pnp_find_dev(struct pnp_card *card, 248 unsigned short vendor, 249 unsigned short function, 250 struct pnp_dev *from) 251 252