252 lines
6.8 KiB
Text
252 lines
6.8 KiB
Text
Linux Plug and Play Documentation
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by Adam Belay <ambx1@neo.rr.com>
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last updated: Oct. 16, 2002
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---------------------------------------------------------------------------------------
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Overview
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--------
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Plug and Play provides a means of detecting and setting resources for legacy or
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otherwise unconfigurable devices. The Linux Plug and Play Layer provides these
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services to compatible drivers.
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The User Interface
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------------------
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The Linux Plug and Play user interface provides a means to activate PnP devices
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for legacy and user level drivers that do not support Linux Plug and Play. The
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user interface is integrated into sysfs.
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In addition to the standard sysfs file the following are created in each
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device's directory:
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id - displays a list of support EISA IDs
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options - displays possible resource configurations
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resources - displays currently allocated resources and allows resource changes
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-activating a device
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#echo "auto" > resources
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this will invoke the automatic resource config system to activate the device
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-manually activating a device
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#echo "manual <depnum> <mode>" > resources
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<depnum> - the configuration number
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<mode> - static or dynamic
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static = for next boot
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dynamic = now
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-disabling a device
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#echo "disable" > resources
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EXAMPLE:
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Suppose you need to activate the floppy disk controller.
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1.) change to the proper directory, in my case it is
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/driver/bus/pnp/devices/00:0f
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# cd /driver/bus/pnp/devices/00:0f
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# cat name
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PC standard floppy disk controller
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2.) check if the device is already active
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# cat resources
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DISABLED
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- Notice the string "DISABLED". THis means the device is not active.
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3.) check the device's possible configurations (optional)
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# cat options
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Dependent: 01 - Priority acceptable
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port 0x3f0-0x3f0, align 0x7, size 0x6, 16-bit address decoding
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port 0x3f7-0x3f7, align 0x0, size 0x1, 16-bit address decoding
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irq 6
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dma 2 8-bit compatible
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Dependent: 02 - Priority acceptable
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port 0x370-0x370, align 0x7, size 0x6, 16-bit address decoding
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port 0x377-0x377, align 0x0, size 0x1, 16-bit address decoding
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irq 6
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dma 2 8-bit compatible
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4.) now activate the device
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# echo "auto" > resources
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5.) finally check if the device is active
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# cat resources
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io 0x3f0-0x3f5
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io 0x3f7-0x3f7
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irq 6
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dma 2
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also there are a series of kernel parameters:
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pnp_reserve_irq=irq1[,irq2] ....
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pnp_reserve_dma=dma1[,dma2] ....
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pnp_reserve_io=io1,size1[,io2,size2] ....
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pnp_reserve_mem=mem1,size1[,mem2,size2] ....
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The Unified Plug and Play Layer
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-------------------------------
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All Plug and Play drivers, protocols, and services meet at a central location
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called the Plug and Play Layer. This layer is responsible for the exchange of
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information between PnP drivers and PnP protocols. Thus it automatically
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forwards commands to the proper protocol. This makes writing PnP drivers
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significantly easier.
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The following functions are available from the Plug and Play Layer:
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pnp_get_protocol
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- increments the number of uses by one
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pnp_put_protocol
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- deincrements the number of uses by one
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pnp_register_protocol
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- use this to register a new PnP protocol
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pnp_unregister_protocol
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- use this function to remove a PnP protocol from the Plug and Play Layer
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pnp_register_driver
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- adds a PnP driver to the Plug and Play Layer
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- this includes driver model integration
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- returns zero for success or a negative error number for failure; count
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calls to the .add() method if you need to know how many devices bind to
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the driver
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pnp_unregister_driver
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- removes a PnP driver from the Plug and Play Layer
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Plug and Play Protocols
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-----------------------
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This section contains information for PnP protocol developers.
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The following Protocols are currently available in the computing world:
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- PNPBIOS: used for system devices such as serial and parallel ports.
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- ISAPNP: provides PnP support for the ISA bus
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- ACPI: among its many uses, ACPI provides information about system level
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devices.
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It is meant to replace the PNPBIOS. It is not currently supported by Linux
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Plug and Play but it is planned to be in the near future.
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Requirements for a Linux PnP protocol:
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1.) the protocol must use EISA IDs
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2.) the protocol must inform the PnP Layer of a devices current configuration
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- the ability to set resources is optional but preferred.
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The following are PnP protocol related functions:
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pnp_add_device
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- use this function to add a PnP device to the PnP layer
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- only call this function when all wanted values are set in the pnp_dev
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structure
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pnp_init_device
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- call this to initialize the PnP structure
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pnp_remove_device
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- call this to remove a device from the Plug and Play Layer.
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- it will fail if the device is still in use.
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- automatically will free mem used by the device and related structures
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pnp_add_id
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- adds a EISA ID to the list of supported IDs for the specified device
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For more information consult the source of a protocol such as
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/drivers/pnp/pnpbios/core.c.
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Linux Plug and Play Drivers
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---------------------------
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This section contains information for linux PnP driver developers.
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The New Way
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...........
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1.) first make a list of supported EISA IDS
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ex:
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static const struct pnp_id pnp_dev_table[] = {
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/* Standard LPT Printer Port */
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{.id = "PNP0400", .driver_data = 0},
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/* ECP Printer Port */
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{.id = "PNP0401", .driver_data = 0},
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{.id = ""}
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};
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Please note that the character 'X' can be used as a wild card in the function
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portion (last four characters).
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ex:
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/* Unknown PnP modems */
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{ "PNPCXXX", UNKNOWN_DEV },
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Supported PnP card IDs can optionally be defined.
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ex:
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static const struct pnp_id pnp_card_table[] = {
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{ "ANYDEVS", 0 },
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{ "", 0 }
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};
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2.) Optionally define probe and remove functions. It may make sense not to
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define these functions if the driver already has a reliable method of detecting
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the resources, such as the parport_pc driver.
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ex:
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static int
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serial_pnp_probe(struct pnp_dev * dev, const struct pnp_id *card_id, const
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struct pnp_id *dev_id)
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{
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. . .
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ex:
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static void serial_pnp_remove(struct pnp_dev * dev)
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{
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. . .
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consult /drivers/serial/8250_pnp.c for more information.
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3.) create a driver structure
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ex:
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static struct pnp_driver serial_pnp_driver = {
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.name = "serial",
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.card_id_table = pnp_card_table,
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.id_table = pnp_dev_table,
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.probe = serial_pnp_probe,
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.remove = serial_pnp_remove,
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};
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* name and id_table cannot be NULL.
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4.) register the driver
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ex:
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static int __init serial8250_pnp_init(void)
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{
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return pnp_register_driver(&serial_pnp_driver);
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}
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The Old Way
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...........
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a series of compatibility functions have been created to make it easy to convert
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ISAPNP drivers. They should serve as a temporary solution only.
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they are as follows:
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struct pnp_card *pnp_find_card(unsigned short vendor,
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unsigned short device,
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struct pnp_card *from)
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struct pnp_dev *pnp_find_dev(struct pnp_card *card,
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unsigned short vendor,
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unsigned short function,
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struct pnp_dev *from)
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