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