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+Linux Plug and Play Documentation
+by 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 driverfs.
+
+In addition to the standard driverfs 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
+
+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 devices current configuration
+- the ability to set resources is optional but prefered.
+
+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 a 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:
+        /* Unkown 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 can not 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)
+