Date: Thu, 16 Jan 1997 13:35:11 -0800
From: dmk@uask4it-95.Eng.Sun.Com (David Kahn)
Subject: Item #405: pci v2.0: Add 'vendor-id' to 'compatible'

P1275 Openboot Working Group Proposal -- Proposal #:405 Ver 1

NOTE:		This was proposed (and accepted) at the January meeting
		as #dmk-01.

Title:		Add vendor-id to "compatible" when subsystem-id is non-zero.

Author:		David Kahn

Date:		Jan 13, 1997

Ed/Tech:	Technical

Synopsis:	Add vendor-id to "compatible" property when subsystem-id is
		non-zero.

Doc & Version:	PCI binding, Version 2.0.  See also #380 which added the
		pciclass,NNNNNN name.

Problem:	Certain OS drivers may be able to use a more generic
		'vendor-id' driver even when the card reports a non-zero
		subsystem-id. An OS could automatically find the vendor-id
		driver if we created the "compatible" property as follows:

		    subsytem-id-name + vendor-id-name + class-code-name

		Currently, pci V2.0 specifies the subsystem-id name if the
		subsystem-id is non-zero, otherwise the vendor-id name is
		published in "compatible".  Proposal #380, accepted after pci
		binding v2.0 was published, added the class-code name to the
		end of the "compatible" property.

		There is the potential that this proposal could cause
		problems if a new card has a vendor-id driver, but no
		subsystem-id driver and the vendor-id driver causes the
		system to crash.

Proposal:

		Change the text in pci V2.0, page 9, lines 38-40 for
		"compatible". Construct a composite string property containing
		the following elements in the following order with each element
		constructed as with ENCODE-STRING and each additional element
		included as with ENCODE+.


                1. If the subsystem-id is non-zero, the first encoded string
                   (the most specific entry in the property) is of the
                   form pciVVVV,DDDD where VVVV,DDDD shall be the subsystem
                   vendor-id and the subsystem-id, respectively.  VVVV and
                   DDDD are lower case ASCII hexadecimal numbers without
                   leading zeros.  If the subsystem-id is zero, this entry is
                   not included in "compatible".

                2. Construct an encoded-string of the form pciVVVV,DDDD where
                   VVVV,DDDD is the vendor-id and device-id, respectively.
                   VVVV and DDDD are lower case ASCII hexadecimal numbers
                   without leading zeros.

                3. Construct an encoded-string of the form pciclass,NNNNNN
                   where NNNNNN is the device's class-code, in lower case,
                   ASCII hexadecimal numbers *WITH* leading zeros. This entry
                   is always the least specific entry (the last entry included
                   with ENCODE+) in "compatible".

	[ Note: The editor is free to change the VVVV,DDDD characters
	  to something more appropro for case 1. ]

[ P1275 Item #405 -- Received: Thu Jan 16 13:35:05 PST 1997 ]