RE: Device at address 0

[Richard Walter <rwalter@brocade.com>]

Folks,

<I'm about to get up on my soap-box...>

In PCI 2.2, page xix, at the bottom of the page:

"Implementation Notes:    Implementation notes are enclosed in a box.  They
are ***NOT*** part of the PCI specification and are included for
clarification and illustration only."  (My emphasis added.)

This explanation was also included in PCI 2.1, for which I will provide a
page reference on Monday.  (I can't right now because I don't have PCI 2.1
in the office, but keep it at home.)

Therefore, Wen's reference to section 3.2.2 is specifically ***NOT*** part
of the spec.

PCI 2.1 ***DOES NOT*** state that a 0 BAR is invalid.

I believe that this traces it's roots to an issue about partially
configuring a device (assigning some BARs and not others) and unfortunately
ended up with a confusing, poorly worded "solution" that just clouded things
further.  *sigh*.

Thank you for allowing me to vent... :)

<Getting down off of my soap box>

-Richard Walter
Note: I speak for myself, not for Brocade.

-----Original Message-----
From: wen-king@myri.com [mailto:wen-king@myri.com]
Sent: Friday, August 02, 2002 3:21 PM
To: pci-sig@znyx.com
Subject: RE: Device at address 0


In PCI 2.1 spec, section 3.2.2 at the end of the text box titled
"Implementation Note: Device Address Space", the last sentence says: A
base address register does not contain a valid address when it is equal
to "0".

In PCI 2.2 spec, in the same section and same text box, the sentence is
removed.  If its removal means having an all-0 address is now valid, it
would means it is now impossible for a card to be simultaneously
compliant to 2.1 and 2.2.

What happened?  I must have missed something.  I searched the PCISIG
web site, and looked into "2.1 to 2.2 Change summary", and I don't see
a mention of this change.

PDF file on http://www.pcisig.com/specifications/conventional_pci

It says something about 3.2.2 being re-written for improved readability,
but nothing to imply any functional changes of that sort.  I wish I
could "diff" the electronic versions of the specs.

								- Wen