From: "Petr Vandrovec" <VANDROVE@vc.cvut.cz>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: PCI code: why need outb (0x01, 0xCFB); ?
Date: Wed, 8 Jan 2003 21:49:39 +0100 [thread overview]
Message-ID: <CACAEBD1F1C@vcnet.vc.cvut.cz> (raw)
On 8 Jan 03 at 10:52, H. Peter Anvin wrote:
>
> > 1. which device is at port address 0xCFB?
>
> Hopefully none.
Actually I'm not sure. This code is here since at least 2.0.28,
and during googling I even found code for direct PCI access
(http://www-user.tu-chemnitz.de/~heha/viewzip.cgi/hs_freeware/gerald.zip/DIRECTNT.CPP?auto=CPP)
which sets lowest bit at 0xCFB to 1 before doing PCI config
accesses and reset it back to original value afterward.
So I believe that there were some chipsets (probably in 486&PCI times)
which did conf1/conf2 accesses depending on value of this bit.
Unfortunately I was not able to confirm this - almost nobody provides
northbridge datasheets from '94 era, even Intel does not provide them
(f.e. Neptune) anymore :-(
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz
next reply other threads:[~2003-01-08 20:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-08 20:49 Petr Vandrovec [this message]
2003-01-08 21:22 ` PCI code: why need outb (0x01, 0xCFB); ? Maciej W. Rozycki
-- strict thread matches above, loose matches on Subject: below --
2003-01-08 21:33 Petr Vandrovec
2003-01-08 21:53 ` Maciej W. Rozycki
2003-01-08 19:10 Nakajima, Jun
2003-01-08 20:40 ` H. Peter Anvin
2003-01-08 21:37 ` Richard B. Johnson
2003-01-07 2:24 fretre lewis
2003-01-06 13:02 fretre lewis
2003-01-06 9:26 fretre lewis
2003-01-06 12:41 ` Gianni Tedesco
2003-01-08 18:52 ` H. Peter Anvin
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