From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Adam Belay <ambx1@neo.rr.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] PnP Fixes for 2.6.0-test5
Date: Mon, 22 Sep 2003 12:32:15 +0100 [thread overview]
Message-ID: <1064230334.8592.7.camel@dhcp23.swansea.linux.org.uk> (raw)
In-Reply-To: <20030921201133.GE24897@neo.rr.com>
On Sul, 2003-09-21 at 21:11, Adam Belay wrote:
> # --------------------------------------------
> # 03/09/21 ambx1@neo.rr.com 1.1357
> # [PNP] remove DMA 0 restrictions
> #
> # The original argument for blocking DMA 0 was to avoid conflicts with
> # "memory refresh" but such configurations are only found on very old
> # 8-bit systems that are likely not supported by the linux kernel.
DMA0 is used by lots of 386/486 era systems for memory refresh. It is
also "borrowed" by some other systems that know it isnt available to the
OS. There are a couple of heuristics I've seen suggested by vendors of
things like sound cards
1. Check the PnPBIOS information (never looked into this myself)
2. Assume DMA 0 is free if the machine has a PCI bus detected
3. Read the DMA 0 counter a few times. If it is continually changing
don't use DMA 0
#2 is certainly a good idea IMHO, I don't know how well the others work.
next prev parent reply other threads:[~2003-09-22 11:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-21 20:09 Adam Belay
2003-09-21 20:10 ` Adam Belay
2003-09-21 20:10 ` Adam Belay
2003-09-21 20:11 ` Adam Belay
2003-09-22 11:32 ` Alan Cox [this message]
2003-09-24 16:25 ` Adam Belay
2003-09-21 20:11 ` Adam Belay
2003-09-21 20:12 ` Adam Belay
2003-09-21 20:12 ` Adam Belay
2003-09-21 20:13 ` Adam Belay
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