Re: [PATCH] PnP Fixes for 2.6.0-test5

[Adam Belay <ambx1@neo.rr.com>]

On Mon, Sep 22, 2003 at 12:32:15PM +0100, Alan Cox wrote:
> 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)

Assuming the PnPBIOS provides this information through device nodes, the
current pnp code will ensure that dma 0 is not used.

> 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.

Thanks, I'll look into these further.

Regards,
Adam