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Subject: Re: [PATCH] ALSA update [6/10] - 2002/07/20
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "David S. Miller" <davem@redhat.com>
Cc: perex@suse.cz, jgarzik@pobox.com, linux-kernel@vger.kernel.org,
       alan@redhat.com
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On Mon, 2002-09-30 at 01:53, David S. Miller wrote:
>    From: Jaroslav Kysela <perex@suse.cz>
>    Date: Sun, 29 Sep 2002 22:34:51 +0200 (CEST)
>     
>    -	if (hwdev == NULL || ((u32)hwdev->dma_mask != 0xffffffff))
>    +	if (hwdev == NULL || (u32)hwdev->dma_mask <= 0x00ffffff)
>     		gfp |= GFP_DMA;
> 
> So alan, why is this really broken?
> 
> EISA/ISA DMA is defined as using a hwdev of NULL or requiring
> <16MB address, he is preserving GFP_DMA in those cases.

Firstly the DMA mask on x86 can't be below 24bits, we don't support
allocation from a smaller zone. Secondly what about PCI for 25-31bits -
there we do need to force gfp_dma to have any chance of getting the
right pages

Giving the page allocator a mask argument does sound a lot nicer

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