linux-kernel - Re: [PATCH v2] dmaengine: care sd_dma_address/len in dmaengine_prep_slave

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Date:	Wed, 25 Apr 2012 16:18:23 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dmaengine: care sd_dma_address/len in dmaengine_prep_slave_single()

On 02/01/2012 07:22 PM, Russell King - ARM Linux wrote:
> On Mon, Jan 30, 2012 at 05:13:30PM -0800, Kuninori Morimoto wrote:
>> +	sg_init_table(&sg, 1);
>> +	sg_set_page(&sg, pfn_to_page(PFN_DOWN(buf)),
>> +		    len, offset_in_page(buf));
> 
> There's not much point setting this - the page/virtual address should
> not be used by DMA engines as that may not reflect what's being requested
> (especially if there's an IOMMU in the way.)

I was just looking at this again and there are actually quite a few dma
engine drivers which use sg->length and sg_phys(sg). I guess these would
break if the sg_set_page was to be removed. Should these drivers be changed
to use sg_dma_len and sg_dma_address?

Thanks
- Lars
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