Re: [PATCH v2] dmaengine: care sd_dma_address/len in dmaengine_prep_slave_single()

From: Lars-Peter Clausen
Date: Wed Apr 25 2012 - 10:15:59 EST


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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