Re: [PATCH v3 02/25] drm: core: fix common struct sg_table related issues

[Marek Szyprowski]

Hi Christoph,

On 08.05.2020 09:16, Christoph Hellwig wrote:
> On Fri, May 08, 2020 at 09:12:13AM +0200, Marek Szyprowski wrote:
>> Then we would just need one more helper to construct scatterlist, as the
>> above two are read-only don't allow to modify scatterlist:
>>
>> #define for_each_sgtable_sg(sgt, sg, i)ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ \
>>   ÂÂÂÂÂÂ for_each_sg(sgt->sgl, sg, sgt->orig_nents, i)
>>
>> With the above 3 helpers we can probably get rid of all instances of
>> sg_table->{nents,orig_nents} from the DRM code. I will prepare patches soon.
> Sounds great, thanks!

It turned out that the 4th helper (for_each_sgtable_dma_sg) was needed 
as some drivers makes use of the larger than the PAGE_SIZE unit for DMA 
mapped pages.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland