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

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Christoph,

On 05.05.2020 12:15, Christoph Hellwig wrote:
>> -		for_each_sg_page(st->sgl, &sg_iter, st->nents, 0)
>> +		for_each_sg_page(st->sgl, &sg_iter, st->orig_nents, 0)
> Would it make sense to also add a for_each_sgtable_page helper that
> hides the use of orig_nents?  To be used like:
>
> 		for_each_sgtable_page(st, &sg_iter, 0) {

We would need two helpers:

for_each_sgtable_cpu_page() and for_each_sgtable_dma_page().

I considered them, but then I found that there are already 
for_each_sg_page(), for_each_sg_dma_page() and various special iterators 
like sg_page_iter, sg_dma_page_iter and sg_mapping_iter. Too bad that 
they are almost not used, at least in the DRM subsystem. I wonder if it 
make sense to apply them or simply provide the two above mentioned 
wrappers?

>> +	for_each_sg(sgt->sgl, sg, sgt->orig_nents, count) {
> Same here, e.g.
>
> 	for_each_sgtable_entry(sgt, sg, count) {
>
> ?
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland