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

[Christoph Hellwig]

On Tue, May 05, 2020 at 12:51:58PM +0200, Marek Szyprowski wrote:
> 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?

None of the helpers helps with passing the right parameters from the
sg_table.  So in doube we'd need wrappers for all of the above, or
none..