[PATCH 02/23] drm: omapdrm: fb: Don't store format BPP for each plane

[Laurent Pinchart]

Hi Tomi, Rob and Daniel,

On Tuesday 10 May 2016 10:14:17 Tomi Valkeinen wrote:
> On 09/05/16 23:57, Laurent Pinchart wrote:
> >> fwiw, I guess a lot of data from that table could these days be
> >> replaced w/ some of the drm format helpers
> >> (drm_format_num_planes()/drm_format_plane_cpp()/drm_format_{horz,vert}_ch
> >> rom a_subsampling()/etc)
> > 
> > I don't like those helpers as they're inefficient. Drivers often need to
> > know multiple pieces of information about a format, and the API forces
> > look-ups for every piece of information needed.
> > 
> > Would it make sense to add a drm_format_info() function that returns a
> > pointer to a data structure that describes the format, and reimplement
> > the existing helpers on top of that ?
> 
> I do like that idea.

Rob and Daniel, what do you think ?

> A table implementation might possibly be faster even with the current
> API. Those big switch-cases compile into a big pile of
> if-else-if-else-ifs, whereas a for loop would compile into just a few
> instructions. But just guessing here =).
> 
> In theory, the table could be sorted, making the lookup much faster, but
> I'm not sure if that's worth the effort.

-- 
Regards,

Laurent Pinchart