[Mesa-dev] [PATCH 02/10] dri_interface: add __DRI_IMAGE_TRANSFER_USER_STRIDE

[Marek Olšák]

Why would you want to modify it? It's exactly what you get when you map it,
but that stride can't be used for modesetting.

Marek

On Wed, Apr 25, 2018 at 11:14 PM, Gurchetan Singh <
gurchetansingh at chromium.org> wrote:

> That sounds fine to me.  We can just modify the stride after
> dri_bo_create(..).
>
> On Wed, Apr 25, 2018 at 7:30 PM, Marek Olšák <maraeo at gmail.com> wrote:
> > On Wed, Apr 25, 2018 at 6:56 PM, Gurchetan Singh
> > <gurchetansingh at chromium.org> wrote:
> >>
> >> On Wed, Apr 25, 2018 at 2:16 PM, Marek Olšák <maraeo at gmail.com> wrote:
> >> > From: Nicolai Hähnle <nicolai.haehnle at amd.com>
> >> >
> >> > Allow the caller to specify the row stride (in bytes) with which an
> >> > image
> >> > should be mapped. Note that completely ignoring USER_STRIDE is a valid
> >> > implementation of mapImage.
> >> >
> >> > This is horrible API design. Unfortunately, cros_gralloc does indeed
> >> > have
> >> > a horrible API design -- in that arbitrary images should be allowed to
> >> > be
> >> > mapped with the stride that a linear image of the same width would
> have.
> >>
> >> Yes, unfortunately the gralloc API doesn't return the stride when
> >> (*lock) is called.  However, the stride is returned during (*alloc).
> >> Currently, for the dri backend, minigbm uses
> >> __DRI_IMAGE_ATTRIB_STRIDE to compute the pixel stride given to
> >> Android.
> >>
> >> Is AMD seeing problems with the current approach (I haven't seen any
> >> bugs filed for this issue)?
> >>
> >> Another possible solution is to call mapImage()/unmapImage right after
> >> allocating the image, and use the stride returned by mapImage() to
> >> compute the pixel stride.  That could also fix whatever bugs AMD is
> >> seeing.
> >
> >
> > Thanks. You cleared it up to me. It looks like that everything we've been
> > told so far is BS. This series isn't needed.
> >
> > The solution is to do this in the amdgpu minigbm backend at alloc time:
> >    stride = align(width * Bpp, 64);
> >
> > Later chips should change that to:
> >    stride = align(width * Bpp, 256);
> >
> > No querying needed. What do you think?
> >
> > Marek
>
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