[PATCH 2/3] drm: Make drm_gem_fb_alloc available for drivers to use

Thu Aug 16 10:42:59 UTC 2018

On Thu, Aug 16, 2018 at 12:25 PM, Liviu Dudau <liviu.dudau at arm.com> wrote:
> On Wed, Aug 15, 2018 at 03:40:17PM +0200, Daniel Vetter wrote:
>> On Wed, Aug 15, 2018 at 2:27 PM, Alexandru-Cosmin Gheorghe
>> <Alexandru-Cosmin.Gheorghe at arm.com> wrote:
>> > On Wed, Aug 15, 2018 at 01:54:12PM +0200, Daniel Vetter wrote:
>> >> On Wed, Aug 15, 2018 at 12:08:38PM +0100, Liviu Dudau wrote:
>> >> > On Thu, Jul 26, 2018 at 03:10:04PM +0100, Alexandru Gheorghe wrote:
>> >> > > Some drivers can't use drm_gem_fb_create, so instead of copying the
>> >> > > logic that does the framebuffer allocation allow them to use core
>> >> > > drm_gem_fb_alloc.
>> >> > >
>> >> > > Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe at arm.com>
>> >> >
>> >> > To me it looks like an useful thing to have exported, so for what is worth:
>> >> >
>> >> > Acked-by: Liviu Dudau <liviu.dudau at arm.com>
>> >> >
>> >> > Sean, Maarten, Laurent, Gustavo, Daniel(s), do you have any objections?
>> >>
>> >> In general please add meaningful kernel-doc for exported functions,
>> >> explaing what's different and how it works together.
>> >>
>> >> Wrt the specific issue, I think we should teach drm core and helpers how
>> >> to allocate formats with tiled blocks. Means we need to extend
>> >> drm_format_info a bit. Your YUV formats won't be the only ones where the
>> >> format itself arranges pixels in blocks, and hence has format-based
>> >> alignment criteria for pitch and size (due to line rounding).
>> >
>> > Something like a tile_size or do you have other ideas ?
>> > Any idea if there are any tile formats out there where the tile it's
>> > not a square ?
>>
>> I think both tile_w/_h in pixels and tile_size in bytes is what you
>> want for full description of all options. And yes I think some of the
>> compressed GL formats aren't square. Not that I expect we'll ever have
>> to scan those out, but who knows. This would also allow drivers to let
>> the core check basic tiled layouts by supplying that information for a
>> (fourcc, modifier) pair.
>>
>> The tricky part is then how you expect stride to be set, since that's
>> in bytes per line, which might not align. But since all the tiles I've
>> seen are power-of-two in height, shouldn't be an issue in practice. A
>> check + WARN_ON would be good though.
>
> Another option would be to add to the drm_framebuffer_funcs structure a
> hook that drivers could implement that does the validation of the fb and
> could be used to bypass the more strict check in drm_gem_fb_create_fb_with_funcs()

Can't call an fb operation if you don't yet have an fb :-)
-Daniel

>
> Best regards,
> Liviu
>
>> -Daniel
>>
>> >> I think this would also fit better into the overall design where drivers
>> >> can overwrite the drm_format_info for specific (fourcc, modifier)
>> >> combinations.
>> >> -Daniel
>> >>
>> >>
>> >> >
>> >> > Best regards,
>> >> > Liviu
>> >> >
>> >> > > ---
>> >> > >  drivers/gpu/drm/drm_gem_framebuffer_helper.c | 3 ++-
>> >> > >  include/drm/drm_gem_framebuffer_helper.h     | 5 +++++
>> >> > >  2 files changed, 7 insertions(+), 1 deletion(-)
>> >> > >
>> >> > > diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
>> >> > > index 2810d4131411..64eddf5a1bd9 100644
>> >> > > --- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
>> >> > > +++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
>> >> > > @@ -57,7 +57,7 @@ struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
>> >> > >  }
>> >> > >  EXPORT_SYMBOL_GPL(drm_gem_fb_get_obj);
>> >> > >
>> >> > > -static struct drm_framebuffer *
>> >> > > +struct drm_framebuffer *
>> >> > >  drm_gem_fb_alloc(struct drm_device *dev,
>> >> > >            const struct drm_mode_fb_cmd2 *mode_cmd,
>> >> > >            struct drm_gem_object **obj, unsigned int num_planes,
>> >> > > @@ -85,6 +85,7 @@ drm_gem_fb_alloc(struct drm_device *dev,
>> >> > >
>> >> > >   return fb;
>> >> > >  }
>> >> > > +EXPORT_SYMBOL_GPL(drm_gem_fb_alloc);
>> >> > >
>> >> > >  /**
>> >> > >   * drm_gem_fb_destroy - Free GEM backed framebuffer
>> >> > > diff --git a/include/drm/drm_gem_framebuffer_helper.h b/include/drm/drm_gem_framebuffer_helper.h
>> >> > > index a38de7eb55b4..d20c1356000a 100644
>> >> > > --- a/include/drm/drm_gem_framebuffer_helper.h
>> >> > > +++ b/include/drm/drm_gem_framebuffer_helper.h
>> >> > > @@ -14,6 +14,11 @@ struct drm_simple_display_pipe;
>> >> > >
>> >> > >  struct drm_gem_object *drm_gem_fb_get_obj(struct drm_framebuffer *fb,
>> >> > >                                     unsigned int plane);
>> >> > > +struct drm_framebuffer *
>> >> > > +drm_gem_fb_alloc(struct drm_device *dev,
>> >> > > +          const struct drm_mode_fb_cmd2 *mode_cmd,
>> >> > > +          struct drm_gem_object **obj, unsigned int num_planes,
>> >> > > +          const struct drm_framebuffer_funcs *funcs);
>> >> > >  void drm_gem_fb_destroy(struct drm_framebuffer *fb);
>> >> > >  int drm_gem_fb_create_handle(struct drm_framebuffer *fb, struct drm_file *file,
>> >> > >                        unsigned int *handle);
>> >> > > --
>> >> > > 2.18.0
>> >> > >
>> >> >
>> >> > --
>> >> > ====================
>> >> > | I would like to |
>> >> > | fix the world,  |
>> >> > | but they're not |
>> >> > | giving me the   |
>> >> >  \ source code!  /
>> >> >   ---------------
>> >> >     ¯\_(ツ)_/¯
>> >>
>> >> --
>> >> Daniel Vetter
>> >> Software Engineer, Intel Corporation
>> >> http://blog.ffwll.ch
>> >
>> > --
>> > Cheers,
>> > Alex G
>>
>>
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
> --
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ¯\_(ツ)_/¯


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch