[FFmpeg-devel] [PATCH v2 3/3] hwcontext_vaapi: #if guard VAAPI_DRM specifics

[Emil Velikov]

On Thu, 21 Jul 2022 at 22:06, Mark Thompson <sw at jkqxz.net> wrote:
>
> On 20/07/2022 11:56, Emil Velikov wrote:
> > From: Emil Velikov <emil.velikov at collabora.com>
> >
> > Similar to the VAAPI_X11 bits, guard all the VAAPI_DRM parts behind a
> > compiler guard.
> >
> > Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> > ---
> >   libavutil/hwcontext_vaapi.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/libavutil/hwcontext_vaapi.c b/libavutil/hwcontext_vaapi.c
> > index 7734a50fc0..7aea3e7b96 100644
> > --- a/libavutil/hwcontext_vaapi.c
> > +++ b/libavutil/hwcontext_vaapi.c
> > @@ -18,6 +18,10 @@
> >
> >   #include "config.h"
> >
> > +#if !HAVE_VAAPI_X11 && !HAVE_VAAPI_DRM
> > +#error "At least one VAAPI winsys is required X11 or DRM"
>
> No it isn't.
>
> Originally there wasn't a possibility to link with any winsys here - libavcodec users had to get the device themselves and pass it in.
>
> The winsys link was added to the ffmpeg utility initially for command-line use and then moved to libavutil when it was clear that it would be useful to other library users; there isn't any requirement to use it, though.  (E.g. disable it and note that programs handling the winsys themselves like mpv and vlc still work perfectly well.)
>

Assuming I'm reading the code correctly, currently when both are
undefined vaapi_device_create() will be basically a dummy, doing some
basic malloc + opts parsing and erroring out.

So as-is functions like av_hwdevice_ctx_alloc() will return success,
although as av_hwdevice_ctx_create() is called later on it will always
fail.
My aim was to effectively omit the HWContextType vaapi instance in the
final libavutil, since it cannot work. Perhaps there's a better way to
achieve that?

In either case, I will drop that check for now.

Thank you o/
Emil