[FFmpeg-devel] [PATCH v2 1/2] lavu: Add DRM hwcontext

[wm4]

On Thu, 6 Jul 2017 00:02:08 +0100
Mark Thompson <sw at jkqxz.net> wrote:

> ---
> Updated following discussion:
> * Back to using nested arrays.
> * Documentation improved.
> * Configure option now called libdrm.
> * Other minor fixups.
> 
> 
>  configure                      |   3 +
>  libavutil/Makefile             |   2 +
>  libavutil/hwcontext.c          |   4 +
>  libavutil/hwcontext.h          |   1 +
>  libavutil/hwcontext_drm.c      | 294 +++++++++++++++++++++++++++++++++++++++++
>  libavutil/hwcontext_drm.h      | 166 +++++++++++++++++++++++
>  libavutil/hwcontext_internal.h |   1 +
>  libavutil/pixdesc.c            |   4 +
>  libavutil/pixfmt.h             |   4 +
>  9 files changed, 479 insertions(+)
>  create mode 100644 libavutil/hwcontext_drm.c
>  create mode 100644 libavutil/hwcontext_drm.h

Generally LGTM, though I don't know when LongChair can try it.

> +#include <fcntl.h>
> +#include <sys/mman.h>
> +#if HAVE_UNISTD_H
> +#   include <unistd.h>
> +#endif

Is there really going to be a system that has fcntl.h and sys/mman.h,
but not unistd.h? This code is going to work on POSIX only anyway,
which requires this header.

> +typedef struct AVDRMObjectDescriptor {
> +    /**
> +     * DRM PRIME fd for the object.
> +     */
> +    int fd;
> +    /**
> +     * Total size of the object.
> +     *
> +     * (This includes any parts not which do not contain image data.)
> +     */
> +    size_t size;
> +    /**
> +     * Format modifier applied to the object (DRM_FORMAT_MOD_*).
> +     */
> +    uint64_t format_modifier;
> +} AVDRMObjectDescriptor;

So I guess this thing really is worth the trouble, but I still don't
entirely understand it. Why is the size needed, and what do the
format_modifiers do?