Re: [RFC PATCH] drm: Add new fb flags to pass interlaced alternate field

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Sep 24, 2018 at 06:54:02PM +0000, Satish Kumar Nagireddy wrote:
> This patch adds two new framebuffer flags, so that application can
> communicate alternate interlaced field information to DRM.
> 
> This patch also modifies the validation of framebuffer flags in DRM
> core framework. This is to ensure that application is setting the
> right framebuffer flags.
> 
> Signed-off-by: Satish Kumar Nagireddy <satish.nagireddy.nagireddy@xilinx.com>

Yeah as a draft this seems more reasonable. What we now need is fleshing
out the full stack:
- Full kernel-side implementation, including driver code.
- igt testcase to validate all the corner-cases, e.g. how exactly does
  this interact with FB_INTERLACED? What happens if the client fails to
  supply the next field?
- Userspace compositor/app driving this. See

	https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements

  for full details.

Cheers, Daniel

> ---
>  drivers/gpu/drm/drm_framebuffer.c | 3 ++-
>  include/uapi/drm/drm_mode.h       | 2 ++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 28a0108..d330256 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -241,7 +241,8 @@ drm_internal_framebuffer_create(struct drm_device *dev,
>         struct drm_framebuffer *fb;
>         int ret;
> 
> -       if (r->flags & ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS)) {
> +       if (r->flags & ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS |
> +               DRM_MODE_FB_ALTERNATE_TOP | DRM_MODE_FB_ALTERNATE_BOTTOM)) {
>                 DRM_DEBUG_KMS("bad framebuffer flags 0x%08x\n", r->flags);
>                 return ERR_PTR(-EINVAL);
>         }
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index ce7efe2..b857ed4 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -388,6 +388,8 @@ struct drm_mode_fb_cmd {
> 
>  #define DRM_MODE_FB_INTERLACED (1<<0) /* for interlaced framebuffers */
>  #define DRM_MODE_FB_MODIFIERS  (1<<1) /* enables ->modifer[] */
> +#define DRM_MODE_FB_ALTERNATE_TOP      (1<<2) /* for alternate top field */
> +#define DRM_MODE_FB_ALTERNATE_BOTTOM   (1<<3) /* for alternate bottom field */
> 
>  struct drm_mode_fb_cmd2 {
>         __u32 fb_id;
> --
> 2.7.4
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> dri-devel@lists.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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