Re: [PATCH v2 04/10] drm: Add Gamma correction structure

Matt Roper
2015-06-06T01:00:49Z

On Thu, Jun 04, 2015 at 07:12:35PM +0530, Kausal Malladi wrote:
> From: Kausal Malladi <Kausal.Malladi@intel.com>
>
> This patch adds a new structure in DRM layer for Gamma color correction.
> This structure will be used by all user space agents to configure
> appropriate Gamma precision and Gamma level.
>
> struct drm_intel_gamma {
> __u32 gamma_level;
> (The gamma_level variable indicates if the Gamma correction is to be
> applied on Pipe/plane)

I'm not sure I understand the need for this one...you're getting the
set_property call against a specific DRM object, so I don't think there
should be any confusion at that point about what the values apply to?

> __u32 gamma_precision;
> (The Gamma precision indicates the Gamma mode to be applied)
>
> Supported precisions are -
> #define I915_GAMMA_PRECISION_UNKNOWN 0
> #define I915_GAMMA_PRECISION_CURRENT 0xFFFFFFFF
> #define I915_GAMMA_PRECISION_LEGACY (1 << 0)
> #define I915_GAMMA_PRECISION_10BIT (1 << 1)
> #define I915_GAMMA_PRECISION_12BIT (1 << 2)
> #define I915_GAMMA_PRECISION_14BIT (1 << 3)
> #define I915_GAMMA_PRECISION_16BIT (1 << 4)

I feel like the precision would work better as a separate enum property
rather than being part of your blob; I think it would be cleaner if your
blob only held the actual values if possible.

>
> __u32 num_samples;
> (The num_samples indicates the number of Gamma correction
> coefficients)
> __u32 reserved;
> __u16 values[0];
> (An array of size 0, to accommodate the "num_samples" number of
> R16G16B16 pixels, dynamically)
> };
>
> v2: Addressing Daniel Stone's comment, added a variable sized array to
> carry Gamma correction values as blob property.
>
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> Signed-off-by: Kausal Malladi <Kausal.Malladi@intel.com>
> ---
> include/drm/drm_crtc.h | 3 +++
> include/uapi/drm/drm.h | 10 ++++++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 2a75d7d..bc44f27 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -483,6 +483,9 @@ struct drm_crtc {
> * acquire context.
> */
> struct drm_modeset_acquire_ctx *acquire_ctx;
> +
> + /* Color Management Blob IDs */
> + u32 gamma_blob_id;
> };
>
> /**
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 3801584..fc2661c 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -829,6 +829,16 @@ struct drm_event_vblank {
> __u32 reserved;
> };
>
> +/* Color Management structure for Gamma */
> +struct drm_gamma {
> + __u32 flags;

The flags aren't described in your commit message...what are they used
for? I guess it will become more clear as I read farther through your
patch series.

Matt

> + __u32 gamma_level;
> + __u32 gamma_precision;
> + __u32 num_samples;
> + __u32 reserved;
> + __u16 values[0];
> +};
> +
> /* typedef area */
> #ifndef __KERNEL__
> typedef struct drm_clip_rect drm_clip_rect_t;
> --
> 2.4.2
>

--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795