> -----Original Message-----
> From: Murthy, Arun R <arun.r.mur...@intel.com>
> Sent: Tuesday, January 28, 2025 9:21 PM
> To: intel...@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; dri-
> de...@lists.freedesktop.org
> Cc: Kandpal, Suraj <suraj.kand...@intel.com>; dmitry.barysh...@linaro.org;
> Murthy, Arun R <arun.r.mur...@intel.com>
> Subject: [PATCH v8 01/14] drm: Define histogram structures exposed to user
>
> Display Histogram is an array of bins and can be generated in many ways
> referred to as modes.
> Ex: HSV max(RGB), Wighted RGB etc.
>
> Understanding the histogram data format(Ex: HSV max(RGB)) Histogram is just
> the pixel count.
> For a maximum resolution of 10k (10240 x 4320 = 44236800)
> 25 bits should be sufficient to represent this along with a buffer of 7
> bits(future
> use) u32 is being considered.
> max(RGB) can be 255 i.e 0xFF 8 bit, considering the most significant 5 bits,
> hence 32 bins.
> Below mentioned algorithm illustrates the histogram generation in hardware.
>
> hist[32] = {0};
> for (i = 0; i < resolution; i++) {
> bin = max(RGB[i]);
> bin = bin >> 3; /* consider the most significant bits */
> hist[bin]++;
> }
> If the entire image is Red color then max(255,0,0) is 255 so the pixel count
> of
> each pixels will be placed in the last bin. Hence except hist[31] all other
> bins
> will have a value zero.
> Generated histogram in this case would be hist[32] = {0,0,....44236800}
>
> Description of the structures, properties defined are documented in the header
> file include/uapi/drm/drm_mode.h
>
> v8: Added doc for HDR planes, removed reserved variables (Dmitry)
>
> Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
> ---
> include/uapi/drm/drm_mode.h | 65
> +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 65 insertions(+)
>
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index
> c082810c08a8b234ef2672ecf54fc8c05ddc2bd3..b8b7b18843ae7224263a9c61b
> 20ac6cbf5df69e9 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -1355,6 +1355,71 @@ struct drm_mode_closefb {
> __u32 pad;
> };
>
> +/**
> + * enum drm_mode_histogram
> + *
> + * @DRM_MODE_HISTOGRAM_HSV_MAX_RGB:
> + * Maximum resolution at present 10k, 10240x4320 = 44236800
> + * can be denoted in 25bits. With an additional 7 bits in buffer each
> +bin
> + * can be a u32 value.
> + * For SDL, Maximum value of max(RGB) is 255, so max 255 bins.
Type: SDR
> + * If the most significant 5 bits are considered, then bins = 2^5
> + * will be 32 bins.
> + * For HDR, maximum value of max(RGB) is 65535, so max 65535 bins.
> + * For illustration consider a full RED image of 10k resolution
> +considering all
> + * 8 bits histogram would look like hist[255] = {0,0,....44236800} with
> +SDR
> + * plane similarly with HDR the same would look like hist[65535] =
> + * {0,0,0,....44236800}
> + */
> +enum drm_mode_histogram {
> + DRM_MODE_HISTOGRAM_HSV_MAX_RGB = 0x01, };
> +
> +/**
> + * struct drm_histogram_caps
> + *
> + * @histogram_mode: histogram generation modes, defined in the
> + * enum drm_mode_histogram
> + * @bins_count: number of bins for a chosen histogram mode. For illustration
> + * refer the above defined histogram mode.
> + */
> +struct drm_histogram_caps {
> + __u32 histogram_mode;
Do we really need __u32 for histogram mode don't you think a __u16 should
suffice?
> + __u32 bins_count;
Nit: bin_count sounds better.
> +};
> +
> +/**
> + * struct drm_histogram_config
> + *
> + * @hist_mode_data: address to the histogram mode specific data if any
> + * @nr_hist_mode_data: number of elements pointed by the address in
> + * hist_mode_data
> + * @hist_mode: histogram mode(HSV max(RGB), RGB, LUMA etc)
> + * @enable: flag to enable/disable histogram */ struct
> +drm_histogram_config {
> + __u64 hist_mode_data;
> + __u32 nr_hist_mode_data;
> + enum drm_mode_histogram hist_mode;
> + bool enable;
> +};
> +
> +/**
> + * struct drm_histogram
> + *
> + * @config: histogram configuration data pointed by struct
> +drm_histogram_config
> + * @data_ptr: pointer to the array of histogram.
> + * Histogram is an array of bins. Data format for each bin depends
> + * on the histogram mode. Refer to the above histogram modes for
I think you can write the drm_histogram_mode_caps instead of writing histogram
mode
So people can directly jump to it
Regards,
Suraj Kandpal
> + * more information.
> + * @nr_elements: number of bins in the histogram.
> + */
> +struct drm_histogram {
> + struct drm_histogram_config config;
> + __u64 data_ptr;
> + __u32 nr_elements;
> +};
> +
> #if defined(__cplusplus)
> }
> #endif
>
> --
> 2.25.1
