[PATCHv3 01/10] drm/crtc: Add histogram properties

[Dmitry Baryshkov]

On Mon, Dec 09, 2024 at 09:54:55PM +0530, Arun R Murthy wrote:
> Add variables for histogram drm_property, its corrsponding crtc_state
> variables and define the structure pointed by the blob property.
> 
> struct drm_histogram and drm_iet defined in include/uapi/drm/drm_mode.h
> 
> The property HISTOGRAM_ENABLE allows user to enable/disable the
> histogram feature in the hardware. Upon KMD enabling by writing to the
> hardware registers, a histogram is generated. Histogram is composed of
> 'n' bins with each bin being an integer(pixel count).

Is it really a count of pixels that fall into one of the bins?

> An event HISTOGRAM will be sent to the user. User upon recieving this
> event user can read the hardware generated histogram using crtc property

Nit: here and further, it's CRTC, not crtc

> HISTOGRAM_DATA. User can use this histogram data, apply various
> equilization techniques to come up with a pixel factor. This pixel
> factor is an array of integer with 'n+1' elements. This is fed back to
> the KMD by crtc property HISTOGRAM_IET. KMD will write this IET data
> back to the hardware to see the enhancement/equilization done to the
> images on that pipe.
> The crtc property HISTOGRAM_DATA and HISTOGRAM_IET is of type blob.
> 
> For crtc property HISTOGRAM_DATA,
> the blob data pointer will be the address of the struct drm_histogram.
> struct drm_histogram {
> 	u64 data_ptr;
> 	u32 nr_elements;
> }
> Histogram is composed of @nr_elements of bins with each bin being an
> integer value, referred to as pixel_count.
> The element @data_ptr holds the address of histogam.
> Sample:
> Historgram[0] = 2050717
> Historgram[1] = 244619
> Historgram[2] = 173368
> ....
> Historgram[31] = 21631
> 
> For crtc_property HISTOGRAM_IET,
> the blob data pointer will be the address of the struct drm_iet.
> struct drm_iet {
> 	u64 data_ptr;
> 	u32 nr_elements;
> }
> ImageEnhancemenT(IET) is composed of @nr_elements of bins with each bin
> being an integer value, referred to as pixel factor.

What are pixel factors? How are they supposed to be used? You have
specified the format of the data, but one still can not implement
proper HISTOGRAM support for the VKMS.

> The element @data_ptr holds the addess of pixel factor.
> Sample:
> Pixel Factor[0] = 1023
> Pixel Factor[1] = 695
> Pixel Factor[2] = 1023
> ....
> Pixel Factor[32] = 512
> 
> Histogram is the statistics generated with 'n' number of frames on a
> pipe.
> Usually the size of pixel factor is one more than the size of histogram
> data.

What does that mean? What does it mean if this "Usually" isn't being
followed? Previously you've written that it always has n+1 elements.

> 
> Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> ---
>  include/drm/drm_crtc.h      | 51 +++++++++++++++++++++++++++++++++++++
>  include/uapi/drm/drm_mode.h | 24 +++++++++++++++++
>  2 files changed, 75 insertions(+)
> 

-- 
With best wishes
Dmitry