[RFC v4 1/8] drm: Add Enhanced Gamma LUT precision structure

[Shankar, Uma]

>-----Original Message-----
>From: Alexandru-Cosmin Gheorghe [mailto:Alexandru-
>Cosmin.Gheorghe at arm.com]
>Sent: Tuesday, August 21, 2018 3:00 PM
>To: Shankar, Uma <uma.shankar at intel.com>
>Cc: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org;
>dcastagna at chromium.org; emil.l.velikov at gmail.com; seanpaul at chromium.org;
>Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
><maarten.lankhorst at intel.com>; nd at arm.com
>Subject: Re: [RFC v4 1/8] drm: Add Enhanced Gamma LUT precision structure
>
>Hi Uma,
>
>On Fri, Aug 17, 2018 at 07:48:44PM +0530, Uma Shankar wrote:
>> Existing LUT precision structure is having only 16 bit precision. This
>> is not enough for upcoming enhanced hardwares and advance usecases
>> like HDR processing. Hence added a new structure with 32 bit precision
>> values. Also added the code, for extracting the same from values
>> passed from userspace.
>>
>> v4: Rebase
>>
>> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>> ---
>>  drivers/gpu/drm/drm_plane.c | 19 +++++++++++++++++++
>> include/uapi/drm/drm_mode.h | 15 +++++++++++++++
>>  2 files changed, 34 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
>> index 6153cbd..cd71fd0 100644
>> --- a/drivers/gpu/drm/drm_plane.c
>> +++ b/drivers/gpu/drm/drm_plane.c
>> @@ -430,6 +430,25 @@ void drm_plane_force_disable(struct drm_plane
>> *plane)  }  EXPORT_SYMBOL(drm_plane_force_disable);
>>
>> +/*
>> + * Added to accommodate enhanced LUT precision.
>> + * Max LUT precision is 32 bits.
>> + */
>> +uint32_t drm_color_lut_extract_ext(uint32_t user_input, uint32_t
>> +bit_precision)
>
>You should declare this function in a header file as well.

Thanks Alexandru for the review. Sure, will fix that and resend.

>With that fixed
>Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe at arm.com>
>
>
>> +{
>> +	uint32_t val = user_input;
>> +	uint32_t max = 0xffffffff >> (32 - bit_precision);
>> +
>> +	/* Round only if we're not using full precision. */
>> +	if (bit_precision < 32) {
>> +		val += 1UL << (32 - bit_precision - 1);
>> +		val >>= 32 - bit_precision;
>> +	}
>> +
>> +	return clamp_val(val, 0, max);
>> +}
>> +EXPORT_SYMBOL(drm_color_lut_extract_ext);
>> +
>>  /**
>>   * drm_mode_plane_set_obj_prop - set the value of a property
>>   * @plane: drm plane object to set property value for diff --git
>> a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h index
>> 8d67243..874407b 100644
>> --- a/include/uapi/drm/drm_mode.h
>> +++ b/include/uapi/drm/drm_mode.h
>> @@ -629,6 +629,21 @@ struct drm_color_lut {
>>  	__u16 reserved;
>>  };
>>
>> +/*
>> + * Creating 32 bit palette entries for better data
>> + * precision. This will be required for HDR and
>> + * similar color processing usecases.
>> + */
>> +struct drm_color_lut_ext {
>> +	/*
>> +	 * Data is U0.32 fixed point format.
>> +	 */
>> +	__u32 red;
>> +	__u32 green;
>> +	__u32 blue;
>> +	__u32 reserved;
>> +};
>> +
>>  #define DRM_MODE_PAGE_FLIP_EVENT 0x01  #define
>> DRM_MODE_PAGE_FLIP_ASYNC 0x02  #define
>> DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
>> --
>> 1.9.1
>>
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>
>--
>Cheers,
>Alex G