Re: [PATCH 5/5] drm/edid: Set YQ bits in the AVI infoframe according to CEA-861-F

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 12 Jan 2017, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Thu, Jan 12, 2017 at 12:13:47PM +0200, Jani Nikula wrote:
>> On Wed, 11 Jan 2017, ville.syrjala@linux.intel.com wrote:
>> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> >
>> > CEA-861-F tells us:
>> > "When transmitting any RGB colorimetry, the Source should set the
>> >  YQ-field to match the RGB Quantization Range being transmitted
>> >  (e.g., when Limited Range RGB, set YQ=0 or when Full Range RGB,
>> >  set YQ=1) and the Sink shall ignore the YQ-field."
>> >
>> > So let's go ahead and do that. Perhaps there are sinks that don't
>> > ignore the YQ as they should for RGB?
>> >
>> > I wasn't able to find similar text in CEA-861-E, so it would seem
>> > to be a fairly "recent" addition.
>> >
>> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/drm_edid.c | 14 ++++++++++++++
>> >  1 file changed, 14 insertions(+)
>> >
>> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> > index caa2435bac31..6ba9a1a6eae4 100644
>> > --- a/drivers/gpu/drm/drm_edid.c
>> > +++ b/drivers/gpu/drm/drm_edid.c
>> > @@ -4320,6 +4320,20 @@ drm_hdmi_avi_infoframe_quant_range(struct hdmi_avi_infoframe *frame,
>> >  		frame->quantization_range = rgb_quant_range;
>> >  	else
>> >  		frame->quantization_range = HDMI_QUANTIZATION_RANGE_DEFAULT;
>> > +
>> > +	/*
>> > +	 * CEA-861-F:
>> > +	 * "When transmitting any RGB colorimetry, the Source should set the
>> > +	 *  YQ-field to match the RGB Quantization Range being transmitted
>> > +	 *  (e.g., when Limited Range RGB, set YQ=0 or when Full Range RGB,
>> > +	 *  set YQ=1) and the Sink shall ignore the YQ-field."
>> > +	 */
>> 
>> *rolls eyes* but that's what the spec says.
>> 
>> > +	if (rgb_quant_range == HDMI_QUANTIZATION_RANGE_LIMITED)
>> > +		frame->ycc_quantization_range =
>> > +			HDMI_YCC_QUANTIZATION_RANGE_LIMITED;
>> > +	else
>> > +		frame->ycc_quantization_range =
>> > +			HDMI_YCC_QUANTIZATION_RANGE_FULL;
>> 
>> Shouldn't this take into account QS=0 and rgb_quant_range != default?
>
> There is no YQ setting similar to the default Q=0. YQ=0 means "limited",
> YQ=1 means "full", others values are reserved. So we can't really not
> specify the YCC quantization range. So I can't really see any better
> option than telling the truth.

Hmm, I was confused about the caller choosing the range based on the
mode already.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>



-- 
Jani Nikula, Intel Open Source Technology Center
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