linux-kernel - Re: [PATCH 2/3] drm/connector: hdmi: Add support for YUV420 format verification

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Message-ID: <a00ba6bb-aa91-4ecf-a4e7-88d80e29dedc@collabora.com>
Date: Mon, 2 Dec 2024 13:15:36 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] drm/connector: hdmi: Add support for YUV420 format
 verification

Hi Maxime,

On 12/2/24 12:50 PM, Maxime Ripard wrote:
> On Sat, Nov 30, 2024 at 01:56:33AM +0200, Cristian Ciocaltea wrote:
>> Provide the necessary constraints verification in
>> sink_supports_format_bpc() in order to support handling of YUV420
>> output format.
>>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>> ---
>>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 40 +++++++++++++++++++++++--
>>  1 file changed, 37 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> index 0cbcee7e77cd8dff387044487ce28ee5748f5587..3a55881a544a519bb1254968db891c814f831a0f 100644
>> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> @@ -3,6 +3,7 @@
>>  #include <drm/drm_atomic.h>
>>  #include <drm/drm_connector.h>
>>  #include <drm/drm_edid.h>
>> +#include <drm/drm_modes.h>
>>  #include <drm/drm_print.h>
>>  
>>  #include <drm/display/drm_hdmi_helper.h>
>> @@ -114,6 +115,12 @@ sink_supports_format_bpc(const struct drm_connector *connector,
>>  		return false;
>>  	}
>>  
>> +	if (drm_mode_is_420_only(info, mode) && format != HDMI_COLORSPACE_YUV420) {
>> +		drm_dbg_kms(dev, "%s format unsupported by the sink for VIC%u.\n",
>> +			    drm_hdmi_connector_get_output_format_name(format), vic);
>> +		return false;
>> +	}
>> +
>>  	switch (format) {
>>  	case HDMI_COLORSPACE_RGB:
>>  		drm_dbg_kms(dev, "RGB Format, checking the constraints.\n");
>> @@ -144,9 +151,36 @@ sink_supports_format_bpc(const struct drm_connector *connector,
>>  		return true;
>>  
>>  	case HDMI_COLORSPACE_YUV420:
>> -		/* TODO: YUV420 is unsupported at the moment. */
>> -		drm_dbg_kms(dev, "YUV420 format isn't supported yet.\n");
>> -		return false;
>> +		drm_dbg_kms(dev, "YUV420 format, checking the constraints.\n");
>> +
>> +		if (!(info->color_formats & DRM_COLOR_FORMAT_YCBCR420)) {
>> +			drm_dbg_kms(dev, "Sink doesn't support YUV420.\n");
>> +			return false;
>> +		}
>> +
>> +		if (!drm_mode_is_420(info, mode)) {
>> +			drm_dbg_kms(dev, "Sink doesn't support YUV420 for VIC%u.\n", vic);
>> +			return false;
>> +		}
>> +
>> +		if (bpc == 10 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_30)) {
>> +			drm_dbg_kms(dev, "10 BPC but sink doesn't support Deep Color 30.\n");
>> +			return false;
>> +		}
>> +
>> +		if (bpc == 12 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_36)) {
>> +			drm_dbg_kms(dev, "12 BPC but sink doesn't support Deep Color 36.\n");
>> +			return false;
>> +		}
>> +
>> +		if (bpc == 16 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_48)) {
>> +			drm_dbg_kms(dev, "16 BPC but sink doesn't support Deep Color 48.\n");
>> +			return false;
>> +		}
>> +
>> +		drm_dbg_kms(dev, "YUV420 format supported in that configuration.\n");
>> +
>> +		return true;
> 
> We also need to check whether the source supports it or not.

I assumed the following check does already handle that:

	if (!(connector->hdmi.supported_formats & BIT(format))) {
		drm_dbg_kms(dev, "%s format unsupported by the connector.\n",

Is there anything else missing?

Thanks,
Cristian