linux-kernel - Re: [PATCH v2 2/7] drm/connector: hdmi: Add support for YUV420 format verification

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Message-ID: <abc73fd1-d7a3-43c7-809a-9dce5b07c3eb@collabora.com>
Date: Tue, 11 Mar 2025 19:06:43 +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>,
 Dave Stevenson <dave.stevenson@...pberrypi.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] drm/connector: hdmi: Add support for YUV420 format
 verification

On 3/11/25 5:30 PM, Maxime Ripard wrote:
> On Tue, Mar 11, 2025 at 12:57:34PM +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 6bc96d5d1ab9115989e208d9899e16cd22254fb6..e99d868edc1854eddc5ebf8692ccffb9e2338268 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_audio_helper.h>
>> @@ -115,6 +116,12 @@ 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);
> 
> We don't necessarily have a VIC for the mode we pass, so it's not super
> useful to pass it. I'd rather mention that the mode is supposed to be
> YUV420 only, but the format isn't YUV420.

Ack, I'll change the message as suggested.

>> +		return false;
>> +	}
>> +
>>  	switch (format) {
>>  	case HDMI_COLORSPACE_RGB:
>>  		drm_dbg_kms(dev, "RGB Format, checking the constraints.\n");
>> @@ -145,9 +152,36 @@ 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);
> 
> Again, we shouldn't print the VIC here. There's a printk format we can
> use to print drm_display_mode if you want to, but we should keep things
> consistent.

Agree, will proceed as above.

Thanks for the review,
Cristian