linux-kernel - Re: [PATCH v4 23/23] drm/tests: hdmi: Add test for unsupported RGB/YUV420 mode

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Message-ID: <a37b4045-0d94-4148-bb1e-fc08104e6173@collabora.com>
Date: Mon, 19 May 2025 13:55:10 +0300
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@....qualcomm.com>,
 Dmitry Baryshkov <lumag@...nel.org>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 23/23] drm/tests: hdmi: Add test for unsupported
 RGB/YUV420 mode

On 5/19/25 11:42 AM, Maxime Ripard wrote:
> Hi,
> 
> On Fri, Apr 25, 2025 at 01:27:14PM +0300, Cristian Ciocaltea wrote:
>> Provide a test to verify that if both driver and screen support RGB and
>> YUV420 formats, drm_atomic_helper_connector_hdmi_check() cannot succeed
>> when trying to set a mode unsupported by the display.
>>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>> ---
>>  drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 66 ++++++++++++++++++++++
>>  1 file changed, 66 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
>> index d79084cfb516b69c4244098c0767d604ad02f2c3..6337a1c52b86810c638f446c4995e7ee63dbc084 100644
>> --- a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
>> +++ b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
>> @@ -1622,6 +1622,71 @@ static void drm_test_check_driver_unsupported_fallback_yuv420(struct kunit *test
>>  	drm_modeset_acquire_fini(&ctx);
>>  }
>>  
>> +/*
>> + * Test that if a driver and screen supports RGB and YUV420 formats, but the
>> + * chosen mode cannot be supported by the screen, we end up with unsuccessful
>> + * fallback attempts.
>> + */
>> +static void drm_test_check_display_unsupported_fallback_rgb_yuv420(struct kunit *test)
>> +{
>> +	struct drm_atomic_helper_connector_hdmi_priv *priv;
>> +	struct drm_modeset_acquire_ctx ctx;
>> +	struct drm_crtc_state *crtc_state;
>> +	struct drm_atomic_state *state;
>> +	struct drm_display_info *info;
>> +	struct drm_display_mode *preferred, *unsupported_mode;
>> +	struct drm_connector *conn;
>> +	struct drm_device *drm;
>> +	struct drm_crtc *crtc;
>> +	int ret;
>> +
>> +	priv = drm_kunit_helper_connector_hdmi_init_with_edid_funcs(test,
>> +				BIT(HDMI_COLORSPACE_RGB) |
>> +				BIT(HDMI_COLORSPACE_YUV420),
>> +				10,
>> +				&dummy_connector_hdmi_funcs,
>> +				test_edid_hdmi_4k_rgb_yuv420_dc_max_340mhz);
>> +	KUNIT_ASSERT_NOT_NULL(test, priv);
>> +
>> +	drm = &priv->drm;
>> +	crtc = priv->crtc;
>> +	conn = &priv->connector;
>> +	info = &conn->display_info;
>> +	KUNIT_ASSERT_TRUE(test, info->is_hdmi);
>> +	KUNIT_ASSERT_TRUE(test, conn->ycbcr_420_allowed);
>> +
>> +	preferred = find_preferred_mode(conn);
>> +	KUNIT_ASSERT_NOT_NULL(test, preferred);
>> +
>> +	unsupported_mode = drm_kunit_display_mode_from_cea_vic(test, drm, 96);
>> +	KUNIT_ASSERT_NOT_NULL(test, unsupported_mode);
> 
> I'm not sure what this one is supposed to test. If the mode is
> unsupported by the screen, it will be for both YUV and RGB, right? So
> what are we testing here?

That would be the case suggested at [1]:

"We still need to do the same with a driver that supports both, but the
monitor doesn't."

Should we drop it?

[1] https://lore.kernel.org/all/20250410-singing-scarlet-carp-d136f9@houat/