linux-kernel - Re: [PATCH v12 13/15] drm/vkms: Create KUnit tests for YUV conversions

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Message-ID: <Zwk2RSgfV75LVLpR@louis-chauvet-laptop>
Date: Fri, 11 Oct 2024 16:29:25 +0200
From: Louis Chauvet <louis.chauvet@...tlin.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
	Melissa Wen <melissa.srw@...il.com>,
	Maaara Canal <mairacanal@...eup.net>,
	Haneen Mohammed <hamohammed.sa@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Jonathan Corbet <corbet@....net>,
	Simona Vetter <simona@...ll.ch>, rdunlap@...radead.org,
	arthurgrillo@...eup.net, pekka.paalanen@...oniitty.fi,
	Simona Vetter <simona.vetter@...ll.ch>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, thomas.petazzoni@...tlin.com,
	jeremie.dautheribes@...tlin.com, miquel.raynal@...tlin.com,
	seanpaul@...gle.com, marcheu@...gle.com, nicolejadeyee@...gle.com,
	Pekka Paalanen <pekka.paalanen@...labora.com>
Subject: Re: [PATCH v12 13/15] drm/vkms: Create KUnit tests for YUV
 conversions

On 11/10/24 - 12:49, Maxime Ripard wrote:
> On Tue, Oct 08, 2024 at 11:23:22AM GMT, Louis Chauvet wrote:
> > 
> > Hi, 
> > 
> > > > + * The YUV color representation were acquired via the colour python framework.
> > > > + * Below are the function calls used for generating each case.
> > > > + *
> > > > + * For more information got to the docs:
> > > > + * https://colour.readthedocs.io/en/master/generated/colour.RGB_to_YCbCr.html
> > > > + */
> > > > +static struct yuv_u8_to_argb_u16_case yuv_u8_to_argb_u16_cases[] = {
> > > > +	/*
> > > > +	 * colour.RGB_to_YCbCr(<rgb color in 16 bit form>,
> > > > +	 *                     K=colour.WEIGHTS_YCBCR["ITU-R BT.601"],
> > > > +	 *                     in_bits = 16,
> > > > +	 *                     in_legal = False,
> > > > +	 *                     in_int = True,
> > > > +	 *                     out_bits = 8,
> > > > +	 *                     out_legal = False,
> > > > +	 *                     out_int = True)
> > > > +	 */
> > > 
> > > We should really detail what the intent and expected outcome is supposed
> > > to be here. Relying on a third-party python library call for
> > > documentation isn't great.
> >
> > This was requested by Pekka in the [v2] of this series.
> 
> Ok.
> 
> > I can add something like this before each tests, but I think having the 
> > exact python code used may help people to understand what should be the 
> > behavior, and refering to the python code to understand the conversion.
> 
> Help, sure. Be the *only* documentation, absolutely not.
> 
> Let's turn this around. You run kunit, one of these tests fail:
> 
>  - It adds cognitive load to try to identify and make sense of an
>    unknown lib.
> 
>  - How can we check that the arguments you provided there are the one
>    you actually wanted to provide, and you didn't make a typo?
> 
> > I can add something like this before each tests to clarify the tested 
> > case:
> > 
> > 	Test cases for conversion between YUV BT601 limited range and 
> > 	RGB using the ITU-R BT.601 weights.
> > 
> > Or maybe just documenting the structure yuv_u8_to_argb_u16_case:
> > 
> > 	@encoding: Encoding used to convert RGB to YUV
> > 	@range: Range used to convert RGB to YUV
> > 	@n_colors: Count of test colors in this case
> > 	@format_pair.name: Name used for this color conversion, used to 
> > 			   clarify the test results
> > 	@format_pair.rgb: RGB color tested
> > 	@format_pair.yuv: Same color as @format_pair.rgb, but converted to 
> > 			  YUV using @encoding and @range.
> > 
> > What do you think?
> 
> That it's welcome, but it still doesn't allow to figure out what your
> intent was with this test 2 years from now.

I don't really understand what you want to add. Can you explain what you 
expect here? Did you mean you want a description like this above the test 
function?

/*
 * vkms_format_test_yuv_u8_to_argb_u16 - Testing the conversion between YUV
 * colors to ARGB colors in VKMS
 *
 * This test will use the functions get_conversion_matrix_to_argb_u16 and
 * argb_u16_from_yuv888 to convert YUV colors (stored in
 * yuv_u8_to_argb_u16_cases) into ARGB colors.
 *
 * As there is a different range between YUV input (8 bits) and RGB output (16
 * bits), the values are not checked exactly but ensured that they are within
 * the uncertainty range.
 */

Thanks,
Louis Chauvet

> Maxime