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

[Maxime Ripard]

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.

Maxime

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