Re: [PATCH 0/4] KUnit tests for RGB565 conversion

From: "José Expósito" <jose.exposito89@gmail.com>
To: David Gow <davidgow@google.com>
Cc: "Javier Martinez Canillas" <javierm@redhat.com>,
	"Daniel Latypov" <dlatypov@google.com>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"David Airlie" <airlied@linux.ie>,
	maarten.lankhorst@linux.intel.com,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Maíra Canal" <maira.canal@usp.br>,
	"Isabella Basso" <isabbasso@riseup.net>,
	magalilemes00@gmail.com, tales.aparecida@gmail.com,
	dri-devel@lists.freedesktop.org,
	"KUnit Development" <kunit-dev@googlegroups.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/4] KUnit tests for RGB565 conversion
Date: Sun, 3 Jul 2022 17:19:26 +0200	[thread overview]
Message-ID: <20220703151926.GA130430@elementary> (raw)
In-Reply-To: <CABVgOSmC6WJxMo58VH0WSD7wdLn7_TmTktm=6txrn0ECXCNJZQ@mail.gmail.com>

Hi David,

Sorry for not getting back to you sooner, I've been swamped with work
this week.

On Wed, Jun 29, 2022 at 03:27:44PM +0800, David Gow wrote:
> These look pretty good overall to me, but there is one big issue
> (which is actually with the previous series -- oops!), and a few small
> stylistic thoughts.
> 
> For the big issue: these tests don't work on big-endian systems. The
> 'swab' bit in this series reminded me to check, and sure enough, all
> of the tests fail (including the rgb332 ones).
> 
> I tested it on PowerPC with:
>  ./tools/testing/kunit/kunit.py run
> --kunitconfig=drivers/gpu/drm/tests --arch=powerpc
> --cross_compile=powerpc64-linux-gnu-
> 
> So that's something which needs to be fixed.

Oops, yes, definitely something that I need to fix!
I'll include an extra patch at the beginning of v2 fixing this bug.

> The smaller stylistic thoughts basically all revolve around the
> complexity of convert_xrgb8888_cases: there are arrays of structs with
> arrays of unions of structs (with function pointers in them). This
> isn't a problem: it's actually a lot more readable than that
> description implies, but there are other ways it could be tackled
> (which have their own tradeoffs, of course).
> 
> One possibility would be to split up the test into a separate test per
> destination format. They could reuse the convert_xrgb8888_cases array,
> and just each access a different result. You could make things even
> clearer (IMO) by replacing the results[] array with a separate, named,
> member (since you don't need to iterate over them any more), and
> remove the need to have the function pointer and swab union/members by
> just hardcoding those in the separate test functions. It'd also make
> the results a bit clearer, as each destination format would get its
> own separate set of results.
> 
> Of course, that's just an idea: I don't actually have a problem with
> the existing design either (other than the endianness issue, of
> course).

I like from your approach that the output of the tests would be easier
to understand. At the moment, if a test fails, there is not enough
context to know which target format failed. I'll explore this approach
and see how it looks like.

Thanks,
Jose

> Cheers,
> -- David