linux-kernel - Re: [PATCH RESEND] drm/display: Drop obsolete dependency on COMPILE

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Message-ID: <20240617132348.5f20bf89@endymion.delvare>
Date: Mon, 17 Jun 2024 13:23:48 +0200
From: Jean Delvare <jdelvare@...e.de>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, LKML <linux-kernel@...r.kernel.org>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Andrew Morton
 <akpm@...ux-foundation.org>
Subject: Re: [PATCH RESEND] drm/display: Drop obsolete dependency on
 COMPILE_TEST

Hi Dmitry,

Thanks for your feedback.

On Mon, 17 Jun 2024 12:57:19 +0300, Dmitry Baryshkov wrote:
> On Mon, Jun 17, 2024 at 10:30:30AM GMT, Jean Delvare wrote:
> > Since commit 0166dc11be91 ("of: make CONFIG_OF user selectable"), it
> > is possible to test-build any driver which depends on OF on any
> > architecture by explicitly selecting OF. Therefore depending on
> > COMPILE_TEST as an alternative is no longer needed.  
> 
> The goal of this clause is to allow build-testing the driver with OF
> being disabled (meaning that some of OF functions are stubbed and some
> might disappear). I don't see how user-selectable OF provides the same
> result.

Historically, the goal of this clause *was* to allow build-testing the
driver on architectures which did not support OF, and that did make
sense back then. As I understand it, building the driver without OF
support was never a goal per se (if it was, then the driver wouldn't be
set to depend on OF in the first place).

Some of my other submissions include the following explanation which
you might find useful (I ended up stripping it on resubmission after
being told I was being too verbose, but maybe it was needed after all):

It is actually better to always build such drivers with OF enabled,
so that the test builds are closer to how each driver will actually be
built on its intended target. Building them without OF may not test
much as the compiler will optimize out potentially large parts of the
code. In the worst case, this could even pop false positive warnings.
Dropping COMPILE_TEST here improves the quality of our testing and
avoids wasting time on non-existent issues.

-- 
Jean Delvare
SUSE L3 Support