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Mon, 17 Jun 2024 18:18:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id zlhvNel9cGa4HQAAD6G6ig (envelope-from ); Mon, 17 Jun 2024 18:18:17 +0000 Date: Mon, 17 Jun 2024 20:18:14 +0200 From: Jean Delvare To: Dmitry Baryshkov Cc: Douglas Anderson , dri-devel@lists.freedesktop.org, LKML , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Andrew Morton Subject: Re: [PATCH RESEND] drm/display: Drop obsolete dependency on COMPILE_TEST Message-ID: <20240617201814.73a07702@endymion.delvare> In-Reply-To: References: <20240617103018.515f0bf1@endymion.delvare> <20240617132348.5f20bf89@endymion.delvare> Organization: SUSE Linux X-Mailer: Claws Mail 4.1.1 (GTK 3.24.34; x86_64-suse-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spam-Level: X-Spam-Flag: NO X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; HAS_ORG_HEADER(0.00)[]; FREEMAIL_CC(0.00)[chromium.org,lists.freedesktop.org,vger.kernel.org,linux.intel.com,kernel.org,suse.de,gmail.com,ffwll.ch,linux-foundation.org]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_SEVEN(0.00)[10]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[] On Mon, 17 Jun 2024 14:55:22 +0300, Dmitry Baryshkov wrote: > On Mon, Jun 17, 2024 at 01:23:48PM GMT, Jean Delvare wrote: > > 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. > > This doesn't seem to match the COMPILE_TEST usage that I observe in > other places. For example, we frequently use 'depends on ARCH_QCOM || > COMPILE_TEST'. Which means that the driver itself doesn't make sense > without ARCH_QCOM, but we want for it to be tested on non-ARCH_QCOM > cases. I think the same logic applies to 'depends on OF || > COMPILE_TEST' clauses. The driver (DP AUX bus) depends on OF to be fully > functional, but it should be compilable even without OF case. The major difference is that one can't possibly enable ARCH_QCOM if building on X86 for example. Therefore COMPILE_TEST is the only way to let everyone (including randconfig/allmodconfig build farms) test-build your code. On the other hand, if you want to test-build drm_dp_aux_bus, you can simply enable OF, because it is available on all architectures and doesn't depend on anything. No need for COMPILE_TEST. For clarity, I'm not advocating against the use of COMPILE_TEST, actually if you check the history of my kernel contributions 10 years back, you'll find commits from me adding COMPILE_TEST in addition to arch-specific dependencies to many drivers. All I'm saying is that it should only be used when it is the only way to enable the build. -- Jean Delvare SUSE L3 Support