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Wed, 28 Jan 2026 02:42:24 -0800 (PST) Date: Wed, 28 Jan 2026 11:42:24 +0100 From: Maxime Ripard To: Linus Torvalds Cc: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Wilczynski , Richard Genoud Subject: Re: [GIT PULL] pwm: Two fixes and a maintainer update Message-ID: <20260128-splendid-complex-mouflon-8f3dff@houat> References: <20260122-bold-sticky-wapiti-1dffa2@houat> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="feuizyhgjj4dalgk" Content-Disposition: inline In-Reply-To: --feuizyhgjj4dalgk Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [GIT PULL] pwm: Two fixes and a maintainer update MIME-Version: 1.0 Hi, On Thu, Jan 22, 2026 at 10:07:56AM -0800, Linus Torvalds wrote: > On Thu, 22 Jan 2026 at 06:39, Maxime Ripard wrote: > > > > > > > > Obviously some changes are more likely to be user-visible than others, > > > so people should take that into account in how careful you need to be > > > about a patch. > > > > Where do we draw the line then, if there's any? >=20 > Users complaining is the only real line in the end. >=20 > So something like a test-suite complaining is then often a *very* good > indication that maybe users will hit some problem, and test suite > issues should be taken very seriously just because they might be the > first sign of upcoming trouble, and the earlier something is caught > and fixed, the easier it's going to be. >=20 > But a test-suite error isn't necessarily where you have to draw the > line - it's a big red flag, but it *could* be something like "the > error checking was done in a different order, and the error number > changed in some situations, but it doesn't actually change behavior > except for the error message that is printed". >=20 > So then a test suite failure is a "let's ignore it, but keep an eye on > it in case some program really did care about that *particular* error > number". >=20 > But a user complaining should basically result in an immediate fix - > possibly a "revert and rethink". >=20 > So a user complaining about some kernel change breaking their flow is > when you don't even start arguing. The issue is over and done, and the > change needs to be undone. >=20 > There are _very_ few exceptions to that rule, the main one being "the > problem was a fundamental huge and gaping security issue and we *had* > to make that change, and we couldn't even make your limited use-case > just continue to work". >=20 > The other exception is "the problem was reported years after it was > introduced, and now most people rely on the new behavior". >=20 > But starting to argue about users reporting breaking changes is > basically the final line for me. I have a couple of people that I have > in my spam block-list and refuse to have anything to do with, and they > have generally been about exactly that. >=20 > Note how it's not about making mistakes and _causing_ the regression. > That's normal. That's development. But then arguing about it is a > no-no. >=20 > So in the kernel tree, we don't argue about regressions. We fix them. > That's basically the only really hard rule I have. >=20 > Almost everything else is "just explain it, we have various rules for > development, but rules are meant to be broken". Not the user-reported > regression one. > > > Should we just consider those drivers "wrong", treat it as a bugfix, and > > expect userspace applications to request the format they actually rely > > on? Or should we continue what we've tried to do and try to support the > > right format, and the old format for backward compatibility? >=20 > If it used to work, and people relied on it, you add a new "right" > format, and keep the old one around. Possibly with some hack to only > affect some particular special case, with the hope that the special > case and hack can be removed. >=20 > Now, if it's one or two users and you can just get them to recompile, > that's one thing. Niche hardware and odd use-cases can sometimes be > solved that way, and regressions can sometimes be fixed by handholding > every single reporter if the reporter is willing and able to change > his or her workflow. >=20 > But the basic rule is: be so good about backwards compatibility that > users never have to worry about upgrading. They should absolutely feel > confident that any kernel-reported problem will either be solved, or > have an easy solution that is appropriate for *them* (ie a > non-technical user shouldn't be expected to be able to do a lot). >=20 > Because the last thing we want is people holding back from trying new > kernels. Ack, thanks a lot for your answer. We'll keep working on backward-compatible version then :) Maxime --feuizyhgjj4dalgk Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCaXnoCwAKCRAnX84Zoj2+ dgWpAX4qRYZrIRntzPOrPSpAw7kAd/ZPYumEXm6uqC5hdPmy/O/Kh5wKnocu5aVV TG8AL5oBfR1DX7rI0Hp9bUCb5ckCVjTV6Veup+ifBDa+ZrNV2jmqssNd42SyP+Yq TSB4QDDyEg== =j21N -----END PGP SIGNATURE----- --feuizyhgjj4dalgk--