From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FCDEC31E59 for ; Mon, 17 Jun 2019 13:01:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 31EC22089E for ; Mon, 17 Jun 2019 13:01:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727958AbfFQNBz (ORCPT ); Mon, 17 Jun 2019 09:01:55 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:45909 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725983AbfFQNBz (ORCPT ); Mon, 17 Jun 2019 09:01:55 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id E7E9680258; Mon, 17 Jun 2019 15:01:40 +0200 (CEST) Date: Mon, 17 Jun 2019 15:01:51 +0200 From: Pavel Machek To: Matthias Kaehlcke Cc: Daniel Thompson , Brian Norris , Enric Balletbo i Serra , Doug Anderson , Rob Herring , Jingoo Han , Richard Purdie , Jacek Anaszewski , Guenter Roeck , Lee Jones , Alexandru Stan , linux-leds@vger.kernel.org, devicetree , Linux Kernel , kernel@collabora.com Subject: Re: [PATCH v3 3/4] backlight: pwm_bl: compute brightness of LED linearly to human eye. Message-ID: <20190617130150.GA21113@amd> References: <20180208113032.27810-1-enric.balletbo@collabora.com> <20180208113032.27810-4-enric.balletbo@collabora.com> <20190607220947.GR40515@google.com> <20190608210226.GB2359@xo-6d-61-c0.localdomain> <20190610205233.GB137143@google.com> <20190611104913.egsbwcedshjdy3m5@holly.lan> <20190611223019.GH137143@google.com> <20190612110325.xdn3q2aod52oalge@holly.lan> <20190612192642.GK137143@google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="sdtB3X0nJg68CQEu" Content-Disposition: inline In-Reply-To: <20190612192642.GK137143@google.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --sdtB3X0nJg68CQEu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > Certainly "linear" (this device will work more or less correctly if the > > userspace applies perceptual curves). Not sure about logarithmic since > > what is actually useful is something that is "perceptually linear" > > (logarithmic is merely a way to approximate that). > >=20 > > I do wonder about a compatible string like most-detailed to > > least-detailed description. This for a PWM with the auto-generated > > tables we'd see something like: > >=20 > > cie-1991,perceptual,non-linear > >=20 > > For something that is non-linear but we are not sure what its tables are > > we can offer just "non-linear". >=20 > Thanks for the feedback! >=20 > It seems clear that we want a string for the added flexibility. I can > work on a patch with the compatible string like description you > suggested and we can discuss in the review if we want to go with that > or prefer something else. Compatible-like string seems overly complicated. > > Instead one valid value for the sysfs should be "unknown" and this be > > the default for drivers we have not analysed (this also makes it easy to > > introduce change here). >=20 > An "unknown" value sounds good, it allows userspace to just do what it > did/would hace done before this attribute existed. What about simply not presenting the attribute when we don't have the information? Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --sdtB3X0nJg68CQEu Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl0Hjz4ACgkQMOfwapXb+vJICwCgw2oDqZxKwg0bd8+7Xh6ZsIX9 /MsAn2woctEoRe0BmsGCFOw5p1KQMS68 =vCQf -----END PGP SIGNATURE----- --sdtB3X0nJg68CQEu--