Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933152AbdDGMyv (ORCPT ); Fri, 7 Apr 2017 08:54:51 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:33141 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753282AbdDGMyo (ORCPT ); Fri, 7 Apr 2017 08:54:44 -0400 Date: Fri, 7 Apr 2017 14:54:40 +0200 From: Pavel Machek To: Jacek Anaszewski Cc: Bjorn Andersson , Rob Herring , Richard Purdie , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org, linux-arm-msm@vger.kernel.org, Mark Rutland , devicetree@vger.kernel.org Subject: Re: [PATCH 1/2] leds: Add driver for Qualcomm LPG Message-ID: <20170407125440.GD4756@amd> References: <20170323055435.29197-1-bjorn.andersson@linaro.org> <20170323203749.GB8563@amd> <20170329021734.afhqmfpmbcjyv7bu@rob-hp-laptop> <20170329190725.GN20094@minitux> <20170329222301.GB7977@amd> <20170330000955.GP20094@minitux> <20170330074309.GA28533@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="EP0wieDxd4TSJjHq" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1657 Lines: 51 --EP0wieDxd4TSJjHq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > Second, there are more issues than just patterns with the RGB > > LED. Most important is ability to set particular colors. You want to > > set the RGB LED to "white", but that does not mean you can set > > red=3Dgreen=3Dblue=3D1.0. You want color to look the same on LCD and on= the > > LED, which means coefficients for white and some kind of function for > > brightness-to-PWM conversion. >=20 > Shouldn't we leave that entirely to the userspace? Can we come up > with coefficients that will guarantee the same result on all existing > LCD devices? I don't think we should. We want (red =3D 70%, green =3D 80%, blue =3D 20%) to look approximately the same on all the hardware. That's currently not the case; even (red =3D green =3D blue =3D 100%) is not white. I believe easiest solution is "the kernel does the work", as it does for LCD screens. [Now... as long as userspace has enough information to display white and specific colors, I don't care much -- having kernel present coefficients for userspace would work, too.] Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --EP0wieDxd4TSJjHq Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAljnjBAACgkQMOfwapXb+vIsPwCaAuSwGfzfcVoXSxU/XgiNB0gs sPkAn1HXmiqsDLIGCLDlb9+jgz+FuLYE =paYp -----END PGP SIGNATURE----- --EP0wieDxd4TSJjHq--