From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755284AbdEKVXP (ORCPT ); Thu, 11 May 2017 17:23:15 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:59545 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755018AbdEKVXN (ORCPT ); Thu, 11 May 2017 17:23:13 -0400 Date: Thu, 11 May 2017 23:23:11 +0200 From: Pavel Machek To: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Cc: Gerd Hoffmann , dri-devel@lists.freedesktop.org, Daniel Vetter , Pekka Paalanen , Ilia Mirkin , Michel =?iso-8859-1?Q?D=E4nzer?= , Alex Deucher , amd-gfx@lists.freedesktop.org, Jani Nikula , Sean Paul , David Airlie , open list Subject: Re: [PATCH] drm: fourcc byteorder: brings header file comments in line with reality. Message-ID: <20170511212311.GA6780@amd> References: <20170421075825.6307-1-kraxel@redhat.com> <20170421092530.GE30290@intel.com> <1492768218.25675.33.camel@redhat.com> <20170421110804.GH30290@intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="FL5UXtIhxfXey3p5" Content-Disposition: inline In-Reply-To: <20170421110804.GH30290@intel.com> 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 --FL5UXtIhxfXey3p5 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri 2017-04-21 14:08:04, Ville Syrj=E4l=E4 wrote: > On Fri, Apr 21, 2017 at 11:50:18AM +0200, Gerd Hoffmann wrote: > > On Fr, 2017-04-21 at 12:25 +0300, Ville Syrj=E4l=E4 wrote: > > > On Fri, Apr 21, 2017 at 09:58:24AM +0200, Gerd Hoffmann wrote: > > > > While working on graphics support for virtual machines on ppc64 (wh= ich > > > > exists in both little and big endian variants) I've figured the com= ments > > > > for various drm fourcc formats in the header file don't match reali= ty. > > > >=20 > > > > Comments says the RGB formats are little endian, but in practice th= ey > > > > are native endian. Look at the drm_mode_legacy_fb_format() helper.= It > > > > maps -- for example -- bpp/depth 32/24 to DRM_FORMAT_XRGB8888, no m= atter > > > > whenever the machine is little endian or big endian. The users of = this > > > > function (fbdev emulation, DRM_IOCTL_MODE_ADDFB) expect the framebu= ffer > > > > is native endian, not little endian. Most userspace also operates = on > > > > native endian only. > > >=20 > > > I'm not a fan of "native". Native to what? "CPU" or "host" is what I'd > > > call it. > >=20 > > native =3D=3D whatever the cpu is using. > >=20 > > I personally find "native" more intuitive, but at the end of the day I > > don't mind much. If people prefer "host" over "native" I'll change it. >=20 > "native" to me feels more like "native to the GPU" since these things > really are tied to the GPU not the CPU. That's also why I went with the > explicit endianness originally so that the driver could properly declare > what the GPU supports. You can easily have more than one GPU in the system. Plus these are used by cameras / frame grabbers, too. So anything else than CPU endianness is badly defined. (And I agree with the rest of the thread -- we should really be explicit; fourcc should specify what format the image data are in, and it should be possible to write fourcc + raw data into file and transfer it between machines.) Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --FL5UXtIhxfXey3p5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlkU1j8ACgkQMOfwapXb+vIh6wCfZjgH6oTBa6xqGIzLdV1h7Jng Y4IAnRX16sng3cEHUpZGPz7dGWIkH6oE =9SnD -----END PGP SIGNATURE----- --FL5UXtIhxfXey3p5--