From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: [PATCH] drm: fourcc byteorder: brings header file comments in line with reality. Date: Fri, 21 Apr 2017 14:49:13 +0300 Message-ID: <20170421114913.GK30290@intel.com> References: <20170421075825.6307-1-kraxel@redhat.com> <20170421092530.GE30290@intel.com> <1492768218.25675.33.camel@redhat.com> <20170421110804.GH30290@intel.com> <20170421144018.411861d6@eldfell> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20170421144018.411861d6@eldfell> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Pekka Paalanen Cc: amd-gfx@lists.freedesktop.org, Michel =?iso-8859-1?Q?D=E4nzer?= , open list , dri-devel@lists.freedesktop.org, Gerd Hoffmann , Daniel Vetter List-Id: amd-gfx.lists.freedesktop.org T24gRnJpLCBBcHIgMjEsIDIwMTcgYXQgMDI6NDA6MThQTSArMDMwMCwgUGVra2EgUGFhbGFuZW4g d3JvdGU6Cj4gT24gRnJpLCAyMSBBcHIgMjAxNyAxNDowODowNCArMDMwMAo+IFZpbGxlIFN5cmrD pGzDpCA8dmlsbGUuc3lyamFsYUBsaW51eC5pbnRlbC5jb20+IHdyb3RlOgo+IAo+ID4gT24gRnJp LCBBcHIgMjEsIDIwMTcgYXQgMTE6NTA6MThBTSArMDIwMCwgR2VyZCBIb2ZmbWFubiB3cm90ZToK PiA+ID4gT24gRnIsIDIwMTctMDQtMjEgYXQgMTI6MjUgKzAzMDAsIFZpbGxlIFN5cmrDpGzDpCB3 cm90ZTogIAo+ID4gPiA+IE9uIEZyaSwgQXByIDIxLCAyMDE3IGF0IDA5OjU4OjI0QU0gKzAyMDAs IEdlcmQgSG9mZm1hbm4gd3JvdGU6ICAKPiA+ID4gPiA+IFdoaWxlIHdvcmtpbmcgb24gZ3JhcGhp Y3Mgc3VwcG9ydCBmb3IgdmlydHVhbCBtYWNoaW5lcyBvbiBwcGM2NCAod2hpY2gKPiA+ID4gPiA+ IGV4aXN0cyBpbiBib3RoIGxpdHRsZSBhbmQgYmlnIGVuZGlhbiB2YXJpYW50cykgSSd2ZSBmaWd1 cmVkIHRoZSBjb21tZW50cwo+ID4gPiA+ID4gZm9yIHZhcmlvdXMgZHJtIGZvdXJjYyBmb3JtYXRz IGluIHRoZSBoZWFkZXIgZmlsZSBkb24ndCBtYXRjaCByZWFsaXR5Lgo+ID4gPiA+ID4gCj4gPiA+ ID4gPiBDb21tZW50cyBzYXlzIHRoZSBSR0IgZm9ybWF0cyBhcmUgbGl0dGxlIGVuZGlhbiwgYnV0 IGluIHByYWN0aWNlIHRoZXkKPiA+ID4gPiA+IGFyZSBuYXRpdmUgZW5kaWFuLiAgTG9vayBhdCB0 aGUgZHJtX21vZGVfbGVnYWN5X2ZiX2Zvcm1hdCgpIGhlbHBlci4gIEl0Cj4gPiA+ID4gPiBtYXBz IC0tIGZvciBleGFtcGxlIC0tIGJwcC9kZXB0aCAzMi8yNCB0byBEUk1fRk9STUFUX1hSR0I4ODg4 LCBubyBtYXR0ZXIKPiA+ID4gPiA+IHdoZW5ldmVyIHRoZSBtYWNoaW5lIGlzIGxpdHRsZSBlbmRp YW4gb3IgYmlnIGVuZGlhbi4gIFRoZSB1c2VycyBvZiB0aGlzCj4gPiA+ID4gPiBmdW5jdGlvbiAo ZmJkZXYgZW11bGF0aW9uLCBEUk1fSU9DVExfTU9ERV9BRERGQikgZXhwZWN0IHRoZSBmcmFtZWJ1 ZmZlcgo+ID4gPiA+ID4gaXMgbmF0aXZlIGVuZGlhbiwgbm90IGxpdHRsZSBlbmRpYW4uICBNb3N0 IHVzZXJzcGFjZSBhbHNvIG9wZXJhdGVzIG9uCj4gPiA+ID4gPiBuYXRpdmUgZW5kaWFuIG9ubHku ICAKPiA+ID4gPiAKPiA+ID4gPiBJJ20gbm90IGEgZmFuIG9mICJuYXRpdmUiLiBOYXRpdmUgdG8g d2hhdD8gIkNQVSIgb3IgImhvc3QiIGlzIHdoYXQgSSdkCj4gPiA+ID4gY2FsbCBpdC4gIAo+ID4g PiAKPiA+ID4gbmF0aXZlID09IHdoYXRldmVyIHRoZSBjcHUgaXMgdXNpbmcuCj4gPiA+IAo+ID4g PiBJIHBlcnNvbmFsbHkgZmluZCAibmF0aXZlIiBtb3JlIGludHVpdGl2ZSwgYnV0IGF0IHRoZSBl bmQgb2YgdGhlIGRheSBJCj4gPiA+IGRvbid0IG1pbmQgbXVjaC4gIElmIHBlb3BsZSBwcmVmZXIg Imhvc3QiIG92ZXIgIm5hdGl2ZSIgSSdsbCBjaGFuZ2UgaXQuICAKPiA+IAo+ID4gIm5hdGl2ZSIg dG8gbWUgZmVlbHMgbW9yZSBsaWtlICJuYXRpdmUgdG8gdGhlIEdQVSIgc2luY2UgdGhlc2UgdGhp bmdzCj4gPiByZWFsbHkgYXJlIHRpZWQgdG8gdGhlIEdQVSBub3QgdGhlIENQVS4gVGhhdCdzIGFs c28gd2h5IEkgd2VudCB3aXRoIHRoZQo+ID4gZXhwbGljaXQgZW5kaWFubmVzcyBvcmlnaW5hbGx5 IHNvIHRoYXQgdGhlIGRyaXZlciBjb3VsZCBwcm9wZXJseSBkZWNsYXJlCj4gPiB3aGF0IHRoZSBH UFUgc3VwcG9ydHMuCj4gCj4gSGksCj4gCj4geWVhaCwgb25lIHNob3VsZCByZWFsbHkgYmUgZXhw bGljaXQgb24gd2hpY2ggY29tcG9uZW50J3MgZW5kaWFuZXNzIGRvZXMKPiAibmF0aXZlIiByZWZl ciB0by4gSSBqdXN0IGNhbid0IGltYWdpbmUgIkdQVSBuYXRpdmUiIHRvIGV2ZXIgYmUgYW4KPiBv cHRpb24sIGJlY2F1c2UgdGhlbiB1c2Vyc3BhY2UgbmVlZHMgYSB3YXkgdG8gZGlzY292ZXIgd2hh dCB0aGUKPiBHUFUgZW5kaWFuZXNzIGlzLAoKSXQgaGFzIHRvIGtub3cgdGhhdC4gSG93IGVsc2Ug d291bGQgaXQga25vdyBob3cgdG8gd3JpdGUgdGhlIGJ5dGVzIGludG8KbWVtb3J5IGluIHRoZSBy aWdodCBvcmRlciBmb3IgdGhlIEdQVSB0byBjb25zdW1lLCBvciByZWFkIHRoZSBzdHVmZiB0aGUK R1BVIHByb2R1Y2VkPwoKPiBhbmQgSSBiZWxpZXZlIHRoYXQgd291bGQgb25seSBkZWVwZW4gdGhl IHN3YW1wLCBub3QKPiBkcmFpbiBpdCwgYmVjYXVzZSBzdWRkZW5seSB5b3UgbmVlZCB0d28gZW51 bXMgdG8gZGVzY3JpYmUgb25lIGZvcm1hdC4KPiAKPiBWaWxsZSwgd29yZGluZyBhc2lkZSwgd2hh dCBkbyB0aGluayBhYm91dCBjaGFuZ2luZyB0aGUgZW5kaWFuZXNzCj4gZGVmaW5pdGlvbj8gSXMg aXQgZ29pbmcgaW4gdGhlIHJpZ2h0IGRpcmVjdGlvbj8KCkkgZG9uJ3QgdGhpbmsgc28sIGJ1dCBJ IGd1ZXNzIEknbSBpbiB0aGUgbWlub3JpdHkuCgotLSAKVmlsbGUgU3lyasOkbMOkCkludGVsIE9U QwpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpkcmktZGV2 ZWwgbWFpbGluZyBsaXN0CmRyaS1kZXZlbEBsaXN0cy5mcmVlZGVza3RvcC5vcmcKaHR0cHM6Ly9s aXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9kcmktZGV2ZWwK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1036897AbdDULtY (ORCPT ); Fri, 21 Apr 2017 07:49:24 -0400 Received: from mga09.intel.com ([134.134.136.24]:5286 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1036199AbdDULtU (ORCPT ); Fri, 21 Apr 2017 07:49:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,229,1488873600"; d="scan'208";a="848375616" Date: Fri, 21 Apr 2017 14:49:13 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Pekka Paalanen Cc: Gerd Hoffmann , dri-devel@lists.freedesktop.org, Daniel Vetter , 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: <20170421114913.GK30290@intel.com> References: <20170421075825.6307-1-kraxel@redhat.com> <20170421092530.GE30290@intel.com> <1492768218.25675.33.camel@redhat.com> <20170421110804.GH30290@intel.com> <20170421144018.411861d6@eldfell> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170421144018.411861d6@eldfell> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 21, 2017 at 02:40:18PM +0300, Pekka Paalanen wrote: > On Fri, 21 Apr 2017 14:08:04 +0300 > Ville Syrjälä wrote: > > > On Fri, Apr 21, 2017 at 11:50:18AM +0200, Gerd Hoffmann wrote: > > > On Fr, 2017-04-21 at 12:25 +0300, Ville Syrjälä wrote: > > > > On Fri, Apr 21, 2017 at 09:58:24AM +0200, Gerd Hoffmann wrote: > > > > > While working on graphics support for virtual machines on ppc64 (which > > > > > exists in both little and big endian variants) I've figured the comments > > > > > for various drm fourcc formats in the header file don't match reality. > > > > > > > > > > Comments says the RGB formats are little endian, but in practice they > > > > > 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 matter > > > > > whenever the machine is little endian or big endian. The users of this > > > > > function (fbdev emulation, DRM_IOCTL_MODE_ADDFB) expect the framebuffer > > > > > is native endian, not little endian. Most userspace also operates on > > > > > native endian only. > > > > > > > > I'm not a fan of "native". Native to what? "CPU" or "host" is what I'd > > > > call it. > > > > > > native == whatever the cpu is using. > > > > > > 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. > > > > "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. > > Hi, > > yeah, one should really be explicit on which component's endianess does > "native" refer to. I just can't imagine "GPU native" to ever be an > option, because then userspace needs a way to discover what the > GPU endianess is, It has to know that. How else would it know how to write the bytes into memory in the right order for the GPU to consume, or read the stuff the GPU produced? > and I believe that would only deepen the swamp, not > drain it, because suddenly you need two enums to describe one format. > > Ville, wording aside, what do think about changing the endianess > definition? Is it going in the right direction? I don't think so, but I guess I'm in the minority. -- Ville Syrjälä Intel OTC