From: Geert Uytterhoeven <geert@linux-m68k.org> To: "Michel Dänzer" <michel.daenzer@mailbox.org> Cc: "Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>, "Maxime Ripard" <mripard@kernel.org>, "Thomas Zimmermann" <tzimmermann@suse.de>, "David Airlie" <airlied@linux.ie>, "Daniel Vetter" <daniel@ffwll.ch>, "Noralf Trønnes" <noralf@tronnes.org>, "Gerd Hoffmann" <kraxel@redhat.com>, "Linux Fbdev development list" <linux-fbdev@vger.kernel.org>, Linux/m68k <linux-m68k@vger.kernel.org>, "DRI Development" <dri-devel@lists.freedesktop.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats Date: Mon, 11 Jul 2022 17:30:30 +0200 [thread overview] Message-ID: <CAMuHMdUgdbZeoFLFL8+Hm-6fG9cg5Wzq++JED3KR5P9YZtRQ4A@mail.gmail.com> (raw) In-Reply-To: <96a87833-d878-dde9-e335-9ea51a4ba406@mailbox.org> Hi Michel, On Mon, Jul 11, 2022 at 5:23 PM Michel Dänzer <michel.daenzer@mailbox.org> wrote: > On 2022-07-08 20:21, Geert Uytterhoeven wrote: > > As of commit eae06120f1974e1a ("drm: refuse ADDFB2 ioctl for broken > > bigendian drivers"), drivers must set the > > quirk_addfb_prefer_host_byte_order quirk to make the drm_mode_addfb() > > compat code work correctly on big-endian machines. > > > > While that works fine for big-endian XRGB8888 and ARGB8888, which are > > mapped to the existing little-endian BGRX8888 and BGRA8888 formats, it > > does not work for big-endian XRGB1555 and RGB565, as the latter are not > > listed in the format database. > > > > Fix this by adding the missing formats. Limit this to big-endian > > platforms, as there is currently no need to support these formats on > > little-endian platforms. > > > > Fixes: 6960e6da9cec3f66 ("drm: fix drm_mode_addfb() on big endian machines.") > > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> > > --- > > Cirrus is the only driver setting quirk_addfb_prefer_host_byte_order > > and supporting RGB565 or XRGB1555, but no one tried that on big-endian? > > Cirrus does not support DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN > > in cirrus_fb_create, so you cannot get a graphical text console. > > > > Do we need these definitions on little-endian platforms, too? > > Would it be better to use "DRM_FORMAT_{XRGB1555,RGB565} | > > DRM_FORMAT_BIG_ENDIAN" instead of "DRM_FORMAT_HOST_{XRGB1555,RGB565}" in > > formats[]? > > The intention of DRM_FORMAT_HOST_* is that they are macros in include/drm/drm_fourcc.h which just map to little endian formats defined in drivers/gpu/drm/drm_fourcc.c. Since this is not possible for big endian hosts for XRGB1555 or RGB565 (or any other format with non-8-bit components), this isn't applicable here. I read that as that you prefer to write "DRM_FORMAT_{XRGB1555,RGB565} | DRM_FORMAT_BIG_ENDIAN" in formats[]? > It's also doubtful that Cirrus hardware would access these formats as big endian (drivers/gpu/drm/tiny/cirrus.c has no endianness references at all, and the hardware was surely designed for x86 first and foremost). > > Instead, fbcon (and user space) needs to convert to little endian when using DRM_FORMAT_HOST_{XRGB1555,RGB565} with the cirrus driver on big endian hosts. Yeah, probably the cirrus driver can use some fixes... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
WARNING: multiple messages have this Message-ID (diff)
From: Geert Uytterhoeven <geert@linux-m68k.org> To: "Michel Dänzer" <michel.daenzer@mailbox.org> Cc: "Linux Fbdev development list" <linux-fbdev@vger.kernel.org>, "Thomas Zimmermann" <tzimmermann@suse.de>, "David Airlie" <airlied@linux.ie>, "DRI Development" <dri-devel@lists.freedesktop.org>, Linux/m68k <linux-m68k@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Noralf Trønnes" <noralf@tronnes.org>, "Gerd Hoffmann" <kraxel@redhat.com> Subject: Re: [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats Date: Mon, 11 Jul 2022 17:30:30 +0200 [thread overview] Message-ID: <CAMuHMdUgdbZeoFLFL8+Hm-6fG9cg5Wzq++JED3KR5P9YZtRQ4A@mail.gmail.com> (raw) In-Reply-To: <96a87833-d878-dde9-e335-9ea51a4ba406@mailbox.org> Hi Michel, On Mon, Jul 11, 2022 at 5:23 PM Michel Dänzer <michel.daenzer@mailbox.org> wrote: > On 2022-07-08 20:21, Geert Uytterhoeven wrote: > > As of commit eae06120f1974e1a ("drm: refuse ADDFB2 ioctl for broken > > bigendian drivers"), drivers must set the > > quirk_addfb_prefer_host_byte_order quirk to make the drm_mode_addfb() > > compat code work correctly on big-endian machines. > > > > While that works fine for big-endian XRGB8888 and ARGB8888, which are > > mapped to the existing little-endian BGRX8888 and BGRA8888 formats, it > > does not work for big-endian XRGB1555 and RGB565, as the latter are not > > listed in the format database. > > > > Fix this by adding the missing formats. Limit this to big-endian > > platforms, as there is currently no need to support these formats on > > little-endian platforms. > > > > Fixes: 6960e6da9cec3f66 ("drm: fix drm_mode_addfb() on big endian machines.") > > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> > > --- > > Cirrus is the only driver setting quirk_addfb_prefer_host_byte_order > > and supporting RGB565 or XRGB1555, but no one tried that on big-endian? > > Cirrus does not support DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN > > in cirrus_fb_create, so you cannot get a graphical text console. > > > > Do we need these definitions on little-endian platforms, too? > > Would it be better to use "DRM_FORMAT_{XRGB1555,RGB565} | > > DRM_FORMAT_BIG_ENDIAN" instead of "DRM_FORMAT_HOST_{XRGB1555,RGB565}" in > > formats[]? > > The intention of DRM_FORMAT_HOST_* is that they are macros in include/drm/drm_fourcc.h which just map to little endian formats defined in drivers/gpu/drm/drm_fourcc.c. Since this is not possible for big endian hosts for XRGB1555 or RGB565 (or any other format with non-8-bit components), this isn't applicable here. I read that as that you prefer to write "DRM_FORMAT_{XRGB1555,RGB565} | DRM_FORMAT_BIG_ENDIAN" in formats[]? > It's also doubtful that Cirrus hardware would access these formats as big endian (drivers/gpu/drm/tiny/cirrus.c has no endianness references at all, and the hardware was surely designed for x86 first and foremost). > > Instead, fbcon (and user space) needs to convert to little endian when using DRM_FORMAT_HOST_{XRGB1555,RGB565} with the cirrus driver on big endian hosts. Yeah, probably the cirrus driver can use some fixes... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
next prev parent reply other threads:[~2022-07-11 15:30 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-08 18:21 [PATCH 0/3] drm: Endianness fixes Geert Uytterhoeven 2022-07-08 18:21 ` Geert Uytterhoeven 2022-07-08 18:21 ` [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats Geert Uytterhoeven 2022-07-08 18:21 ` Geert Uytterhoeven 2022-07-11 15:22 ` Michel Dänzer 2022-07-11 15:30 ` Geert Uytterhoeven [this message] 2022-07-11 15:30 ` Geert Uytterhoeven 2022-07-11 16:28 ` Michel Dänzer 2022-07-11 16:28 ` Michel Dänzer 2022-07-12 7:47 ` Gerd Hoffmann 2022-07-12 7:47 ` Gerd Hoffmann 2022-07-12 8:01 ` Geert Uytterhoeven 2022-07-12 8:01 ` Geert Uytterhoeven 2022-07-12 8:39 ` Gerd Hoffmann 2022-07-12 8:39 ` Gerd Hoffmann 2022-07-12 8:43 ` Geert Uytterhoeven 2022-07-12 8:43 ` Geert Uytterhoeven 2022-07-12 9:03 ` Gerd Hoffmann 2022-07-12 9:03 ` Gerd Hoffmann 2022-07-12 9:09 ` Michel Dänzer 2022-07-12 9:09 ` Michel Dänzer 2022-07-12 9:10 ` Geert Uytterhoeven 2022-07-12 9:10 ` Geert Uytterhoeven 2022-07-12 8:31 ` Gerd Hoffmann 2022-07-12 8:31 ` Gerd Hoffmann 2022-07-08 18:21 ` [PATCH 2/3] drm/format-helper: Fix endianness in drm_fb_*_to_*() conversion helpers Geert Uytterhoeven 2022-07-08 18:21 ` Geert Uytterhoeven 2022-07-08 18:21 ` [PATCH 3/3] drm/gud: Fix endianness in gud_xrgb8888_to_color() helper Geert Uytterhoeven 2022-07-08 18:21 ` Geert Uytterhoeven 2022-07-19 14:39 ` Noralf Trønnes 2022-07-19 14:39 ` Noralf Trønnes
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