From: "Arnd Bergmann" <arnd@arndb.de>
To: "Thomas Zimmermann" <tzimmermann@suse.de>,
"Javier Martinez Canillas" <javierm@redhat.com>,
"David Airlie" <airlied@linux.ie>,
"Daniel Vetter" <daniel@ffwll.ch>, "Helge Deller" <deller@gmx.de>,
maxime@cerno.tech, sam@ravnborg.org,
"Michal Suchanek" <msuchanek@suse.de>,
"Michael Ellerman" <mpe@ellerman.id.au>,
benh@kernel.crashing.org, "Paul Mackerras" <paulus@samba.org>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
mark.cave-ayland@ilande.co.uk
Cc: linux-fbdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v4 5/5] drm/ofdrm: Support big-endian scanout buffers
Date: Tue, 11 Oct 2022 22:06:59 +0200 [thread overview]
Message-ID: <9162f41f-28c3-493c-ab54-b1c4a2fdf494@app.fastmail.com> (raw)
In-Reply-To: <83071743-a7f2-f761-baa3-da688f26b5e3@suse.de>
On Tue, Oct 11, 2022, at 1:30 PM, Thomas Zimmermann wrote:
> Am 11.10.22 um 09:46 schrieb Javier Martinez Canillas:
>>> +static bool display_get_big_endian_of(struct drm_device *dev, struct device_node *of_node)
>>> +{
>>> + bool big_endian;
>>> +
>>> +#ifdef __BIG_ENDIAN
>>> + big_endian = true;
>>> + if (of_get_property(of_node, "little-endian", NULL))
>>> + big_endian = false;
>>> +#else
>>> + big_endian = false;
>>> + if (of_get_property(of_node, "big-endian", NULL))
>>> + big_endian = true;
>>> +#endif
>>> +
>>> + return big_endian;
>>> +}
>>> +
>>
>> Ah, I see. The heuristic then is whether the build is BE or LE or if the Device
>> Tree has an explicit node defining the endianess. The patch looks good to me:
>
> Yes. I took this test from offb.
Has the driver been tested with little-endian kernels though? While
ppc32 kernels are always BE, you can build kernels as either big-endian
or little-endian for most (modern) powerpc64 and arm/arm64 hardware,
and I don't see why that should change the defaults of the driver
when describing the same framebuffer hardware.
I could understand having a default to e.g. big-endian on all powerpc and
a default for little-endian on all arm, but having it tied to the
way the kernel is built seems wrong, and doesn't make sense in a
DT binding either.
Arnd
next prev parent reply other threads:[~2022-10-11 20:08 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 10:50 [PATCH v4 0/5] drm: Add driver for PowerPC OF displays Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 1/5] drm/ofdrm: Add ofdrm for Open Firmware framebuffers Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 2/5] drm/ofdrm: Add CRTC state Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 3/5] drm/ofdrm: Add per-model device function Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 4/5] drm/ofdrm: Support color management Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 5/5] drm/ofdrm: Support big-endian scanout buffers Thomas Zimmermann
2022-09-28 11:12 ` Michal Suchánek
2022-09-28 11:30 ` Thomas Zimmermann
2022-10-11 7:46 ` Javier Martinez Canillas
2022-10-11 11:30 ` Thomas Zimmermann
2022-10-11 20:06 ` Arnd Bergmann [this message]
2022-10-11 21:38 ` Michal Suchánek
2022-10-12 6:29 ` Arnd Bergmann
2022-10-12 7:23 ` Michal Suchánek
2022-10-12 6:46 ` Thomas Zimmermann
2022-10-12 7:17 ` Arnd Bergmann
2022-10-12 7:40 ` Thomas Zimmermann
2022-10-12 7:44 ` Arnd Bergmann
2022-10-12 8:27 ` Thomas Zimmermann
2022-10-12 8:38 ` Arnd Bergmann
2022-10-12 12:00 ` Thomas Zimmermann
2022-10-12 13:12 ` Arnd Bergmann
2022-10-12 14:27 ` Michal Suchánek
2022-10-13 7:39 ` Javier Martinez Canillas
2022-10-17 6:44 ` Benjamin Herrenschmidt
2022-10-12 14:31 ` Thomas Zimmermann
2022-10-12 14:59 ` Ville Syrjälä
2022-10-12 16:01 ` Michal Suchánek
2022-10-12 12:07 ` Michal Suchánek
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