[Mesa-dev] [PATCH 2/2] mesa: _mesa_format_convert should be endian agnostic

Emil Velikov emil.l.velikov at gmail.com
Fri Aug 7 10:55:59 PDT 2015

On 4 August 2015 at 17:57, Oded Gabbay <oded.gabbay at gmail.com> wrote:

> On Mon, Aug 3, 2015 at 6:40 PM, Emil Velikov <emil.l.velikov at gmail.com>
> wrote:
>> Hi Oded,
>> On 2 August 2015 at 11:37, Oded Gabbay <oded.gabbay at gmail.com> wrote:
>> > This patch fixes a bug that is manifested in the read path of mesa when
>> > running on big-endian machines. The effects can be seen when running
>> > piglit sanity test and/or taking a screen capture.
>> >
>> > The bug is caused when _mesa_format_convert receives src_format as
>> > mesa_format, which it thens changes to mesa_array_format. During this
>> > change, it checks for endianness and swaps the bytes accordingly.
>> > However, because the bytes are _already_ swapped in the memory itself
>> > (being written there by llvmpipe), and src_format value matches the
>> > _actual_ contents of the memory, the result of the read is wrong.
>> >
>> I'm assuming that you're looked at swrast + softpipe as well - do they
>> use the same approach or is llvmpipe the odd one out ?
>> ​Hi Emil,
> ​I checked it with swrast, softpipe AND llvmpipe.
> Without my patch, all methods fail piglit sanity on ppc64
> With my patch, all ​methods pass piglit sanity
> I've mentioned the other drivers, as your commit message explicitly
mentions llvmpipe alone. Perhaps dropping that hunk or adding the other two
would be ok ? Props for checking all the drivers though !

I'm afraid that I've never looked into the BE codepaths so don't know how
useful of a review I can do here.

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