media: v4l2-tpg: reduce stack usage for kasan builds

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tpg_fill_plane_buffer() is a rather complex function. While there is
nothing wrong with it per se, I have run into corner cases with clang-22
on s390 using KASAN that makes it run out of registers and blow the
stack warning limit from excessive spills:

drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2629:6: error: stack frame size (1560) exceeds limit (1536)
      in 'tpg_fill_plane_buffer' [-Werror,-Wframe-larger-than]
 2629 | void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,

Forcing the two largest callees out of line completely avoids the problem
and prevents all the register spills, with the stack usage for each function
going down to a few bytes for the local variables.

Arguably this is a problem caused by clang rather than the code, but
a noinline_for_stack annotation is an easy workaround.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

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Arnd Bergmann 2026-06-18 16:32:47 +02:00 • committed by Hans Verkuil

parent 627a121c15

commit c49cdaafa4

1 changed files with 8 additions and 6 deletions

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drivers/media/common/v4l2-tpg/v4l2-tpg-core.c

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