media: atomisp: Avoid overflow in compute_blending
Clang warns: drivers/staging/media/atomisp/pci/isp/kernels/xnr/xnr_3.0/ia_css_xnr3.host.c:129:35: warning: implicit conversion from 'unsigned long' to 'int32_t' (aka 'int') changes value from 18446744073709543424 to -8192 [-Wconstant-conversion] return MAX(MIN(isp_strength, 0), -XNR_BLENDING_SCALE_FACTOR); ~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ XNR_BLENDING_SCALE_FACTOR is BIT(13), or 8192, which will easily fit into a signed 32-bit integer. However, it is an unsigned long, which means that negating it is the same as subtracting that value from ULONG_MAX + 1, which causes it to be larger than a signed 32-bit integer so it gets implicitly converted. We can avoid this by using the variable isp_scale, which holds the value of XNR_BLENDING_SCALE_FACTOR already, where the implicit conversion from unsigned long to s32 already happened. If that were to ever overflow, clang would warn: https://godbolt.org/z/EeSxLG Link: https://github.com/ClangBuiltLinux/linux/issues/1036Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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