Re: [PATCH] mmc: sdhci-of-dwcmshc: Use logical OR instead of bitwise OR in dwcmshc_probe()

[Drew Fustini <dfustini@baylibre.com>]

On Thu, Nov 16, 2023 at 06:46:00PM -0700, Nathan Chancellor wrote:
> Clang warns (or errors with CONFIG_WERROR=y):
> 
>   drivers/mmc/host/sdhci-of-dwcmshc.c:873:7: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
>     873 |                 if ((device_property_read_bool(dev, "mmc-ddr-1_8v")) |
>         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     874 |                     (device_property_read_bool(dev, "mmc-hs200-1_8v")) |
>         |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         |                                                                        ||
>     875 |                     (device_property_read_bool(dev, "mmc-hs400-1_8v")))
>         |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   drivers/mmc/host/sdhci-of-dwcmshc.c:873:7: note: cast one or both operands to int to silence this warning
>   drivers/mmc/host/sdhci-of-dwcmshc.c:873:7: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
>     873 |                 if ((device_property_read_bool(dev, "mmc-ddr-1_8v")) |
>         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         |                                                                      ||
>     874 |                     (device_property_read_bool(dev, "mmc-hs200-1_8v")) |
>         |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   drivers/mmc/host/sdhci-of-dwcmshc.c:873:7: note: cast one or both operands to int to silence this warning
>   2 errors generated.
> 
> There is little reason for this if statement to use bitwise ORs, as the
> short circuiting of logical OR does not need to be avoided in this
> context; it would be wasteful to call device_property_read_bool() three
> times if the first two calls returned true. Switch to logical OR to fix
> the warning.
> 
> While in the area, the parentheses around the calls to
> device_property_read_bool() are not necessary and make the if statement
> harder to read, so remove them.
> 
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1960
> Fixes: aff35fbc7830 ("mmc: sdhci-of-dwcmshc: Add support for T-Head TH1520")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Tested-by: Drew Fustini <dfustini@baylibre.com>

Thanks for fixing this. I'll add clang to my testing going forward.

Drew