RE: [PATCH 3/3] media: atomisp: Use max() macros

[David Laight <David.Laight@ACULAB.COM>]

From: Ricardo Ribalda
> Sent: 27 September 2024 10:42
> 
> The max() macro produce nicer code and also fixes the following cocci
> errors:
> 
> drivers/staging/media/atomisp/pci/sh_css_frac.h:40:17-18: WARNING opportunity for max()
> drivers/staging/media/atomisp/pci/sh_css_frac.h:50:17-18: WARNING opportunity for max()
> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/staging/media/atomisp/pci/sh_css_frac.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/sh_css_frac.h
> b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> index 8ba65161f7a9..9642506d2388 100644
> --- a/drivers/staging/media/atomisp/pci/sh_css_frac.h
> +++ b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> @@ -37,7 +37,7 @@ static inline int sDIGIT_FITTING(int v, int a, int b)
>  	int fit_shift = sFRACTION_BITS_FITTING(a) - b;
> 
>  	v >>= sSHIFT;

IIRC right shifts of signed values are undefined.
(C does not require a cpu to have a right shift that replicates the
sign bit.)

> -	v >>= fit_shift > 0 ? fit_shift : 0;
> +	v >>= max(fit_shift, 0);

If the shift isn't done the return value is garbage.
So the code better not let it happen.
In which case you might as well let the cpu generate a (different)
random value - so delete the conditional.

> 
>  	return clamp_t(int, v, sISP_VAL_MIN, sISP_VAL_MAX);

all three values seem to be 'int' - so no need for the _t variant
and all the associated casts.

>  }
> @@ -47,7 +47,7 @@ static inline unsigned int uDIGIT_FITTING(unsigned int v, int a, int b)
>  	int fit_shift = uFRACTION_BITS_FITTING(a) - b;
> 
>  	v >>= uSHIFT;
> -	v >>= fit_shift > 0 ? fit_shift : 0;
> +	v >>= max(fit_shift, 0);
> 
>  	return clamp_t(unsigned int, v, uISP_VAL_MIN, uISP_VAL_MAX);

as above, but it is just min(v, iISP_VAL_MAX)

	David

>  }
> 
> --
> 2.46.1.824.gd892dcdcdd-goog
> 

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