Re: [PATCH] drm/stm: fix warning about multiplication in condition

[Philippe CORNU]

On 07/25/2017 05:40 PM, Arnd Bergmann wrote:
> gcc-7 complains about multiplying within a condition being
> suspicious:
> 
> drivers/gpu/drm/stm/dw_mipi_dsi-stm.c: In function 'dsi_pll_get_clkout_khz':
> drivers/gpu/drm/stm/dw_mipi_dsi-stm.c:117:10: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]
> 
> The code here is correct, but can be easily rephrased to make
> that more obvious. I also swap out the error handling and the normal
> code path for clarity.

Hi Arnd,
And many thanks for this new & much better code.

Acked-by: Philippe Cornu <philippe.cornu@xxxxxx>
Tested-by: Philippe Cornu <philippe.cornu@xxxxxx>

Philippe :-)

> 
> Fixes: b0f09a3c69d9 ("drm/stm: Add STM32 DSI controller driver")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>   drivers/gpu/drm/stm/dw_mipi_dsi-stm.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
> index 568c5d0461ea..e5b6310240fe 100644
> --- a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
> +++ b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
> @@ -113,11 +113,13 @@ static enum dsi_color dsi_color_from_mipi(enum mipi_dsi_pixel_format fmt)
>   
>   static int dsi_pll_get_clkout_khz(int clkin_khz, int idf, int ndiv, int odf)
>   {
> +	int divisor = idf * odf;
> +
>   	/* prevent from division by 0 */
> -	if (idf * odf)
> -		return DIV_ROUND_CLOSEST(clkin_khz * ndiv, idf * odf);
> +	if (!divisor)
> +		return 0;
>   
> -	return 0;
> +	return DIV_ROUND_CLOSEST(clkin_khz * ndiv, divisor);
>   }
>   
>   static int dsi_pll_get_params(int clkin_khz, int clkout_khz,
>