[PATCH] drm/panel: himax-hx8279: Initialize goa_{even, odd}_valid in hx8279_check_goa_config()

[Neil Armstrong]

On 22/04/2025 23:20, Nathan Chancellor wrote:
> Clang warns (or errors with CONFIG_WERROR=y):
> 
>    drivers/gpu/drm/panel/panel-himax-hx8279.c:838:6: error: variable 'goa_even_valid' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>      838 |         if (num_zero == ARRAY_SIZE(desc->goa_even_timing))
>          |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/gpu/drm/panel/panel-himax-hx8279.c:842:23: note: uninitialized use occurs here
>      842 |         if (goa_odd_valid != goa_even_valid)
>          |                              ^~~~~~~~~~~~~~
>    drivers/gpu/drm/panel/panel-himax-hx8279.c:838:2: note: remove the 'if' if its condition is always true
>      838 |         if (num_zero == ARRAY_SIZE(desc->goa_even_timing))
>          |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>      839 |                 goa_even_valid = false;
>    drivers/gpu/drm/panel/panel-himax-hx8279.c:818:36: note: initialize the variable 'goa_even_valid' to silence this warning
>      818 |         bool goa_odd_valid, goa_even_valid;
>          |                                           ^
>          |                                            = 0
> 
> Even though only the even valid variable gets flagged, both valid
> variables appear to have the same issue of possibly being used
> uninitialized if the if statement initializing them to false is not
> taken.
> 
> Initialize both values to true to clear up the warning and remove any
> possibility of encountering undefined behavior.
> 
> Fixes: 38d42c261389 ("drm: panel: Add driver for Himax HX8279 DDIC panels")
> Signed-off-by: Nathan Chancellor <nathan at kernel.org>
> ---
>   drivers/gpu/drm/panel/panel-himax-hx8279.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-himax-hx8279.c b/drivers/gpu/drm/panel/panel-himax-hx8279.c
> index b48b350b62da..92f351e66c25 100644
> --- a/drivers/gpu/drm/panel/panel-himax-hx8279.c
> +++ b/drivers/gpu/drm/panel/panel-himax-hx8279.c
> @@ -815,7 +815,7 @@ static int hx8279_check_gmux_config(struct hx8279 *hx, struct device *dev)
>   static int hx8279_check_goa_config(struct hx8279 *hx, struct device *dev)
>   {
>   	const struct hx8279_panel_desc *desc = hx->desc;
> -	bool goa_odd_valid, goa_even_valid;
> +	bool goa_odd_valid = true, goa_even_valid = true;
>   	int i, num_zero, num_clr = 0;
>   
>   	/* Up to 4 zero values is a valid configuration. Check them all. */
> 
> ---
> base-commit: dcbd5dcc956e2331414fd7020b4655df08deeb87
> change-id: 20250422-panel-himax-hx8279-fix-sometimes-uninitialized-207354fb930c
> 
> Best regards,

Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>