[PATCH] media: cedrus: don't initialize pointers with zero

[Hans Verkuil]

On 12/07/2018 11:56 AM, Mauro Carvalho Chehab wrote:
> A common mistake is to assume that initializing a var with:
> 	struct foo f = { 0 };
> 
> Would initialize a zeroed struct. Actually, what this does is
> to initialize the first element of the struct to zero.
> 
> According to C99 Standard 6.7.8.21:
> 
>     "If there are fewer initializers in a brace-enclosed
>      list than there are elements or members of an aggregate,
>      or fewer characters in a string literal used to initialize
>      an array of known size than there are elements in the array,
>      the remainder of the aggregate shall be initialized implicitly
>      the same as objects that have static storage duration."
> 
> So, in practice, it could zero the entire struct, but, if the
> first element is not an integer, it will produce warnings:
> 
> 	drivers/staging/media/sunxi/cedrus/cedrus.c:drivers/staging/media/sunxi/cedrus/cedrus.c:78:49:  warning: Using plain integer as NULL pointer
> 	drivers/staging/media/sunxi/cedrus/cedrus_dec.c:drivers/staging/media/sunxi/cedrus/cedrus_dec.c:29:35:  warning: Using plain integer as NULL pointer
> 
> A proper way to initialize it with gcc is to use:
> 
> 	struct foo f = { };
> 
> But that seems to be a gcc extension. So, I decided to check upstream

No, this is not a gcc extension. It's part of the latest C standard.

It's used all over in the kernel, so please use {} instead of { NULL }.

Personally I think {} is a fantastic invention and I wish C++ had it as
well.

Regards,

	Hans

> what's the most commonly pattern. The gcc pattern has about 2000 entries:
> 
> 	$ git grep -E "=\s*\{\s*\}"|wc -l
> 	1951
> 
> The standard-C compliant pattern has about 2500 entries:
> 
> 	$ git grep -E "=\s*\{\s*NULL\s*\}"|wc -l
> 	137
> 	$ git grep -E "=\s*\{\s*0\s*\}"|wc -l
> 	2323
> 
> So, let's initialize those structs with:
> 	 = { NULL }
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung at kernel.org>
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus.c     | 2 +-
>  drivers/staging/media/sunxi/cedrus/cedrus_dec.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
> index b538eb0321d8..44c45c687503 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> @@ -75,7 +75,7 @@ static int cedrus_init_ctrls(struct cedrus_dev *dev, struct cedrus_ctx *ctx)
>  	memset(ctx->ctrls, 0, ctrl_size);
>  
>  	for (i = 0; i < CEDRUS_CONTROLS_COUNT; i++) {
> -		struct v4l2_ctrl_config cfg = { 0 };
> +		struct v4l2_ctrl_config cfg = { NULL };
>  
>  		cfg.elem_size = cedrus_controls[i].elem_size;
>  		cfg.id = cedrus_controls[i].id;
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> index e40180a33951..4099a42dba2d 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> @@ -26,7 +26,7 @@ void cedrus_device_run(void *priv)
>  {
>  	struct cedrus_ctx *ctx = priv;
>  	struct cedrus_dev *dev = ctx->dev;
> -	struct cedrus_run run = { 0 };
> +	struct cedrus_run run = { NULL };
>  	struct media_request *src_req;
>  	unsigned long flags;
>  
>