Re: [PATCH 2/2] media: v4l2-ctrl: Move compound control initialization

[Boris Brezillon <boris.brezillon@collabora.com>]

Hi Ezequiel,

On Wed, 29 May 2019 16:28:11 -0300
Ezequiel Garcia <ezequiel@collabora.com> wrote:

> Rework std_init adding an explicit initialization for
> compound controls.
> 
> While here, make sure the control is initialized to zero,
> before providing default values for all its fields.
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 55 +++++++++++++++++-----------
>  1 file changed, 34 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index c7d5fdb8efb4..44afda1d77b3 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1506,25 +1506,49 @@ static bool std_equal(const struct v4l2_ctrl *ctrl, u32 idx,
>  	}
>  }
>  
> -static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> +static void std_init_compound(const struct v4l2_ctrl *ctrl, u32 idx,
>  		     union v4l2_ctrl_ptr ptr)
>  {
>  	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
>  
> +	memset(ptr.p, 0, ctrl->elem_size);
> +

Hm, shouldn't we have

	idx *= ctrl->elem_size;
	memset(ptr.p + idx, 0, ctrl->elem_size);

instead?

Looks like your solution always resets the first element of an array
even if idx > 0.

>  	/*
>  	 * The cast is needed to get rid of a gcc warning complaining that
>  	 * V4L2_CTRL_TYPE_MPEG2_SLICE_PARAMS is not part of the
>  	 * v4l2_ctrl_type enum.
>  	 */
>  	switch ((u32)ctrl->type) {
> +	case V4L2_CTRL_TYPE_MPEG2_SLICE_PARAMS:
> +		p_mpeg2_slice_params = ptr.p;
> +		/* 4:2:0 */
> +		p_mpeg2_slice_params->sequence.chroma_format = 1;
> +		/* 8 bits */
> +		p_mpeg2_slice_params->picture.intra_dc_precision = 0;
> +		/* interlaced top field */
> +		p_mpeg2_slice_params->picture.picture_structure = 1;
> +		p_mpeg2_slice_params->picture.picture_coding_type =
> +					V4L2_MPEG2_PICTURE_CODING_TYPE_I;
> +		return;
> +	default:
> +		idx *= ctrl->elem_size;
> +		memset(ptr.p + idx, 0, ctrl->elem_size);
> +		return;

If you fix the first memset() you can get rid of this one. Also don't
see why you use return instead of break in this switch-case block
(there's no reason to bail out early in this function).

> +	}
> +}
> +
> +static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> +		     union v4l2_ctrl_ptr ptr)
> +{
> +	switch (ctrl->type) {
>  	case V4L2_CTRL_TYPE_STRING:
>  		idx *= ctrl->elem_size;
>  		memset(ptr.p_char + idx, ' ', ctrl->minimum);
>  		ptr.p_char[idx + ctrl->minimum] = '\0';
> -		break;
> +		return;
>  	case V4L2_CTRL_TYPE_INTEGER64:
>  		ptr.p_s64[idx] = ctrl->default_value;
> -		break;
> +		return;
>  	case V4L2_CTRL_TYPE_INTEGER:
>  	case V4L2_CTRL_TYPE_INTEGER_MENU:
>  	case V4L2_CTRL_TYPE_MENU:
> @@ -1533,32 +1557,21 @@ static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
>  	case V4L2_CTRL_TYPE_BUTTON:
>  	case V4L2_CTRL_TYPE_CTRL_CLASS:
>  		ptr.p_s32[idx] = ctrl->default_value;
> -		break;
> +		return;
>  	case V4L2_CTRL_TYPE_U8:
>  		ptr.p_u8[idx] = ctrl->default_value;
> -		break;
> +		return;
>  	case V4L2_CTRL_TYPE_U16:
>  		ptr.p_u16[idx] = ctrl->default_value;
> -		break;
> +		return;
>  	case V4L2_CTRL_TYPE_U32:
>  		ptr.p_u32[idx] = ctrl->default_value;
> -		break;
> -	case V4L2_CTRL_TYPE_MPEG2_SLICE_PARAMS:
> -		p_mpeg2_slice_params = ptr.p;
> -		/* 4:2:0 */
> -		p_mpeg2_slice_params->sequence.chroma_format = 1;
> -		/* 8 bits */
> -		p_mpeg2_slice_params->picture.intra_dc_precision = 0;
> -		/* interlaced top field */
> -		p_mpeg2_slice_params->picture.picture_structure = 1;
> -		p_mpeg2_slice_params->picture.picture_coding_type =
> -					V4L2_MPEG2_PICTURE_CODING_TYPE_I;
> -		break;
> +		return;
>  	default:
> -		idx *= ctrl->elem_size;
> -		memset(ptr.p + idx, 0, ctrl->elem_size);
> -		break;
> +		std_init_compound(ctrl, idx, ptr);
> +		return;

Same comment here: I see no reasons to have return instead of break.

>  	}
> +

You can get rid of this blank line.

>  }
>  
>  static void std_log(const struct v4l2_ctrl *ctrl)

Regards,

Boris