Re: [PATCH] media: v4l2: Initialize mpeg slice controls

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

On Wed, 29 May 2019 17:42:58 +0200
Hans Verkuil <hverkuil@xs4all.nl> wrote:

> On 5/29/19 5:36 PM, Ezequiel Garcia wrote:
> > On Wed, 2019-05-29 at 16:41 +0200, Hans Verkuil wrote:  
> >> On 5/3/19 1:42 PM, Boris Brezillon wrote:  
> >>> Make sure the default value at least passes the std_validate() tests.
> >>>
> >>> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> >>> ---
> >>>  drivers/media/v4l2-core/v4l2-ctrls.c | 20 +++++++++++++++++++-
> >>>  1 file changed, 19 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> index b1ae2e555c68..19d40cc6e565 100644
> >>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> @@ -1461,7 +1461,14 @@ static bool std_equal(const struct v4l2_ctrl *ctrl, u32 idx,
> >>>  static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> >>>  		     union v4l2_ctrl_ptr ptr)
> >>>  {
> >>> -	switch (ctrl->type) {
> >>> +	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
> >>> +
> >>> +	/*
> >>> +	 * 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_STRING:
> >>>  		idx *= ctrl->elem_size;
> >>>  		memset(ptr.p_char + idx, ' ', ctrl->minimum);
> >>> @@ -1486,6 +1493,17 @@ static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> >>>  	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;  
> >>
> >> Oops, this isn't complete. It should still zero the p_mpeg2_slice_params
> >> struct first. Right now any fields not explicitly set just have whatever
> >> was in memory.

Oops.

> >>
> >> Can you post a patch fixing this?
> >>
> >>  
> > 
> > 
> > I was wondering if we want to zero all the cases, and not just
> > the struct types ones.  
> 
> The others either overwrite the data with the default_value, or memset
> the whole control (default case). It's only for these compound controls
> that something special needs to be done.
> 
> The code can be restructured, though: instead of break do return in all
> the simple type cases.
> 
> Then call memset followed by a new switch for the compound types where you
> need to set some fields to non-zero.

memset(0) will fix the undefined val issue, the question is, is it the
default we want? I haven't worked on MPEG2 (just posted patches
Ezequiel worked on) so I can't tell.