Re: [REVIEW PATCH 02/11] vb2: fix handling of data_offset and v4l2_plane.reserved[]

[Hans Verkuil <hverkuil@xs4all.nl>]

On 04/07/2014 07:11 AM, Pawel Osciak wrote:
> On Tue, Mar 11, 2014 at 6:20 AM, Hans Verkuil <hverkuil@xs4all.nl> wrote:
>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>
>> The videobuf2-core did not zero the reserved array of v4l2_plane as it
>> should.
>>
>> More serious is the fact that data_offset was not handled correctly:
>>
>> - for capture devices it was never zeroed, which meant that it was
>>   uninitialized. Unless the driver sets it it was a completely random
>>   number.
>>
>> - __qbuf_dmabuf had a completely incorrect length check that included
>>   data_offset.
>>
>> - in the single-planar case data_offset was never correctly set to 0.
>>   The single-planar API doesn't support data_offset, so setting it
>>   to 0 is the right thing to do.
>>
>> All these issues were found with v4l2-compliance.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>> ---
>>  drivers/media/v4l2-core/videobuf2-core.c | 19 ++++++++++---------
>>  1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>> index f9059bb..1a09442 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -1141,6 +1141,12 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
>>         unsigned int plane;
>>
>>         if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
>> +               for (plane = 0; plane < vb->num_planes; ++plane) {
>> +                       memset(v4l2_planes[plane].reserved, 0,
>> +                              sizeof(v4l2_planes[plane].reserved));
>> +                       v4l2_planes[plane].data_offset = 0;
>> +               }
>> +
> 
> Perhaps we should just memset the whole v4l2_planes array to 0 over
> all elements (ARRAY_SIZE)?

You can't do that here since in the mmap case the v4l2_planes array has already
fields filled in. However, by doing a memset in __qbuf_userptr and __qbuf_dmabuf,
before calling __fill_vb2_buffer, this can be solved neatly and correctly.

> Also I would extract this above the if and zero out everything for
> both multi and singleplanar.
> You shouldn't need to zero it out below then.
> 
>>                 /* Fill in driver-provided information for OUTPUT types */
>>                 if (V4L2_TYPE_IS_OUTPUT(b->type)) {
>>                         /*
>> @@ -1169,8 +1175,6 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
>>                                         b->m.planes[plane].m.fd;
>>                                 v4l2_planes[plane].length =
>>                                         b->m.planes[plane].length;
>> -                               v4l2_planes[plane].data_offset =
>> -                                       b->m.planes[plane].data_offset;

I've added an explicit explanation for this change to the commit log as
well:

- in __fill_vb2_buffer in the DMABUF case the data_offset field was
  unconditionally copied from v4l2_buffer to v4l2_plane when this
  should only happen in the output case.

Regards,

	Hans

>>                         }
>>                 }
>>         } else {
>> @@ -1180,10 +1184,10 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
>>                  * In videobuf we use our internal V4l2_planes struct for
>>                  * single-planar buffers as well, for simplicity.
>>                  */
>> -               if (V4L2_TYPE_IS_OUTPUT(b->type)) {
>> +               if (V4L2_TYPE_IS_OUTPUT(b->type))
>>                         v4l2_planes[0].bytesused = b->bytesused;
>> -                       v4l2_planes[0].data_offset = 0;
>> -               }
>> +               /* Single-planar buffers never use data_offset */
>> +               v4l2_planes[0].data_offset = 0;
>>
>>                 if (b->memory == V4L2_MEMORY_USERPTR) {
>>                         v4l2_planes[0].m.userptr = b->m.userptr;
>> @@ -1193,9 +1197,7 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
>>                 if (b->memory == V4L2_MEMORY_DMABUF) {
>>                         v4l2_planes[0].m.fd = b->m.fd;
>>                         v4l2_planes[0].length = b->length;
>> -                       v4l2_planes[0].data_offset = 0;
>>                 }
>> -
>>         }
>>
>>         /* Zero flags that the vb2 core handles */
>> @@ -1374,8 +1376,7 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const struct v4l2_buffer *b)
>>                 if (planes[plane].length == 0)
>>                         planes[plane].length = dbuf->size;
>>
>> -               if (planes[plane].length < planes[plane].data_offset +
>> -                   q->plane_sizes[plane]) {
>> +               if (planes[plane].length < q->plane_sizes[plane]) {
> 
> Good catch!
> 
>>                         dprintk(1, "qbuf: invalid dmabuf length for plane %d\n",
>>                                 plane);
>>                         ret = -EINVAL;
>> --
>> 1.9.0
>>
> 
> 
>