On 1/18/24 12:14, Tomasz Figa wrote:
> Hi Hans,
>
> On Tue, Jan 16, 2024 at 11:05 PM Hans Verkuil <hverkuil-cisco@xxxxxxxxx> wrote:
>>
>> Several functions implementing VIDIOC_REQBUFS and _CREATE_BUFS all use almost
>> the same code to fill in the flags and capability fields. Refactor this into a
>> new vb2_set_flags_and_caps() function that replaces the old fill_buf_caps()
>> and validate_memory_flags() functions.
>>
>> This also fixes a bug where vb2_ioctl_create_bufs() would not set the
>> V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS cap and also not fill in the
>> max_num_buffers field.
>>
>> Fixes: d055a76c0065 ("media: core: Report the maximum possible number of buffers for the queue")
>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
>> ---
>> .../media/common/videobuf2/videobuf2-v4l2.c | 55 +++++++++----------
>> 1 file changed, 26 insertions(+), 29 deletions(-)
>>
>
> Thanks for the patch! Please check my comments inline.
>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> index 54d572c3b515..c575198e8354 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -671,8 +671,20 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
>> }
>> EXPORT_SYMBOL(vb2_querybuf);
>>
>> -static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>> +static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>> + u32 *flags, u32 *caps, u32 *max_num_bufs)
>> {
>> + if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP) {
>> + /*
>> + * This needs to clear V4L2_MEMORY_FLAG_NON_COHERENT only,
>> + * but in order to avoid bugs we zero out all bits.
>> + */
>> + *flags = 0;
>> + } else {
>> + /* Clear all unknown flags. */
>> + *flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>> + }
>> +
>> *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>> if (q->io_modes & VB2_MMAP)
>> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>> @@ -686,21 +698,9 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS;
>> if (q->supports_requests)
>> *caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
>> -}
>> -
>> -static void validate_memory_flags(struct vb2_queue *q,
>> - int memory,
>> - u32 *flags)
>> -{
>> - if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP) {
>> - /*
>> - * This needs to clear V4L2_MEMORY_FLAG_NON_COHERENT only,
>> - * but in order to avoid bugs we zero out all bits.
>> - */
>> - *flags = 0;
>> - } else {
>> - /* Clear all unknown flags. */
>> - *flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>> + if (max_num_bufs) {
>> + *max_num_bufs = q->max_num_buffers;
>> + *caps |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
>> }
>> }
>>
>> @@ -709,8 +709,8 @@ int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>> int ret = vb2_verify_memory_type(q, req->memory, req->type);
>> u32 flags = req->flags;
>
> I think we have a bug here, we check the memory type, but just let the
> code continue even if it's invalid.
It should be harmless. The old code did the same, BTW.
>
>>
>> - fill_buf_caps(q, &req->capabilities);
>> - validate_memory_flags(q, req->memory, &flags);
>> + vb2_set_flags_and_caps(q, req->memory, &flags,
>> + &req->capabilities, NULL);
>> req->flags = flags;
>> return ret ? ret : vb2_core_reqbufs(q, req->memory,
>> req->flags, &req->count);
>> @@ -751,11 +751,9 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>> int ret = vb2_verify_memory_type(q, create->memory, f->type);
>> unsigned i;
>>
>
> Ditto.
>
>> - fill_buf_caps(q, &create->capabilities);
>> - validate_memory_flags(q, create->memory, &create->flags);
>> create->index = vb2_get_num_buffers(q);
>> - create->max_num_buffers = q->max_num_buffers;
>> - create->capabilities |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
>> + vb2_set_flags_and_caps(q, create->memory, &create->flags,
>> + &create->capabilities, &create->max_num_buffers);
>> if (create->count == 0)
>> return ret != -EBUSY ? ret : 0;
>>
>> @@ -1006,8 +1004,8 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
>> int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
>> u32 flags = p->flags;
>>
>> - fill_buf_caps(vdev->queue, &p->capabilities);
>> - validate_memory_flags(vdev->queue, p->memory, &flags);
>> + vb2_set_flags_and_caps(vdev->queue, p->memory, &flags,
>> + &p->capabilities, NULL);
>
> Could we just call vb2_reqbufs() instead of vb2_core_reqbufs() and
> avoid all the duplicate checks?
>
>> p->flags = flags;
>> if (res)
>> return res;
>> @@ -1026,12 +1024,11 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,
>> struct v4l2_create_buffers *p)
>> {
>> struct video_device *vdev = video_devdata(file);
>> - int res = vb2_verify_memory_type(vdev->queue, p->memory,
>> - p->format.type);
>> + int res = vb2_verify_memory_type(vdev->queue, p->memory, p->format.type);
>>
>> - p->index = vdev->queue->num_buffers;
>> - fill_buf_caps(vdev->queue, &p->capabilities);
>> - validate_memory_flags(vdev->queue, p->memory, &p->flags);
>> + p->index = vb2_get_num_buffers(vdev->queue);
>> + vb2_set_flags_and_caps(vdev->queue, p->memory, &p->flags,
>> + &p->capabilities, &p->max_num_buffers);
>
> This function in fact already calls vb2_create_bufs() which includes
> all the checks above, except the one for vb2_queue_is_bus() that
> continues down below, so maybe we can just remove them?
Same answer for both reqbufs and create_bufs: it has to do with the
order in which checks are done.
When using vb2_ioctl_reqbufs you want to first check vb2_verify_memory_type()
and return if that's wrong. Next you check if the queue is busy and return
-EBUSY. Only then do you call vb2_core_reqbufs() (or vb2_create_bufs()).
Note that this is a fixes patch (that should have been in the subject, sorry
for that), and I don't want to make more changes than strictly necessary.
What really should happen is that the last users of vb2_reqbufs and
vb2_create_bufs are converted to use vb2_ioctl_reqbufs/create_bufs. But
that's another story.
Regards,
Hans
>
> Best regards,
> Tomasz
>
>> /*
>> * If count == 0, then just check if memory and type are valid.
>> * Any -EBUSY result from vb2_verify_memory_type can be mapped to 0.
>> --
>> 2.42.0
>>
>>
