[PATCH] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

[PATCH] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

[Ricardo Ribalda Delgado]

According to the doc, V4L2_BUF_FLAG_DONE is cleared after DQBUF:

V4L2_BUF_FLAG_DONE 0x00000004  ... After calling the VIDIOC_QBUF or
VIDIOC_DQBUF it is always cleared ...

Unfortunately, it seems that videobuf2 keeps it set after DQBUF. This
can be tested with vivid and dev_debug:

[257604.338082] video1: VIDIOC_DQBUF: 71:33:25.00260479 index=3,
type=vid-cap, flags=0x00002004, field=none, sequence=163,
memory=userptr, bytesused=460800, offset/userptr=0x344b000,
length=460800

This patch changes the order when fill_user_buffer() is called,
to follow the documentation.

Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
 drivers/media/v4l2-core/videobuf2-core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 633fc1ab1d7a..63981f28075e 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1771,10 +1771,6 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
 	if (pindex)
 		*pindex = vb->index;
 
-	/* Fill buffer information for the userspace */
-	if (pb)
-		call_void_bufop(q, fill_user_buffer, vb, pb);
-
 	/* Remove from videobuf queue */
 	list_del(&vb->queued_entry);
 	q->queued_count--;
@@ -1784,6 +1780,10 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
 	/* go back to dequeued state */
 	__vb2_dqbuf(vb);
 
+	/* Fill buffer information for the userspace */
+	if (pb)
+		call_void_bufop(q, fill_user_buffer, vb, pb);
+
 	dprintk(1, "dqbuf of buffer %d, with state %d\n",
 			vb->index, vb->state);
 
-- 
2.8.1

Re: [PATCH] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

[Hans Verkuil]

On 06/20/2016 11:01 AM, Ricardo Ribalda Delgado wrote:
> According to the doc, V4L2_BUF_FLAG_DONE is cleared after DQBUF:
> 
> V4L2_BUF_FLAG_DONE 0x00000004  ... After calling the VIDIOC_QBUF or
> VIDIOC_DQBUF it is always cleared ...
> 
> Unfortunately, it seems that videobuf2 keeps it set after DQBUF. This
> can be tested with vivid and dev_debug:
> 
> [257604.338082] video1: VIDIOC_DQBUF: 71:33:25.00260479 index=3,
> type=vid-cap, flags=0x00002004, field=none, sequence=163,
> memory=userptr, bytesused=460800, offset/userptr=0x344b000,
> length=460800
> 
> This patch changes the order when fill_user_buffer() is called,
> to follow the documentation.
> 
> Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>

Sorry, this won't work. Calling __vb2_dqbuf will overwrite the state
VB2_BUF_STATE_ERROR and so the V4L2_BUF_FLAG_ERROR flag will never be
set. The same is true for the last 'if' in the __fill_v4l2_buffer()
function.

I think it might be better to keep this code and instead change the
vb2_internal_dqbuf function to just clear the DONE flag after calling
vb2_core_dqbuf.

It would be nice to have a v4l2_compliance check for this as well.

Regards,

	Hans

> ---
>  drivers/media/v4l2-core/videobuf2-core.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 633fc1ab1d7a..63981f28075e 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1771,10 +1771,6 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>  	if (pindex)
>  		*pindex = vb->index;
>  
> -	/* Fill buffer information for the userspace */
> -	if (pb)
> -		call_void_bufop(q, fill_user_buffer, vb, pb);
> -
>  	/* Remove from videobuf queue */
>  	list_del(&vb->queued_entry);
>  	q->queued_count--;
> @@ -1784,6 +1780,10 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>  	/* go back to dequeued state */
>  	__vb2_dqbuf(vb);
>  
> +	/* Fill buffer information for the userspace */
> +	if (pb)
> +		call_void_bufop(q, fill_user_buffer, vb, pb);
> +
>  	dprintk(1, "dqbuf of buffer %d, with state %d\n",
>  			vb->index, vb->state);
>  
> 

Re: [PATCH] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

[Ricardo Ribalda Delgado]

Good catch :)

I will prepare the new version. Btw, can I also merge
vb2_internal_dqbuf and vb2_dqbuf in one function? Seems a bit
overkilled that split.

Regarding v42l_compliance... I can take care of that if you dare :)

Best regards!

On Mon, Jun 20, 2016 at 11:53 AM, Hans Verkuil <hverkuil@xs4all.nl> wrote:
> On 06/20/2016 11:01 AM, Ricardo Ribalda Delgado wrote:
>> According to the doc, V4L2_BUF_FLAG_DONE is cleared after DQBUF:
>>
>> V4L2_BUF_FLAG_DONE 0x00000004  ... After calling the VIDIOC_QBUF or
>> VIDIOC_DQBUF it is always cleared ...
>>
>> Unfortunately, it seems that videobuf2 keeps it set after DQBUF. This
>> can be tested with vivid and dev_debug:
>>
>> [257604.338082] video1: VIDIOC_DQBUF: 71:33:25.00260479 index=3,
>> type=vid-cap, flags=0x00002004, field=none, sequence=163,
>> memory=userptr, bytesused=460800, offset/userptr=0x344b000,
>> length=460800
>>
>> This patch changes the order when fill_user_buffer() is called,
>> to follow the documentation.
>>
>> Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
>
> Sorry, this won't work. Calling __vb2_dqbuf will overwrite the state
> VB2_BUF_STATE_ERROR and so the V4L2_BUF_FLAG_ERROR flag will never be
> set. The same is true for the last 'if' in the __fill_v4l2_buffer()
> function.
>
> I think it might be better to keep this code and instead change the
> vb2_internal_dqbuf function to just clear the DONE flag after calling
> vb2_core_dqbuf.
>
> It would be nice to have a v4l2_compliance check for this as well.
>
> Regards,
>
>         Hans
>
>> ---
>>  drivers/media/v4l2-core/videobuf2-core.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>> index 633fc1ab1d7a..63981f28075e 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -1771,10 +1771,6 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>>       if (pindex)
>>               *pindex = vb->index;
>>
>> -     /* Fill buffer information for the userspace */
>> -     if (pb)
>> -             call_void_bufop(q, fill_user_buffer, vb, pb);
>> -
>>       /* Remove from videobuf queue */
>>       list_del(&vb->queued_entry);
>>       q->queued_count--;
>> @@ -1784,6 +1780,10 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>>       /* go back to dequeued state */
>>       __vb2_dqbuf(vb);
>>
>> +     /* Fill buffer information for the userspace */
>> +     if (pb)
>> +             call_void_bufop(q, fill_user_buffer, vb, pb);
>> +
>>       dprintk(1, "dqbuf of buffer %d, with state %d\n",
>>                       vb->index, vb->state);
>>
>>



-- 
Ricardo Ribalda

Re: [PATCH] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

[Hans Verkuil]

On 06/20/2016 12:12 PM, Ricardo Ribalda Delgado wrote:
> Good catch :)
> 
> I will prepare the new version. Btw, can I also merge
> vb2_internal_dqbuf and vb2_dqbuf in one function? Seems a bit
> overkilled that split.

No, that's not possible. vb2_internal_dqbuf is used in the threading
code to implement read() and vb2_fileio_is_active() returns true in that
case.

> 
> Regarding v42l_compliance... I can take care of that if you dare :)

It would be great if you can add a test for this.

Regards,

	Hans

> 
> Best regards!
> 
> On Mon, Jun 20, 2016 at 11:53 AM, Hans Verkuil <hverkuil@xs4all.nl> wrote:
>> On 06/20/2016 11:01 AM, Ricardo Ribalda Delgado wrote:
>>> According to the doc, V4L2_BUF_FLAG_DONE is cleared after DQBUF:
>>>
>>> V4L2_BUF_FLAG_DONE 0x00000004  ... After calling the VIDIOC_QBUF or
>>> VIDIOC_DQBUF it is always cleared ...
>>>
>>> Unfortunately, it seems that videobuf2 keeps it set after DQBUF. This
>>> can be tested with vivid and dev_debug:
>>>
>>> [257604.338082] video1: VIDIOC_DQBUF: 71:33:25.00260479 index=3,
>>> type=vid-cap, flags=0x00002004, field=none, sequence=163,
>>> memory=userptr, bytesused=460800, offset/userptr=0x344b000,
>>> length=460800
>>>
>>> This patch changes the order when fill_user_buffer() is called,
>>> to follow the documentation.
>>>
>>> Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
>>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
>>
>> Sorry, this won't work. Calling __vb2_dqbuf will overwrite the state
>> VB2_BUF_STATE_ERROR and so the V4L2_BUF_FLAG_ERROR flag will never be
>> set. The same is true for the last 'if' in the __fill_v4l2_buffer()
>> function.
>>
>> I think it might be better to keep this code and instead change the
>> vb2_internal_dqbuf function to just clear the DONE flag after calling
>> vb2_core_dqbuf.
>>
>> It would be nice to have a v4l2_compliance check for this as well.
>>
>> Regards,
>>
>>         Hans
>>
>>> ---
>>>  drivers/media/v4l2-core/videobuf2-core.c | 8 ++++----
>>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>>> index 633fc1ab1d7a..63981f28075e 100644
>>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>>> @@ -1771,10 +1771,6 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>>>       if (pindex)
>>>               *pindex = vb->index;
>>>
>>> -     /* Fill buffer information for the userspace */
>>> -     if (pb)
>>> -             call_void_bufop(q, fill_user_buffer, vb, pb);
>>> -
>>>       /* Remove from videobuf queue */
>>>       list_del(&vb->queued_entry);
>>>       q->queued_count--;
>>> @@ -1784,6 +1780,10 @@ int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
>>>       /* go back to dequeued state */
>>>       __vb2_dqbuf(vb);
>>>
>>> +     /* Fill buffer information for the userspace */
>>> +     if (pb)
>>> +             call_void_bufop(q, fill_user_buffer, vb, pb);
>>> +
>>>       dprintk(1, "dqbuf of buffer %d, with state %d\n",
>>>                       vb->index, vb->state);
>>>
>>>
> 
> 
>