Re: [PATCHv17 26/34] videobuf2-v4l2: add vb2_request_queue/validate helpers

[Mauro Carvalho Chehab <mchehab+samsung@kernel.org>]

Em Tue, 14 Aug 2018 09:19:08 +0200
Hans Verkuil <hverkuil@xs4all.nl> escreveu:

> On 13/08/18 16:53, Mauro Carvalho Chehab wrote:
> > Em Sat,  4 Aug 2018 14:45:18 +0200
> > Hans Verkuil <hverkuil@xs4all.nl> escreveu:
> >   
> >> From: Hans Verkuil <hans.verkuil@cisco.com>
> >>
> >> The generic vb2_request_validate helper function checks if
> >> there are buffers in the request and if so, prepares (validates)
> >> all objects in the request.
> >>
> >> The generic vb2_request_queue helper function queues all buffer
> >> objects in the validated request.
> >>
> >> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> >> ---
> >>  .../media/common/videobuf2/videobuf2-v4l2.c   | 44 +++++++++++++++++++
> >>  include/media/videobuf2-v4l2.h                |  4 ++
> >>  2 files changed, 48 insertions(+)
> >>
> >> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> index 9c652afa62ab..88d8f60c742b 100644
> >> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> @@ -1100,6 +1100,50 @@ void vb2_ops_wait_finish(struct vb2_queue *vq)
> >>  }
> >>  EXPORT_SYMBOL_GPL(vb2_ops_wait_finish);
> >>  
> >> +int vb2_request_validate(struct media_request *req)
> >> +{
> >> +	struct media_request_object *obj;
> >> +	int ret = 0;
> >> +
> >> +	if (!vb2_request_has_buffers(req))
> >> +		return -ENOENT;  
> > 
> > This holds the spinlock...  
> 
> The spinlock in vb2_request_has_buffers() is not needed if vb2_request_has_buffers()
> is called from this validate function. While validating no new objects can be
> added to the request, and since nothing has been queued yet objects cannot be
> deleted either. That's true for this whole vb2_request_validate() function.
> 
> But should vb2_request_has_buffers() ever be called from a non-validate context,
> then the spinlock would be needed.
> 
> I want to keep the spinlock in that function for now as it is more robust.

Now your comment to patch 25/34 makes sense, but please document it, as
it is confusing for anyone reviewing the code.

> 
> Regards,
> 
> 	Hans
> 
> >   
> >> +
> >> +	list_for_each_entry(obj, &req->objects, list) {
> >> +		if (!obj->ops->prepare)
> >> +			continue;
> >> +
> >> +		ret = obj->ops->prepare(obj);
> >> +		if (ret)
> >> +			break;
> >> +	}
> >> +  
> > 
> > Shouldn't this logic hold it too?
> >   
> >> +	if (ret) {
> >> +		list_for_each_entry_continue_reverse(obj, &req->objects, list)
> >> +			if (obj->ops->unprepare)
> >> +				obj->ops->unprepare(obj);
> >> +		return ret;
> >> +	}
> >> +	return 0;
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_request_validate);
> >> +
> >> +void vb2_request_queue(struct media_request *req)
> >> +{
> >> +	struct media_request_object *obj, *obj_safe;
> >> +
> >> +	/* Queue all non-buffer objects */
> >> +	list_for_each_entry_safe(obj, obj_safe, &req->objects, list)
> >> +		if (obj->ops->queue && !vb2_request_object_is_buffer(obj))
> >> +			obj->ops->queue(obj);
> >> +
> >> +	/* Queue all buffer objects */
> >> +	list_for_each_entry_safe(obj, obj_safe, &req->objects, list) {
> >> +		if (obj->ops->queue && vb2_request_object_is_buffer(obj))
> >> +			obj->ops->queue(obj);
> >> +	}
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_request_queue);
> >> +
> >>  MODULE_DESCRIPTION("Driver helper framework for Video for Linux 2");
> >>  MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>, Marek Szyprowski");
> >>  MODULE_LICENSE("GPL");
> >> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
> >> index 91a2b3e1a642..727855463838 100644
> >> --- a/include/media/videobuf2-v4l2.h
> >> +++ b/include/media/videobuf2-v4l2.h
> >> @@ -303,4 +303,8 @@ void vb2_ops_wait_prepare(struct vb2_queue *vq);
> >>   */
> >>  void vb2_ops_wait_finish(struct vb2_queue *vq);
> >>  
> >> +struct media_request;
> >> +int vb2_request_validate(struct media_request *req);
> >> +void vb2_request_queue(struct media_request *req);
> >> +
> >>  #endif /* _MEDIA_VIDEOBUF2_V4L2_H */  
> > 
> > 
> > 
> > Thanks,
> > Mauro
> >   
> 



Thanks,
Mauro