Re: [PATCH v3 4/9] media: venus: vdec: add video decoder files

[Hans Verkuil]

On 18/11/16 10:11, Stanimir Varbanov wrote:
> Hi Hans,
>
> > > > +
> > > > +static int
> > > > +vdec_reqbufs(struct file *file, void *fh, struct v4l2_requestbuffers *b)
> > > > +{
> > > > +	struct vb2_queue *queue = to_vb2q(file, b->type);
> > > > +
> > > > +	if (!queue)
> > > > +		return -EINVAL;
> > > > +
> > > > +	return vb2_reqbufs(queue, b);
> > > > +}
> > >
> > > Is there any reason why the v4l2_m2m_ioctl_reqbufs et al helper functions
> > > can't be used? I strongly recommend that, unless there is a specific reason
> > > why that won't work.
> >
> > So that means I need to completely rewrite the v4l2 part and adopt it
> > for mem2mem device APIs.
> >
> > If that is what you meant I can invest some time to make a estimation
> > what would be the changes and time needed. After that we can decide what
> > to do - take the driver as is and port it to mem2mem device APIs later
> > on or wait for the this transition to happen before merging.
>
> I made an attempt to adopt v4l2 part of the venus driver to m2m API's
> and the result was ~300 less lines of code, but with the price of few
> extensions in m2m APIs (and I still have issues with running
> simultaneously multiple instances).
>
> I have to add few functions/macros to iterate over a list (list_for_each
> and friends). This is used to find the returned from decoder buffers by
> address and associate them to vb2_buffer, because the decoder can change
> the order of the output buffers.
>
> The main problem I have is registering of the capture buffers before
> session_start. This is requirement (disadvantage) of the firmware
> implementation i.e. I need to announce capture buffers (address and size
> of the buffer) to the firmware before start buffer interaction by
> session_start.
>
> So having that I think I will need one more week to stabilize the driver
> to the state that it was before this m2m transition.
>
> Thoughts?

It sounds like this it worth doing, since if you need these extensions, then
it is likely someone else will need it as well.

Can you mail me a preliminary patch with the core m2m changes? That will be
helpful for me to look at.

Regards,

	Hans