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

From: Stanimir Varbanov
Date: Fri Nov 18 2016 - 04:11:46 EST

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

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.