[FFmpeg-devel] [PATCHv3 4/4] libavcodec: v4l2: add support for v4l2 mem2mem codecs

[Jorge Ramirez]

On 08/03/2017 01:53 AM, Mark Thompson wrote:

agree with all your previous comments up to here (will fix).

>> +    case V4L2_BUF_TYPE_VIDEO_OUTPUT:
>> +    case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
>> +        pfd.events = POLLOUT | POLLERR | POLLWRNORM;
>> +        break;
>> +    default:
>> +        pfd.events = POLLIN | POLLERR | POLLRDNORM;
> What hits this default case?

nothing, it can't happen will remove.
>
>> +    }
>> +
>> +    ret = poll(&pfd, 1, timeout);
> Can this poll be interrupted?
yes. when that happens, we indicate no buffer available.
I think the main program should set the necessary masks.

>> +    if (ret <=  0)
>> +        return NULL;
>> +
>> +    memset(&buf, 0, sizeof(buf));
>> +    buf.memory = bp->memory;
>> +    buf.type = bp->type;
>> +    if (V4L2_TYPE_IS_MULTIPLANAR(bp->type)) {
>> +        memset(planes, 0, sizeof(planes));
>> +        buf.length = VIDEO_MAX_PLANES;
>> +        buf.m.planes = planes;
>> +    }
>> +    ret = ioctl(bp->fd, VIDIOC_DQBUF, &buf);
>> +    if (ret) {
>> +        if (errno != EAGAIN && errno != EINVAL) {
> EINVAL is considered ok?

no any ioctl that returns non zero is a fault condition.
EINVAL (just as EAGAIN) is just not an unrecoverable error (we will just 
return null indicating that there is no buffer available)
>
>> +            av_log(bp->log_ctx, AV_LOG_DEBUG, "%s: VIDIOC_DQBUF, errno (%d)\n", bp->name, errno);
>> +            bp->broken = errno;
> errno can be overwritten by the av_log() call.

OK.

>
>> +        }
>> +        return NULL;
>> +    }
>> +