Re: [PATCH v3 2/3] media: au0828 - convert to use videobuf2

Shuah Khan
2015-01-22T15:05:33Z

On 01/22/2015 08:00 AM, Devin Heitmueller wrote:
>>> - fh->type = type;
>>> - fh->dev = dev;
>>> - v4l2_fh_init(&fh->fh, vdev);
>>> - filp->private_data = fh;
>>> + dprintk(1,
>>> + "%s called std_set %d dev_state %d stream users %d users %d\n",
>>> + __func__, dev->std_set_in_tuner_core, dev->dev_state,
>>> + dev->streaming_users, dev->users);
>>>
>>> - if (mutex_lock_interruptible(&dev->lock)) {
>>> - kfree(fh);
>>> + if (mutex_lock_interruptible(&dev->lock))
>>> return -ERESTARTSYS;
>>> +
>>> + ret = v4l2_fh_open(filp);
>>> + if (ret) {
>>> + au0828_isocdbg("%s: v4l2_fh_open() returned error %d\n",
>>> + __func__, ret);
>>> + mutex_unlock(&dev->lock);
>>> + return ret;
>>> }
>>> +
>>> if (dev->users == 0) {
>>
>> you can use v4l2_fh_is_singular_file() and get rid of users member ?
>
> That won't work because the underlying resources are shared between
> /dev/videoX and /dev/vbiX device nodes. Hence if you were to move to
> v4l2_fh_is_singular_file(), the video device would get opened, the
> stream would get reset, the VBI device would get opened, and that
> would cause the analog stream to get enabled/reset *again*.
>

Thanks Devin for a detailed explanation. I did see this behavior when I
was removed users and used v4l2_fh_is_singular_file() instead. I didn't
understand that this is due to resource sharing between /dev/videoX and
/dev/vbiX .

thanks,
-- Shuah

--
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@osg.samsung.com | (970) 217-8978