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Date: Thu, 22 Jan 2015 10:00:16 -0500
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Subject: Re: [PATCH v3 2/3] media: au0828 - convert to use videobuf2
From: Devin Heitmueller <dheitmueller@kernellabs.com>
To: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>,
        Mauro Carvalho Chehab <m.chehab@samsung.com>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        laurent pinchart <laurent.pinchart@ideasonboard.com>,
        ttmesterr <ttmesterr@gmail.com>,
        linux-media <linux-media@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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>> -       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*.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com