Re: v4l2 ioctls

[Shuah Khan <shuahkh@osg.samsung.com>]

On 09/15/2014 05:53 PM, Mauro Carvalho Chehab wrote:
> Em Mon, 15 Sep 2014 17:15:52 -0600
> Shuah Khan <shuahkh@osg.samsung.com> escreveu:
> 
>> On 09/15/2014 05:54 AM, Mauro Carvalho Chehab wrote:
>>> Hi Shuah,
>>>
>>> Em Fri, 12 Sep 2014 18:37:13 -0600
>>> Shuah Khan <shuahkh@osg.samsung.com> escreveu:
>>>
>>>> Mauro/Hans,
>>>>
>>>> Thanks for both for your replies. I finally have it working with
>>>> the following:
>>>
>>> One additional info: While in DVB mode, opening the device in
>>> readonly mode should not take the tuner locking.
>>
>> That's what the code does for dvb. It gets the tuner lock in
>> dvb_frontend_start() which is called from dvb_frontend_open()
>> when dvb is opened in R/W mode.
> 
> Yeah, I think that the FE kthread is only started in R/W mode, 
> but it doesn't hurt to double-check it and to do some tests to
> avoid regressions.

Here is the code snippet:

       if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
                /* normal tune mode when opened R/W */
                fepriv->tune_mode_flags &= ~FE_TUNE_MODE_ONESHOT;
                fepriv->tone = -1;
                fepriv->voltage = -1;

                ret = dvb_frontend_start (fe);
                if (ret)
                        goto err2;

                /*  empty event queue */
                fepriv->events.eventr = fepriv->events.eventw = 0;
        }


I can do some testing to make sure

-- Shuah


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