Re: [RFCv4 PATCH 6/8] v4l2-ioctl.c: prefill tuner type for g_frequency and g/s_tuner.

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em 12-06-2011 12:46, Hans Verkuil escreveu:
> On Sunday, June 12, 2011 16:36:11 Mauro Carvalho Chehab wrote:
>> Em 12-06-2011 07:59, Hans Verkuil escreveu:
>>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>>
>>> The subdevs are supposed to receive a valid tuner type for the g_frequency
>>> and g/s_tuner subdev ops. Some drivers do this, others don't. So prefill
>>> this in v4l2-ioctl.c based on whether the device node from which this is
>>> called is a radio node or not.
>>>
>>> The spec does not require applications to fill in the type, and if they
>>> leave it at 0 then the 'supported_mode' call in tuner-core.c will return
>>> false and the ioctl does nothing.
>>
>> Interesting solution. Yes, this is the proper fix, but only after being sure
>> that no drivers allow switch to radio using the video device, and vice-versa.
> 
> Why would that be a problem? What this patch does is that it fixes those
> drivers that do *not* set vf/vt->type (i.e. leave it at 0). For those that already
> set it nothing changes.

Yeah, I realized it after after answering. Yes, your patch seems to be ok, as
bridge drivers can override it.

> 
>> Unfortunately, this is not the case, currently.
>>
>> Most drivers allow this, following the previous V4L2 specs. Changing such
>> behavior will probably require to write something at 
>> Documentation/feature-removal-schedule.txt, as we're changing the behavior.
> 
> I think in the longer term we need to change the spec so that:
> 
> 1) Opening a radio node no longer switches to radio mode. Instead, you need to
>    call VIDIOC_S_FREQUENCY for that.
> 2) When VIDIOC_S_FREQUENCY the type field should match the video/radio node it
>    is called on. So for /dev/radio type should be RADIO, for others it should be
>    ANALOG_TV. Otherwise -EINVAL is called.
> 
> So this might be a good feature removal for 3.2 or 3.3.

I'm OK with that.

> 
> Regards,
> 
> 	Hans
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