Re: [PATCH RFC 3/4] v4l: add new tuner types for SDR

[Antti Palosaari <crope@iki.fi>]

On 12.12.2013 19:12, Antti Palosaari wrote:
> On 12.12.2013 09:50, Hans Verkuil wrote:
>> On 12/12/2013 12:54 AM, Antti Palosaari wrote:

>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c
>>> b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> index bc10684..ee91a9f 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> @@ -1288,8 +1288,13 @@ static int v4l_g_frequency(const struct
>>> v4l2_ioctl_ops *ops,
>>>       struct video_device *vfd = video_devdata(file);
>>>       struct v4l2_frequency *p = arg;
>>>
>>> -    p->type = (vfd->vfl_type == VFL_TYPE_RADIO) ?
>>> -            V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
>>> +    if (vfd->vfl_type == VFL_TYPE_SDR) {
>>> +        if (p->type != V4L2_TUNER_ADC && p->type != V4L2_TUNER_SDR)
>>> +            return -EINVAL;
>>
>> This isn't right. p->type is returned by the driver, not set by the user.
>> In the case of TYPE_SDR I would just set it to TUNER_SDR and let the
>> driver
>> update it for ADC tuners. You can also just leave it alone. This does
>> make
>> the assumption that SDR and ADC tuners are always separate tuners.
>> I.e., not
>> like radio and TV tuners that can be one physical tuner with two mutually
>> exclusive modes. It's my understanding that that is by definition true
>> for
>> SDR.
>
> Aaah, so it is possible to use same tuner and that type is aimed for
> selecting tuner operation mode. Makes sense.
>
> So if I now understand V4L2 driver model correctly, there should be one
> tuner that implements different functionality by using tuner type field.
>
> I could change it easily, no problem.

http://hverkuil.home.xs4all.nl/spec/media.html#vidioc-g-frequency
I still don't understand that. Why both index and type should be defined 
for VIDIOC_S_FREQUENCY, but the opposite command VIDIOC_G_FREQUENCY 
requires only index and returns type too? It does not sound correct 
behavior.
If S_FREQUENCY/G_FREQUENCY should be able to handle multiple tuner types 
for same tuner index, then type must be also given that driver could 
detect required mode.

http://hverkuil.home.xs4all.nl/spec/media.html#vidioc-g-tuner
How I can enumerate tuners. There is G_TUNER/S_TUNER for enumerating, 
but documentation of these IOCTLs looks like only one tuner type per 
tuner index is supported. That offers enumeration per tuner index.

regards
Antti

-- 
http://palosaari.fi/