Re: [PATCHv7 2/9] v4l2: video device: Add V4L2_CTRL_CLASS_FM_TX controls

[Trent Piepho <xyzzy@speakeasy.org>]

On Tue, 16 Jun 2009, Eduardo Valentin wrote:
> On Sun, Jun 14, 2009 at 06:59:13PM +0200, ext Hans Verkuil wrote:
> > On Sunday 14 June 2009 18:23:41 Trent Piepho wrote:
> > > > > similar V4L2_CID_MPEG_EMPHASIS control and others might well appear in the
> > > > > future, so I think this name should be more specific to the FM_TX API.
> > >
> > > The cx88 driver could get support for setting the fm preemphasis via a
> > > control.  I added support via a module option, but a control would be
> > > better.  You're saying it shouldn't use this fm preemphasis control?
> >
> > Correct. This set the pre-emphasis when transmitting. For receiving you want
> > a separate control. Although the enum should be made generic. So FM_TX can be
> > removed from the enum.
> >
> > Why should we have one rx and one tx control for this? Because you can have
> > both receivers and transmitters in one device and you want independent control
> > of the two.
>
> Yes, agreed here. There is the possibility to have receiver and transmitter
> both in the same device. So, I think it is better to have separated controls.

Is both a receiver and transmitter in the same device different than having
two receivers or two transmitters?  In which case, since controls are not
assigned to a specific input, how does one handle that?