[pvrusb2] Newbie Question Switch Audio Input

Mike Isely isely at isely.net
Wed Mar 7 13:28:45 CST 2007

On Wed, 7 Mar 2007, devsk wrote:

> > You can also simply open the /dev/radio0 (or whatever it's named 
> > on your system) device node - doing that will imply a switch to radio 
> > mode.
> does it make sense to have an alias for "composite" input as well i.e. 
> open a device /dev/composite and it automatically switches the input 
> to "composite". It is painful to sudo echo first and then open 
> /dev/video0.

It doesn't really make sense.

I'll grant that it's a creative idea though.

The "radio" device node is really only there because it's expected of a 
V4L device.  I consider that to be a bit of a hack.  I don't think we 
would want to start cluttering /dev with cloned device entries per each 
possible input.  Also, any attempt at such a scheme is going to be 
clunky anyway because there really isn't a "range" of minor V4L device 
ids for something such as this.  Conceptually it's far smarter to have a 
single device node with appropriate API(s) implemented there to control 
its state.

The reality of the situation is that the V4L API includes a method to 
set the input.  Any V4L app should really be using that to select the 
correct input.  Radio is kind of an outlier because since the /dev/radio 
node is expected to exist I think any radio app just presumes that radio 
mode will be enabled when the device node is opened.

BTW, if all you are ever using is the composite input, I wonder if you 
can set up a udev rule that did the switch for you (via sysfs) when the 
device appeared...


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