[linux-dvb] How to access /dev/videoK from /dev/dvb/adapterN?

Michael Krufky mkrufky at linuxtv.org
Fri Jun 16 22:51:24 CEST 2006

Kenneth Aafløy wrote:
> Ralph Metzler skrev:
>> Since upcoming cards with decoder and V4L interface for those will
>> need it too, should we add a call for this? In the DVB video device?
>> We might also need something like this for audio.
> Sounds like a good enhancement, maybe even make this a common 
> V4L/DVB/?? ioctl, that applications can query for relations between 
> devices?
I agree with the idea, although (slightly unrelated) I also think we 
should have some relation established between the v4l devices and dvb 
devices on hybrid devices as well.  This isn't exactly the same idea as 
what Klaus is talking about, however.

In Klaus's case, he wants to create a relation between the dvb device 
and the v4l device on FF cards.  I agree with the idea, but in addition, 
I would also like a relation drawn between dvb and video interfaces on 
hybrid cards that provide separate functionality of v4l inputs vs dvb 
inputs, where only one function may be used at a time.

For instance, MythTV allows concurrent use of multiple v4l/dvb devices 
all at the same time, however, on a given hybrid device, if the 
application is already recording a dvb stream, and it suddenly wants to 
use the v4l interface of the same device to record an analog stream, it 
fails.  It would be nice if the driver had a way to tell userspace that 
the /dev/videoX and /dev/dvb/adapterX/* all belong to the same physical 
device, so that the apps knows NOT to try to use a device that is 
already in use.    Maybe it is just as simple as returning -EBUSY , but 
right now i dont even think that the drivers have a way to do that.

As it is now, a hybrid device looks like it is two separate devices...

I dont know how to do it, but we should handle this for both cases 
(hybrid v4l/dvb devices and Full-Featured dvb devices)


Michael Krufky

More information about the linux-dvb mailing list