[ale] RH9/General modules setup question

tfreeman at intel.digichem.net tfreeman at intel.digichem.net
Tue May 4 18:33:16 EDT 2004


I don't think I'm asking the right question here, so bear with me please. 
If I can get the question(s) (could be more than one I guess) straight, I 
should have better luck searching out the answer in various doc sets.

Background. I purchased a Haupphauge TV/Radio card a few weeks ago, and 
have it running with the application xawtv. Well, I also have a usb web 
cam or three lying around, so I started plugging them in. And in a  
fashion, I  have both the web cam and the TV capture board coexisting, and 
expect to be able to add another web cam just for the excess of it. Sort 
of.

The rub comes after a reboot. If I boot the system, access the TV card, 
and then plug in the first web cam everything cooperates nicely. However, 
reboot the system and just plug in the usb web cam can lead to trouble, as 
the 
web cam grabs /dev/video0, which the TV card expects to get. I have 
managed (some how) to get both the web cam and the TV card to fight and 
slow the system down to a crawl once, although I don't know exactly _how_ 
I did that and haven't been able to recreate it.

What I want to do is specify that the TV card will attach and service 
/dev/video0, while the web cam(s) line up with /dev/video[12345]. My 
/etc/modules.conf file has the line "alias char-major-81 bttv" already, on 
the advice of the bttv-HOWTO, which allows the bttv module & others to 
dynamically load when starting xawtv.

In addition to having the video devices line up _my_ way, I'd like to 
understand how the kernel attaches a device module to a /dev/* entry. 
Additionally, how useful is the alias command (example above) to setting 
up a module to manage a specific device?

Hopefully this has all made sense to somebody. Your help and listening is 
appreciated.

FWIW - I gather that this sort of challenge is part of what the (?) devfs 
file system is supposed to address.

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