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Old 08-06-2008, 07:23 AM   #1
jmoody
LQ Newbie
 
Registered: Mar 2004
Posts: 24

Rep: Reputation: 15
Udev inconsistent behavior.


I'm having trouble writing a udev rule.

I have a couple devices that plug into a USB port. The manufacturer uses a usb-serial chip to implement his USB interface, and they supply drivers in the form of patched kernel files: fdti_sio[c,h]. I built the kernel, and plug this device in. udev properly creates /dev/ttyUSB0 (or 1, or 2..) depending on what other usb serial devices are installed.

What I want to have happen is that when this device is plugged in a symlink is created. Although other usb-serial devices may be plugged in, only one of this particular device will ever be plugged into a computer, so I want udev to call the device "/dev/mydevice".

I've written a rule that I think is unambiguous and should work, and it does work - the first time only. Sometimes. If I unplug the device my symlink goes away. Then I reinsert but the symlink is not re-created. Yes, the corresponding ttyUSBx entry is always correctly created and removed.

So it seems my symlink rule is running only once until something else is restarted. Or there is a race condition somewhere. My rule sits in a file starting with 10- so it gets processed early on. Yes, other rules in that file are working correctly so I know the file is being processed.

I am reluctant to post pages of possibly irrelevant dmesg or udevinfo output, but will be happy to provide specifics.

Any suggestions?
Thanks. --Jim
 
Old 08-07-2008, 12:50 PM   #2
tredegar
LQ 5k Club
 
Registered: May 2003
Location: London, UK
Distribution: Debian "Jessie"
Posts: 6,012

Rep: Reputation: 367Reputation: 367Reputation: 367Reputation: 367
30Hrs, and no reply

Nobody is answering your question because you are not giving us enough information (And sometimes we cannot be bothered even to point this out yet AGAIN).

What is this mysterious "device"? I am guessing a "Free Pr0n Fast, USB dongle", in which case I am not patching my kernel with any code they may be offering!

Why did the kernel need to be patched?

Would you like to offer us some of the links you have been following, or do you expect us to guess these / start searching from scratch?

What is your USB rule?
Why did you choose to have it "processed early on"?

Quote:
I am reluctant to post pages of possibly irrelevant dmesg or udevinfo output
Why so? People have posted PAGES of (mostly useless) information here before. If you feel guilty about cluttering up LQ's servers with pages of text, you could post it somewhere like here: http://rafb.net/paste/ and give us a link to it.

Go ahead and post what you consider to be the relevant information, and I expect someone'll help. Maybe not myself, as I am still struggling with udev rules, but will watch this thread's progress.
 
  


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