Device naming in udev...

Device naming in udev...

[Kris van Rens]

Hi there,

I'm maintaining a kernel-driver for which udev generates a character
device file. I set up a rule to keep a consistent place for
applications to find the device file.

The driver module is called 'dtx'.

This is the rule:

BUS="usb", SYSFS{manufacturer}="FOOBAR", NAME="usb/foobar/%k"

The match for the rule works fine, but the name assignment seems to be
udev-version dependent.

Here's what appeared in /dev in a faulty situation (on plug-in of
multiple devices):

/dev/dtx-0
/dev/dtx-1
...
...

and

/dev/usb/foobar/usbdev1.1
/dev/usb/foobar/usbdev1.2
...
...

What I want is the device file 'dtx-0...' in the directory '/dev/usb/foobar'.

After an exhaustive series of trials with different versions of udev,
it appeared that the problem showed up with versions of udev before
058, and was gone for versions 058 and higher. I checked the
udev-Changelog but couldn't find any explicit changes.

I have customers that apparently have old versions of udev and my
driver package must be backwards compatible to some extent.

My question: is there a way around this? Of course it's easy to just
demand customers to upgrade their system but that's easier said than
done. The best option probably is a script to generate static device
files...hmmm

I've been spending too much time on this anyhow...oh well.

Thanks in advance,

Kris

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Re: Device naming in udev...

[Greg KH]

On Wed, Oct 11, 2006 at 05:22:59PM +0200, Kris van Rens wrote:
> Hi there,
> 
> I'm maintaining a kernel-driver for which udev generates a character
> device file.

Which driver is this?  Have a pointer to it anywhere?

> I set up a rule to keep a consistent place for
> applications to find the device file.
> 
> The driver module is called 'dtx'.
> 
> This is the rule:
> 
> BUS="usb", SYSFS{manufacturer}="FOOBAR", NAME="usb/foobar/%k"
> 
> The match for the rule works fine, but the name assignment seems to be
> udev-version dependent.
> 
> Here's what appeared in /dev in a faulty situation (on plug-in of
> multiple devices):
> 
> /dev/dtx-0
> /dev/dtx-1
> ...
> ...
> 
> and
> 
> /dev/usb/foobar/usbdev1.1
> /dev/usb/foobar/usbdev1.2

I think you are picking up the usbfs device node here in your rule,
which is not what you want to have happen.  Try triggering off of the
kernel name for the device as well as the manufacturer name in order to
make sure you only catch the proper device.

Hope this helps,

greg k-h

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