Re: How can I specify a specific 'sub-device' of a device for udev

[Kay Sievers <kay.sievers@vrfy.org>]

On Mon, 2004-03-01 at 07:08, Jonathan Steinert wrote:
> Morning everybody,
> 
> I'm trying to find how I can write a rule which allows me to say "The 
> usb-serial bus interface inside the usb device with a sysfs serial of 
> "304087" should be named "foo"
> 
> I'll paste my udevinfo output for the device in question (A Belkin USB 
> to serial dongle) at the bottom, but I am running into a similar issue 
> with my Griffin Powermate.
> 
> The rule I came up with, which does not work nor seem correct in the 
> first place is:
> 
> BUS="usb-serial", SYSFS{serial}="304087", NAME="foo"

Yes, the rule is incorrect. It's not on the same device.

> Since this does not work, I am asuming that the sysfs attributes to not 
> trickle down a driver chain for matching in more specific devices.

It walks down, just like udevinfo does. But you can only match
attributes of _one_ device not combine attributes from different devices
on the chain.

> This does leave me puzzled about two things:
> 
> 1) Why does udev have a flag to crawl up the sysfs tree (Asuming my 
> observations of udev are correct) but no flag to show the attributes of 
> only the device I specify? or only 'n' layers down for that matter?

Do you really need this? Why?

> 2) How can I write a rule to match the usb-serial interface of a usb 
> device with a particular serial number?

>   looking at the device chain at 
> '/sys/devices/pci0000:00/0000:00:1d.2/usb2/2-1':
>     BUS="usb"
...
>     SYSFS{serial}="304087"

Your serial number belongs the "usb"-device and not the virtual
"usb-serial"-device. A match for the "hardware" behind your serial
device should work fine:

  BUS="usb", SYSFS{serial}="304087", NAME="foo"

If you really need to match this particular device interface, you may
use its bus-id:

  BUS="usb", ID="2-1:1.0", NAME="foo"


hope that helps,
Kay



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