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

[Jonathan Steinert <hachi@kuiki.net>]

Kay Sievers wrote:
> On Mon, 2004-03-01 at 07:08, Jonathan Steinert wrote:
> 
 >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?

That's not quite what I intended with the question. My observation is 
that udevinfo shows you all the attributes as you walk up the tree, but 
udev has no way to match attributes as you walk up the tree.

I'm not sure if this is intended to confuse people, but it most 
certainly makes me think that there should be a way to match attributes 
as you walk up the tree with udev, otherwise why does it show it to you?

> 
> 
>>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"

Sure, but matching this usb device does not yield me a tty.

> 
> 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"

The bus ID is dependant on the order it was plugged into the device 
chain, so this is kinda useless for detecting a particular device or 
particular kind of device. Plus this is once again a usb device, not a 
usb-serial device, and as such will not yield me a tty.

> 
> 
> hope that helps,
> Kay
> 

It does help me to know that there is no (current) way to make udev do 
this, however now I'd like to ask for ways to match the usb-serial 
device which is on an interface of this particular usb device. This is 
ultimately the problem I am trying to solve.

Thanks much,

Jonathan Steinert



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