How can I specify a specific 'sub-device' of a device for udev naming?

[Jonathan Steinert <hachi@kuiki.net>]

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"

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.

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?

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

I have no idea what to call this act, apart from 'walking' the sysfs 
tree when checking the rules, so after reading all the documentation 
with udev that I noticed, and all of the messages on the list that I 
thought might be related I've come up with nothing.

Can anyone fill me in on this, possibly telling me what this is called, 
and what I am getting wrong?

Thanks much,

Jonathan Steinert


root@yuumi:/dev# udevinfo -a -p /sys/class/tty/ttyUSB0

device '/sys/class/tty/ttyUSB0' has major:minor 188:0
  looking at class device '/sys/class/tty/ttyUSB0':
    SYSFS{dev}="188:0"

follow the class device's "device"
  looking at the device chain at 
'/sys/devices/pci0000:00/0000:00:1d.2/usb2/2-1/2-1:1.0/ttyUSB0':
    BUS="usb-serial"
    ID="ttyUSB0"
    SYSFS{detach_state}="0"

  looking at the device chain at 
'/sys/devices/pci0000:00/0000:00:1d.2/usb2/2-1/2-1:1.0':
    BUS="usb"
    ID="2-1:1.0"
    SYSFS{detach_state}="0"
    SYSFS{bInterfaceNumber}="00"
    SYSFS{bAlternateSetting}=" 0"
    SYSFS{bNumEndpoints}="03"
    SYSFS{bInterfaceClass}="ff"
    SYSFS{bInterfaceSubClass}="ff"
    SYSFS{bInterfaceProtocol}="ff"
    SYSFS{iInterface}="00"

  looking at the device chain at 
'/sys/devices/pci0000:00/0000:00:1d.2/usb2/2-1':
    BUS="usb"
    ID="2-1"
    SYSFS{detach_state}="0"
    SYSFS{bNumConfigurations}="1"
    SYSFS{bNumInterfaces}=" 1"
    SYSFS{bConfigurationValue}="1"
    SYSFS{bmAttributes}="a0"
    SYSFS{bMaxPower}="100mA"
    SYSFS{idVendor}="050d"
    SYSFS{idProduct}="0109"
    SYSFS{bcdDevice}="0102"
    SYSFS{bDeviceClass}="00"
    SYSFS{bDeviceSubClass}="00"
    SYSFS{bDeviceProtocol}="00"
    SYSFS{speed}="12"
    SYSFS{manufacturer}="Belkin USB PDA Adapter"
    SYSFS{product}="Belkin Components"
    SYSFS{serial}="304087"

  looking at the device chain at 
'/sys/devices/pci0000:00/0000:00:1d.2/usb2':
    BUS="usb"
    ID="usb2"
    SYSFS{detach_state}="0"
    SYSFS{bNumInterfaces}=" 1"
    SYSFS{bConfigurationValue}="1"
    SYSFS{bmAttributes}="40"
    SYSFS{bMaxPower}="  0mA"
    SYSFS{idVendor}="0000"
    SYSFS{idProduct}="0000"
    SYSFS{bcdDevice}="0206"
    SYSFS{bDeviceClass}="09"
    SYSFS{bDeviceSubClass}="00"
    SYSFS{bDeviceProtocol}="00"
    SYSFS{bNumConfigurations}="1"
    SYSFS{speed}="12"
    SYSFS{manufacturer}="Linux 2.6.3 uhci_hcd"
    SYSFS{product}="UHCI Host Controller"
    SYSFS{serial}="0000:00:1d.2"

  looking at the device chain at '/sys/devices/pci0000:00/0000:00:1d.2':
    BUS="pci"
    ID="0000:00:1d.2"
    SYSFS{detach_state}="0"
    SYSFS{vendor}="0x8086"
    SYSFS{device}="0x2487"
    SYSFS{subsystem_vendor}="0x8086"
    SYSFS{subsystem_device}="0x4541"
    SYSFS{class}="0x0c0300"
    SYSFS{irq}="11"

  looking at the device chain at '/sys/devices/pci0000:00':
    BUS=""
    ID="pci0000:00"
    SYSFS{detach_state}="0"



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