Re: The DRIVER rule doesn't seem to work

[Anthony Wright <anthony@communitymesh.com>]

Kay Sievers wrote:
>>>> What I believe is happening is that DRIVER is looking at the device's 
>>>> ancestor's drivers (parent, grandparent etc, but not the device itself), 
>>>> and returning their driver if they have one.
>>>>         
>>> Sure, it looks a the device itself, but also walks up the parents and
>>> finds a DRIVER value there.
>>>       
>> I had a good look at this, and from what I can tell it only looks at the 
>> device's parents, not the device itself. I compiled and ran udev with 
>> debug to see what was going on (and have lots of logs if you're 
>> interested), but the short version is that while udev makes a DRIVER 
>> test for the device, it looks like the driver field hasn't been loaded 
>> for the device, only for the device's parents. From my  logs, it seems 
>> that to load values for the device the function 
>> sysfs_device_set_values() is called in isolation, while for the parents 
>> sysfs_device_get() is called which calls sysfs_device_set_values(), but 
>> also sets the driver field.
>>     
> If you ask for a class device, it will never be set, cause class devices
> don't have a driver, only parent devices which are created by a bus
I don't think they are class devices, but I can't be 100% sure as I'm 
still learning how all the device handling works.

The path to the devices and their driver symbolic links are:

      Path                                                   Driver Symlink
a)    /sys/devices/pci0000:00/0000:00:1d.1                   uhci_hcd
b)    /sys/devices/pci0000:00/0000:00:1d.1/usb2              usb
c)    /sys/devices/pci0000:00/0000:00:1d.1/usb2/2-0:1.0      hub
d)    /sys/devices/pci0000:00/0000:00:1d.1/usb2/2-1          usb
e)    /sys/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1:1.0  NONE
f)    /sys/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1:1.1  NONE
g)    /sys/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1:1.2  NONE

and there are a lot of references to the bus sub-directories in the logs.

The rule DRIVER="?*" for each of these devices according to match_key 
matches the following matching values:

      Matching value
a)    MATCHING FAILS
b)    uhci_hcd
c)    usb
d)    usb
e)    usb
f)    usb
g)    usb

This is consistant with DRIVER matching against a device's parents only, 
not the device itself. If DRIVER also matched against the device I 
believe the matching values should be as follows.

      Matching value
a)    uhci_hcd
b)    usb
c)    hub
d)    usb
e)    usb
f)    usb
g)    usb

Cheers,

Tony.



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