Re: Which routine does make dev file of usb char device ?

[Greg KH <greg@xxxxxxxxx>]

On Fri, Nov 07, 2008 at 12:38:44AM +0900, J.H.Kim wrote:
> Hi, everyone
>
> I'm looking for codes which makes dev files (for example, /dev/usb/lp0 for 
> usb printer) of USB character devices.
>
> Is it udev or kernel driver module?

udev.

> If it is udev, how does it determine the major and minor number of the 
> device?

From the "dev" file in the sys/class/... file for the device, or from
the uevent itself.  newer versions of udev only use the uevent, and
don't need sysfs.

> The uevent message from kernel for usb printer seems not to include the 
> information on the major and minor numbers.
> Captured uevent message for usb printer was like this :
> 	ACTION=add
> 	DEVPATH=/devices/pci0000:00/0000:00:1d.3/usb4/4-2/4-2:1.0
> 	SUBSYSTEM=usb
> 	DEVTYPE=usb_interface
> 	DRIVER=usblp
> 	PHYSDEVBUS=usb
> 	PHYSDEVDRIVER=usblp
> 	DEVICE=/proc/bus/usb/004/002
> 	PRODUCT=3f0/8604/100
> 	TYPE=0/0/0
> 	INTERFACE=7/1/2
> 	MODALIAS=usb:v03F0p8604d0100dc00dsc00dp00ic07isc01ip02
> 	SEQNUM=940

That's not the device that you are looking for to create the dev node.

Wait a bit and look at the uevent for the USB lp0 device.

thanks,

greg k-h

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