Re: Want to use hotplug

[David Brownell <david-b@pacbell.net>]

Karl F. Larsen wrote:
> 	I'm working on documentation for installing a scanner in Linux 
> and now that almost all scanners are USB port users we now need to load 
> the scanner module and two hex numbers to the kernel as we boot up. I am 
> doing it with insmod and /etc/modules.conf. 
> 
> 	I'm told hotplug is easier and better, but I don't know how to 
> do it.Hmm, let's see.  There are two basic ways you might be working:

  - kernel driver.  /etc/modules.conf would have the product and
    vendor ids as module parameters.

  - user mode driver.  how do those get set up?  (this seems to
    be the direction for future scanner support.)

In both cases you'd likely create /etc/hotplug/usb/scanner.usermap
to list the product and vendor ID for the scanners you're interested
in.  The 2.5 kernel driver doesn't have a MODULE_DEVICE_TABLE in the
driver, which complicates things especially if you've got more
than one kind of scanner  But presumably you know how to deal with
that issue if you're documenting current practice.

I'd basically expect some /etc/hotplug/usb/scanner shell script
to do whatever magic is needed to let the user mode code know
about the scanner.  It might use the $REMOVER mechanism, which
you'll see in /etc/hotplug/usb.agent, and ensure that specific
usbfs device ($DEVICE) is accessible (chown/chmod) and published
(symlink killed by $REMOVER?) to the user mode driver.

You can see http://linux-hotplug.sourceforge.net/?selected=usb
for background, some of which may help you.

- Dave



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