[sane-devel] HAL and scanners.

[Johannes Meixner]

Hello,

a bit off-topic but related: "Automated backend activation"

On Mar 18 17:48 abel deuring wrote (shortened):
> ... But the HAL callout could also mess with dll.conf and
> enable those backends that "fit" to a newly detected scanner.

No HAL is needed for automated backend activation.
Only udev is needed for this.

Currently we (i.e. Suse) have a first implementation of it, see
https://bugzilla.novell.com/show_bug.cgi?id=347943
"full automated USB scanner setup via udev"


Some background information:

Actually it is udev which notices a "new device" first,
then HAL gets a "new device" event from udev.

If all what matters are "device add"/device remove" events,
and run a program once for such events, udev is sufficient.

I think HAL is only needed because applications use HAL
and HAL can store information as long as the system runs.

Why do we (i.e. Suse) need "automated backend activation" at all?
Aren't most backends enabled by default in upstream dll.conf?
But we prefer to have only those backends enabled
which are actually used
- to avoid that more than one backend is enabled for the same
  device (e.g. epson, epson2 and epkowa or plustek and epkowa),
- it looks not nice when many backends run by default for each
  new scanner access and all do their scanner autodetection,
- for problematic models (which need firmware upload, where
  the support status is less than "good", or which require
  a non-free 32-bit-only iscan/epkowa driver library)
  we like to guide the user via the YaST scanner config


> Though this might also be a bit dangerous: The callout should
> not touch any backends for devices that are for example
> accessible via ethernet.

Could you explain what you mean?

As far as I know a network scanner is not detected by udev/HAL
so that for a network scanner no callout should be run.


Kind Regards
Johannes Meixner
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