[sane-devel] scripting hooks for scanner backend

[Felix Salfelder]

Hello list.

As some of you might have experienced, and as it is frequently
subjected, scsi scanners have to be manually added to the scsi subsystem
by invoking some scsi-add command as root before talking to the scanner
is possible. I am currently experimenting with shell-aliases and
overriding paths, to hook this routine into the various sane
executables.

Now all of this seems a bit clumsy, and brought me to the idea to simply
add scripting hooks into the sane-backend. i would think of about two
additional configuration options like "prescan-hook" and "postscan-hook"
to be added to the respective backend configuration files
/etc/sane.d/abcd.conf. Here paths executables could be set to be hooked
before a device is initialized and after is is left alone respectively.

This would not only allow a simple solution (workaround?) to the
motivating scsi-add issue. These hooks could be used for instance to
toggle the power-supply of a scanner, or open/close firewalls, when
using a network-device. This could also give a qu^H^Hdirty ad-hoc fix to
future driver/udev bugs requiring the user to, say, reload modules or
create nodes before/after scanning. I bet there are even better and
useful applications for this.

Now since the manuals don't mention something like this, I suppose it
has not been implemented yet. Would anybody find this useful? Or is
there a better/simpler approach for hooking scripts? Is there even a
clean solution for the scsi-add thing I have not considered? Does
anybody completely dislike the idea of this sort of hooking?

Regards
Felix