HAL and scanners

[Étienne Bersac]

Hi,

> There is a reason for exclusive access to a scanner

Right, device access must be exclusive.

> Just make sure that you don't break existing Sane frontends by
> keeping the device file constantly open for the button monitor.

Hmm, i'm in the situation where i provide a Gnome frontend to SANE. I
guess i should provide a system wide dbus daemon wich open devices,
monitor button and execute acquisitions, providing dbus calls and
signals for that. I first step without button handling won't open
devices, but if we want button handling using sane … scanbuttond does
not use SANE, but directly libusb. I don't find that very nice, however,
sane has an insane button handling.

> Another problem: Sane already has a working IPC protocol
> implementation, saned and the net backend. If you want to completely
> abandon direct device access by appications, you'll need to develop a
> much faster IPC protocol. And no, I have no idea, where the
> bottlenecks are.

That's out of my skills and off topic.

> If this new backend
> crashes a specialized button daemon, this is just annoying for
> scanner usage -- but if this crashes hald, users could quickly
> complain that HAL is crap ;)

ACK, I really don't think anymore that a hal-addon should call sane.
Better to add a dbus daemon one time if we want to implement button
support.

Étienne.
-- 
Verso l'Alto !
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