[sane-devel] Workaround for CONFIG_USB_SUSPEND now in CVS

[Julien BLACHE]

Sitsofe Wheeler <sitsofe at yahoo.com> wrote:

Hi,

> I'm not 100% sure this is the right thing. Perhaps there should be a
> whitelist packaged up with SANE that tracks those scanners that do not
> need USB autosupsend disabled? I mention this because any power savings

We've had this problem with pretty much every popular brand of
scanners, so if there are non-buggy scanners out of there I can
probably count them on the fingers of my right hand. (before you ask,
I've got 5 fingers on each hand ;)

> that USB autosupend was intended to implement will be undone by this if
> a scanner is plugged in (although you can argue that you probably don't
> care about power if you use a scanner).

The power savings only benefits to laptop users when they're on
battery. Moreover, most scanners aren't bus-powered. For laptop users,
they'll just learn to unplug their scanner and that's it. (keeping the
scanner plugged in usually means that the lamp will stay on until it's
unplugged, so they'll save on that too)

> Additionally, is it possible to only implement this just before
> scanning?

Not easily. As most scanners do an unplug/plug cycle when they're
suspended, their address on the bus changes and their device ID may
change too, which makes it even harder to go and disable suspend when
the application is started. You can add to that all the scanners that
change their USB ID and do an unplug/plug cycle once they've got their
firmware... Countless hours of fun.

Anyway, you're free to use this workaround or not :)


Now, for the manufacturers that may read us, if you could fix your
hardware...

JB.

-- 
Julien BLACHE                                   <http://www.jblache.org> 
<jb at jblache.org>                                  GPG KeyID 0xF5D65169