> > One way to address this has been prototyped for printers: let the
> > hotplug subsystem tell the scanner subsystem about device types,
> > since it's already got that data available:
>
> This does not help you on installation, which causes most problems.
Depends on the particulars. I've worked with hotplug-like systems
where there's a straightforward bit of logic that goes like
if (first time I've seen this device) {
run first-time setup program;
}
Where the setup program could drop an event into some sysadmin
alert system, which might in some systems pop up a pre-initted GUI.
Or lots of other interesting things.
> [..]
> > Or, it could go the other way around. If you're scanning /dev/...
> > nodes, add a corresponding ioctl to find which USB device is
> > involved, and then use the existing USB support to find VID/PID.
>
> This is very helpful.
> We should do this as generic as possible.
I find it no less helpful than doing it the other way around, in fact.
Both are generic approaches. One of them works well with
today's hotplug, which seems healthy to me.
> > And there's also Alan's suggestion, to do scanner drivers entirely in
> > usermode, focussing development work on usbdevfs and APIs to it.
> > (I think the Java USB API is more powerful than libusb, but that can
> > just be a hacker challenge ... :)
>
> 1. No persistent device permissions
> 2. Some scanners have interrupt endpoints
> 3. Very hard to use without hotplugging, which is beta at best
> 4. There was this little problem with control messages and usbdevfs
Johannes commented on #2/#4 ... Re #1, device permissions do
need more work in any scenario (particularly with the current mount
options bug!!) but hotplugging can easily chmod things. Re #3, that's
just not true ... the usermode API wouldn't depend on hotplugging
except maybe for device permissions.
> In this case I disagree with Alan.
You just want to create and fix a different set of bugs ... not
that I'm sure what it would be! :)
- Dave
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