[Libdlo] Equivalent for $DISPLAY

[Bernie Thompson]

Hi Phil,

Every DisplayLink device should have a unique USB PID/serial number combo.
So you'd need both in your id string, but then that sounds like a good
strategy for uniquely identifying a particular device.

Thanks for raising this issue of ownership of devices between drivers and
apps!  libdlo doesn't really try to deal with this system-wide yet.  Also
very interested in hearing how precedents might guide us.

It may be these type of devices are somewhat unique in that they're, in a
sense, mostly stateless.  Just screens to scribble on.  Assuming we want to
allow for uses other than through X, we do need to have some concepts of
current ownership and end-user intent about the purposes they want a screen
to be dedicated to.  But also don't want to make this too complex, as most
people probably will be using through X eventually.

Thanks again,
Bernie

On Sat, May 23, 2009 at 7:50 AM, Phil Endecott <
spam_from_libdlo at chezphil.org> wrote:

>
> This leaves the question of how to name the displays.  We can see
> serial numbers in the dlo_devinfo_t; is this really a unique number?
> I.e. do the devices have PROMs in them?  I've dismantled my dongle and
> it does indeed have an I2C PROM, but is this essential to the design or
> is it the first thing that el cheapo OEM will not implement?  (I have
> seen other USB devices that present a default set of IDs if no PROM is
> attached.)
>
> I'm trying to think of precedents, but I can only think of things where
> the kernel and udev choose names; that doesn't apply to libusb stuff.
> What else uses libusb?  How does SANE name devices?
>
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