[cups-devel] Hacking USB uris to make them more predictable

Justin Carlson foozle at gmail.com
Wed Feb 22 12:49:19 PST 2017


If we have a couple of printers that are identical and have no serial
number, I don't think we have a way to distinguish them in the current
code, do we?  Or are you saying there are classes of devices which *do* set
the ieee1284 serial field, but not the USB one?

In general, I think I'm willing to accept "if you plug in multiple copies
of printers that provide no reliable way to distinguish them to the same
device, then we won't take heroic measures to try to distinguish them" as
an outcome.

As I understand it (and I'm not a USB guru by any stretch of the
imagination) bus addressing can change across restarts and/or topology
changes, so incorporating that into the URI means you'll make the
URI-device mapping fragile in other ways.

-J


On Wed, Feb 22, 2017 at 12:10 PM Vadim A. Misbakh-Soloviov <cups at mva.name>
wrote:

> > probably something like usb://{vendor_id}/{product_id}?serial={serial}.
>
> > Is this a terrible idea for some reason that I'm not seeing?  Are there
> > subtle dependencies on the existing URI scheme of which I may not be
> > aware?  Happy to get any feedback at all on this.
>
> Let's imagine you have a couple of chinese noname printers, having same
> vid/
> pid, and both has 0000000 as serial (just like it is common case for
> android
> smartphones).
>
> How would you differ which exactly printer do you want to call with your
> URI
> scheme? :)
>
> // So, in my opinion, it should, at least, also contain usb bus info (bus
> ID
> and device-on-bus ID)._______________________________________________
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