Re: [Libusb-devel] distinguishing of identical devices

[Greg KH <gr...@kr...>]

On Thu, Mar 20, 2008 at 10:00:04PM -0700, Michael Bender wrote:
> 
> On Mar 20, 2008, at 9:59 PM, Greg KH wrote:
> > On Thu, Mar 20, 2008 at 09:44:28PM -0700, Michael Bender wrote:
> >>
> >> We should all push back on vendors to create proper USB  
> >> implementations
> >> and FOLLOW THE SPECS so that we don't have to spend our time writing
> >> software to get around bad design.
> >
> > The spec says that unique serial numbers are not required except for  
> > USB
> > printers.
> 
> Ugh... silly spec writers.

You need to remember the original constraints that USB was created for.
It was a replacement for mice and keyboard connections, and as such, the
hardware had to cost less than $1 way back in the 90's.  Making a unique
serial number a requirement would be very difficult to make devices to
meet these constraints.  Not to mention making manufacturing very
difficult as well.

They did realize that printers were different and people really did want
to keep their printers apart and have a way to uniquely identify them.
So they changed the printer spec to accomidate that.

Hope this helps,

greg k-h