Re: [Libusb-devel] USB VID/PID for open source projects

[Xiaofan C. <xia...@gm...>]

On Sat, Mar 26, 2011 at 7:09 AM, Segher Boessenkool
<se...@ke...> wrote:
>> What is bad to require to read the device string?
>
> Then vid/pid alone isn't enough to identify the device; which is the
> purpose of vid/pid.

A counter example will be the product revision, you will often
come out a new product revision which has basically the same
functionality as the old device while addressing problems like
component obsolescence. You do not want to change the
PID in the case if there are no form/fit/function change.

You can use the version field for this.

> The purpose of the device string is not to identify a device for
> programmatic purposes (instead, it is for human consumption only);
> using a single datum for two conflicting purposes is not a good thing.
>
> There is no mechanism in place to prevent allocating the same device
> string to two different devices, not even when those devices share
> the same vid/pid.

When you decide to use the device strings, then you need
to come out a scheme to make it unique. no different from
other number allocation scheme.

> In practice, using the device string to distinguish between _a few_
> devices that share a vid/pid usually works fine of course.
>


-- 
Xiaofan