Re: USB devices changing UIDs
Re: USB devices changing UIDs
- Subject: Re: USB devices changing UIDs
- From: Mark Cookson <email@hidden>
- Date: Wed, 12 Dec 2001 12:38:39 -0800
On 12/12/01 12:03 PM, "Jeff Moore" <email@hidden> wrote:
>
on 12/12/01 12:40 AM, Sven Duwenhorst <email@hidden> wrote:
>
>
> the Roland UA-30 changes its uniqued ID string, when switching thr sampling
>
> frequency from 44.1 to 48. This is a strange behaviour, because unique IDs
>
> of devices shouldn't change at all, especially when changing a property of
>
> the device.
>
>
>
> The unique ID string should NEVER contain any setup information of the
>
> device as sampling frequency, number of channels, bit depth, clock source,
>
> input ...
>
>
Agreed! Please write a bug report about this.
>
>
That said, the UID for a device can change since it is derived in part from
>
its position in the USB network topology, assuming the device doesn't have
>
it's own UID as described in the USB spec.
What changes? I haven't looked at my UA-30 that closely.
The UID is:
AppleUSBAudioEngine
:<manufacturerString>:<productString>:<locationIDString>:<interfaceNumberStr
ing>
if it doesn't have a serial number, or:
AppleUSBAudioEngine
:<manufacturerString>:<productString>:<serialNumberString>:<interfaceNumberS
tring>
if it has a serial number.
The only thing that I would think could possibly change is the interface
number, but I wouldn't expect that to change since normally you talk to the
same interface all the time (like 0 for control, 1 for input, and 2 for
output).
If the interface number is changing, there is nothing that I can do about
that since a device like the Roland with both input and output on it would
appear to be two of the same devices if I didn't put the interface number on
it.
What information do you suggest I make the UID with?
--
Mark Cookson
Engineering Droid
Apple Computer, Inc.
Core Audio CPU Software
6 Infinite Loop MS 306-2CW
Cupertino, CA 95014