Re: Unsupported device message, Compliance C.2, part 4

Alan Stern <[email protected]>
Newsgroups gmane.linux.usb.devel
Message-ID <[email protected]>
On Fri, 5 Oct 2007, Aras Vaichas wrote:

> Hi,
> 
> We need to comply with the "USB-IF Embedded Host Compliance Plan", section C.2, 
> part 4 which states:
> 
> "4. Messaging (No Silent Failure):
> 	a. Unsupported device message. Attach a device that is known not to be 
> supported. An appropriate message should be displayed.
> 	b. If hubs are not supported, a "Hubs not supported" or similar message must 
> appear. A generic "device not supported" message is not acceptable on a hub 
> connect."

Is this meant to apply to all USB hosts?  Only "embedded" hosts 
(whatever they are)?  Only OTG devices?

The requirements are not entirely clear.  What does it mean for a
device to be supported?  Is it supported if there is a driver compiled
into the kernel?  What if there is a driver in a loadable module?  
What if there is a userspace driver?  What if there is a driver for
some of a device's interfaces but not all of them?

Also, what does it mean for a device to be "known" not to be supported?  
Are there any USB devices "known" not be supported by Linux?

Part b shouldn't matter; hub support is built into the Linux USB core.

> Does anyone have any thoughts on how I would go about this? Has anyone else had 
> to deal with this?
> 
> I was thinking that it might well be a udev question, but as it's USB 
> compliance related I thought I would start on this list.

The requirements are so fuzzy, I don't see how anyone could ever tell
whether they were fulfilled or not.  Unless it's for something like
OTG, where there really is a whitelist of supported devices.

Alan Stern


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