Re: USB SUBSYSTEM - drivers/usb/core/config.c

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Hi,

John Skelton <jskel@xxxxxxx> writes:
> Apologies if this ought to have gone to the USB maintainer (but his
> auto-reply implies not).
>
> I'm particularly interested in drivers/usb/core/config.c
> which appears to enforce the USB specification by refusing to allow a
> low speed CDC ACM.  (Comment "Some buggy low-speed devices ...", at
> about line 300.)
>
> However, such devices exist and some are potentially quite useful (such
> as Arduinos & digistump).  Various people have posted about not being
> able to use them with Linux and I think the above file is the reason
> (another well known OS family allows them).
>
> I'd like to ask if there's a sane (Linux) way to allow them or are you
> open to one being created?
>
> If so, as I don't know the best way then if you have any ideas I'd
> certainly be pleased to hear them.  Some sort of quirk?
>
> To make it easy for non-expert/novice Linux users to connect
> non-conforming USB devices and have them "just work" please consider
> a way that is either the default or easy, i.e. so they don't have to
> config/build a kernel.
>
> I am a bit surprised that the code does what it currently does, as it
> basically makes such devices unusable so far as I can tell and may as
> well just reject them entirely.

Here's the comment:

	/* Some buggy low-speed devices have Bulk endpoints, which is
	 * explicitly forbidden by the USB spec.  In an attempt to make
	 * them usable, we will try treating them as Interrupt endpoints.
	 */

The code isn't forbidding CDC ACM low speed devices, it's forbidding
Bulk endpoints on Low speed, which don't exist :-) Are you saying there
are Bulk endpoints on low speed Arduinos?

-- 
balbi
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