On Tue, Feb 07, 2017 at 06:56:20PM +0100, John Skelton wrote: > > From: "Felipe Balbi" <felipe.balbi@xxxxxxxxxxxxxxx> > > > 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). > > > > 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? > > Yes - or I may have misunderstood the situation. > > It is code which is derived from V-USB > https://www.obdev.at/products/vusb/index.html > and is described at > http://www.recursion.jp/prose/avrcdc/cdc-232.html > > If it worked with Linux it would be a handy way to provide output (such as > debug data) from low-cost Arduinos and such like via USB. > > To be clear: I am not saying the Linux USB code is wrong. But it would > be good to have a way to have the above kind of code work, such that > screen / minicom etc can be used with it. > That page says that any kernel newer than 2.6.31 should work just fine, have you tried this out and had it fail? For Windows, you note that you have to patch it. Remember, this is a spec violation, you really shouldn't be doing this :) thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
