> From: "Greg KH" <g...@kroah.com>
> To: "John Skelton" <js...@gmx.com>
[snip]
> > > > 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?
> > 
> > It does say that but it does not work.  I get the dev_warn message that it
> > has changed the Bulk endpoint to Interrupt but that's it.
> 
> What happens after that?  Does the cdc-acm driver refuse to bind?  Any
> other types of error/warning messages?

Along the lines of:
usb 2-1.2: >new low-speed USB device number 95 using ehci_hcd
usb 2-1.2: >device descriptor read/64, error -32
usb 2-1.2: >config 1 interface 1 altsetting 0 endpoint 0x1 is Bulk; changing to 
Interrupt
usb 2-1.2: >config 1 interface 1 altsetting 0 endpoint 0x81 is Bulk; changing 
to Interrupt
usb 2-1.2: >New USB device found, idVendor=16d0, idProduct=087e
usb 2-1.2: >New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 2-1.2: >Product: Digispark Serial
usb 2-1.2: >Manufacturer: digistump.com
cdc_acm 2-1.2:1.0: >ttyACM0: USB ACM device

But screen /dev/ttyACM0 (with or without a "baud" rate) just hangs.

> Doing this type of thing really isn't a good idea for the obvious reason
> that hubs might just die a horrible death.  Who knows what a USB 3
> controller would do with a low speed device like this as well (hubs are
> crazy complex, and low speed makes them really sad.)

Ah.  Maybe it's my laptop's internal hub that hangs.  Though the other USB
ports carry on working.

> You would be better off spending a few cents and getting a better USB
> device controller.  It will save everyone here, and yourself, a lot of
> time and money...

True :(

Consider it closed if you'd rather.  I'd rather not take up the ML's useful time
if there's no reasonable workaround.  People can debug via flashing LEDs etc...

John
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