Re: ttyACM: disabled by hub (EMI?), re-enabling... Causes garbage chars & disconnect

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Am Mittwoch, den 27.05.2020, 09:40 +0000 schrieb Joakim Tjernlund:
> On Wed, 2020-05-27 at 10:38 +0200, Oliver Neukum wrote:
> > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> > 
> > 
> > Am Dienstag, den 26.05.2020, 17:19 +0000 schrieb Joakim Tjernlund:
> > > 
> > > This "u-boot SPL" is the first thing u-boot writes and somehow this is remembered, I assume, by cdc_acm
> > > and gets echoed back when I open ttyACM0
> > 
> > Hi,
> > 
> > that makes sense, but it is not something that we could really
> > change in CDC-ACM, I am afraid.
> 
> Why not? CDC-ACM should echo back anything it has received before open of ttyACM

Well, there is an inherent race condition with loading the module I am
afraid. By default cdc-acm should actually echo. You can set the
DISABLE_ECHO echo quirk for your device if you want to get rid of it.

Is CDC-ACM violating some standard with respect to echoing? Changing
defaults really hurts users, no matter what you do.

	Regards
		Oliver




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