Re: ttyACM and BREAK chars ?

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Am Donnerstag, den 12.09.2019, 07:09 +0000 schrieb Joakim Tjernlund:
> On Wed, 2019-09-11 at 20:27 +0200, Oliver Neukum wrote:
> > Am Mittwoch, den 11.09.2019, 14:34 +0000 schrieb Joakim Tjernlund:
> > > On Wed, 2019-09-11 at 16:22 +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 Mittwoch, den 11.09.2019, 12:39 +0000 schrieb Joakim Tjernlund:
> > > > > Every now and then my ttyACM0 hangs up or sends a BREAK char to my device.
> > > > > I am trying to make ttyACM ignore incoming(over USB) and not emit
> > > > > any BREAK automatically using termios (IGN_BRK) but that does not make a difference.
> > > > > 
> > > > > Is BREAK handling unimpl. in ttyACM ?
> > > > 
> > > > acm_send_break() implements it.
> > > 
> > > Yes, I se that funktion but I don't see how one can ignore received BREAKs
> > > If I set IGN_BRK on /dev/ttyACM0 I expect that every BREAK should just be ignored
> > 
> > Handling breaks looks a bit broken on CDC-ACM.
> > Could you test the attached patch?
> > 
> 
> Sure, I can test it but from looking at the patch it seems like ACM already ignores
> BREAKs(hardcoded) and with your patch you actually start reporting them.

Well, what is not reported cannot really be ignored.
AFAICT  n_tty_receive_break() should solve the issue generically.

> My problem is sudden disconnects I cannot explain but I think they are connect to BREAKs
> I have seen these errors in dmesg though, not sure if they help the diagnose:
> [181780.167987] usb usb1-port6: disabled by hub (EMI?), re-enabling...

The relevant fault happens likely just before that.

> [181780.168208] cdc_acm 1-6.3:1.1: acm_ctrl_irq - usb_submit_urb failed: -19
> [181780.167996] usb 1-6: USB disconnect, device number 30
> [181780.176548] usb 1-6-port2: attempt power cycle
> [181781.772847] usb 1-6.3: USB disconnect, device number 32
> [181781.773134] cdc_acm 1-6.3:1.1: failed to set dtr/rts

Either your cabling is indeed crap, or something crashes your device.

	Regards
		Oliver




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