On Wed, 2020-05-27 at 12:41 +0200, Oliver Neukum wrote: > 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. > /* * Suppress initial echoing for some devices which might send data * immediately after acm driver has been installed. */ if (acm->quirks & DISABLE_ECHO) tty->termios.c_lflag &= ~ECHO; That seems to be what I needed, should be default I think ... Need to test som more but looks much better. I guess all cdc_acm's are could suffer from this? Will depend the target in the other end. Jocke
