On Fri, Jul 10, 2020 at 10:16:33AM +0000, Joakim Tjernlund wrote: > On Fri, 2020-07-10 at 11:54 +0200, Johan Hovold 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. > > > > > > On Fri, Jul 10, 2020 at 11:35:18AM +0200, Joakim Tjernlund wrote: > > > BO will disable USB input until the device opens. This will > > > avoid garbage chars waiting flood the TTY. This mimics a real UART > > > device better. > > > For initial termios to reach USB core, USB driver has to be > > > registered before TTY driver. > > > > > > Signed-off-by: Joakim Tjernlund <joakim.tjernlund@xxxxxxxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > --- > > > > > > I hope this change makes sense to you, if so I belive > > > ttyUSB could do the same. > > > > No, this doesn't make sense. B0 is used to hang up an already open tty. > > This is at module init so there is no tty yet. > acm_probe() will later set: > acm->line.dwDTERate = cpu_to_le32(9600); > acm->line.bDataBits = 8; > acm_set_line(acm, &acm->line); > > > > > Furthermore, this change only affects the initial terminal settings and > > won't have any effect the next time you open the same port. > > hmm, it is not ideal but acm_probe() will later set: > acm->line.dwDTERate = cpu_to_le32(9600); > acm->line.bDataBits = 8; > acm_set_line(acm, &acm->line); > > But, would it not make sense to not accept input until TTY is opened ? > That would be more inline with a real RS232, would it not? You can't keep the chip in the usb-to-serial device from accepting data before you do anything with it, that requires firmware to not do this. Are you sure your firmware is correct? > > Why not fix your firmware so that it doesn't transmit before DTR is > > asserted during open()? > > I would but it is not my firmware, it is a ready made USB to UART chip. will talk > to the manufacturer though. What chip is this? thanks, greg k-h
