On Fri, 2020-07-10 at 11:54 +0200, Johan Hovold wrote:
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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@infinera.com Cc: stable@vger.kernel.org
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?
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.
drivers/usb/class/cdc-acm.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 751f00285ee6..5680f71200e5 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1999,19 +1999,19 @@ static int __init acm_init(void) acm_tty_driver->subtype = SERIAL_TYPE_NORMAL, acm_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV; acm_tty_driver->init_termios = tty_std_termios;
acm_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD |
acm_tty_driver->init_termios.c_cflag = B0 | CS8 | CREAD |HUPCL | CLOCAL; tty_set_operations(acm_tty_driver, &acm_ops);
retval = tty_register_driver(acm_tty_driver);
retval = usb_register(&acm_driver);if (retval) { put_tty_driver(acm_tty_driver); return retval; }
retval = usb_register(&acm_driver);
retval = tty_register_driver(acm_tty_driver);if (retval) {
tty_unregister_driver(acm_tty_driver);
usb_deregister(&acm_driver);put_tty_driver(acm_tty_driver); return retval; }
Johan