On Thu, May 11, 2017 at 09:12:48PM +0300, Peter Mamonov wrote: > The patch implements TIOCSSERIAL ioctl call. The following fields of the > `struct serial_struct` are processed: > > - flags: ASYNC_SPD_MASK bits are processed. > > - baud_base: allow a user to specify arbitrary value less or equal the > maximum port speed. Use it later in conjunction with custom_divisor to > calculate the desired baud rate. > > - custom_divisor: save a user supplied value, use it later for baud rate > calculation. > > Custom baud rate may be applied using any combination of baud_base / > custom_divisor as follows: > > # stty -F /dev/ttyUSBX 38400 > # setserial /dev/ttyUSBX baud_base 1000 divisor 1 spd_cust # 1 kBaud > # setserial /dev/ttyUSBX baud_base 42000 divisor 42 spd_cust # 1 kBaud > > The patch is based on the code from the drivers/usb/serial/ftdi_sio.c. > > Signed-off-by: Peter Mamonov <pmamonov@xxxxxxxxx> First, sorry for not getting back to you sooner on this one. The short story is that setting the speed using TIOCSSERIAL has been deprecated for a very long time, and the alt-speed handling (e.g. SPD_WARP) has been broken in tty core for about four years without anyone noticing. I've cleaned this up now, and specifically added a deprecation warning also to ftdi_sio. Instead you should be using BOTHER and the "new" TCSETS2 ioctl for setting non-standard baud rates. It's a bit cumbersome to use due to missing libc support, but it is the right interface for this. Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
