tty/serial: Need clarification on Support for 4+M Baudrate

[Alan Cox]

On Thu, 12 Jan 2012 15:20:46 +0100
Rajanikanth H V <rajanikanth.hv at stericsson.com> wrote:

> Alan,
> 
> FYI: I am not using application, rather I have a Bluetooth driver invoking
> encode_baud_rate(...), please find log below.
> 
> I made sure that c_ispeed = c_ospeed = 4.05M Baud, however I see 
> tty_termios_encode_baud_rate(...) is normalizing to 4.0
> 
> 
> manual trace log below:
> ======================================================================================
> 
> 4.05M Arbitrary Baud Setting Sequence:
> [    9.664703] alloc_set_baud_rate_cmd Setting arbitrary baudrate using BOTHER baudrate:89 c_cflag:020000016262
> [    9.774658] XXXXXX_hci_uart_set_baudrate c_cflag:020000016262 baud:4050000

4050000 seems a bit odd - you want cflag&CBAUD == BOTHER so I'd expect
the low bits to end rather different things to 6262 ?

So something like

	struct ktermios new = *tty->termios;
	new.c_cflag &= ~(CBAUD|CIBAUD);
	new.c_cflag |= BOTHER;
	new.c_ispeed = 4050000;
	new.c_ospeed = 4050000;
	tty_set_termios(tty, &new);	/* Can sleep */

	/* Returned new will now hold actual values selected */

should do the trick providing the low level driver supports the rate.

Alan