On Thu, Jun 03, 2010 at 01:55:02PM +0200, Daniel Mack wrote:
> Call set_mctrl() and clear_mctrl() according to the flow control mode
> selected. This makes serial communication for FT232 connected devices
> work when CRTSCTS is not set.
>
> This fixes a regression introduced by 4175f3e31 ("tty_port: If we are
> opened non blocking we still need to raise the carrier"). This patch
> calls the low-level driver's dtr_rts() function which consequently sets
> TIOCM_DTR | TIOCM_RTS. A later call to set_termios() without CRTSCTS in
> cflags, however, does not reset these bits, and so data is not actually
> sent out on the serial wire.
>
> Signed-off-by: Daniel Mack <daniel@xxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxx>
> Cc: Johan Hovold <jhovold@xxxxxxxxx>
> Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
> Cc: linux-usb@xxxxxxxxxxxxxxx
Oops. I forgot to Cc: stable@xxxxxxxxxxx
This is in fact broken since 2.6.31-something.
> ---
> drivers/usb/serial/ftdi_sio.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
> index 050211a..79dd1ae 100644
> --- a/drivers/usb/serial/ftdi_sio.c
> +++ b/drivers/usb/serial/ftdi_sio.c
> @@ -2005,6 +2005,8 @@ static void ftdi_set_termios(struct tty_struct *tty,
> "urb failed to set to rts/cts flow control\n");
> }
>
> + /* raise DTR/RTS */
> + set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
> } else {
> /*
> * Xon/Xoff code
> @@ -2052,6 +2054,8 @@ static void ftdi_set_termios(struct tty_struct *tty,
> }
> }
>
> + /* lower DTR/RTS */
> + clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
> }
> return;
> }
> --
> 1.7.1
>
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