Commit 7041d9c3 authored by Florian Zumbiehl's avatar Florian Zumbiehl Committed by Johan Hovold
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USB: serial: pl2303: add support for tx xon/xoff flow control

Support hardware-level Xon/Xoff flow control in transmit direction with

I only know how to get the hardware to do IXON/!IXANY with ^S/^Q as control
characters, so I preserve the old behaviour for all other cases.

Signed-off-by: default avatarFlorian Zumbiehl <>
[ johan: rewrite logic using pl2303_termios_change() helper ]
Signed-off-by: default avatarJohan Hovold <>
parent 7b0c6b38
......@@ -533,6 +533,17 @@ static int pl2303_set_line_request(struct usb_serial_port *port,
return 0;
static bool pl2303_termios_change(const struct ktermios *a, const struct ktermios *b)
bool ixon_change;
ixon_change = ((a->c_iflag ^ b->c_iflag) & (IXON | IXANY)) ||
a->c_cc[VSTART] != b->c_cc[VSTART] ||
a->c_cc[VSTOP] != b->c_cc[VSTOP];
return tty_termios_hw_change(a, b) || ixon_change;
static void pl2303_set_termios(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old_termios)
......@@ -544,7 +555,7 @@ static void pl2303_set_termios(struct tty_struct *tty,
int ret;
u8 control;
if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
if (old_termios && !pl2303_termios_change(&tty->termios, old_termios))
buf = kzalloc(7, GFP_KERNEL);
......@@ -662,6 +673,9 @@ static void pl2303_set_termios(struct tty_struct *tty,
pl2303_vendor_write(serial, 0x0, 0x41);
pl2303_vendor_write(serial, 0x0, 0x61);
} else if (I_IXON(tty) && !I_IXANY(tty) && START_CHAR(tty) == 0x11 &&
STOP_CHAR(tty) == 0x13) {
pl2303_vendor_write(serial, 0x0, 0xc0);
} else {
pl2303_vendor_write(serial, 0x0, 0x0);
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