USB: serial: pl2303: fix non-supported xon/xoff

Older pl2303 devices do not support automatic xon/xoff flow control, so
add add a flag to prevent trying to enable it for legacy device types.

Refactor the IXON test into a helper function to improve readability.

Fixes: 7041d9c3f01b ("USB: serial: pl2303: add support for tx xon/xoff flow control")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index bb3f9aa4a9093fe4fcf6ebc192cf1d040d6dc8c3..f1d904706758033c146fb82bccb3f2d45a2c9adf 100644 (file)
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -156,6 +156,7 @@ enum pl2303_type {
 struct pl2303_type_data {
        speed_t max_baud_rate;
        unsigned long quirks;
+       unsigned int no_autoxonxoff:1;
 };
 
 struct pl2303_serial_private {
@@ -173,11 +174,12 @@ struct pl2303_private {
 
 static const struct pl2303_type_data pl2303_type_data[TYPE_COUNT] = {
        [TYPE_01] = {
-               .max_baud_rate =        1228800,
-               .quirks =               PL2303_QUIRK_LEGACY,
+               .max_baud_rate          = 1228800,
+               .quirks                 = PL2303_QUIRK_LEGACY,
+               .no_autoxonxoff         = true,
        },
        [TYPE_HX] = {
-               .max_baud_rate =        12000000,
+               .max_baud_rate          = 12000000,
        },
 };
 
@@ -552,6 +554,20 @@ static bool pl2303_termios_change(const struct ktermios *a, const struct ktermio
        return tty_termios_hw_change(a, b) || ixon_change;
 }
 
+static bool pl2303_enable_xonxoff(struct tty_struct *tty, const struct pl2303_type_data *type)
+{
+       if (!I_IXON(tty) || I_IXANY(tty))
+               return false;
+
+       if (START_CHAR(tty) != 0x11 || STOP_CHAR(tty) != 0x13)
+               return false;
+
+       if (type->no_autoxonxoff)
+               return false;
+
+       return true;
+}
+
 static void pl2303_set_termios(struct tty_struct *tty,
                struct usb_serial_port *port, struct ktermios *old_termios)
 {
@@ -681,8 +697,7 @@ static void pl2303_set_termios(struct tty_struct *tty,
                        pl2303_vendor_write(serial, 0x0, 0x41);
                else
                        pl2303_vendor_write(serial, 0x0, 0x61);
-       } else if (I_IXON(tty) && !I_IXANY(tty) && START_CHAR(tty) == 0x11 &&
-                       STOP_CHAR(tty) == 0x13) {
+       } else if (pl2303_enable_xonxoff(tty, spriv->type)) {
                pl2303_vendor_write(serial, 0x0, 0xc0);
        } else {
                pl2303_vendor_write(serial, 0x0, 0x0);