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path: root/drivers/usb/serial
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Diffstat (limited to 'drivers/usb/serial')
-rw-r--r--drivers/usb/serial/pl2303.c34
1 files changed, 25 insertions, 9 deletions
diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index 1e3318dfa1cb..beb8edce4ef2 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -142,6 +142,8 @@ struct pl2303_private {
spinlock_t lock;
u8 line_control;
u8 line_status;
+
+ u8 line_settings[7];
};
static int pl2303_vendor_read(__u16 value, __u16 index,
@@ -339,11 +341,6 @@ static void pl2303_set_termios(struct tty_struct *tty,
int i;
u8 control;
- /*
- * The PL2303 is reported to lose bytes if you change serial settings
- * even to the same values as before. Thus we actually need to filter
- * in this specific case.
- */
if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
return;
@@ -428,10 +425,29 @@ static void pl2303_set_termios(struct tty_struct *tty,
dev_dbg(&port->dev, "parity = none\n");
}
- i = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
- SET_LINE_REQUEST, SET_LINE_REQUEST_TYPE,
- 0, 0, buf, 7, 100);
- dev_dbg(&port->dev, "0x21:0x20:0:0 %d\n", i);
+ /*
+ * Some PL2303 are known to lose bytes if you change serial settings
+ * even to the same values as before. Thus we actually need to filter
+ * in this specific case.
+ *
+ * Note that the tty_termios_hw_change check above is not sufficient
+ * as a previously requested baud rate may differ from the one
+ * actually used (and stored in old_termios).
+ *
+ * NOTE: No additional locking needed for line_settings as it is
+ * only used in set_termios, which is serialised against itself.
+ */
+ if (!old_termios || memcmp(buf, priv->line_settings, 7)) {
+ i = usb_control_msg(serial->dev,
+ usb_sndctrlpipe(serial->dev, 0),
+ SET_LINE_REQUEST, SET_LINE_REQUEST_TYPE,
+ 0, 0, buf, 7, 100);
+
+ dev_dbg(&port->dev, "0x21:0x20:0:0 %d\n", i);
+
+ if (i == 7)
+ memcpy(priv->line_settings, buf, 7);
+ }
/* change control lines if we are switching to or from B0 */
spin_lock_irqsave(&priv->lock, flags);