- i = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
- SET_LINE_REQUEST, SET_LINE_REQUEST_TYPE,
- 0, 0, buf, 7, 100);
- dbg("0x21:0x20:0:0 %d", 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);
+
+ dbg("0x21:0x20:0:0 %d", i);
+
+ if (i == 7)
+ memcpy(priv->line_settings, buf, 7);
+ }