Some PL2303 chips are reported to lose bytes if the serial settings are set to
the same values as before.
At least HXD chips are affected, HX chips seem to be ok.
The current code tries to avoid this by calling tty_termios_hw_change(), but
this check isn't sufficient because different requested baud rates can result
in identic encoded baud rates.
The solution is to save and compare the encoded settings instead.
Signed-off-by: Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
---
drivers/usb/serial/pl2303.c | 22 ++++++++++++++--------
1 Datei geändert, 14 Zeilen hinzugefügt(+), 8 Zeilen entfernt(-)
diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index bedf8e4..27a2691 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -155,6 +155,7 @@ struct pl2303_private {
spinlock_t lock;
u8 line_control;
u8 line_status;
+ u8 line_settings_enc[7]; /* baud rate, data bits, stop bits, parity */
};
static int pl2303_vendor_read(__u16 value, __u16 index,
@@ -500,14 +501,6 @@ 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;
-
buf = kzalloc(7, GFP_KERNEL);
if (!buf) {
dev_err(&port->dev, "%s - out of memory.\n", __func__);
@@ -591,10 +584,23 @@ static void pl2303_set_termios(struct tty_struct *tty,
dev_dbg(&port->dev, "parity = none\n");
}
+ /*
+ * Some PL2303 chips are reported to lose bytes if you change the
+ * serial settings even to the same values as before.
+ * At least HXD chips are affected, HX chips seem to be ok.
+ * Thus we actually need to filter in this specific case.
+ * NOTE: a tty_termios_hw_change() check isn't sufficient, because
+ * different baud rates can result in identic encoded values.
+ */
+ if (!memcmp(priv->line_settings_enc, buf, 7))
+ return;
+
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(buf, priv->line_settings_enc, 7);
/* change control lines if we are switching to or from B0 */
spin_lock_irqsave(&priv->lock, flags);
--
1.7.10.4
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