USB: serial: handle Data Carrier Detect changes

Alan's commit 335f8514f200e63d689113d29cb7253a5c282967 introduced
.carrier_raised function in several drivers.  That also means
tty_port_block_til_ready can now suspend the process trying to open the serial
port when Carrier Detect is low and put it into tty_port.open_wait queue.  We
need to wake up the process when Carrier Detect goes high and trigger TTY
hangup when CD goes low.

Some of the devices do not report modem status line changes, or at least we
don't understand the status message, so for those we remove .carrier_raised
again.

Signed-off-by: Libor Pechacek <lpechacek@suse.cz>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 63f7cc45bcac..7b8815ddf368 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -486,12 +486,22 @@ static void ch341_read_int_callback(struct urb *urb)
         if (actual_length >= 4) {
                 struct ch341_private *priv = usb_get_serial_port_data(port);
                 unsigned long flags;
+                u8 prev_line_status = priv->line_status;
 
                 spin_lock_irqsave(&priv->lock, flags);
                 priv->line_status = (~(data[2])) & CH341_BITS_MODEM_STAT;
                 if ((data[1] & CH341_MULT_STAT))
                         priv->multi_status_change = 1;
                 spin_unlock_irqrestore(&priv->lock, flags);
+
+                if ((priv->line_status ^ prev_line_status) & CH341_BIT_DCD) {
+                        struct tty_struct *tty = tty_port_tty_get(&port->port);
+                        if (tty)
+                                usb_serial_handle_dcd_change(port, tty,
+                                            priv->line_status & CH341_BIT_DCD);
+                        tty_kref_put(tty);
+                }
+
                 wake_up_interruptible(&priv->delta_msr_wait);
         }