USB: ftdi_sio: fix status line change handling for TIOCMIWAIT and TIOCGICOUNT

commit fca5430d48d53eaf103498c33fd0d1984b9f448b upstream.

Handling of TIOCMIWAIT was changed by commit 1d749f9afa657f6ee9336b2bc1fcd750a647d157
 USB: ftdi_sio.c: Use ftdi async_icount structure for TIOCMIWAIT, as in other drivers

FTDI_STATUS_B0_MASK does not indicate the changed modem status lines,
it indicates the value of the current modem status lines. An xor is
still required to determine which lines have changed.

The count was only being incremented if the line was high. The only
reason TIOCMIWAIT still worked was because the status packet is
repeated every 1ms, so the count was always changing. The wakeup
itself still ran based on the status lines changing.

This change fixes handling of updates to the modem status lines and
allows multiple processes to use TIOCMIWAIT concurrently.

Tested with two processes waiting on different status lines being
toggled independently.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Cc: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index f2c9ef780b1824db583bb7aea58b4834e05a9cd4..cfc8e59636a4d2decbc1fee49c4eede893ee7400 100644 (file)
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -75,7 +75,7 @@ struct ftdi_private {
        unsigned long last_dtr_rts;     /* saved modem control outputs */
        struct async_icount     icount;
        wait_queue_head_t delta_msr_wait; /* Used for TIOCMIWAIT */
-       char prev_status, diff_status;        /* Used for TIOCMIWAIT */
+       char prev_status;        /* Used for TIOCMIWAIT */
        char transmit_empty;    /* If transmitter is empty or not */
        struct usb_serial_port *port;
        __u16 interface;        /* FT2232C, FT2232H or FT4232H port interface
@@ -1979,17 +1979,19 @@ static int ftdi_process_packet(struct tty_struct *tty,
           N.B. packet may be processed more than once, but differences
           are only processed once.  */
        status = packet[0] & FTDI_STATUS_B0_MASK;
-       if (status & FTDI_RS0_CTS)
-               priv->icount.cts++;
-       if (status & FTDI_RS0_DSR)
-               priv->icount.dsr++;
-       if (status & FTDI_RS0_RI)
-               priv->icount.rng++;
-       if (status & FTDI_RS0_RLSD)
-               priv->icount.dcd++;
        if (status != priv->prev_status) {
-               priv->diff_status |= status ^ priv->prev_status;
-               wake_up_interruptible(&priv->delta_msr_wait);
+               char diff_status = status ^ priv->prev_status;
+
+               if (diff_status & FTDI_RS0_CTS)
+                       priv->icount.cts++;
+               if (diff_status & FTDI_RS0_DSR)
+                       priv->icount.dsr++;
+               if (diff_status & FTDI_RS0_RI)
+                       priv->icount.rng++;
+               if (diff_status & FTDI_RS0_RLSD)
+                       priv->icount.dcd++;
+
+               wake_up_interruptible_all(&priv->delta_msr_wait);
                priv->prev_status = status;
        }