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ftdi_sio: fix status line change handling for TIOCMIWAIT and TIOCGICOUNT

PATCH Simon Arlott 2 participants 2 messages Mar 26, 2012

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USB USB serial
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Simon Arlott

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#0 lore raw

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 <[email protected]>
Cc Uwe Bonnes <[email protected]>
---
 drivers/usb/serial/ftdi_sio.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)
drivers/usb/serial/ftdi_sio.c +13 -11
index f770415..d260b79 100644
@@ -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

@@ -1962,17 +1962,19 @@ 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;
 	}
Signature · 4 lines
1.7.4.1

-- 
Simon Arlott
maintainer
#1 lore raw
Quoted 12 lines · Simon Arlott

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.

Quoted 5 lines

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.

Nice, do you happen to have the source for such a test tool anywhere around? I'd like to use it for future testing if at all possible.

I'll queue this up after 3.4-rc1 is out.

greg k-h