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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Tobias Herzog <t-herzog@gmx.de>,
        Oliver Neukum <oneukum@suse.com>
Subject: [PATCH 4.9 163/171] cdc-acm: correct counting of UART states in serial state notification
Date:   Thu,  8 Nov 2018 13:52:13 -0800
Message-Id: <20181108215138.757983166@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tobias Herzog <t-herzog@gmx.de>

commit f976d0e5747ca65ccd0fb2a4118b193d70aa1836 upstream.

The usb standard ("Universal Serial Bus Class Definitions for Communication
Devices") distiguishes between "consistent signals" (DSR, DCD), and
"irregular signals" (break, ring, parity error, framing error, overrun).
The bits of "irregular signals" are set, if this error/event occurred on
the device side and are immeadeatly unset, if the serial state notification
was sent.
Like other drivers of real serial ports do, just the occurence of those
events should be counted in serial_icounter_struct (but no 1->0
transitions).

Signed-off-by: Tobias Herzog <t-herzog@gmx.de>
Acked-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/class/cdc-acm.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -333,17 +333,17 @@ static void acm_ctrl_irq(struct urb *urb
 
 		if (difference & ACM_CTRL_DSR)
 			acm->iocount.dsr++;
-		if (difference & ACM_CTRL_BRK)
-			acm->iocount.brk++;
-		if (difference & ACM_CTRL_RI)
-			acm->iocount.rng++;
 		if (difference & ACM_CTRL_DCD)
 			acm->iocount.dcd++;
-		if (difference & ACM_CTRL_FRAMING)
+		if (newctrl & ACM_CTRL_BRK)
+			acm->iocount.brk++;
+		if (newctrl & ACM_CTRL_RI)
+			acm->iocount.rng++;
+		if (newctrl & ACM_CTRL_FRAMING)
 			acm->iocount.frame++;
-		if (difference & ACM_CTRL_PARITY)
+		if (newctrl & ACM_CTRL_PARITY)
 			acm->iocount.parity++;
-		if (difference & ACM_CTRL_OVERRUN)
+		if (newctrl & ACM_CTRL_OVERRUN)
 			acm->iocount.overrun++;
 		spin_unlock(&acm->read_lock);