linux-kernel - [PATCH 2/2] cdc-acm: correct counting of UART states in serial state notification

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Message-Id: <1537647071-2691-2-git-send-email-t-herzog@gmx.de>
Date:   Sat, 22 Sep 2018 22:11:11 +0200
From:   Tobias Herzog <t-herzog@....de>
To:     oneukum@...e.com
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] cdc-acm: correct counting of UART states in serial state notification

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

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 50339ca..187f386 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -310,17 +310,17 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
 
 		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_irqrestore(&acm->read_lock, flags);
 
-- 
2.1.4