netdev - [PATCH 4/7] can: mcp251x: read-modify-write eflag only when needed

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Date:	Fri, 15 Oct 2010 12:49:19 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	socketcan-core@...ts.berlios.de
Cc:	netdev@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 4/7] can: mcp251x: read-modify-write eflag only when needed

From: Sascha Hauer <s.hauer@...gutronix.de>

Use read-modify-write instead of a simple write to change the register
contents, to close existing the race window between the original manual
read and write.

Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/mcp251x.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index 9b3466a..7e2f951 100644
--- a/drivers/net/can/mcp251x.c
+++ b/drivers/net/can/mcp251x.c
@@ -785,7 +785,8 @@ static irqreturn_t mcp251x_can_ist(int irq, void *dev_id)
 
 		mcp251x_write_bits(spi, CANINTF, intf, 0x00);
 
-		mcp251x_write_reg(spi, EFLG, 0x00);
+		if (eflag)
+			mcp251x_write_bits(spi, EFLG, eflag, 0x00);
 
 		/* Update can state */
 		if (eflag & EFLG_TXBO) {
-- 
1.7.0.4

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