linux-kernel - [PATCH 4.18 054/168] i2c: uniphier-f: issue STOP only for last message or I2C_M

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Date:   Mon,  8 Oct 2018 20:30:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 054/168] i2c: uniphier-f: issue STOP only for last message or I2C_M_STOP

4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Masahiro Yamada <yamada.masahiro@...ionext.com>

[ Upstream commit 4c85609b08c4761eca0a40fd7beb06bc650f252d ]

This driver currently emits a STOP if the next message is not
I2C_MD_RD.  It should not do it because it disturbs the I2C_RDWR
ioctl, where read/write transactions are combined without STOP
between.

Issue STOP only when the message is the last one _or_ flagged with
I2C_M_STOP.

Fixes: 6a62974b667f ("i2c: uniphier_f: add UniPhier FIFO-builtin I2C driver")
Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/i2c/busses/i2c-uniphier-f.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/drivers/i2c/busses/i2c-uniphier-f.c
+++ b/drivers/i2c/busses/i2c-uniphier-f.c
@@ -401,11 +401,8 @@ static int uniphier_fi2c_master_xfer(str
 		return ret;
 
 	for (msg = msgs; msg < emsg; msg++) {
-		/* If next message is read, skip the stop condition */
-		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
-		/* but, force it if I2C_M_STOP is set */
-		if (msg->flags & I2C_M_STOP)
-			stop = true;
+		/* Emit STOP if it is the last message or I2C_M_STOP is set. */
+		bool stop = (msg + 1 == emsg) || (msg->flags & I2C_M_STOP);
 
 		ret = uniphier_fi2c_master_xfer_one(adap, msg, stop);
 		if (ret)