[3.13.y.z extended stable] Patch "i2c: rcar: bail out on zero length transfers" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i2c: rcar: bail out on zero length transfers

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 21d60d248702074195b006cc8ca8968c6cdc5b46 Mon Sep 17 00:00:00 2001
From: Wolfram Sang <wsa+renesas at sang-engineering.com>
Date: Mon, 5 May 2014 18:36:21 +0200
Subject: i2c: rcar: bail out on zero length transfers

commit d7653964c590ba846aa11a8f6edf409773cbc492 upstream.

This hardware does not support zero length transfers. Instead, the
driver does one (random) byte transfers currently with undefined results
for the slaves. We now bail out.

Signed-off-by: Wolfram Sang <wsa+renesas at sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/i2c/busses/i2c-rcar.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 2c2fd7c..56de337 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -567,6 +567,12 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,

 	ret = -EINVAL;
 	for (i = 0; i < num; i++) {
+		/* This HW can't send STOP after address phase */
+		if (msgs[i].len == 0) {
+			ret = -EOPNOTSUPP;
+			break;
+		}
+
 		/*-------------- spin lock -----------------*/
 		spin_lock_irqsave(&priv->lock, flags);

@@ -631,7 +637,8 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,

 static u32 rcar_i2c_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+	/* This HW can't do SMBUS_QUICK and NOSTART */
+	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
 }

 static const struct i2c_algorithm rcar_i2c_algo = {
--
1.9.1