[3.11.y.z extended stable] Patch "hwmon: (ina2xx) Cast to s16 on shunt and current regs" has been added to staging queue

[Luis Henriques]

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

    hwmon: (ina2xx) Cast to s16 on shunt and current regs

to the linux-3.11.y-queue branch of the 3.11.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-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3667c23c0f1a91a1385157b4cc7dfcb3f45cd415 Mon Sep 17 00:00:00 2001
From: Fabio Baltieri <fabio.baltieri at gmail.com>
Date: Sun, 8 Jun 2014 22:06:24 +0100
Subject: hwmon: (ina2xx) Cast to s16 on shunt and current regs

commit c0214f98943b1fe43f7be61b7782b0c8f0836f28 upstream.

All devices supported by ina2xx are bidirectional and report the
measured shunt voltage and power values as a signed 16 bit, but the
current driver implementation caches all registers as u16, leading
to an incorrect sign extension when reporting to userspace in
ina2xx_get_value().

This patch fixes the problem by casting the signed registers to s16.
Tested on an INA219.

Signed-off-by: Fabio Baltieri <fabio.baltieri at gmail.com>
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/hwmon/ina2xx.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index d917a2d8c30f..5cb02dd74984 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -148,7 +148,8 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg)

 	switch (reg) {
 	case INA2XX_SHUNT_VOLTAGE:
-		val = DIV_ROUND_CLOSEST(data->regs[reg],
+		/* signed register */
+		val = DIV_ROUND_CLOSEST((s16)data->regs[reg],
 					data->config->shunt_div);
 		break;
 	case INA2XX_BUS_VOLTAGE:
@@ -160,8 +161,8 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg)
 		val = data->regs[reg] * data->config->power_lsb;
 		break;
 	case INA2XX_CURRENT:
-		/* LSB=1mA (selected). Is in mA */
-		val = data->regs[reg];
+		/* signed register, LSB=1mA (selected), in mA */
+		val = (s16)data->regs[reg];
 		break;
 	default:
 		/* programmer goofed */
--
1.9.1