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

[Kamal Mostafa]

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-3.13.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 3.13.11.5.

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 83ca0c3af9bcc29dad48c5eb1ca996625b3030ef 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: Kamal Mostafa <kamal 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 93d26e8..bfd3f3e 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