[PATCH 3.12 095/170] hwmon: (ina2xx) Cast to s16 on shunt and current regs

Jiri Slaby
2014-07-18T13:18:31Z

From: Fabio Baltieri <fabio.baltieri@gmail.com>

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

===============

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@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
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 70a39a8ac016..554f5c3fe5c4 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 */
--
2.0.0