[PATCH] olpc_battery: Fix endian neutral breakage for s16 values

[PATCH] olpc_battery: Fix endian neutral breakage for s16 values

[Daniel Drake]

From: Richard A. Smith <richard@laptop.org>

When the driver was updated to be endian neutral (8e9c7716c)
the signed part of the s16 values was lost.  This is because be16_to_cpu()
returns a signed value.  This patch casts the values back to a s16 number
prior to the the cast up to an int.

Signed-off-by: Richard A. Smith <richard@laptop.org>
Signed-off-by: Daniel Drake <dsd@laptop.org>
---
 drivers/power/olpc_battery.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/power/olpc_battery.c b/drivers/power/olpc_battery.c
index aafc1c5..74024e4 100644
--- a/drivers/power/olpc_battery.c
+++ b/drivers/power/olpc_battery.c
@@ -271,14 +271,14 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 9760L / 32;
+		val->intval = (int)((s16)be16_to_cpu(ec_word)) * 9760L / 32;
 		break;
 	case POWER_SUPPLY_PROP_CURRENT_AVG:
 		ret = olpc_ec_cmd(EC_BAT_CURRENT, NULL, 0, (void *)&ec_word, 2);
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 15625L / 120;
+		val->intval = (int)((s16)be16_to_cpu(ec_word)) * 15625L / 120;
 		break;
 	case POWER_SUPPLY_PROP_CAPACITY:
 		ret = olpc_ec_cmd(EC_BAT_SOC, NULL, 0, &ec_byte, 1);
@@ -299,7 +299,7 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 100 / 256;
+		val->intval = (int)((s16)be16_to_cpu(ec_word)) * 100 / 256;
 		break;
 	case POWER_SUPPLY_PROP_TEMP_AMBIENT:
 		ret = olpc_ec_cmd(EC_AMB_TEMP, NULL, 0, (void *)&ec_word, 2);
@@ -313,7 +313,7 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 6250 / 15;
+		val->intval = (int)((s16)be16_to_cpu(ec_word)) * 6250 / 15;
 		break;
 	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
 		ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);
-- 
1.7.2.2

Re: [PATCH] olpc_battery: Fix endian neutral breakage for s16 values

[Anton Vorontsov]

On Fri, Sep 24, 2010 at 08:31:33PM +0100, Daniel Drake wrote:
> From: Richard A. Smith <richard@laptop.org>
> 
> When the driver was updated to be endian neutral (8e9c7716c)
> the signed part of the s16 values was lost.  This is because be16_to_cpu()
> returns a signed value.  This patch casts the values back to a s16 number
> prior to the the cast up to an int.
> 
> Signed-off-by: Richard A. Smith <richard@laptop.org>
> Signed-off-by: Daniel Drake <dsd@laptop.org>

Good catch.

[...]
> -		val->intval = (int)be16_to_cpu(ec_word) * 9760L / 32;
> +		val->intval = (int)((s16)be16_to_cpu(ec_word)) * 9760L / 32;

Do we really need "(int)" then?

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2