[PATCH v2] olpc_battery: Fix endian neutral breakage for s16 values

[PATCH v2] 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 implicit 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(-)

v2 drops the unneeded int casts, which are implicit.

diff --git a/drivers/power/olpc_battery.c b/drivers/power/olpc_battery.c
index aafc1c5..5bc1dcf 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 = (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 = (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 = (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 = (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 v2] olpc_battery: Fix endian neutral breakage for s16 values

[Richard A. Smith]

On 09/25/2010 02:19 PM, 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 implicit cast up to an int.

Seems the comment has a error.  Should be 'returns an unsigned' rather 
than signed.  Other than that it looks good.

-- 
Richard A. Smith  <richard@laptop.org>
One Laptop per Child

Re: [PATCH v2] olpc_battery: Fix endian neutral breakage for s16 values

[Anton Vorontsov]

On Mon, Sep 27, 2010 at 10:51:35AM -0400, Richard A. Smith wrote:
> On 09/25/2010 02:19 PM, 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 implicit cast up to an int.
> 
> Seems the comment has a error.  Should be 'returns an unsigned'
> rather than signed.  Other than that it looks good.

Fixed and applied w/ Cc: <stable@kernel.org>, thanks!

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