Messages in this thread Patch in this message | | | Date | Tue, 13 May 2008 12:23:30 -0400 | From | Andres Salomon <> | Subject | Re: [PATCH] power_supply: add CHARGE_COUNTER property and olpc_battery support for it |
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On Tue, 13 May 2008 10:20:15 -0400 "Richard A. Smith" <richard@laptop.org> wrote:
> Andres Salomon wrote: > > > + ec_word = be16_to_cpu(ec_word); > > + val->intval = ec_word * 4167 / 10; > > Whats wrong with: > > > + val->intval = ((int)ec_word) * 6250 / 15; > > Which does not have overflow problems and keeps more precision. >
You're right, of course. Anton, can you please apply the following?
Subject: [PATCH] power_supply: fix up CHARGE_COUNTER output to be more precise
As Richard Smith pointed out, ACR * 6250 / 15 provides for less precision loss than ACR * 4167 / 10, _and_ it doesn't overflow. Switch to using that equation for CHARGE_COUNTER.
Signed-off-by: Andres Salomon <dilinger@debian.org> --- drivers/power/olpc_battery.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/power/olpc_battery.c b/drivers/power/olpc_battery.c index a928165..f5d712a 100644 --- a/drivers/power/olpc_battery.c +++ b/drivers/power/olpc_battery.c @@ -19,7 +19,7 @@ #define EC_BAT_VOLTAGE 0x10 /* uint16_t, *9.76/32, mV */ #define EC_BAT_CURRENT 0x11 /* int16_t, *15.625/120, mA */ -#define EC_BAT_ACR 0x12 /* int16_t, *416.7, µAh */ +#define EC_BAT_ACR 0x12 /* int16_t, *6250/15, µAh */ #define EC_BAT_TEMP 0x13 /* uint16_t, *100/256, °C */ #define EC_AMB_TEMP 0x14 /* uint16_t, *100/256, °C */ #define EC_BAT_STATUS 0x15 /* uint8_t, bitmask */ @@ -295,7 +295,7 @@ static int olpc_bat_get_property(struct power_supply *psy, return ret; ec_word = be16_to_cpu(ec_word); - val->intval = ec_word * 4167 / 10; + val->intval = ec_word * 6250 / 15; break; case POWER_SUPPLY_PROP_SERIAL_NUMBER: ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8); -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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