lkml.org 
[lkml]   [2008]   [May]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] power_supply: add CHARGE_COUNTER property and olpc_battery support for it
On Tue, May 13, 2008 at 12:23:30PM -0400, Andres Salomon wrote:
> 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?

Sorry for the delay... Applied, thanks!

> 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

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

\
 
 \ /
  Last update: 2008-05-18 23:51    [W:0.048 / U:3.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site