From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758258AbYEMQTi (ORCPT ); Tue, 13 May 2008 12:19:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755622AbYEMQT3 (ORCPT ); Tue, 13 May 2008 12:19:29 -0400 Received: from mail.queued.net ([207.210.101.209]:3809 "EHLO mail.queued.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755324AbYEMQT2 convert rfc822-to-8bit (ORCPT ); Tue, 13 May 2008 12:19:28 -0400 Date: Tue, 13 May 2008 12:23:30 -0400 From: Andres Salomon To: richard@laptop.org Cc: avorontsov@ru.mvista.com, Andrew Morton , cbou@mail.ru, linux-kernel@vger.kernel.org, dwmw2@infradead.org Subject: Re: [PATCH] power_supply: add CHARGE_COUNTER property and olpc_battery support for it Message-ID: <20080513122330.4c81e289@ephemeral> In-Reply-To: <4829A39F.7050308@laptop.org> References: <20080508003454.722ba511@ephemeral> <20080508105145.GA32017@polina.dev.rtsoft.ru> <20080508130102.3218f1e9@ephemeral> <20080508171320.GA8226@polina.dev.rtsoft.ru> <48234C25.4040807@laptop.org> <20080508193614.GA31188@polina.dev.rtsoft.ru> <4823663B.6060409@laptop.org> <20080512214629.443a5999@ephemeral> <4829A39F.7050308@laptop.org> X-Mailer: Claws Mail 3.4.0 (GTK+ 2.12.9; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 May 2008 10:20:15 -0400 "Richard A. Smith" 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 --- 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