power_supply: add CHARGE_COUNTER property and olpc_battery support for it

This adds PROP_CHARGE_COUNTER to the power supply class (documenting it
as well).  The OLPC battery driver uses this for spitting out its ACR
values (in uAh).  We have some rounding errors (the data sheet claims
416.7, the math actually works out to 416.666667, so we're forced to
choose between overflows or precision loss.  I chose precision loss,
and stuck w/ data sheet values), but I don't think anyone will care
that much.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

4 files changed, 16 insertions, 1 deletions

diff --git a/Documentation/power/power_supply_class.txt b/Documentation/power/power_supply_class.txt
index a8686e5a6857..c6cd4956047c 100644
--- a/Documentation/power/power_supply_class.txt
+++ b/Documentation/power/power_supply_class.txt
@@ -101,6 +101,10 @@ of charge when battery became full/empty". It also could mean "value of
 charge when battery considered full/empty at given conditions (temperature,
 age)". I.e. these attributes represents real thresholds, not design values.
 
+CHARGE_COUNTER - the current charge counter (in µAh).  This could easily
+be negative; there is no empty or full value.  It is only useful for
+relative, time-based measurements.
+
 ENERGY_FULL, ENERGY_EMPTY - same as above but for energy.
 
 CAPACITY - capacity in percents.
diff --git a/drivers/power/olpc_battery.c b/drivers/power/olpc_battery.c
index c8b596a7fc94..9dd1589733c2 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
+#define EC_BAT_ACR      0x12    /* int16_t,     *416.7,      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 */
@@ -289,6 +289,14 @@ static int olpc_bat_get_property(struct power_supply *psy,
                 ec_word = be16_to_cpu(ec_word);
                 val->intval = ec_word * 100 / 256;
                 break;
+        case POWER_SUPPLY_PROP_CHARGE_COUNTER:
+                ret = olpc_ec_cmd(EC_BAT_ACR, NULL, 0, (void *)&ec_word, 2);
+                if (ret)
+                        return ret;
+
+                ec_word = be16_to_cpu(ec_word);
+                val->intval = ec_word * 4167 / 10;
+                break;
         case POWER_SUPPLY_PROP_SERIAL_NUMBER:
                 ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);
                 if (ret)
@@ -317,6 +325,7 @@ static enum power_supply_property olpc_bat_props[] = {
         POWER_SUPPLY_PROP_TEMP_AMBIENT,
         POWER_SUPPLY_PROP_MANUFACTURER,
         POWER_SUPPLY_PROP_SERIAL_NUMBER,
+        POWER_SUPPLY_PROP_CHARGE_COUNTER,
 };
 
 /* EEPROM reading goes completely around the power_supply API, sadly */
diff --git a/drivers/power/power_supply_sysfs.c b/drivers/power/power_supply_sysfs.c
index c444d6b10c58..82e1246eeb0a 100644
--- a/drivers/power/power_supply_sysfs.c
+++ b/drivers/power/power_supply_sysfs.c
@@ -99,6 +99,7 @@ static struct device_attribute power_supply_attrs[] = {
         POWER_SUPPLY_ATTR(charge_empty),
         POWER_SUPPLY_ATTR(charge_now),
         POWER_SUPPLY_ATTR(charge_avg),
+        POWER_SUPPLY_ATTR(charge_counter),
         POWER_SUPPLY_ATTR(energy_full_design),
         POWER_SUPPLY_ATTR(energy_empty_design),
         POWER_SUPPLY_ATTR(energy_full),
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 68ed19ccf1f7..ea96ead1d39d 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -78,6 +78,7 @@ enum power_supply_property {
         POWER_SUPPLY_PROP_CHARGE_EMPTY,
         POWER_SUPPLY_PROP_CHARGE_NOW,
         POWER_SUPPLY_PROP_CHARGE_AVG,
+        POWER_SUPPLY_PROP_CHARGE_COUNTER,
         POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN,
         POWER_SUPPLY_PROP_ENERGY_EMPTY_DESIGN,
         POWER_SUPPLY_PROP_ENERGY_FULL,