Merge git://git.infradead.org/~dwmw2/battery-2.6 (5f60cfd9) · Commits · e / devices / android_kernel_sony_msm8994

Documentation/power_supply_class.txt

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			Linux power supply class
			========================

			Synopsis
			~~~~~~~~
			Power supply class used to represent battery, UPS, AC or DC power supply
			properties to user-space.

			It defines core set of attributes, which should be applicable to (almost)
			every power supply out there. Attributes are available via sysfs and uevent
			interfaces.

			Each attribute has well defined meaning, up to unit of measure used. While
			the attributes provided are believed to be universally applicable to any
			power supply, specific monitoring hardware may not be able to provide them
			all, so any of them may be skipped.

			Power supply class is extensible, and allows to define drivers own attributes.
			The core attribute set is subject to the standard Linux evolution (i.e.
			if it will be found that some attribute is applicable to many power supply
			types or their drivers, it can be added to the core set).

			It also integrates with LED framework, for the purpose of providing
			typically expected feedback of battery charging/fully charged status and
			AC/USB power supply online status. (Note that specific details of the
			indication (including whether to use it at all) are fully controllable by
			user and/or specific machine defaults, per design principles of LED
			framework).


			Attributes/properties
			~~~~~~~~~~~~~~~~~~~~~
			Power supply class has predefined set of attributes, this eliminates code
			duplication across drivers. Power supply class insist on reusing its
			predefined attributes and their units.

			So, userspace gets predictable set of attributes and their units for any
			kind of power supply, and can process/present them to a user in consistent
			manner. Results for different power supplies and machines are also directly
			comparable.

			See drivers/power/ds2760_battery.c and drivers/power/pda_power.c for the
			example how to declare and handle attributes.


			Units
			~~~~~
			Quoting include/linux/power_supply.h:

			All voltages, currents, charges, energies, time and temperatures in µV,
			µA, µAh, µWh, seconds and tenths of degree Celsius unless otherwise
			stated. It's driver's job to convert its raw values to units in which
			this class operates.


			Attributes/properties detailed
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

			~ ~ ~ ~ ~ ~ ~ Charge/Energy/Capacity - how to not confuse ~ ~ ~ ~ ~ ~ ~
			~ ~
			~ Because both "charge" (µAh) and "energy" (µWh) represents "capacity" ~
			~ of battery, this class distinguish these terms. Don't mix them! ~
			~ ~
			~ CHARGE_* attributes represents capacity in µAh only. ~
			~ ENERGY_* attributes represents capacity in µWh only. ~
			~ CAPACITY attribute represents capacity in percents, from 0 to 100. ~
			~ ~
			~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

			Postfixes:
			_AVG - hardware averaged value, use it if your hardware is really able to
			report averaged values.
			_NOW - momentary/instantaneous values.

			STATUS - this attribute represents operating status (charging, full,
			discharging (i.e. powering a load), etc.). This corresponds to
			BATTERY_STATUS_* values, as defined in battery.h.

			HEALTH - represents health of the battery, values corresponds to
			POWER_SUPPLY_HEALTH_*, defined in battery.h.

			VOLTAGE_MAX_DESIGN, VOLTAGE_MIN_DESIGN - design values for maximal and
			minimal power supply voltages. Maximal/minimal means values of voltages
			when battery considered "full"/"empty" at normal conditions. Yes, there is
			no direct relation between voltage and battery capacity, but some dumb
			batteries use voltage for very approximated calculation of capacity.
			Battery driver also can use this attribute just to inform userspace
			about maximal and minimal voltage thresholds of a given battery.

			CHARGE_FULL_DESIGN, CHARGE_EMPTY_DESIGN - design charge values, when
			battery considered full/empty.

			ENERGY_FULL_DESIGN, ENERGY_EMPTY_DESIGN - same as above but for energy.

			CHARGE_FULL, CHARGE_EMPTY - These attributes means "last remembered value
			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.

			ENERGY_FULL, ENERGY_EMPTY - same as above but for energy.

			CAPACITY - capacity in percents.
			CAPACITY_LEVEL - capacity level. This corresponds to
			POWER_SUPPLY_CAPACITY_LEVEL_*.

			TEMP - temperature of the power supply.
			TEMP_AMBIENT - ambient temperature.

			TIME_TO_EMPTY - seconds left for battery to be considered empty (i.e.
			while battery powers a load)
			TIME_TO_FULL - seconds left for battery to be considered full (i.e.
			while battery is charging)


			Battery <-> external power supply interaction
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
			Often power supplies are acting as supplies and supplicants at the same
			time. Batteries are good example. So, batteries usually care if they're
			externally powered or not.

			For that case, power supply class implements notification mechanism for
			batteries.

			External power supply (AC) lists supplicants (batteries) names in
			"supplied_to" struct member, and each power_supply_changed() call
			issued by external power supply will notify supplicants via
			external_power_changed callback.


			QA
			~~
			Q: Where is POWER_SUPPLY_PROP_XYZ attribute?
			A: If you cannot find attribute suitable for your driver needs, feel free
			to add it and send patch along with your driver.

			The attributes available currently are the ones currently provided by the
			drivers written.

			Good candidates to add in future: model/part#, cycle_time, manufacturer,
			etc.


			Q: I have some very specific attribute (e.g. battery color), should I add
			this attribute to standard ones?
			A: Most likely, no. Such attribute can be placed in the driver itself, if
			it is useful. Of course, if the attribute in question applicable to
			large set of batteries, provided by many drivers, and/or comes from
			some general battery specification/standard, it may be a candidate to
			be added to the core attribute set.


			Q: Suppose, my battery monitoring chip/firmware does not provides capacity
			in percents, but provides charge_{now,full,empty}. Should I calculate
			percentage capacity manually, inside the driver, and register CAPACITY
			attribute? The same question about time_to_empty/time_to_full.
			A: Most likely, no. This class is designed to export properties which are
			directly measurable by the specific hardware available.

			Inferring not available properties using some heuristics or mathematical
			model is not subject of work for a battery driver. Such functionality
			should be factored out, and in fact, apm_power, the driver to serve
			legacy APM API on top of power supply class, uses a simple heuristic of
			approximating remaining battery capacity based on its charge, current,
			voltage and so on. But full-fledged battery model is likely not subject
			for kernel at all, as it would require floating point calculation to deal
			with things like differential equations and Kalman filters. This is
			better be handled by batteryd/libbattery, yet to be written.

drivers/Kconfig

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	@@ -52,6 +52,8 @@ source "drivers/spi/Kconfig"

	source "drivers/w1/Kconfig"		source "drivers/w1/Kconfig"

			source "drivers/power/Kconfig"

	source "drivers/hwmon/Kconfig"		source "drivers/hwmon/Kconfig"

	source "drivers/mfd/Kconfig"		source "drivers/mfd/Kconfig"

drivers/Makefile

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	@@ -61,6 +61,7 @@ obj-$(CONFIG_I2O) += message/
	obj-$(CONFIG_RTC_LIB) += rtc/		obj-$(CONFIG_RTC_LIB) += rtc/
	obj-y += i2c/		obj-y += i2c/
	obj-$(CONFIG_W1) += w1/		obj-$(CONFIG_W1) += w1/
			obj-$(CONFIG_POWER_SUPPLY) += power/
	obj-$(CONFIG_HWMON) += hwmon/		obj-$(CONFIG_HWMON) += hwmon/
	obj-$(CONFIG_PHONE) += telephony/		obj-$(CONFIG_PHONE) += telephony/
	obj-$(CONFIG_MD) += md/		obj-$(CONFIG_MD) += md/

drivers/power/Kconfig

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			menuconfig POWER_SUPPLY
			tristate "Power supply class support"
			help
			Say Y here to enable power supply class support. This allows
			power supply (batteries, AC, USB) monitoring by userspace
			via sysfs and uevent (if available) and/or APM kernel interface
			(if selected below).

			if POWER_SUPPLY

			config POWER_SUPPLY_DEBUG
			bool "Power supply debug"
			help
			Say Y here to enable debugging messages for power supply class
			and drivers.

			config PDA_POWER
			tristate "Generic PDA/phone power driver"
			help
			Say Y here to enable generic power driver for PDAs and phones with
			one or two external power supplies (AC/USB) connected to main and
			backup batteries, and optional builtin charger.

			config APM_POWER
			tristate "APM emulation for class batteries"
			depends on APM_EMULATION
			help
			Say Y here to enable support APM status emulation using
			battery class devices.

			config BATTERY_DS2760
			tristate "DS2760 battery driver (HP iPAQ & others)"
			select W1
			select W1_SLAVE_DS2760
			help
			Say Y here to enable support for batteries with ds2760 chip.

			config BATTERY_PMU
			tristate "Apple PMU battery"
			depends on ADB_PMU
			help
			Say Y here to expose battery information on Apple machines
			through the generic battery class.

			config BATTERY_OLPC
			tristate "One Laptop Per Child battery"
			depends on X86_32 && OLPC
			help
			Say Y to enable support for the battery on the OLPC laptop.

			endif # POWER_SUPPLY

drivers/power/Makefile

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			power_supply-objs := power_supply_core.o

			ifeq ($(CONFIG_SYSFS),y)
			power_supply-objs += power_supply_sysfs.o
			endif

			ifeq ($(CONFIG_LEDS_TRIGGERS),y)
			power_supply-objs += power_supply_leds.o
			endif

			ifeq ($(CONFIG_POWER_SUPPLY_DEBUG),y)
			EXTRA_CFLAGS += -DDEBUG
			endif

			obj-$(CONFIG_POWER_SUPPLY) += power_supply.o

			obj-$(CONFIG_PDA_POWER) += pda_power.o
			obj-$(CONFIG_APM_POWER) += apm_power.o

			obj-$(CONFIG_BATTERY_DS2760) += ds2760_battery.o
			obj-$(CONFIG_BATTERY_PMU) += pmu_battery.o
			obj-$(CONFIG_BATTERY_OLPC) += olpc_battery.o