Charger Manager
  	(C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL
  
  Charger Manager provides in-kernel battery charger management that
  requires temperature monitoring during suspend-to-RAM state
  and where each battery may have multiple chargers attached and the userland
  wants to look at the aggregated information of the multiple chargers.
  
  Charger Manager is a platform_driver with power-supply-class entries.
  An instance of Charger Manager (a platform-device created with Charger-Manager)
  represents an independent battery with chargers. If there are multiple
  batteries with their own chargers acting independently in a system,
  the system may need multiple instances of Charger Manager.
  
  1. Introduction
  ===============
  
  Charger Manager supports the following:
  
  * Support for multiple chargers (e.g., a device with USB, AC, and solar panels)
  	A system may have multiple chargers (or power sources) and some of
  	they may be activated at the same time. Each charger may have its
  	own power-supply-class and each power-supply-class can provide
  	different information about the battery status. This framework
  	aggregates charger-related information from multiple sources and
  	shows combined information as a single power-supply-class.
  
  * Support for in suspend-to-RAM polling (with suspend_again callback)
  	While the battery is being charged and the system is in suspend-to-RAM,
  	we may need to monitor the battery health by looking at the ambient or
  	battery temperature. We can accomplish this by waking up the system
  	periodically. However, such a method wakes up devices unnecessarily for
  	monitoring the battery health and tasks, and user processes that are
  	supposed to be kept suspended. That, in turn, incurs unnecessary power
  	consumption and slow down charging process. Or even, such peak power
  	consumption can stop chargers in the middle of charging
  	(external power input < device power consumption), which not
  	only affects the charging time, but the lifespan of the battery.
  
  	Charger Manager provides a function "cm_suspend_again" that can be
  	used as suspend_again callback of platform_suspend_ops. If the platform
  	requires tasks other than cm_suspend_again, it may implement its own
  	suspend_again callback that calls cm_suspend_again in the middle.
  	Normally, the platform will need to resume and suspend some devices
  	that are used by Charger Manager.
  
  * Support for premature full-battery event handling
  	If the battery voltage drops by "fullbatt_vchkdrop_uV" after
  	"fullbatt_vchkdrop_ms" from the full-battery event, the framework
  	restarts charging. This check is also performed while suspended by
  	setting wakeup time accordingly and using suspend_again.
  
  * Support for uevent-notify
  	With the charger-related events, the device sends
  	notification to users with UEVENT.
  
  2. Global Charger-Manager Data related with suspend_again
  ========================================================
  In order to setup Charger Manager with suspend-again feature
  (in-suspend monitoring), the user should provide charger_global_desc
  with setup_charger_manager(struct charger_global_desc *).
  This charger_global_desc data for in-suspend monitoring is global
  as the name suggests. Thus, the user needs to provide only once even
  if there are multiple batteries. If there are multiple batteries, the
  multiple instances of Charger Manager share the same charger_global_desc
  and it will manage in-suspend monitoring for all instances of Charger Manager.
  
  The user needs to provide all the three entries properly in order to activate
  in-suspend monitoring:
  
  struct charger_global_desc {
  
  char *rtc_name;
  	: The name of rtc (e.g., "rtc0") used to wakeup the system from
  	suspend for Charger Manager. The alarm interrupt (AIE) of the rtc
  	should be able to wake up the system from suspend. Charger Manager
  	saves and restores the alarm value and use the previously-defined
  	alarm if it is going to go off earlier than Charger Manager so that
  	Charger Manager does not interfere with previously-defined alarms.
  
  bool (*rtc_only_wakeup)(void);
  	: This callback should let CM know whether
  	the wakeup-from-suspend is caused only by the alarm of "rtc" in the
  	same struct. If there is any other wakeup source triggered the
  	wakeup, it should return false. If the "rtc" is the only wakeup
  	reason, it should return true.
  
  bool assume_timer_stops_in_suspend;
  	: if true, Charger Manager assumes that
  	the timer (CM uses jiffies as timer) stops during suspend. Then, CM
  	assumes that the suspend-duration is same as the alarm length.
  };
  
  3. How to setup suspend_again
  =============================
  Charger Manager provides a function "extern bool cm_suspend_again(void)".
  When cm_suspend_again is called, it monitors every battery. The suspend_ops
  callback of the system's platform_suspend_ops can call cm_suspend_again
  function to know whether Charger Manager wants to suspend again or not.
  If there are no other devices or tasks that want to use suspend_again
  feature, the platform_suspend_ops may directly refer to cm_suspend_again
  for its suspend_again callback.
  
  The cm_suspend_again() returns true (meaning "I want to suspend again")
  if the system was woken up by Charger Manager and the polling
  (in-suspend monitoring) results in "normal".
  
  4. Charger-Manager Data (struct charger_desc)
  =============================================
  For each battery charged independently from other batteries (if a series of
  batteries are charged by a single charger, they are counted as one independent
  battery), an instance of Charger Manager is attached to it.
  
  struct charger_desc {
  
  char *psy_name;
  	: The power-supply-class name of the battery. Default is
  	"battery" if psy_name is NULL. Users can access the psy entries
  	at "/sys/class/power_supply/[psy_name]/".
  
  enum polling_modes polling_mode;
  	: CM_POLL_DISABLE: do not poll this battery.
  	  CM_POLL_ALWAYS: always poll this battery.
  	  CM_POLL_EXTERNAL_POWER_ONLY: poll this battery if and only if
  				       an external power source is attached.
  	  CM_POLL_CHARGING_ONLY: poll this battery if and only if the
  				 battery is being charged.
  
  unsigned int fullbatt_vchkdrop_ms;
  unsigned int fullbatt_vchkdrop_uV;
  	: If both have non-zero values, Charger Manager will check the
  	battery voltage drop fullbatt_vchkdrop_ms after the battery is fully
  	charged. If the voltage drop is over fullbatt_vchkdrop_uV, Charger
  	Manager will try to recharge the battery by disabling and enabling
  	chargers. Recharge with voltage drop condition only (without delay
  	condition) is needed to be implemented with hardware interrupts from
  	fuel gauges or charger devices/chips.
  
  unsigned int fullbatt_uV;
  	: If specified with a non-zero value, Charger Manager assumes
  	that the battery is full (capacity = 100) if the battery is not being
  	charged and the battery voltage is equal to or greater than
  	fullbatt_uV.
  
  unsigned int polling_interval_ms;
  	: Required polling interval in ms. Charger Manager will poll
  	this battery every polling_interval_ms or more frequently.
  
  enum data_source battery_present;
  	: CM_BATTERY_PRESENT: assume that the battery exists.
  	CM_NO_BATTERY: assume that the battery does not exists.
  	CM_FUEL_GAUGE: get battery presence information from fuel gauge.
  	CM_CHARGER_STAT: get battery presence from chargers.
  
  char **psy_charger_stat;
  	: An array ending with NULL that has power-supply-class names of
  	chargers. Each power-supply-class should provide "PRESENT" (if
  	battery_present is "CM_CHARGER_STAT"), "ONLINE" (shows whether an
  	external power source is attached or not), and "STATUS" (shows whether
  	the battery is {"FULL" or not FULL} or {"FULL", "Charging",
  	"Discharging", "NotCharging"}).
  
  int num_charger_regulators;
  struct regulator_bulk_data *charger_regulators;
  	: Regulators representing the chargers in the form for
  	regulator framework's bulk functions.
  
  char *psy_fuel_gauge;
  	: Power-supply-class name of the fuel gauge.
  
  int (*temperature_out_of_range)(int *mC);
  bool measure_battery_temp;
  	: This callback returns 0 if the temperature is safe for charging,
  	a positive number if it is too hot to charge, and a negative number
  	if it is too cold to charge. With the variable mC, the callback returns
  	the temperature in 1/1000 of centigrade.
  	The source of temperature can be battery or ambient one according to
  	the value of measure_battery_temp.
  };
  
  5. Notify Charger-Manager of charger events: cm_notify_event()
  =========================================================
  If there is an charger event is required to notify
  Charger Manager, a charger device driver that triggers the event can call
  cm_notify_event(psy, type, msg) to notify the corresponding Charger Manager.
  In the function, psy is the charger driver's power_supply pointer, which is
  associated with Charger-Manager. The parameter "type"
  is the same as irq's type (enum cm_event_types). The event message "msg" is
  optional and is effective only if the event type is "UNDESCRIBED" or "OTHERS".
  
  6. Other Considerations
  =======================
  
  At the charger/battery-related events such as battery-pulled-out,
  charger-pulled-out, charger-inserted, DCIN-over/under-voltage, charger-stopped,
  and others critical to chargers, the system should be configured to wake up.
  At least the following should wake up the system from a suspend:
  a) charger-on/off b) external-power-in/out c) battery-in/out (while charging)
  
  It is usually accomplished by configuring the PMIC as a wakeup source.