path: root/drivers/rtc/Kconfig

#
# RTC class/drivers configuration
#

config RTC_LIB
	bool

menuconfig RTC_CLASS
	bool "Real Time Clock"
	default n
	depends on !S390 && !UML
	select RTC_LIB
	help
	  Generic RTC class support. If you say yes here, you will
 	  be allowed to plug one or more RTCs to your system. You will
	  probably want to enable one or more of the interfaces below.

if RTC_CLASS

config RTC_HCTOSYS
	bool "Set system time from RTC on startup and resume"
	default y
	depends on !ALWAYS_USE_PERSISTENT_CLOCK
	help
	  If you say yes here, the system time (wall clock) will be set using
	  the value read from a specified RTC device. This is useful to avoid
	  unnecessary fsck runs at boot time, and to network better.

config RTC_SYSTOHC
	bool "Set the RTC time based on NTP synchronization"
	default y
	depends on !ALWAYS_USE_PERSISTENT_CLOCK
	help
	  If you say yes here, the system time (wall clock) will be stored
	  in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11
	  minutes if userspace reports synchronized NTP status.

config RTC_HCTOSYS_DEVICE
	string "RTC used to set the system time"
	depends on RTC_HCTOSYS = y || RTC_SYSTOHC = y
	default "rtc0"
	help
	  The RTC device that will be used to (re)initialize the system
	  clock, usually rtc0. Initialization is done when the system
	  starts up, and when it resumes from a low power state. This
	  device should record time in UTC, since the kernel won't do
	  timezone correction.

	  The driver for this RTC device must be loaded before late_initcall
	  functions run, so it must usually be statically linked.

	  This clock should be battery-backed, so that it reads the correct
	  time when the system boots from a power-off state. Otherwise, your
	  system will need an external clock source (like an NTP server).

	  If the clock you specify here is not battery backed, it may still
	  be useful to reinitialize system time when resuming from system
	  sleep states. Do not specify an RTC here unless it stays powered
	  during all this system's supported sleep states.

config RTC_DEBUG
	bool "RTC debug support"
	help
	  Say yes here to enable debugging support in the RTC framework
	  and individual RTC drivers.

comment "RTC interfaces"

config RTC_INTF_SYSFS
	boolean "/sys/class/rtc/rtcN (sysfs)"
	depends on SYSFS
	default RTC_CLASS
	help
	  Say yes here if you want to use your RTCs using sysfs interfaces,
	  /sys/class/rtc/rtc0 through /sys/.../rtcN.

	  If unsure, say Y.

config RTC_INTF_PROC
	boolean "/proc/driver/rtc (procfs for rtcN)"
	depends on PROC_FS
	default RTC_CLASS
	help
	  Say yes here if you want to use your system clock RTC through
	  the proc interface, /proc/driver/rtc.
	  Other RTCs will not be available through that API.
	  If there is no RTC for the system clock, then the first RTC(rtc0)
	  is used by default.

	  If unsure, say Y.

config RTC_INTF_DEV
	boolean "/dev/rtcN (character devices)"
	default RTC_CLASS
	help
	  Say yes here if you want to use your RTCs using the /dev
	  interfaces, which "udev" sets up as /dev/rtc0 through
	  /dev/rtcN.

	  You may want to set up a symbolic link so one of these
	  can be accessed as /dev/rtc, which is a name
	  expected by "hwclock" and some other programs. Recent
	  versions of "udev" are known to set up the symlink for you.

	  If unsure, say Y.

config RTC_INTF_DEV_UIE_EMUL
	bool "RTC UIE emulation on dev interface"
	depends on RTC_INTF_DEV
	help
	  Provides an emulation for RTC_UIE if the underlying rtc chip
	  driver does not expose RTC_UIE ioctls. Those requests generate
	  once-per-second update interrupts, used for synchronization.

	  The emulation code will read the time from the hardware
	  clock several times per second, please enable this option
	  only if you know that you really need it.

config RTC_DRV_TEST
	tristate "Test driver/device"
	help
	  If you say yes here you get support for the
	  RTC test driver. It's a software RTC which can be
	  used to test the RTC subsystem APIs. It gets
	  the time from the system clock.
	  You want this driver only if you are doing development
	  on the RTC subsystem. Please read the source code
	  for further details.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-test.

comment "I2C RTC drivers"
	depends on I2C

if I2C

config RTC_DRV_88PM860X
	tristate "Marvell 88PM860x"
	depends on I2C && MFD_88PM860X
	help
	  If you say yes here you get support for RTC function in Marvell
	  88PM860x chips.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-88pm860x.

config RTC_DRV_88PM80X
	tristate "Marvell 88PM80x"
	depends on I2C && MFD_88PM800
	help
	  If you say yes here you get support for RTC function in Marvell
	  88PM80x chips.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-88pm80x.

config RTC_DRV_DS1307
	tristate "Dallas/Maxim DS1307/37/38/39/40, ST M41T00, EPSON RX-8025"
	help
	  If you say yes here you get support for various compatible RTC
	  chips (often with battery backup) connected with I2C. This driver
	  should handle DS1307, DS1337, DS1338, DS1339, DS1340, ST M41T00,
	  EPSON RX-8025 and probably other chips. In some cases the RTC
	  must already have been initialized (by manufacturing or a
	  bootloader).

	  The first seven registers on these chips hold an RTC, and other
	  registers may add features such as NVRAM, a trickle charger for
	  the RTC/NVRAM backup power, and alarms. NVRAM is visible in
	  sysfs, but other chip features may not be available.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-ds1307.

config RTC_DRV_DS1374
	tristate "Dallas/Maxim DS1374"
	depends on I2C
	help
	  If you say yes here you get support for Dallas Semiconductor
	  DS1374 real-time clock chips. If an interrupt is associated
	  with the device, the alarm functionality is supported.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-ds1374.

config RTC_DRV_DS1672
	tristate "Dallas/Maxim DS1672"
	help
	  If you say yes here you get support for the
	  Dallas/Maxim DS1672 timekeeping chip.

	  This driver can also be built as a module. If so, the module
	  will be called rtc-ds1672.

config RTC_DRV_DS3232
	tristate "Dallas/Maxim DS3232"
	depends on I2C
	help
	  If you say yes here you get support for Dallas Semiconductor
	  DS3232 real-time clock chips. If an interrupt is associated
	  with the device, the alarm functionality is supported.

	  This driver can also be built as a module.  If so, the module
	  will be called rtc-