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# RTC class/drivers configuration
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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
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
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