1 What: /dev/rtcX 1 What: /dev/rtcX
2 Date: April 2005 2 Date: April 2005
3 KernelVersion: 2.6.12 3 KernelVersion: 2.6.12
4 Contact: linux-rtc@vger.kernel.org 4 Contact: linux-rtc@vger.kernel.org
5 Description: 5 Description:
6 The ioctl interface to drivers 6 The ioctl interface to drivers for real-time clocks (RTCs).
7 Following actions are supporte 7 Following actions are supported:
8 8
9 * RTC_RD_TIME, RTC_SET_TIME: R 9 * RTC_RD_TIME, RTC_SET_TIME: Read or set the RTC time. Time
10 format is a Gregorian calend 10 format is a Gregorian calendar date and 24 hour wall clock
11 time. 11 time.
12 12
13 * RTC_AIE_ON, RTC_AIE_OFF: Ena 13 * RTC_AIE_ON, RTC_AIE_OFF: Enable or disable the alarm interrupt
14 for RTCs that support alarms 14 for RTCs that support alarms
15 15
16 * RTC_ALM_READ, RTC_ALM_SET: R 16 * RTC_ALM_READ, RTC_ALM_SET: Read or set the alarm time for
17 RTCs that support alarms. Ca 17 RTCs that support alarms. Can be set upto 24 hours in the
18 future. Requires a separate 18 future. Requires a separate RTC_AIE_ON call to enable the
19 alarm interrupt. (Prefer to 19 alarm interrupt. (Prefer to use RTC_WKALM_*)
20 20
21 * RTC_WKALM_RD, RTC_WKALM_SET: 21 * RTC_WKALM_RD, RTC_WKALM_SET: For RTCs that support a more
22 powerful interface, which ca 22 powerful interface, which can issue alarms beyond 24 hours and
23 enable IRQs in the same requ 23 enable IRQs in the same request.
24 24
25 * RTC_PIE_ON, RTC_PIE_OFF: Ena 25 * RTC_PIE_ON, RTC_PIE_OFF: Enable or disable the periodic
26 interrupt for RTCs that supp 26 interrupt for RTCs that support periodic interrupts.
27 27
28 * RTC_UIE_ON, RTC_UIE_OFF: Ena 28 * RTC_UIE_ON, RTC_UIE_OFF: Enable or disable the update
29 interrupt for RTCs that supp 29 interrupt for RTCs that support it.
30 30
31 * RTC_IRQP_READ, RTC_IRQP_SET: 31 * RTC_IRQP_READ, RTC_IRQP_SET: Read or set the frequency for
32 periodic interrupts for RTCs 32 periodic interrupts for RTCs that support periodic interrupts.
33 Requires a separate RTC_PIE_ 33 Requires a separate RTC_PIE_ON call to enable the periodic
34 interrupts. 34 interrupts.
35 35
36 * RTC_VL_READ: Read the voltag 36 * RTC_VL_READ: Read the voltage inputs status of the RTC when
37 supported. The value is a bi 37 supported. The value is a bit field of RTC_VL_*, giving the
38 status of the main and backu 38 status of the main and backup voltages.
39 39
40 * RTC_VL_CLEAR: Clear the volt 40 * RTC_VL_CLEAR: Clear the voltage status of the RTC. Some RTCs
41 need user interaction when t 41 need user interaction when the backup power provider is
42 replaced or charged to be ab 42 replaced or charged to be able to clear the status.
43 43
44 The ioctl() calls supported by 44 The ioctl() calls supported by the older /dev/rtc interface are
45 also supported by the newer RT 45 also supported by the newer RTC class framework. However,
46 because the chips and systems 46 because the chips and systems are not standardized, some PC/AT
47 functionality might not be pro 47 functionality might not be provided. And in the same way, some
48 newer features -- including th 48 newer features -- including those enabled by ACPI -- are exposed
49 by the RTC class framework, bu 49 by the RTC class framework, but can't be supported by the older
50 driver. 50 driver.
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