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| -rw-r--r-- | Documentation/rtc.txt | 29 |
1 files changed, 10 insertions, 19 deletions
diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt index 9104c1062084..250160469d83 100644 --- a/Documentation/rtc.txt +++ b/Documentation/rtc.txt @@ -178,38 +178,29 @@ RTC class framework, but can't be supported by the older driver. setting the longer alarm time and enabling its IRQ using a single request (using the same model as EFI firmware). - * RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, it probably - also offers update IRQs whenever the "seconds" counter changes. - If needed, the RTC framework can emulate this mechanism. + * RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, the RTC framework + will emulate this mechanism. - * RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... another - feature often accessible with an IRQ line is a periodic IRQ, issued - at settable frequencies (usually 2^N Hz). + * RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... these icotls + are emulated via a kernel hrtimer. In many cases, the RTC alarm can be a system wake event, used to force Linux out of a low power sleep state (or hibernation) back to a fully operational state. For example, a system could enter a deep power saving state until it's time to execute some scheduled tasks. -Note that many of these ioctls need not actually be implemented by your -driver. The common rtc-dev interface handles many of these nicely if your -driver returns ENOIOCTLCMD. Some common examples: +Note that many of these ioctls are handled by the common rtc-dev interface. +Some common examples: * RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be called with appropriate values. - * RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: the - set_alarm/read_alarm functions will be called. + * RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: gets or sets + the alarm rtc_timer. May call the set_alarm driver function. - * RTC_IRQP_SET, RTC_IRQP_READ: the irq_set_freq function will be called - to set the frequency while the framework will handle the read for you - since the frequency is stored in the irq_freq member of the rtc_device - structure. Your driver needs to initialize the irq_freq member during - init. Make sure you check the requested frequency is in range of your - hardware in the irq_set_freq function. If it isn't, return -EINVAL. If - you cannot actually change the frequency, do not define irq_set_freq. + * RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the generic code. - * RTC_PIE_ON, RTC_PIE_OFF: the irq_set_state function will be called. + * RTC_PIE_ON, RTC_PIE_OFF: These are also emulated by the generic code. If all else fails, check out the rtc-test.c driver! |