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#include <sys/timeet.h>
struct eventtimer;typedef int et_start_t(struct eventtimer *et, sbintime_t first, sbintime_t period); typedef int et_stop_t(struct eventtimer *et); typedef void et_event_cb_t(struct eventtimer *et, void *arg); typedef int et_deregister_cb_t(struct eventtimer *et, void *arg);
struct eventtimer { SLIST_ENTRY(eventtimer) et_all; char *et_name; int et_flags; #define ET_FLAGS_PERIODIC 1 #define ET_FLAGS_ONESHOT 2 #define ET_FLAGS_PERCPU 4 #define ET_FLAGS_C3STOP 8 #define ET_FLAGS_POW2DIV 16 int et_quality; int et_active; uint64_t et_frequency; sbintime_t et_min_period; sbintime_t et_max_period; et_start_t *et_start; et_stop_t *et_stop; et_event_cb_t *et_event_cb; et_deregister_cb_t *et_deregister_cb; void *et_arg; void *et_priv; struct sysctl_oid *et_sysctl; };
Drivers | Manage hardware to generate requested time events. |
Consumers | |
sys/kern/kern_clocksource.c uses event timers to supply kernel with hardclock(), statclock() and profclock() time events. | |
Glue code | sys/sys/timeet.h, sys/kern/kern_et.c provide APIs for event timer drivers and consumers. |
et_name | |
Unique name of the event timer for management purposes. | |
et_flags | |
Set of flags, describing timer capabilities: | |
ET_FLAGS_PERIODIC | |
Periodic mode supported. | |
ET_FLAGS_ONESHOT | One-shot mode supported. |
ET_FLAGS_PERCPU | Timer is per-CPU. |
ET_FLAGS_C3STOP | Timer may stop in CPU sleep state. |
ET_FLAGS_POW2DIV | Timer supports only 2^n divisors. |
et_quality | |
Abstract value to certify whether this timecounter is better than the others. Higher value means better. | |
et_frequency | |
Timer oscillator's base frequency, if applicable and known. Used by consumers to predict set of possible frequencies that could be obtained by dividing it. Should be zero if not applicable or unknown. | |
et_min_period, et_max_period | |
Minimal and maximal reliably programmable time periods. | |
et_start | |
Driver's timer start function pointer. | |
et_stop | |
Driver's timer stop function pointer. | |
et_priv | |
Driver's private data storage. | |
After the event timer functionality is registered, it is controlled via et_start and et_stop methods. et_start method is called to start the specified event timer. The last two arguments are used to specify time when events should be generated. first argument specifies time period before the first event generated. In periodic mode NULL value specifies that first period is equal to the period argument value. period argument specifies the time period between following events for the periodic mode. The NULL value there specifies the one-shot mode. At least one of these two arguments should be not NULL. When event time arrive, driver should call et_event_cb callback function, passing et_arg as the second argument. et_stop method is called to stop the specified event timer. For the per-CPU event timers et_start and et_stop methods control timers associated with the current CPU.
Driver may deregister its functionality by calling et_deregister().
If the frequency of the clock hardware can change while it is running (for example, during power-saving modes), the driver must call et_change_frequency() on each change. If the given event timer is the active timer, et_change_frequency() stops the timer on all CPUs, updates et->frequency, then restarts the timer on all CPUs so that all current events are rescheduled using the new frequency. If the given timer is not currently active, et_change_frequency() simply updates et->frequency.
After the timer is found and initialized, it can be controlled via et_start() and et_stop(). The arguments are the same as described in driver API. Per-CPU event timers can be controlled only from specific CPUs.
et_ban() allows consumer to mark event timer as broken via clearing both one-shot and periodic capability flags, if it was somehow detected. et_free() is the opposite to et_init(). It releases the event timer for other consumers use.
ET_LOCK() and ET_UNLOCK() macros should be used to manage mutex(9) lock around et_find(), et_init() and et_free() calls to serialize access to the list of the registered event timers and the pointers returned by et_find(). et_start() and et_stop() calls should be serialized in consumer's internal way to avoid concurrent timer hardware access.
EVENTTIMERS (9) | April 2, 2014 |
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