Signed-off-by: Ivan Khoronzhuk <ivan.khoronz...@linaro.org> Signed-off-by: Bill Fischofer <bill.fischo...@linaro.org> --- doc/users-guide/Makefile.am | 1 + doc/users-guide/users-guide-timer.adoc | 97 ++++++++++++++++++++++++++++++++++ doc/users-guide/users-guide.adoc | 2 + 3 files changed, 100 insertions(+) create mode 100644 doc/users-guide/users-guide-timer.adoc
diff --git a/doc/users-guide/Makefile.am b/doc/users-guide/Makefile.am index 6bb0131..d8e7215 100644 --- a/doc/users-guide/Makefile.am +++ b/doc/users-guide/Makefile.am @@ -4,6 +4,7 @@ SRC = $(top_srcdir)/doc/users-guide/users-guide.adoc \ $(top_srcdir)/doc/users-guide/users-guide-cls.adoc \ $(top_srcdir)/doc/users-guide/users-guide-packet.adoc \ $(top_srcdir)/doc/users-guide/users-guide-pktio.adoc \ + $(top_srcdir)/doc/users-guide/users-guide-timer.adoc \ $(top_srcdir)/doc/users-guide/users-guide-tm.adoc TARGET = users-guide.html IMAGES = $(top_srcdir)/doc/images/overview.svg \ diff --git a/doc/users-guide/users-guide-timer.adoc b/doc/users-guide/users-guide-timer.adoc new file mode 100644 index 0000000..a7ebf91 --- /dev/null +++ b/doc/users-guide/users-guide-timer.adoc @@ -0,0 +1,97 @@ +== Timers and Timeout Events +The ODP Timer APIs offer a set of functions that permit applications to react +to the passage of time, and are designed to reflect the underlying hardware +timing features found in various platforms that support ODP implementations. + +Timers are drawn from specialized pools called _timer pools_ that have their +own abstract type (`odp_timer_pool_t`). Each timer pool is a logically +independent time source with its own _resolution_ measured in nanoseconds (ns) +and a maximum number of timers that it can support. Applications can have many +timers active at the same time and can set them to use either relative or +absolute time. Associated with each timer is a queue that is to receive events +when this timer expires. This queue is created by a separate +`odp_queue_create()` call that is passed as a parameter to `odp_timer_alloc()`. + +Timeouts are specialized events of type `odp_timeout_t` that are used to +represent the expiration of timers. Timeouts are drawn from pools of type +`ODP_POOL_TIMEOUT` that are created by the standard `odp_pool_create()` API. +Timeout events are associated with timers when those timers are _set_ and are +enqueued to their timer's associated queue whenever a set timer expires. So the +effect of timer expiration is a timeout event being added to a queue and +delivered via normal ODP event scheduling. + +The relationship between timers and timeouts is shown below: + +.ODP Timer and Timeout State Diagram +image::timer_fsm.svg[align="center"] + +Timers measure time in _ticks_ rather than nanoseconds because each timer pool +may have its own time source and associated conversion ratios. It is thus more +efficient to manipulate time in these native tick values. As a result time +measured in nanoseconds must be converted between timer-pool specific tick +values via the conversion functions `odp_timer_ns_to_tick()` and +`odp_timer_tick_to_ns()` as needed. Both of these functions take a timer pool +as an input parameter to enable the pool-specific conversion ratios to be +used. + +Associated with each timer pool is a free running tick counter that can be +sampled at any time via the `odp_timer_current_tick()` API. Timers can be +set to an absolute future tick value via `odp_timer_set_abs()` or to a +future tick value relative to the current tick via `odp_timer_set_rel()`. + +Before a set timer expires, it can be canceled via the `odp_timer_cancel()` +API. A successful cancel has the same effect as if the timer were never set. +An attempted cancel will fail if the timer is not set or if it has already +expired. + +=== Timer Pool Management +To facilitate implementation of the ODP timer APIs, an additional timer API is +provided. During initialization, applications are expected to create the timer +pools they need and then call `odp_timer_pool_start()`. ODP implementations +may or may not fail further attempts to create timer pools after this API is +called. For best portability, applications should not attempt to create +further timer pools after calling `odp_timer_pool_start()`. Note that no such +restrictions exist on timeout pools, as these are just ordinary ODP pools. + +Following start, applications may allocate, set, cancel, and free, timers +from their associated timer pools. During termination processing, after all +timers allocated from a timer pool have been freed, the pool itself should be +released via a call to `odp_timer_pool_destroy()`. + +=== Timeout Event Management +The purpose of ODP timers is to schedule their associated timeout events, which +are how applications actually react to the passage of time. To help with this, +several additional APIs and conventions are provided. + +Timer allocation is performed via the `odp_timer_alloc()` API: +[source,c] +----- +/** + * Allocate a timer + * + * Create a timer (allocating all necessary resources e.g. timeout event) from + * the timer pool. The user_ptr is copied to timeouts and can be retrieved + * using the odp_timeout_user_ptr() call. + * + * @param tpid Timer pool identifier + * @param queue Destination queue for timeout notifications + * @param user_ptr User defined pointer or NULL to be copied to timeouts + * + * @return Timer handle on success + * @retval ODP_TIMER_INVALID on failure and errno set. + */ +odp_timer_t odp_timer_alloc(odp_timer_pool_t tpid, + odp_queue_t queue, + void *user_ptr); +----- +Note that in addition to the timer pool id and queue, a user pointer is +provided. This is to allow context associated with the timeout to be +communicated. Upon receiving a timeout event, the application can use +the `odp_timeout_user_ptr()` API to retrieve the user pointer associated +with the timer that triggered this event. + +As mentioned, if a timer is canceled after it has already expired, the +request fails and the associated timeout event will still be +delivered. However, upon receiving a timeout event the application can use the +`odp_timeout_fresh()` API to inquire whether the timeout event is fresh or +stale. diff --git a/doc/users-guide/users-guide.adoc b/doc/users-guide/users-guide.adoc index 0221634..3f16608 100644 --- a/doc/users-guide/users-guide.adoc +++ b/doc/users-guide/users-guide.adoc @@ -907,6 +907,8 @@ include::users-guide-packet.adoc[] include::users-guide-pktio.adoc[] +include::users-guide-timer.adoc[] + == Cryptographic services ODP provides support for cryptographic operations required by various security -- 2.5.0 _______________________________________________ lng-odp mailing list lng-odp@lists.linaro.org https://lists.linaro.org/mailman/listinfo/lng-odp