X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fmware%2Fevent.h;h=e9f9e4a2269d01b36ec665ec85e21cc8589ff99f;hb=1c11ac0ab0636d07db3899b02c5d89e2d0b020bc;hp=74a467937ae802b1cffdadf5eac0ce67ad2c93de;hpb=b0c536ad873bb29ed977417a6a5b1aa586414d3b;p=bertos.git diff --git a/bertos/mware/event.h b/bertos/mware/event.h index 74a46793..e9f9e4a2 100644 --- a/bertos/mware/event.h +++ b/bertos/mware/event.h @@ -30,12 +30,63 @@ * Copyright 1999, 2001, 2003 Bernie Innocenti * --> * + * \defgroup event_handling Event handling module + * \ingroup core + * \{ + * * \brief Events handling * * This module implements a common system for executing * a user defined action calling a hook function. * - * \version $Id$ + * + * Device drivers often need to wait the completion of some event, usually to + * allow the hardware to accomplish some asynchronous task. + * + * A common approach is to place a busy wait with a cpu_relax() loop that invokes + * the architecture-specific instructions to say that we're not doing much with + * the processor. + * + * Although technically correct, the busy loop degrades the overall system + * performance in presence of multiple processes and power consumption. + * + * With the kernel the natural way to implement such wait/complete mechanism is to + * use signals via sig_wait() and sig_post()/sig_send(). + * + * However, signals in BeRTOS are only available in presence of the kernel (that + * is just a compile-time option). This means that each device driver must provide + * two different interfaces to implement the wait/complete semantic: one with the + * kernel and another without the kernel. + * + * The purpose of the completion events is to provide a generic interface to + * implement a synchronization mechanism to block the execution of code until a + * specific event happens. + * + * This interface does not depend on the presence of the kernel and it + * automatically uses the appropriate event backend to provide the same + * behaviour with or without the kernel. + * + * Example usage (wait for a generic device driver initialization): + * \code + * static Event e; + * + * static void irq_handler(void) + * { + * // Completion event has happened, resume the execution of init() + * event_do(&e); + * } + * + * static void init(void) + * { + * // Declare the generic completion event + * event_initGeneric(&e); + * // Submit the hardware initialization request + * async_hw_init(); + * // Wait for the completion of the event + * event_wait(&e); + * } + * \endcode + * * \author Bernie Innocenti */ @@ -45,6 +96,9 @@ #include #include "cfg/cfg_proc.h" #include "cfg/cfg_signal.h" +#include "cfg/cfg_timer.h" + +#include /* cpu_relax() */ #if CONFIG_KERN #if defined(CONFIG_KERN_SIGNALS) && CONFIG_KERN_SIGNALS @@ -55,7 +109,6 @@ struct Process; #endif - /// User defined callback type typedef void (*Hook)(void *); @@ -76,12 +129,19 @@ typedef struct Event Hook func; /* Pointer to softint hook */ void *user_data; /* Data to be passed back to user hook */ } Int; + + struct + { + bool completed; /* Generic event completion */ + } Gen; } Ev; } Event; void event_hook_ignore(Event *event); void event_hook_signal(Event *event); void event_hook_softint(Event *event); +void event_hook_generic(Event *event); +void event_hook_generic_timeout(Event *event); /** Initialize the event \a e as a no-op */ #define event_initNone(e) \ @@ -128,10 +188,103 @@ INLINE Event event_createSignal(struct Process *proc, sigbit_t bit) #endif -/** Trigger an event */ +/** + * Prevent the compiler from optimizing access to the variable \a x, enforcing + * a refetch from memory. This also forbid from reordering successing instances + * of ACCESS_SAFE(). + * + * TODO: move this to cfg/compiler.h + */ +#define ACCESS_SAFE(x) (*(volatile typeof(x) *)&(x)) + +#if defined(CONFIG_KERN_SIGNALS) && CONFIG_KERN_SIGNALS +/** Initialize the generic sleepable event \a e */ +#define event_initGeneric(e) \ + event_initSignal(e, proc_current(), SIG_SYSTEM5) +#else +#define event_initGeneric(e) \ + ((e)->action = event_hook_generic, (e)->Ev.Gen.completed = false) +#endif + +/** + * Create a generic sleepable event. + * + * \return the properly initialized generic event structure. + */ +INLINE Event event_createGeneric(void) +{ + Event e; + event_initGeneric(&e); + return e; +} + +/** + * Wait the completion of event \a e. + * + * This function releases the CPU the application is configured to use + * the kernel, otherwise it's just a busy wait. + * \note It's forbidden to use this function inside irq handling functions. + */ +INLINE void event_wait(Event *e) +{ +#if defined(CONFIG_KERN_SIGNALS) && CONFIG_KERN_SIGNALS + e->Ev.Sig.sig_proc = proc_current(); + sig_wait(e->Ev.Sig.sig_bit); +#else + while (ACCESS_SAFE(e->Ev.Gen.completed) == false) + cpu_relax(); + e->Ev.Gen.completed = false; + MEMORY_BARRIER; +#endif +} + +#if CONFIG_TIMER_EVENTS +#include /* timer_clock() */ + +/* TODO: move these macros to drv/timer.h */ +#define TIMER_AFTER(x, y) ((long)(y) - (long)(x) < 0) +#define TIMER_BEFORE(x, y) TIMER_AFTER(y, x) + +/** + * Wait the completion of event \a e or \a timeout elapses. + * + * \note It's forbidden to use this function inside irq handling functions. + */ +INLINE bool event_waitTimeout(Event *e, ticks_t timeout) +{ + bool ret; + +#if defined(CONFIG_KERN_SIGNALS) && CONFIG_KERN_SIGNALS + e->Ev.Sig.sig_proc = proc_current(); + ret = (sig_waitTimeout(e->Ev.Sig.sig_bit, timeout) & SIG_TIMEOUT) ? + false : true; +#else + ticks_t end = timer_clock() + timeout; + + while ((ACCESS_SAFE(e->Ev.Gen.completed) == false) || + TIMER_AFTER(timer_clock(), end)) + cpu_relax(); + ret = e->Ev.Gen.completed; + e->Ev.Gen.completed = false; +#endif + MEMORY_BARRIER; + return ret; +} +#endif /* CONFIG_TIMER_EVENTS */ + +/** + * Trigger an event. + * + * Execute the callback function associated with event \a e. + * + * This function can be used also in interrupt routines, but only if the + * event was created as a signal or generic event. + */ INLINE void event_do(struct Event *e) { e->action(e); } +/** \} */ + #endif /* KERN_EVENT_H */