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Diffstat (limited to 'quantum/deferred_exec.c')
| -rw-r--r-- | quantum/deferred_exec.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/quantum/deferred_exec.c b/quantum/deferred_exec.c new file mode 100644 index 0000000000..5b0a5b1425 --- /dev/null +++ b/quantum/deferred_exec.c @@ -0,0 +1,152 @@ +// Copyright 2021 Nick Brassel (@tzarc) +// SPDX-License-Identifier: GPL-2.0-or-later + +#include <stddef.h> +#include <timer.h> +#include <deferred_exec.h> + +#ifndef MAX_DEFERRED_EXECUTORS +# define MAX_DEFERRED_EXECUTORS 8 +#endif + +typedef struct deferred_executor_t { + deferred_token token; + uint32_t trigger_time; + deferred_exec_callback callback; + void * cb_arg; +} deferred_executor_t; + +static deferred_token current_token = 0; +static uint32_t last_deferred_exec_check = 0; +static deferred_executor_t executors[MAX_DEFERRED_EXECUTORS] = {0}; + +static inline bool token_can_be_used(deferred_token token) { + if (token == INVALID_DEFERRED_TOKEN) { + return false; + } + for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) { + if (executors[i].token == token) { + return false; + } + } + return true; +} + +static inline deferred_token allocate_token(void) { + deferred_token first = ++current_token; + while (!token_can_be_used(current_token)) { + ++current_token; + if (current_token == first) { + // If we've looped back around to the first, everything is already allocated (yikes!). Need to exit with a failure. + return INVALID_DEFERRED_TOKEN; + } + } + return current_token; +} + +deferred_token defer_exec(uint32_t delay_ms, deferred_exec_callback callback, void *cb_arg) { + // Ignore queueing if it's a zero-time delay, or invalid callback + if (delay_ms == 0 || !callback) { + return INVALID_DEFERRED_TOKEN; + } + + // Find an unused slot and claim it + for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) { + deferred_executor_t *entry = &executors[i]; + if (entry->token == INVALID_DEFERRED_TOKEN) { + // Work out the new token value, dropping out if none were available + deferred_token token = allocate_token(); + if (token == INVALID_DEFERRED_TOKEN) { + return false; + } + + // Set up the executor table entry + entry->token = current_token; + entry->trigger_time = timer_read32() + delay_ms; + entry->callback = callback; + entry->cb_arg = cb_arg; + return current_token; + } + } + + // None available + return INVALID_DEFERRED_TOKEN; +} + +bool extend_deferred_exec(deferred_token token, uint32_t delay_ms) { + // Ignore queueing if it's a zero-time delay, or the token is not valid + if (delay_ms == 0 || token == INVALID_DEFERRED_TOKEN) { + return false; + } + + // Find the entry corresponding to the token + for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) { + deferred_executor_t *entry = &executors[i]; + if (entry->token == token) { + // Found it, extend the delay + entry->trigger_time = timer_read32() + delay_ms; + return true; + } + } + + // Not found + return false; +} + +bool cancel_deferred_exec(deferred_token token) { + // Ignore request if the token is not valid + if (token == INVALID_DEFERRED_TOKEN) { + return false; + } + + // Find the entry corresponding to the token + for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) { + deferred_executor_t *entry = &executors[i]; + if (entry->token == token) { + // Found it, cancel and clear the table entry + entry->token = INVALID_DEFERRED_TOKEN; + entry->trigger_time = 0; + entry->callback = NULL; + entry->cb_arg = NULL; + return true; + } + } + + // Not found + return false; +} + +void deferred_exec_task(void) { + uint32_t now = timer_read32(); + + // Throttle only once per millisecond + if (((int32_t)TIMER_DIFF_32(now, last_deferred_exec_check)) > 0) { + last_deferred_exec_check = now; + + // Run through each of the executors + for (int i = 0; i < MAX_DEFERRED_EXECUTORS; ++i) { + deferred_executor_t *entry = &executors[i]; + + // Check if we're supposed to execute this entry + if (entry->token != INVALID_DEFERRED_TOKEN && ((int32_t)TIMER_DIFF_32(entry->trigger_time, now)) <= 0) { + // Invoke the callback and work work out if we should be requeued + uint32_t delay_ms = entry->callback(entry->trigger_time, entry->cb_arg); + + // Update the trigger time if we have to repeat, otherwise clear it out + if (delay_ms > 0) { + // Intentionally add just the delay to the existing trigger time -- this ensures the next + // invocation is with respect to the previous trigger, rather than when it got to execution. Under + // normal circumstances this won't cause issue, but if another executor is invoked that takes a + // considerable length of time, then this ensures best-effort timing between invocations. + entry->trigger_time += delay_ms; + } else { + // If it was zero, then the callback is cancelling repeated execution. Free up the slot. + entry->token = INVALID_DEFERRED_TOKEN; + entry->trigger_time = 0; + entry->callback = NULL; + entry->cb_arg = NULL; + } + } + } + } +} |