Add a more scalable mechanism for the FreeRTOS tick- and idle hooks; idle handler now uses WAITI to reduce power

components/esp32/freertos_hooks.c

@@ -0,0 +1,81 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include "esp_attr.h"
+#include "esp_freertos_hooks.h"
+
+//We use just a static array here because it's not expected many components will need
+//an idle or tick hook.
+#define MAX_HOOKS 8
+
+static esp_freertos_idle_cb_t idle_cb[MAX_HOOKS]={0};
+static esp_freertos_tick_cb_t tick_cb[MAX_HOOKS]={0};
+
+void IRAM_ATTR esp_vApplicationTickHook() 
+{
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (tick_cb[n]!=NULL) {
+            tick_cb[n]();
+        }
+    }
+}
+
+void esp_vApplicationIdleHook() 
+{
+    bool doWait=true;
+    bool r;
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (idle_cb[n]!=NULL) {
+            r=idle_cb[n]();
+            if (!r) doWait=false;
+        }
+    }
+    if (doWait) {
+        //Wait for whatever interrupt comes next... this should save some power.
+        asm("waiti 0");
+    }
+}
+
+
+esp_err_t esp_register_freertos_idle_hook(esp_freertos_idle_cb_t new_idle_cb) 
+{
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (idle_cb[n]==NULL) {
+            idle_cb[n]=new_idle_cb;
+            return ESP_OK;
+        }
+    }
+    return ESP_ERR_NO_MEM;
+}
+
+esp_err_t esp_register_freertos_tick_hook(esp_freertos_tick_cb_t new_tick_cb) 
+{
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (tick_cb[n]==NULL) {
+            tick_cb[n]=new_tick_cb;
+            return ESP_OK;
+        }
+    }
+    return ESP_ERR_NO_MEM;
+}
+
+void esp_deregister_freertos_idle_hook(esp_freertos_idle_cb_t old_idle_cb)
+{
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (idle_cb[n]==old_idle_cb) idle_cb[n]=NULL;
+    }
+}
+
+void esp_deregister_freertos_tick_hook(esp_freertos_tick_cb_t old_tick_cb)
+{
+    int n;
+    for (n=0; n<MAX_HOOKS; n++) {
+        if (tick_cb[n]==old_tick_cb) tick_cb[n]=NULL;
+    }
+}
+