From b476403001fc3cb4e22d14f32b663b3cd16b4ec9 Mon Sep 17 00:00:00 2001
From: Balazs Racz <balazs.racz@gmail.com>
Date: Fri, 1 Jan 2021 22:24:17 +0100
Subject: [PATCH] Support eeprom update notification. (#499)

Adds a weak callback to the eepromemulation driver, triggered
after each write is completed.

Shows with an example how to use this to automatically apply changes
that happened from JMRI configuration UI.
---
 .../freertos.armv7m.ek-tm4c123gxl/main.cxx    | 34 +++++++++++++++++++
 boards/ti-ek-tm4c123gxl-launchpad/HwInit.cxx  |  9 +++++
 .../common/EEPROMEmulation.cxx                |  2 ++
 .../common/EEPROMEmulation.hxx                |  6 ++++
 .../common/EEPROMEmulation_weak.cxx           |  8 +++++
 5 files changed, 59 insertions(+)

diff --git a/applications/io_board/targets/freertos.armv7m.ek-tm4c123gxl/main.cxx b/applications/io_board/targets/freertos.armv7m.ek-tm4c123gxl/main.cxx
index 03cd6e908..a514e76d1 100644
--- a/applications/io_board/targets/freertos.armv7m.ek-tm4c123gxl/main.cxx
+++ b/applications/io_board/targets/freertos.armv7m.ek-tm4c123gxl/main.cxx
@@ -127,6 +127,40 @@ openlcb::ConfiguredProducer producer_sw2(
 openlcb::RefreshLoop loop(
     stack.node(), {producer_sw1.polling(), producer_sw2.polling()});
 
+/// This timer checks the eeprom once a second and if the user has written
+/// something, executes a reload of the configuration via the OpenLCB config
+/// service.
+class AutoUpdateTimer : public ::Timer
+{
+public:
+    AutoUpdateTimer()
+        : ::Timer(stack.executor()->active_timers())
+    {
+        start(SEC_TO_NSEC(1));
+    }
+
+    long long timeout() override
+    {
+        extern uint8_t eeprom_updated;
+        if (eeprom_updated)
+        {
+            needUpdate_ = true;
+            eeprom_updated = 0;
+        }
+        else
+        {
+            if (needUpdate_)
+            {
+                stack.config_service()->trigger_update();
+                needUpdate_ = false;
+            }
+        }
+        return RESTART;
+    }
+
+    bool needUpdate_ {false};
+} update_timer;
+
 /** Entry point to application.
  * @param argc number of command line arguments
  * @param argv array of command line arguments
diff --git a/boards/ti-ek-tm4c123gxl-launchpad/HwInit.cxx b/boards/ti-ek-tm4c123gxl-launchpad/HwInit.cxx
index 4eb4a0fe5..eb087679f 100644
--- a/boards/ti-ek-tm4c123gxl-launchpad/HwInit.cxx
+++ b/boards/ti-ek-tm4c123gxl-launchpad/HwInit.cxx
@@ -110,6 +110,15 @@ StoredBitSet* g_gpio_stored_bit_set = nullptr;
 constexpr unsigned EEPROM_BIT_COUNT = 84;
 constexpr unsigned EEPROM_BITS_PER_CELL = 28;
 
+/// This variable will be set to 1 when a write arrives to the eeprom.
+uint8_t eeprom_updated = 0;
+
+// Overridesthe default behavior to keep track of eeprom writes.
+void EEPROMEmulation::updated_notification()
+{
+    eeprom_updated = 1;
+}
+
 extern "C" {
 void hw_set_to_safe(void);
 
diff --git a/src/freertos_drivers/common/EEPROMEmulation.cxx b/src/freertos_drivers/common/EEPROMEmulation.cxx
index 89630aff5..d220a4701 100644
--- a/src/freertos_drivers/common/EEPROMEmulation.cxx
+++ b/src/freertos_drivers/common/EEPROMEmulation.cxx
@@ -194,6 +194,8 @@ void EEPROMEmulation::write(unsigned int index, const void *buf, size_t len)
     {
         memcpy(shadow_ + shadow_index, shadow_data, shadow_len);
     }
+
+    updated_notification();
 }
 
 /** Write to the EEPROM on a native block boundary.
diff --git a/src/freertos_drivers/common/EEPROMEmulation.hxx b/src/freertos_drivers/common/EEPROMEmulation.hxx
index b8e5d4680..07e646d76 100644
--- a/src/freertos_drivers/common/EEPROMEmulation.hxx
+++ b/src/freertos_drivers/common/EEPROMEmulation.hxx
@@ -154,6 +154,12 @@ protected:
     static const size_t BLOCK_SIZE;
 
 private:
+    /** This function will be called after every write. The default
+     * implementation is a weak symbol with an empty function. It is intended
+     * to be overridden in the application to get callbacks for eeprom writes
+     * that can trigger a reload. */
+    void updated_notification();
+
     /** Write to the EEPROM.  NOTE!!! This is not necessarily atomic across
      * byte boundaries in the case of power loss.  The user should take this
      * into account as it relates to data integrity of a whole block.
diff --git a/src/freertos_drivers/common/EEPROMEmulation_weak.cxx b/src/freertos_drivers/common/EEPROMEmulation_weak.cxx
index e77dcd606..b7b4aca61 100644
--- a/src/freertos_drivers/common/EEPROMEmulation_weak.cxx
+++ b/src/freertos_drivers/common/EEPROMEmulation_weak.cxx
@@ -37,3 +37,11 @@
 // emulation implementation to prevent GCC from mistakenly optimizing away the
 // constant into a linker reference.
 const bool __attribute__((weak)) EEPROMEmulation::SHADOW_IN_RAM = false;
+
+/// This function will be called after every write. The default
+/// implementation is a weak symbol with an empty function. It is intended
+/// to be overridden in the application to get callbacks for eeprom writes
+/// that can trigger a reload.
+void __attribute__((weak)) EEPROMEmulation::updated_notification()
+{
+}