From a12ab13462cea5b7ab4610180364d9abca73018f Mon Sep 17 00:00:00 2001
From: Bruce Luckcuck <github@etracer.net>
Date: Sat, 9 Nov 2019 14:26:08 -0500
Subject: [PATCH] Prevent font upload if max7456 is not detected Prevents wedge
 if a font upload is attempted but the max7456 device wasn't detected during
 initialization.

---
 src/main/drivers/max7456.c | 19 +++++++++++++++----
 src/main/drivers/max7456.h |  3 ++-
 src/main/msp/msp.c         | 15 ++++++++++++---
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/src/main/drivers/max7456.c b/src/main/drivers/max7456.c
index 1bd4bb39c1..1a52e5a1e9 100644
--- a/src/main/drivers/max7456.c
+++ b/src/main/drivers/max7456.c
@@ -193,6 +193,7 @@ static displayPortLayer_e activeLayer = DISPLAYPORT_LAYER_FOREGROUND;
 busDevice_t max7456BusDevice;
 busDevice_t *busdev = &max7456BusDevice;
 
+static bool max7456DeviceDetected = false;
 static uint16_t max7456SpiClock = MAX7456_SPI_CLK;
 
 uint16_t maxScreenSize = VIDEO_BUFFER_CHARS_PAL;
@@ -450,6 +451,8 @@ void max7456PreInit(const max7456Config_t *max7456Config)
 
 bool max7456Init(const max7456Config_t *max7456Config, const vcdProfile_t *pVcdProfile, bool cpuOverclock)
 {
+    max7456DeviceDetected = false;
+
     // initialize all layers
     for (unsigned i = 0; i < MAX7456_SUPPORTED_LAYER_COUNT; i++) {
         max7456ClearLayer(i);
@@ -484,15 +487,15 @@ bool max7456Init(const max7456Config_t *max7456Config, const vcdProfile_t *pVcdP
 
     uint8_t osdm = max7456Send(MAX7456ADD_OSDM|MAX7456ADD_READ, 0xff);
 
+    __spiBusTransactionEnd(busdev);
+
     if (osdm != 0x1B) {
         IOConfigGPIO(busdev->busdev_u.spi.csnPin, IOCFG_IPU);
         return false;
     }
 
-    __spiBusTransactionEnd(busdev);
-
     // At this point, we can claim the ownership of the CS pin
-
+    max7456DeviceDetected = true;
     IOInit(busdev->busdev_u.spi.csnPin, OWNER_OSD_CS, 0);
 
     // Detect device type by writing and reading CA[8] bit at CMAL[6].
@@ -822,8 +825,11 @@ void max7456RefreshAll(void)
     max7456DrawScreenSlow();
 }
 
-void max7456WriteNvm(uint8_t char_address, const uint8_t *font_data)
+bool max7456WriteNvm(uint8_t char_address, const uint8_t *font_data)
 {
+    if (!max7456DeviceDetected) {
+        return false;
+    }
 #ifdef MAX7456_DMA_CHANNEL_TX
     while (dmaTransactionInProgress);
 #endif
@@ -854,6 +860,7 @@ void max7456WriteNvm(uint8_t char_address, const uint8_t *font_data)
     while ((max7456Send(MAX7456ADD_STAT, 0x00) & STAT_NVR_BUSY) != 0x00);
 
     __spiBusTransactionEnd(busdev);
+    return true;
 }
 
 #ifdef MAX7456_NRST_PIN
@@ -877,4 +884,8 @@ void max7456HardwareReset(void)
 #endif
 }
 
+bool max7456IsDeviceDetected(void)
+{
+    return max7456DeviceDetected;
+}
 #endif // USE_MAX7456
diff --git a/src/main/drivers/max7456.h b/src/main/drivers/max7456.h
index d1fc867468..a92d364392 100644
--- a/src/main/drivers/max7456.h
+++ b/src/main/drivers/max7456.h
@@ -37,7 +37,7 @@ bool    max7456Init(const struct max7456Config_s *max7456Config, const struct vc
 void    max7456Invert(bool invert);
 void    max7456Brightness(uint8_t black, uint8_t white);
 void    max7456DrawScreen(void);
-void    max7456WriteNvm(uint8_t char_address, const uint8_t *font_data);
+bool    max7456WriteNvm(uint8_t char_address, const uint8_t *font_data);
 uint8_t max7456GetRowsCount(void);
 void    max7456Write(uint8_t x, uint8_t y, const char *buff);
 void    max7456WriteChar(uint8_t x, uint8_t y, uint8_t c);
@@ -48,3 +48,4 @@ bool    max7456BuffersSynced(void);
 bool    max7456LayerSupported(displayPortLayer_e layer);
 bool    max7456LayerSelect(displayPortLayer_e layer);
 bool    max7456LayerCopy(displayPortLayer_e destLayer, displayPortLayer_e sourceLayer);
+bool    max7456IsDeviceDetected(void);
diff --git a/src/main/msp/msp.c b/src/main/msp/msp.c
index b9cf361895..efdb41d175 100644
--- a/src/main/msp/msp.c
+++ b/src/main/msp/msp.c
@@ -44,6 +44,7 @@
 #include "common/streambuf.h"
 #include "common/utils.h"
 
+#include "config/config.h"
 #include "config/config_eeprom.h"
 #include "config/feature.h"
 
@@ -67,7 +68,6 @@
 #include "drivers/vtx_table.h"
 
 #include "fc/board_info.h"
-#include "config/config.h"
 #include "fc/controlrate_profile.h"
 #include "fc/core.h"
 #include "fc/rc.h"
@@ -110,6 +110,7 @@
 #include "pg/beeper.h"
 #include "pg/board.h"
 #include "pg/gyrodev.h"
+#include "pg/max7456.h"
 #include "pg/motor.h"
 #include "pg/rx.h"
 #include "pg/rx_spi.h"
@@ -796,13 +797,19 @@ static bool mspCommonProcessOutCommand(uint8_t cmdMSP, sbuf_t *dst, mspPostProce
 #define OSD_FLAGS_RESERVED_1            (1 << 2)
 #define OSD_FLAGS_RESERVED_2            (1 << 3)
 #define OSD_FLAGS_OSD_HARDWARE_MAX_7456 (1 << 4)
+#define OSD_FLAGS_MAX7456_DETECTED      (1 << 5)
 
         uint8_t osdFlags = 0;
 #if defined(USE_OSD)
         osdFlags |= OSD_FLAGS_OSD_FEATURE;
 #endif
 #ifdef USE_MAX7456
-        osdFlags |= OSD_FLAGS_OSD_HARDWARE_MAX_7456;
+        if (max7456Config()->csTag && max7456Config()->spiDevice) {
+            osdFlags |= OSD_FLAGS_OSD_HARDWARE_MAX_7456;
+            if (max7456IsDeviceDetected()) {
+                osdFlags |= OSD_FLAGS_MAX7456_DETECTED;
+            }
+        }
 #endif
 
         sbufWriteU8(dst, osdFlags);
@@ -3281,7 +3288,9 @@ static mspResult_e mspCommonProcessInCommand(mspDescriptor_t srcDesc, uint8_t cm
                 font_data[i] = sbufReadU8(src);
             }
             // !!TODO - replace this with a device independent implementation
-            max7456WriteNvm(addr, font_data);
+            if (!max7456WriteNvm(addr, font_data)) {
+                return MSP_RESULT_ERROR;
+            }
         }
         break;
 #else