From f0435819287bdfae461621068cb88eea9e54aa71 Mon Sep 17 00:00:00 2001
From: Silvano Seva <silseva@fastwebnet.it>
Date: Sat, 3 Oct 2020 10:14:19 +0200
Subject: [PATCH] Making the interface for low-level display drivers more
 general: now the pointer to framebuffer is returned as void *. Updated
 existing drivers and test code accordingly.

---
 openrtx/include/interfaces/lcd.h          | 19 +++++++++----------
 platform/drivers/display/HX83XX_md380.c   |  4 ++--
 platform/drivers/display/display_libSDL.c |  4 ++--
 tests/platform/display_test_SDL.c         |  2 +-
 tests/platform/x64_uC.c                   |  4 ++--
 5 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/openrtx/include/interfaces/lcd.h b/openrtx/include/interfaces/lcd.h
index 040f386d..c993ea6c 100644
--- a/openrtx/include/interfaces/lcd.h
+++ b/openrtx/include/interfaces/lcd.h
@@ -26,8 +26,8 @@
  *
  *********************** HOW TO MANAGE FRAMEBUFFER *****************************
  *
- * This driver allocates the framebuffer as a block of memory addressed linearly
- * as an array of SCREEN_HEIGHT*SCREEN_WIDTH 16-bit variables.
+ * This driver allocates the framebuffer as a block of linearly addressed memory
+ * equivalent to an array of SCREEN_HEIGHT*SCREEN_WIDTH elements.
  * With respect to it, screen is indexed in this way:
  *
  *   (0,0)
@@ -39,7 +39,7 @@
  *     y
  *
  * then to set the value of the pixel having coordinates (X,Y), framebuffer has
- * to be indexed in this way buf[X + Y*SCREEN_WIDTH].
+ * to be indexed in this way: buf[X + Y*SCREEN_WIDTH].
  *
  */
 
@@ -101,19 +101,18 @@ void lcd_render();
 bool lcd_renderingInProgress();
 
 /**
- * Get pointer to framebuffer. This buffer is addressed linearly and each
- * location is a pixel whose color coding is RGB565.
+ * Get pointer to framebuffer. Being this a standard interface for all the
+ * low-level display drivers, this function returns a pointer to void: it's up
+ * to the caller performing the correct cast to one of the standard types used
+ * for color coding.
  * Changes to the framebuffer will not be reflected on the display until
  * lcd_render() or lcd_renderRows() are called.
  *
- * IMPORTANT NOTE: to accomodate the display driver chip's needs, this buffer
- * MUST be filled with values in big endian mode! A cleaner way to have the
- * correct endianness, is to use GCC's builtin function __builtin_bswap16().
- *
+ * 
  * WARNING: no bound check is performed! Do not call free() on the pointer
  * returned, doing so will destroy the framebuffer!
  * @return pointer to framebuffer.
  */
-uint16_t *lcd_getFrameBuffer();
+void *lcd_getFrameBuffer();
 
 #endif /* LCD_H */
diff --git a/platform/drivers/display/HX83XX_md380.c b/platform/drivers/display/HX83XX_md380.c
index 05f7d63e..29d5f3ba 100644
--- a/platform/drivers/display/HX83XX_md380.c
+++ b/platform/drivers/display/HX83XX_md380.c
@@ -441,7 +441,7 @@ bool lcd_renderingInProgress()
     return (pinValue == 0) ? 1 : 0;
 }
 
-uint16_t *lcd_getFrameBuffer()
+void *lcd_getFrameBuffer()
 {
-    return frameBuffer;
+    return (void *)(frameBuffer);
 }
diff --git a/platform/drivers/display/display_libSDL.c b/platform/drivers/display/display_libSDL.c
index ae30ab69..85c7bfe4 100644
--- a/platform/drivers/display/display_libSDL.c
+++ b/platform/drivers/display/display_libSDL.c
@@ -140,7 +140,7 @@ bool lcd_renderingInProgress()
     return inProgress;
 }
 
-uint16_t *lcd_getFrameBuffer()
+void *lcd_getFrameBuffer()
 {
-    return frameBuffer;
+    return (void *)(frameBuffer);
 }
diff --git a/tests/platform/display_test_SDL.c b/tests/platform/display_test_SDL.c
index 62b17ef9..d317e348 100644
--- a/tests/platform/display_test_SDL.c
+++ b/tests/platform/display_test_SDL.c
@@ -37,7 +37,7 @@ void drawRect(int x, int y, int width, int height, uint16_t color)
 {
     int x_max = x + width;
     int y_max = y + height;
-    uint16_t *buf = lcd_getFrameBuffer();
+    uint16_t *buf = (uint16_t *)(lcd_getFrameBuffer());
 
     for(int i=y; i < y_max; i++)
     {
diff --git a/tests/platform/x64_uC.c b/tests/platform/x64_uC.c
index d6e40d04..9e35f412 100644
--- a/tests/platform/x64_uC.c
+++ b/tests/platform/x64_uC.c
@@ -25,7 +25,7 @@ void drawRect(int x, int y, int width, int height, uint16_t color)
     int y_max = y + height;
     if(x_max > lcd_screenWidth()) x_max = lcd_screenWidth();
     if(y_max > lcd_screenHeight()) y_max = lcd_screenHeight();
-    uint16_t *buf = lcd_getFrameBuffer();
+    uint16_t *buf = (uint16_t *)(lcd_getFrameBuffer());
 
     for(int i=y; i < y_max; i++)
     {
@@ -38,7 +38,7 @@ void drawRect(int x, int y, int width, int height, uint16_t color)
 
 void clearScreen()
 {
-    uint16_t *buf = lcd_getFrameBuffer();
+    uint16_t *buf = (uint16_t *)(lcd_getFrameBuffer());
 
     for(int i=0; i < lcd_screenHeight(); i++)
     {