# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1541884292 -3600
# Node ID f1ce70172578685b93718dc1d3c5c4584fd369a8
# Parent  04b9cb49f0ac15320133e01b59c29d59af2a82b5
Moved VGA timing and transfer details to the VGA display abstraction,
introducing an initialisation macro and simplifying the general display
abstraction.

diff -r 04b9cb49f0ac -r f1ce70172578 examples/vga/main.c
--- a/examples/vga/main.c	Sat Nov 10 21:39:51 2018 +0100
+++ b/examples/vga/main.c	Sat Nov 10 22:11:32 2018 +0100
@@ -25,26 +25,21 @@
 #include "init.h"
 #include "pic32_c.h"
 #include "utils.h"
-#include "vga_display.h"
 #include "viewport.h"
 
 /* Specific functionality. */
 
 #include "devconfig.h"
 #include "main.h"
-#include "vga.h"
+#include "vga_display.h"
 
 
 
-/* Define DMA channels if not indicated in the build configuration. */
-
-/* CPU-based transfers: no channels. */
+/* Define the scroll increment depending on how many DMA channels are used.
+   CPU-driven transfers permit an increment of 1. */
 
 #ifdef TRANSFER_CPU
 #define SCROLL_XSTEP    1
-
-/* DMA-based transfers: single channel by default. */
-
 #else
 #define SCROLL_XSTEP    LINE_CHANNELS
 #endif
diff -r 04b9cb49f0ac -r f1ce70172578 include/display.h
--- a/include/display.h	Sat Nov 10 21:39:51 2018 +0100
+++ b/include/display.h	Sat Nov 10 22:11:32 2018 +0100
@@ -21,6 +21,7 @@
 #define __DISPLAY_H__
 
 #include <stdint.h>
+#include "vga.h"
 
 
 
@@ -78,27 +79,20 @@
 
     uint32_t cell_size;
 
-    /* DMA transfer sizes. */
-
-    uint32_t transfer_cell_size;
-
-    /* Display line positions. */
-
-    uint32_t hfreq_limit, hsync_start, hsync_end;
-
-    /* Display region scanline positions. */
-
-    uint32_t visible_start, vfp_start, vsync_start, vsync_end;
-
 } display_config_t;
 
 
 
-/* Initialise a display. */
+/* Initialise a display. This macro depends on certain VGA constants being
+   defined, and they are included above.
+
+   Display(<name>, int width, int height, int frames)
+*/
 
 #define Display(NAME, WIDTH, HEIGHT, FRAMES)                            \
     uint8_t __##NAME##_framebuffer[(WIDTH) * (HEIGHT + 1) * (FRAMES)];  \
     uint8_t *__##NAME##_screen_starts[FRAMES];                          \
+                                                                        \
     display_config_t NAME = {                                           \
         .framebuffer=__##NAME##_framebuffer,                            \
         .screen_starts=__##NAME##_screen_starts,                        \
@@ -113,16 +107,7 @@
                                                                         \
         .scanlines = SCANLINES,                                         \
         .line_channels = LINE_CHANNELS,                                 \
-        .cell_size = CELL_SIZE,                                         \
-        .transfer_cell_size = TRANSFER_CELL_SIZE,                       \
-                                                                        \
-        .hfreq_limit = HFREQ_LIMIT,                                     \
-        .hsync_start = HSYNC_START,                                     \
-        .hsync_end = HSYNC_END,                                         \
-        .visible_start = VISIBLE_START,                                 \
-        .vfp_start = VFP_START,                                         \
-        .vsync_start = VSYNC_START,                                     \
-        .vsync_end = VSYNC_END};
+        .cell_size = CELL_SIZE};
 
 /* Configuration functions. */
 
diff -r 04b9cb49f0ac -r f1ce70172578 include/vga_display.h
--- a/include/vga_display.h	Sat Nov 10 21:39:51 2018 +0100
+++ b/include/vga_display.h	Sat Nov 10 22:11:32 2018 +0100
@@ -20,8 +20,9 @@
 #ifndef __VGA_DISPLAY_H__
 #define __VGA_DISPLAY_H__
 
+#include "display.h"
 #include "pic32_c.h"
-#include "display.h"
+#include "vga.h"
 
 
 
@@ -41,6 +42,7 @@
     /* DMA transfer properties. */
 
     int line_channels, transfer_int_num;
+    uint32_t transfer_cell_size;
 
     /* Horizontal and vertical sync peripherals. */
 
@@ -62,11 +64,37 @@
 
     display_config_t *display_config;
 
+    /* Display line positions. */
+
+    uint32_t hfreq_limit, hsync_start, hsync_end;
+
+    /* Display region scanline positions. */
+
+    uint32_t visible_start, vfp_start, vsync_start, vsync_end;
+
 } vga_display_t;
 
 
 
-/* Initialisation. */
+/* Initialise a VGA display object with timing and pixel transfer details.
+   This macro depends on the VGA timing constants being defined, and they are
+   included above.
+
+   VGA_Display(<name>)
+*/
+
+#define VGA_Display(NAME) \
+    vga_display_t NAME = {                          \
+        .transfer_cell_size = TRANSFER_CELL_SIZE,   \
+        .hfreq_limit = HFREQ_LIMIT,                 \
+        .hsync_start = HSYNC_START,                 \
+        .hsync_end = HSYNC_END,                     \
+        .visible_start = VISIBLE_START,             \
+        .vfp_start = VFP_START,                     \
+        .vsync_start = VSYNC_START,                 \
+        .vsync_end = VSYNC_END};
+
+/* Initialisation functions. */
 
 void init_vga(display_config_t *display_config, int line_channels,
               int line_timer, int transfer_int_num);
diff -r 04b9cb49f0ac -r f1ce70172578 lib/vga_display.c
--- a/lib/vga_display.c	Sat Nov 10 21:39:51 2018 +0100
+++ b/lib/vga_display.c	Sat Nov 10 22:11:32 2018 +0100
@@ -17,7 +17,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "pic32_c.h"
 #include "init.h"
 #include "vga_display.h"
 
@@ -25,7 +24,7 @@
 
 /* Display state. */
 
-vga_display_t vga_display;
+VGA_Display(vga_display);
 
 /* Pixel data. */
 
@@ -79,7 +78,7 @@
 
     /* The timers have no prescaling (0). */
 
-    timer_init(line_timer, 0, display_config->hfreq_limit);
+    timer_init(line_timer, 0, vga_display.hfreq_limit);
 
     /* Enable interrupt requests when the CPU needs to perform the transfer, as
        opposed to the DMA channels doing so. */
@@ -183,7 +182,7 @@
     dma_set_interrupt(channel, int_num, 1);
 
     dma_set_destination(channel, HW_PHYSICAL(output), 1);
-    dma_set_cell(channel, vga_display.display_config->transfer_cell_size);
+    dma_set_cell(channel, vga_display.transfer_cell_size);
 }
 
 void vga_configure_zero_channel(int channel, int int_num, int initiating,
@@ -230,8 +229,8 @@
        channel and is handled to drive the display state machine. */
 
     oc_init(hsync_unit, 0b101, vga_display.line_timer);
-    oc_set_pulse(hsync_unit, vga_display.display_config->hsync_end);
-    oc_set_pulse_end(hsync_unit, vga_display.display_config->hsync_start);
+    oc_set_pulse(hsync_unit, vga_display.hsync_end);
+    oc_set_pulse_end(hsync_unit, vga_display.hsync_start);
     oc_init_interrupt(hsync_unit, 7, 3);
     oc_on(hsync_unit);
 
@@ -341,7 +340,7 @@
 
 void vbp_active(void)
 {
-    if (vga_display.line < vga_display.display_config->visible_start)
+    if (vga_display.line < vga_display.visible_start)
         return;
 
     /* Enter the visible region. */
@@ -362,7 +361,7 @@
 {
     display_config_t *cfg = vga_display.display_config;
 
-    if (vga_display.line < cfg->vfp_start)
+    if (vga_display.line < vga_display.vfp_start)
     {
         /* Update the line address and handle wraparound. */
 
@@ -393,7 +392,7 @@
 
 void vfp_active(void)
 {
-    if (vga_display.line < vga_display.display_config->vsync_start)
+    if (vga_display.line < vga_display.vsync_start)
         return;
 
     /* Enter the vertical sync region. */
@@ -409,7 +408,7 @@
 
 void vsync_active(void)
 {
-    if (vga_display.line < vga_display.display_config->vsync_end)
+    if (vga_display.line < vga_display.vsync_end)
         return;
 
     /* Start again at the top of the display. */