Refactoring through example: the core template

src/core/display.c

@@ -0,0 +1,229 @@
+#include "display.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+
+#ifndef DISPLAY_MAX_BUFFERS
+#define DISPLAY_MAX_BUFFERS 2
+#endif
+
+
+typedef struct
+{
+    uint16_t width;
+    uint16_t height;
+
+    uint8_t buffer_count;
+    display_mode_t mode;
+
+    volatile bool dma_busy;
+    volatile bool frame_done_pending;
+
+    display_frame_done_cb_t frame_done_cb;
+
+    uint16_t* buffers[DISPLAY_MAX_BUFFERS];
+
+    uint8_t draw_index;
+    uint8_t scanout_index;
+
+} display_context_t;
+
+
+static display_context_t ctx;
+
+
+/* ============================================================
+   === Hardware abstraction (to be implemented later)
+   ============================================================ */
+
+static void hw_init(uint16_t width, uint16_t height)
+{
+    /* TODO:
+       - init SPI
+       - init DMA
+       - init Core1 if needed
+       - register DMA IRQ
+    */
+}
+
+static void hw_start_dma(uint16_t* buffer, size_t pixel_count)
+{
+    /* TODO:
+       - assert dma not active at HW level
+       - assert CS low
+       - configure DMA transfer
+       - start transfer
+    */
+
+    (void)buffer;
+    (void)pixel_count;
+}
+
+static void hw_raise_cs(void)
+{
+    /* TODO: raise chip select */
+}
+
+
+/* ============================================================
+   === DMA IRQ handler (must be wired to real IRQ later)
+   ============================================================ */
+
+void display_dma_irq_handler(void)
+{
+    /* TODO: clear DMA interrupt flag */
+
+    hw_raise_cs();
+
+    ctx.dma_busy = false;
+    ctx.frame_done_pending = true;
+}
+
+
+/* ============================================================
+   === Public API
+   ============================================================ */
+
+void display_init(const display_config_t* cfg)
+{
+    assert(cfg != NULL);
+    assert(cfg->buffer_count >= 1);
+    assert(cfg->buffer_count <= DISPLAY_MAX_BUFFERS);
+
+    memset(&ctx, 0, sizeof(ctx));
+
+    ctx.width  = cfg->width;
+    ctx.height = cfg->height;
+
+    ctx.buffer_count = cfg->buffer_count;
+    ctx.mode         = cfg->mode;
+    ctx.frame_done_cb = cfg->frame_done_cb;
+
+    size_t pixels = (size_t)ctx.width * ctx.height;
+    size_t bytes  = pixels * sizeof(uint16_t);
+
+    for (uint8_t i = 0; i < ctx.buffer_count; i++)
+    {
+        ctx.buffers[i] = malloc(bytes);
+        assert(ctx.buffers[i] != NULL);
+        memset(ctx.buffers[i], 0, bytes);
+    }
+
+    ctx.draw_index    = 0;
+    ctx.scanout_index = 0;
+
+    ctx.dma_busy = false;
+    ctx.frame_done_pending = false;
+
+    hw_init(ctx.width, ctx.height);
+}
+
+
+/* ------------------------------------------------------------ */
+
+uint16_t* display_get_draw_buffer(void)
+{
+    if (ctx.mode == DISPLAY_MODE_SAFE &&
+        ctx.buffer_count == 1)
+    {
+        while (ctx.dma_busy)
+        {
+            /* busy wait */
+        }
+    }
+
+    return ctx.buffers[ctx.draw_index];
+}
+
+
+/* ------------------------------------------------------------ */
+
+uint16_t* display_get_scanout_buffer(void)
+{
+    return ctx.buffers[ctx.scanout_index];
+}
+
+
+/* ------------------------------------------------------------ */
+
+bool display_swap_buffers(void)
+{
+    if (ctx.mode != DISPLAY_MODE_RAW)
+        return false;
+
+    if (ctx.buffer_count < 2)
+        return false;
+
+    if (ctx.dma_busy)
+        return false;
+
+    uint8_t tmp = ctx.draw_index;
+    ctx.draw_index = ctx.scanout_index;
+    ctx.scanout_index = tmp;
+
+    return true;
+}
+
+
+/* ------------------------------------------------------------ */
+
+bool display_submit(void)
+{
+    if (ctx.dma_busy)
+        return false;
+
+    if (ctx.mode == DISPLAY_MODE_SAFE &&
+        ctx.buffer_count == 2)
+    {
+        uint8_t tmp = ctx.draw_index;
+        ctx.draw_index = ctx.scanout_index;
+        ctx.scanout_index = tmp;
+    }
+
+    size_t pixels = (size_t)ctx.width * ctx.height;
+
+    ctx.dma_busy = true;
+
+    hw_start_dma(
+        ctx.buffers[ctx.scanout_index],
+        pixels
+    );
+
+    return true;
+}
+
+
+/* ------------------------------------------------------------ */
+
+bool display_ready(void)
+{
+    return !ctx.dma_busy;
+}
+
+
+/* ------------------------------------------------------------ */
+
+void display_wait(void)
+{
+    while (ctx.dma_busy)
+    {
+        /* busy wait */
+    }
+}
+
+
+/* ------------------------------------------------------------ */
+
+void display_poll(void)
+{
+    if (ctx.frame_done_pending)
+    {
+        ctx.frame_done_pending = false;
+
+        if (ctx.frame_done_cb)
+        {
+            ctx.frame_done_cb();
+        }
+    }
+}