Create separate renderer and framebuffer modules

build.sh

@@ -4,5 +4,8 @@ cc="gcc"
 warn="-std=c23 -pedantic -Wall -Wextra"
 opt="-O2 -march=native"
 libs="-I/usr/include/libdrm -ldrm"
+defs="-D_POSIX_C_SOURCE=200809L"
 
-$cc $flags $libs main.c -o asteroids
+$cc $flags $libs $defs \
+	-o asteroids \
+	fb.c main.c renderer.c

fb.c

@@ -0,0 +1,49 @@
+#include "fb.h"
+
+#include <assert.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+
+fb_info_t fb_init(int drm_fd, drmModeModeInfo mode)
+{
+	int err;
+
+	struct drm_mode_create_dumb create = {
+		.width = mode.hdisplay,
+		.height = mode.vdisplay,
+		.bpp = 32,
+	};
+	err = ioctl(drm_fd, DRM_IOCTL_MODE_CREATE_DUMB, &create);
+	assert(err != -1);
+
+	uint32_t id;
+	err = drmModeAddFB(
+	    drm_fd, create.width, create.height, 24, 32, create.pitch,
+	    create.handle, &id);
+	assert(err == 0);
+
+	struct drm_mode_map_dumb map = { .handle = create.handle };
+	err = ioctl(drm_fd, DRM_IOCTL_MODE_MAP_DUMB, &map);
+	assert(err != -1);
+
+	uint32_t *buf = mmap(
+	    0, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, drm_fd,
+	    map.offset);
+	assert(buf != MAP_FAILED);
+
+	return (fb_info_t) {
+		.buf = buf,
+		.handle = create.handle,
+		.id = id,
+		.pitch = create.pitch,
+		.size = create.size,
+	};
+}
+
+void fb_cleanup(int drm_fd, fb_info_t fb)
+{
+	munmap(fb.buf, fb.size);
+	drmModeRmFB(drm_fd, fb.id);
+	struct drm_mode_destroy_dumb delete = { .handle = fb.handle };
+	ioctl(drm_fd, DRM_IOCTL_MODE_DESTROY_DUMB, &delete);
+}

fb.h

@@ -0,0 +1,17 @@
+#ifndef FB_H
+#define FB_H
+
+#include <xf86drmMode.h>
+
+typedef struct {
+	uint32_t *buf;
+	uint32_t handle;
+	uint32_t id;
+	uint32_t pitch;
+	uint32_t size;
+} fb_info_t;
+
+fb_info_t fb_init(int drm_fd, drmModeModeInfo mode);
+void fb_cleanup(int drm_fd, fb_info_t fb);
+
+#endif

main.c

@@ -1,90 +1,13 @@
-#define _POSIX_C_SOURCE 200809L
+#include "renderer.h"
 
 #include <assert.h>
 #include <fcntl.h>
 #include <linux/input.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/ioctl.h>
-#include <sys/mman.h>
 #include <sys/select.h>
 #include <unistd.h>
-#include <xf86drm.h>
-#include <xf86drmMode.h>
 
 #define MAX(a, b) ((a) < (b) ? (b) : (a))
 
-typedef struct {
-	uint32_t *buf;
-	uint32_t handle;
-	uint32_t id;
-	uint32_t pitch;
-	uint32_t size;
-} fb_info_t;
-
-static fb_info_t fbs[2];
-static int front = 0, back = 1;
-
-static fb_info_t fb_init(int drm_fd, drmModeModeInfo mode)
-{
-	int err;
-
-	struct drm_mode_create_dumb create = {
-		.width = mode.hdisplay,
-		.height = mode.vdisplay,
-		.bpp = 32,
-	};
-	err = ioctl(drm_fd, DRM_IOCTL_MODE_CREATE_DUMB, &create);
-	assert(err != -1);
-
-	uint32_t id;
-	err = drmModeAddFB(
-	    drm_fd, create.width, create.height, 24, 32, create.pitch,
-	    create.handle, &id);
-	assert(err == 0);
-
-	struct drm_mode_map_dumb map = { .handle = create.handle };
-	err = ioctl(drm_fd, DRM_IOCTL_MODE_MAP_DUMB, &map);
-	assert(err != -1);
-
-	uint32_t *buf = mmap(
-	    0, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, drm_fd,
-	    map.offset);
-	assert(buf != MAP_FAILED);
-
-	return (fb_info_t) {
-		.buf = buf,
-		.handle = create.handle,
-		.id = id,
-		.pitch = create.pitch,
-		.size = create.size,
-	};
-}
-
-static void fb_cleanup(int drm_fd, fb_info_t fb)
-{
-	munmap(fb.buf, fb.size);
-	drmModeRmFB(drm_fd, fb.id);
-	struct drm_mode_destroy_dumb delete = { .handle = fb.handle };
-	ioctl(drm_fd, DRM_IOCTL_MODE_DESTROY_DUMB, &delete);
-}
-
-static void page_flip_handler(int, unsigned, unsigned, unsigned, void *)
-{
-}
-
-static void swap_buffers(int drm_fd, uint32_t crtc_id)
-{
-	const int err = drmModePageFlip(
-	    drm_fd, crtc_id, fbs[back].id, DRM_MODE_PAGE_FLIP_EVENT, nullptr);
-	assert(err == 0);
-
-	front = (front + 1) & 1;
-	back = (back + 1) & 1;
-}
-
 int main()
 {
 	int err;
@@ -92,36 +15,20 @@ int main()
 	const int input_fd = open("/dev/input/event0", O_RDONLY);
 	assert(input_fd != -1);
 
-	const int drm_fd = open("/dev/dri/card1", O_RDWR | O_CLOEXEC);
+	const renderer_params_t renderer_params = renderer_init();
-	assert(drm_fd != -1);
+	const int drm_fd = renderer_params.drm_fd;
 
-	drmModeRes *res = drmModeGetResources(drm_fd);
+	renderer_clear();
-	assert(res != nullptr);
+	renderer_swap();
-	drmModeConnector *conn = drmModeGetConnector(drm_fd, res->connectors[0]);
-	assert(conn != nullptr);
-	drmModeModeInfo mode = conn->modes[0];
-	uint32_t conn_id = conn->connector_id;
-
-	fbs[0] = fb_init(drm_fd, mode);
-	fbs[1] = fb_init(drm_fd, mode);
-
-	err = drmModeSetCrtc(
-	    drm_fd, res->crtcs[0], fbs[front].id, 0, 0, &conn_id, 1, &mode);
-	assert(err == 0);
-	drmModeCrtc *crtc = drmModeGetCrtc(drm_fd, res->crtcs[0]);
-	assert(crtc != nullptr);
-
-	memset(fbs[back].buf, 0, fbs[back].size);
-	swap_buffers(drm_fd, crtc->crtc_id);
 
 	const int max_fd = MAX(input_fd, drm_fd);
 	fd_set set;
 	bool running = true;
-	uint64_t frame = 0;
 	while (running) {
 		FD_ZERO(&set);
 		FD_SET(input_fd, &set);
 		FD_SET(drm_fd, &set);
+
 		select(max_fd + 1, &set, nullptr, nullptr, nullptr);
 
 		if (FD_ISSET(input_fd, &set)) {
@@ -136,37 +43,14 @@ int main()
 		}
 
 		if (FD_ISSET(drm_fd, &set)) {
-			drmEventContext ev = {
+			renderer_handle();
-				.version = DRM_EVENT_CONTEXT_VERSION,
+			renderer_draw();
-				.page_flip_handler = page_flip_handler,
+			renderer_swap();
-			};
-			drmHandleEvent(drm_fd, &ev);
-
-			for (int y = 0; y < mode.vdisplay; ++y) {
-				for (int x = 0; x < mode.hdisplay; ++x) {
-					const uint8_t r = (x + frame) % 256;
-					const uint8_t g = (y + frame) % 256;
-					const uint8_t b = (x + y + frame) % 256;
-					fbs[back].buf[y * (fbs[back].pitch / 4) + x]
-					    = (r << 16) | (g << 8) | b;
-				}
-			}
-
-			swap_buffers(drm_fd, crtc->crtc_id);
-			++frame;
 		}
 	}
 
-	drmModeSetCrtc(
+	renderer_cleanup();
-	    drm_fd, crtc->crtc_id, crtc->buffer_id, crtc->x, crtc->y, &conn_id,
+	close(input_fd);
-	    1, &crtc->mode);
-
-	fb_cleanup(drm_fd, fbs[0]);
-	fb_cleanup(drm_fd, fbs[1]);
-	drmModeFreeCrtc(crtc);
-	drmModeFreeConnector(conn);
-	drmModeFreeResources(res);
-	close(drm_fd);
 
 	return 0;
 }

renderer.c

@@ -0,0 +1,112 @@
+#include "renderer.h"
+
+#include "fb.h"
+
+#include <assert.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <xf86drm.h>
+
+static int drm_fd;
+static drmModeConnector *conn;
+static drmModeCrtc *crtc;
+static uint32_t conn_id;
+
+static fb_info_t fbs[2];
+static int front, back;
+
+static uint32_t width, height;
+static void page_flip_handler(int, unsigned, unsigned, unsigned, void *)
+{
+}
+
+static void
+set_pixel(uint32_t x, uint32_t y, uint8_t r, uint8_t g, uint8_t b)
+{
+	/* x %= width; */
+	/* y %= height; */
+	const uint32_t offset = y * (fbs[back].pitch / 4) + x;
+	assert(offset < fbs[back].size);
+	fbs[back].buf[offset] = (r << 16) | (g << 8) | b;
+}
+
+renderer_params_t renderer_init()
+{
+	drm_fd = open("/dev/dri/card1", O_RDWR | O_CLOEXEC);
+	assert(drm_fd != -1);
+
+	drmModeRes *res = drmModeGetResources(drm_fd);
+	assert(res != nullptr);
+	conn = drmModeGetConnector(drm_fd, res->connectors[0]);
+	assert(conn != nullptr);
+	drmModeModeInfo mode = conn->modes[0];
+	conn_id = conn->connector_id;
+
+	fbs[0] = fb_init(drm_fd, mode);
+	fbs[1] = fb_init(drm_fd, mode);
+	front = 0;
+	back = 1;
+
+	const int err = drmModeSetCrtc(
+	    drm_fd, res->crtcs[0], fbs[front].id, 0, 0, &conn_id, 1, &mode);
+	assert(err == 0);
+	crtc = drmModeGetCrtc(drm_fd, res->crtcs[0]);
+	assert(crtc != nullptr);
+
+	drmModeFreeResources(res);
+
+	width = mode.hdisplay;
+	height = mode.vdisplay;
+
+	return (renderer_params_t) {
+		.drm_fd = drm_fd,
+		.aspect = (float)mode.hdisplay / (float)mode.vdisplay,
+	};
+}
+
+void renderer_cleanup()
+{
+	drmModeSetCrtc(
+	    drm_fd, crtc->crtc_id, crtc->buffer_id, crtc->x, crtc->y, &conn_id,
+	    1, &crtc->mode);
+
+	fb_cleanup(drm_fd, fbs[0]);
+	fb_cleanup(drm_fd, fbs[1]);
+	drmModeFreeCrtc(crtc);
+	drmModeFreeConnector(conn);
+	close(drm_fd);
+}
+
+void renderer_handle()
+{
+	drmEventContext ev = {
+		.version = DRM_EVENT_CONTEXT_VERSION,
+		.page_flip_handler = page_flip_handler,
+	};
+	drmHandleEvent(drm_fd, &ev);
+}
+
+void renderer_clear()
+{
+	memset(fbs[back].buf, 0, fbs[back].size);
+}
+
+void renderer_swap()
+{
+	const int err = drmModePageFlip(
+	    drm_fd, crtc->crtc_id, fbs[back].id, DRM_MODE_PAGE_FLIP_EVENT,
+	    nullptr);
+	assert(err == 0);
+
+	front = (front + 1) & 1;
+	back = (back + 1) & 1;
+}
+
+void renderer_draw()
+{
+	for (unsigned y = 0; y < height; ++y) {
+		for (unsigned x = 0; x < width; ++x)
+			set_pixel(x, y, (x * 255) / width, (y * 255) / height, 128);
+	}
+}

renderer.h

@@ -0,0 +1,19 @@
+#ifndef RENDERER_H
+#define RENDERER_H
+
+#include <stdint.h>
+
+typedef struct {
+	int drm_fd;
+	float aspect;
+} renderer_params_t;
+
+renderer_params_t renderer_init();
+void renderer_cleanup();
+
+void renderer_handle();
+void renderer_clear();
+void renderer_swap();
+
+void renderer_draw();
+#endif