Add main loop with framebuffer color change

1 files changed, 37 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index e08dc19..e3e8b77 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,7 +1,43 @@
 #include<stdio.h>
+#include<stdlib.h>
+#include<stdint.h>
+#include<stdbool.h>
+#include<fcntl.h>
+#include<linux/fb.h>
+#include<sys/ioctl.h>
+#include<sys/mman.h>
 
 int
 main(void) {
-        printf("hello world\n");
+        // Open frambuffer and get the size.
+        int fb = open("/dev/fb0", O_RDWR);
+        if (fb <= 0) {
+                fprintf(stderr, "couldn't open the framebuffer\n");
+                exit(EXIT_FAILURE);
+        }
+        struct fb_var_screeninfo info;
+        if (ioctl(fb, FBIOGET_VSCREENINFO, &info) != 0) {
+                fprintf(stderr, "couldn't get the framebuffer size\n");
+                exit(EXIT_FAILURE);
+        }
+
+        // Mmap the framebuffer to a buffer object.
+        size_t width = info.xres;
+        size_t height = info.yres;
+        size_t len = 4 * width * height;
+        uint32_t *buf = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fb, 0);
+        if (buf == MAP_FAILED) {
+                fprintf(stderr, "couldn't mmap the framebuffer\n");
+                exit(EXIT_FAILURE);
+        }
+        uint8_t shade = 0;
+        while (true) {
+                for (size_t j = 0; j < height; j++) {
+                        for (size_t i = 0; i < width; i++) {
+                                buf[j * width + i] = shade;
+                        }
+                }
+                shade++;
+        }
         return 0;
 }