initial commit

2 files changed, 68 insertions, 0 deletions

diff --git a/piboot.c b/piboot.c
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index 0000000..0aa6326
--- /dev/null
+++ b/piboot.c
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+/*
+    piboot
+    Copyright 2025 metamuffin <metamuffin.org>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, version 3 of the License only.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(int argc, char **argv) {
+  char *fbpath = "/dev/fb0";
+  if (argc >= 2)
+    fbpath = argv[1];
+  int fd = open(fbpath, O_CLOEXEC | O_WRONLY);
+  if (fd < 0) {
+    fprintf(stderr, "cannot open fb0: %s\n", strerror(errno));
+    return 1;
+  }
+
+  int w = 1920, h = 1080;
+  int sidepad = (w - h) / 2;
+  uint8_t *frame = malloc(w * h * 4);
+  memset(frame, 0, w * h * 4);
+
+  for (int y = 0; y < h; y++)
+    for (int x = 0; x < w; x++) {
+      if (x < sidepad || x >= h + sidepad)
+        continue;
+      int base = (x + y * w) * 4;
+      int u = (x - sidepad) * 256 / h, v = y * 256 / h;
+      frame[base + 0] = v;
+      frame[base + 1] = u;
+      frame[base + 2] = 255 - v;
+    }
+
+  int res = write(fd, frame, w * h * 4);
+  if (res < 0) {
+    fprintf(stderr, "cannot write to fb0: %s\n", strerror(errno));
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/readme.txt b/readme.txt
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index 0000000..3616e29
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+++ b/readme.txt
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+piboot
+======
+
+Program that displays the test image that is typical for Raspberry Pi's boot via fbdev.
+
+Compilation: `gcc piboot.c`
+Installation: `install -Dm755 a.out /usr/bin/piboot`
+Usage: `piboot` or `piboot /dev/fbX`
+
+License: AGPL-3.0-only