1 files changed, 51 insertions, 0 deletions
diff --git a/tools/backlight_helper.c b/tools/backlight_helper.c
new file mode 100644
index 00000000..fc16fcea
--- /dev/null
+++ b/tools/backlight_helper.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+int main(int argc, char *argv[])
+{
+	struct stat st;
+	char buf[1024], *b = buf;
+	int len, fd;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <iface>\n", argv[0]);
+		return 1;
+	}
+
+	snprintf(buf, sizeof(buf), "/sys/class/backlight/%s/brightness", argv[1]);
+	fd = open(buf, O_RDWR);
+	if (fd < 0 || fstat(fd, &st) || major(st.st_dev)) {
+		fprintf(stderr, "Cannot access backlight interface '%s'\n", argv[1]);
+		return 1;
+	}
+
+	while ((len = read(0, b, sizeof(buf) - (b - buf) - 1)) > 0) {
+		len += b - buf;
+		buf[len] = '\0';
+
+		b = buf;
+		do {
+			char *end = strchr(b, '\n');
+			if (end == NULL)
+				break;
+
+			++end;
+			if (write(fd, b, end - b) != end - b) {
+				fprintf(stderr, "Failed to update backlight interface '%s'\n", argv[1]);
+				return 2;
+			}
+
+			b = end;
+		} while (1);
+
+		memmove(buf, b, len = buf + len - b);
+		b = buf + len;
+	}
+
+	return 0;
+}