1 files changed, 45 insertions, 0 deletions
diff --git a/src/luxmax.c b/src/luxmax.c
new file mode 100644
index 0000000..b30f02b
--- /dev/null
+++ b/src/luxmax.c
@@ -0,0 +1,45 @@
+/*
+ * BSD Zero Clause License
+ *
+ * Copyright (c) 2022 Thomas Voss
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "lux.h"
+
+int
+luxmax(lux_t *disp)
+{
+	/* The maximum brightness shouldn't change, so we can cache it in the
+	 * struct.
+	 */
+	if (disp->__max != -1)
+		return disp->__max;
+
+	int fd = openat(disp->__dirfd, "max_brightness", O_RDONLY);
+	if (fd == -1)
+		return -1;
+	FILE *stream = fdopen(fd, "r");
+	if (stream == NULL) {
+		close(fd);
+		return -1;
+	}
+
+	fscanf(stream, "%d", &disp->__max);
+	fclose(stream);
+	return disp->__max;
+}