1 files changed, 137 insertions, 0 deletions
diff --git a/intel_backlight_ctl.c b/intel_backlight_ctl.c
new file mode 100644
index 0000000..70f6822
--- /dev/null
+++ b/intel_backlight_ctl.c
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+#include <stdbool.h>
+
+#define CUR_PATH "/sys/class/backlight/intel_backlight/brightness"
+#define MAX_PATH "/sys/class/backlight/intel_backlight/max_brightness"
+#define STEP     10
+
+struct brightness {
+    int max_raw;
+    int raw;
+    int percents;
+};
+
+
+
+int readval(const char *path, int *dst)
+{
+    FILE *f = fopen(path, "r");
+    int retval = 1;
+
+    if (f == NULL) {
+        perror(path);
+        goto end;
+    }
+
+    int raw;
+    if (fscanf(f, "%d", &raw) != 1) {
+        perror(path);
+        goto end;
+    }
+
+    *dst = raw;
+    retval = 0;
+
+end:
+    if (f != NULL)
+        fclose(f);
+    return retval;
+}
+
+
+int get(struct brightness *dst)
+{
+    int retval = 1;
+    if (readval(CUR_PATH, &dst->raw))
+        goto end;
+    if (readval(MAX_PATH, &dst->max_raw))
+        goto end;
+
+    dst->percents = (int)round((double)dst->raw*100/dst->max_raw);
+    retval = 0;
+
+end:
+    return retval;
+}
+
+int set(struct brightness *src)
+{
+    int retval = 1;
+    FILE *f = fopen(CUR_PATH, "w");
+    if (!f) {
+        perror(CUR_PATH);
+        goto end;
+    }
+
+    fprintf(f, "%d", src->raw);
+    retval = 0;
+
+end:
+    if (f != NULL)
+        fclose(f);
+    return retval;
+}
+
+void adjust(struct brightness *b, int value)
+{
+    b->percents += value;
+    if (b->percents > 100)
+        b->percents = 100;
+    else if (b->percents < 0)
+        b->percents = 0;
+    b->raw = (int)ceil((double)b->percents*b->max_raw/100);
+}
+
+
+void dump(struct brightness *b)
+{
+    printf("%d (%d%%)\n", b->raw, b->percents);
+}
+
+
+int main(int argc, char** argv)
+{
+    int retval = 0;
+    struct brightness b;
+    int adjust_val = STEP;
+    bool decr = false;
+
+    if (argc > 1 && strcmp(argv[1], "-h") == 0) {
+        printf("usage: %s [-h] [+/-]\n", argv[0]);
+        goto end;
+    }
+
+    if (get(&b))
+        goto end;
+
+    if (argc <= 1) {
+        dump(&b);
+        goto end;
+    }
+
+    if (strcmp(argv[1], "-") == 0)
+        decr = true;
+    else if (strcmp(argv[1], "+") != 0) {
+        fprintf(stderr, "%s: unknown argument\n", argv[1]);
+        retval = 1;
+        goto end;
+    }
+
+    if (decr)
+        adjust_val *= -1;
+
+    adjust(&b, adjust_val);
+    if (set(&b)) {
+        retval = 1;
+        goto end;
+    }
+
+    dump(&b);
+
+end:
+    return retval;
+}