tests/pm_backlight: Add backlight test

This is a basic sanity test of the backlight sysfs interface.

v2:
 - Add jani's suggestion for immediate readback
 - Remove unused parameter from test_and_verify()
 - Add fade test

Issue: VIZ-3377
Signed-off-by: Antti Koskipaa <antti.koskipaa@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Thomas Wood <thomas.wood@intel.com>

tests/.gitignore

@@ -150,6 +150,7 @@ kms_vblank
 kms_crtc_background_color
 kms_plane_scaling
 kms_panel_fitting
+pm_backlight
 pm_lpsp
 pm_rc6_residency
 pm_rpm

tests/Makefile.sources

@@ -80,6 +80,7 @@ TESTS_progs_M = \
 	kms_crtc_background_color \
 	kms_plane_scaling \
 	kms_panel_fitting \
+	pm_backlight \
 	pm_lpsp \
 	pm_rpm \
 	pm_rps \

tests/pm_backlight.c

@@ -0,0 +1,171 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Author:
+ *    Antti Koskipaa <antti.koskipaa@linux.intel.com>
+ *
+ */
+
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "igt_core.h"
+
+#define TOLERANCE 5 /* percent */
+#define BACKLIGHT_PATH "/sys/class/backlight/intel_backlight"
+
+#define FADESTEPS 10
+#define FADESPEED 100 /* milliseconds between steps */
+
+IGT_TEST_DESCRIPTION("Basic backlight sysfs test");
+
+static int backlight_read(int *result, const char *fname)
+{
+	int fd;
+	char full[PATH_MAX];
+	char dst[64];
+	int r, e;
+
+	igt_assert(snprintf(full, PATH_MAX, "%s/%s", BACKLIGHT_PATH, fname) < PATH_MAX);
+
+	fd = open(full, O_RDONLY);
+	if (fd == -1)
+		return -errno;
+
+	r = read(fd, dst, sizeof(dst));
+	e = errno;
+	close(fd);
+
+	if (r < 0)
+		return -e;
+
+	errno = 0;
+	*result = strtol(dst, NULL, 10);
+	return errno;
+}
+
+static int backlight_write(int value, const char *fname)
+{
+	int fd;
+	char full[PATH_MAX];
+	char src[64];
+	int len;
+
+	igt_assert(snprintf(full, PATH_MAX, "%s/%s", BACKLIGHT_PATH, fname) < PATH_MAX);
+	fd = open(full, O_WRONLY);
+	if (fd == -1)
+		return -errno;
+
+	len = snprintf(src, sizeof(src), "%i", value);
+	len = write(fd, src, len);
+	close(fd);
+
+	if (len < 0)
+		return len;
+
+	return 0;
+}
+
+static void test_and_verify(int val)
+{
+	int result;
+
+	igt_assert(backlight_write(val, "brightness") == 0);
+	igt_assert(backlight_read(&result, "brightness") == 0);
+	/* Check that the exact value sticks */
+	igt_assert(result == val);
+
+	igt_assert(backlight_read(&result, "actual_brightness") == 0);
+	/* Some rounding may happen depending on hw. Just check that it's close enough. */
+	igt_assert(result <= val + val * TOLERANCE / 100 && result >= val - val * TOLERANCE / 100);
+}
+
+static void test_brightness(int max)
+{
+	test_and_verify(0);
+	test_and_verify(max);
+	test_and_verify(max / 2);
+}
+
+static void test_bad_brightness(int max)
+{
+	int val;
+	/* First write some sane value */
+	backlight_write(max / 2, "brightness");
+	/* Writing invalid values should fail and not change the value */
+	igt_assert(backlight_write(-1, "brightness") < 0);
+	backlight_read(&val, "brightness");
+	igt_assert(val == max / 2);
+	igt_assert(backlight_write(max + 1, "brightness") < 0);
+	backlight_read(&val, "brightness");
+	igt_assert(val == max / 2);
+	igt_assert(backlight_write(INT_MAX, "brightness") < 0);
+	backlight_read(&val, "brightness");
+	igt_assert(val == max / 2);
+}
+
+static void test_fade(int max)
+{
+	int i;
+	static const struct timespec ts = { .tv_sec = 0, .tv_nsec = FADESPEED*1000000 };
+
+	/* Fade out, then in */
+	for (i = max; i > 0; i -= max / FADESTEPS) {
+		test_and_verify(i);
+		nanosleep(&ts, NULL);
+	}
+	for (i = 0; i <= max; i += max / FADESTEPS) {
+		test_and_verify(i);
+		nanosleep(&ts, NULL);
+	}
+}
+
+igt_main
+{
+	int max, old;
+
+	igt_skip_on_simulation();
+
+	igt_fixture {
+		/* Get the max value and skip the whole test if sysfs interface not available */
+		igt_skip_on(backlight_read(&old, "brightness"));
+		igt_assert(backlight_read(&max, "max_brightness") > -1);
+	}
+
+	igt_subtest("brightness")
+		test_brightness(max);
+	igt_subtest("bad-brightness")
+		test_bad_brightness(max);
+	igt_subtest("fade")
+		test_fade(max);
+
+	igt_fixture {
+		/* Restore old brightness */
+		backlight_write(old, "brightness");
+	}
+}