tests: provide test_debugfs_get/set_value() helpers

Since linux v5.1 gpio-mockup simulates pull-up/down resistors for dummy
lines. The current pull can be set using debugfs. Since we can no longer
verify if the character device interface properly sets line values, the
debugfs interface now also allows to read line values. This way we can
verify if the ABI works correctly using different code paths.

Provide functions for reading and setting values of mockup GPIO lines.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

2 files changed, 65 insertions, 0 deletions

diff --git a/tests/gpiod-test.c b/tests/gpiod-test.c
index 1f37985b..56ef770f 100644
--- a/tests/gpiod-test.c
+++ b/tests/gpiod-test.c
@@ -3,6 +3,7 @@
  * This file is part of libgpiod.
  *
  * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
+ * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
  */
 
 #include <ctype.h>
@@ -1113,6 +1114,65 @@ unsigned int test_chip_num(unsigned int index)
 	return globals.test_ctx.chips[index]->number;
 }
 
+static int test_debugfs_open(unsigned int chip_index,
+			     unsigned int line_offset, int flags)
+{
+	char *path;
+	int fd;
+
+	path = xappend(NULL, "/sys/kernel/debug/gpio-mockup/gpiochip%u/%u",
+		       chip_index, line_offset);
+
+	fd = open(path, flags);
+	if (fd < 0)
+		die_perr("unable to open the debugfs line ('%s') attribute for reading",
+			 path);
+
+	free(path);
+	return fd;
+}
+
+int test_debugfs_get_value(unsigned int chip_index, unsigned int line_offset)
+{
+	ssize_t rd;
+	char buf;
+	int fd;
+
+	fd = test_debugfs_open(chip_index, line_offset, O_RDONLY);
+
+	rd = read(fd, &buf, 1);
+	if (rd < 0)
+		die_perr("error reading the debugfs line attribute");
+	if (rd != 1)
+		die("unable to read the line value from debugfs");
+	if (buf != '0' && buf != '1')
+		die("invalid line value read from debugfs");
+
+	close(fd);
+	return buf == '0' ? 0 : 1;
+}
+
+void test_debugfs_set_value(unsigned int chip_index,
+			    unsigned int line_offset, int val)
+{
+	char buf[2];
+	ssize_t wr;
+	int fd;
+
+	fd = test_debugfs_open(chip_index, line_offset, O_WRONLY);
+
+	buf[0] = val ? '1' : 0;
+	buf[1] = '\n';
+
+	wr = write(fd, &buf, sizeof(buf));
+	if (wr < 0)
+		die_perr("error writing to the debugfs line attribute");
+	if (wr != sizeof(buf))
+		die("unable to write the line value to debugfs");
+
+	close(fd);
+}
+
 void _test_register(struct _test_case *test)
 {
 	struct _test_case *tmp;
diff --git a/tests/gpiod-test.h b/tests/gpiod-test.h
index 040d993f..c3ca0b19 100644
--- a/tests/gpiod-test.h
+++ b/tests/gpiod-test.h
@@ -3,6 +3,7 @@
  * This file is part of libgpiod.
  *
  * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
+ * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
  */
 
 /* Testing framework - functions and definitions used by test cases. */
@@ -93,6 +94,10 @@ const char *test_chip_path(unsigned int index);
 const char *test_chip_name(unsigned int index);
 unsigned int test_chip_num(unsigned int index);
 
+int test_debugfs_get_value(unsigned int chip_index, unsigned int line_offset);
+void test_debugfs_set_value(unsigned int chip_index,
+			    unsigned int line_offset, int val);
+
 /* Last argument is the delay between line value switches in microseconds. */
 void test_set_event(unsigned int chip_index,
 		    unsigned int line_offset, unsigned int freq);