[libgpiod][PATCH 03/14] core: export gpiod_is_gpiochip_device()

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>

We'll be dropping chip iterators treewide. Instead we'll encourage
scanning /dev for GPIO chip devices. Exporting this function allows
users to easily check if given file represents a GPIO chip character
device.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
---
 include/gpiod.h    |  8 ++++++++
 lib/core.c         |  4 ++--
 tests/tests-chip.c | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/include/gpiod.h b/include/gpiod.h
index 355a99a..742dfc2 100644
--- a/include/gpiod.h
+++ b/include/gpiod.h
@@ -71,6 +71,14 @@ struct gpiod_line_bulk;
  * Functions and data structures dealing with GPIO chips.
  */
 
+/**
+ * @brief Check if the file pointed to by path is a GPIO chip character device.
+ * @param path Path to check.
+ * @return True if the file exists and is a GPIO chip character device or a
+ *         symbolic link to it.
+ */
+bool gpiod_is_gpiochip_device(const char *path) GPIOD_API;
+
 /**
  * @brief Open a gpiochip by path.
  * @param path Path to the gpiochip device file.
diff --git a/lib/core.c b/lib/core.c
index bf52fa6..efba959 100644
--- a/lib/core.c
+++ b/lib/core.c
@@ -177,7 +177,7 @@ void gpiod_line_bulk_foreach_line(struct gpiod_line_bulk *bulk,
 	     (index) < (bulk)->num_lines;				\
 	     (index)++, (line) = (bulk)->lines[(index)])
 
-static bool is_gpiochip_cdev(const char *path)
+bool gpiod_is_gpiochip_device(const char *path)
 {
 	char *name, *realname, *sysfsp, sysfsdev[16], devstr[16];
 	struct stat statbuf;
@@ -282,7 +282,7 @@ struct gpiod_chip *gpiod_chip_open(const char *path)
 	 * We were able to open the file but is it really a gpiochip character
 	 * device?
 	 */
-	if (!is_gpiochip_cdev(path))
+	if (!gpiod_is_gpiochip_device(path))
 		goto err_close_fd;
 
 	chip = malloc(sizeof(*chip));
diff --git a/tests/tests-chip.c b/tests/tests-chip.c
index 289c458..2f19c49 100644
--- a/tests/tests-chip.c
+++ b/tests/tests-chip.c
@@ -11,6 +11,21 @@
 
 #define GPIOD_TEST_GROUP "chip"
 
+GPIOD_TEST_CASE(is_gpiochip_good, 0, { 8 })
+{
+	g_assert_true(gpiod_is_gpiochip_device(gpiod_test_chip_path(0)));
+}
+
+GPIOD_TEST_CASE(is_gpiochip_bad, 0, { 8 })
+{
+	g_assert_false(gpiod_is_gpiochip_device("/dev/null"));
+}
+
+GPIOD_TEST_CASE(is_gpiochip_nonexistent, 0, { 8 })
+{
+	g_assert_false(gpiod_is_gpiochip_device("/dev/nonexistent_gpiochip"));
+}
+
 GPIOD_TEST_CASE(open_good, 0, { 8 })
 {
 	g_autoptr(gpiod_chip_struct) chip = NULL;
-- 
2.29.1