[libgpiod v1.6.x][PATCH] tests: mockup: unbind mockup devices before unloading the module

[Bartosz Golaszewski <brgl@xxxxxxxx>]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

gpio-mockup relies on the GPIO devices being registered in module's __init
function and them being unregistered in __exit. This works with the GPIO
subsystem as it only takes a reference to the underlying owner module when
a GPIO descriptor is requested and not when the GPIO device is
instantiated.

This behavior may change in the future in the kernel so make the behavior
of libgpiomockup more correct and have it unbind all mockup devices over
sysfs before unloading the module.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
 tests/mockup/gpio-mockup.c | 50 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/tests/mockup/gpio-mockup.c b/tests/mockup/gpio-mockup.c
index fa27bd7..387e449 100644
--- a/tests/mockup/gpio-mockup.c
+++ b/tests/mockup/gpio-mockup.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
  */
 
+#include <dirent.h>
 #include <errno.h>
 #include <libkmod.h>
 #include <libudev.h>
@@ -357,6 +358,51 @@ err_out:
 	return -1;
 }
 
+static int dir_filter(const struct dirent *entry)
+{
+	return !strncmp(entry->d_name, "gpio-mockup.", 12);
+}
+
+static void free_dirs(struct dirent **entries, size_t count)
+{
+	size_t i;
+
+	for (i = 0; i < count; i++)
+		free(entries[i]);
+	free(entries);
+}
+
+static int unbind_devices(void)
+{
+	struct dirent **entries;
+	int i, count, fd;
+	ssize_t ret;
+
+	count = scandir("/sys/bus/platform/drivers/gpio-mockup", &entries,
+			dir_filter, alphasort);
+	if (count < 0)
+		return -1;
+
+	fd = open("/sys/bus/platform/drivers/gpio-mockup/unbind", O_WRONLY);
+	if (fd < 0) {
+		free_dirs(entries, count);
+		return -1;
+	}
+
+	for (i = 0; i < count; i++) {
+		ret = write(fd, entries[i]->d_name, strlen(entries[i]->d_name));
+		if (ret < 0) {
+			close(fd);
+			free_dirs(entries, count);
+			return -1;
+		}
+	}
+
+	close(fd);
+	free_dirs(entries, count);
+	return 0;
+}
+
 EXPORT int gpio_mockup_remove(struct gpio_mockup *ctx)
 {
 	unsigned int i;
@@ -367,6 +413,10 @@ EXPORT int gpio_mockup_remove(struct gpio_mockup *ctx)
 		return -1;
 	}
 
+	rv = unbind_devices();
+	if (rv)
+		return -1;
+
 	rv = kmod_module_remove_module(ctx->module, 0);
 	if (rv)
 		return -1;
-- 
2.39.2