lib/string_helpers: Introduce managed variant of kasprintf_strarray()

Some of the users want to have easy way to allocate array of strings
that will be automatically cleaned when associated device is gone.

Introduce managed variant of kasprintf_strarray() for such use cases.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

include/linux/string_helpers.h

@@ -7,6 +7,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 
+struct device;
 struct file;
 struct task_struct;
 
@@ -103,4 +104,6 @@ char *kstrdup_quotable_file(struct file *file, gfp_t gfp);
 char **kasprintf_strarray(gfp_t gfp, const char *prefix, size_t n);
 void kfree_strarray(char **array, size_t n);
 
+char **devm_kasprintf_strarray(struct device *dev, const char *prefix, size_t n);
+
 #endif

lib/string_helpers.c

@@ -10,6 +10,7 @@
 #include <linux/math64.h>
 #include <linux/export.h>
 #include <linux/ctype.h>
+#include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/limits.h>
@@ -730,6 +731,36 @@ void kfree_strarray(char **array, size_t n)
 }
 EXPORT_SYMBOL_GPL(kfree_strarray);
 
+struct strarray {
+	char **array;
+	size_t n;
+};
+
+static void devm_kfree_strarray(struct device *dev, void *res)
+{
+	struct strarray *array = res;
+
+	kfree_strarray(array->array, array->n);
+}
+
+char **devm_kasprintf_strarray(struct device *dev, const char *prefix, size_t n)
+{
+	struct strarray *ptr;
+
+	ptr = devres_alloc(devm_kfree_strarray, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	ptr->array = kasprintf_strarray(GFP_KERNEL, prefix, n);
+	if (!ptr->array) {
+		devres_free(ptr);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	return ptr->array;
+}
+EXPORT_SYMBOL_GPL(devm_kasprintf_strarray);
+
 /**
  * strscpy_pad() - Copy a C-string into a sized buffer
  * @dest: Where to copy the string to