From 12fd0ea93e3164d21aba5e5abe1a2596cacbfd0b Mon Sep 17 00:00:00 2001
From: Gleb Chesnokov <gleb.chesnokov@scst.dev>
Date: Sun, 1 Oct 2023 20:16:17 +0300
Subject: [PATCH] scst/include/backport.h: Backport some debugfs functions

Support the previous commit against kernel versions before v5.0.

See also commit ff9fb72bc077 ("debugfs: return error values,
not NULL") # v5.0.
---
 scst/include/backport.h | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/scst/include/backport.h b/scst/include/backport.h
index 9691bddfd..56d25e4ee 100644
--- a/scst/include/backport.h
+++ b/scst/include/backport.h
@@ -31,6 +31,7 @@
 #include <linux/blk-mq.h>
 #endif
 #include <linux/bsg-lib.h>	/* struct bsg_job */
+#include <linux/debugfs.h>
 #include <linux/dmapool.h>
 #include <linux/eventpoll.h>
 #include <linux/iocontext.h>
@@ -385,6 +386,39 @@ static inline ssize_t debugfs_attr_write(struct file *file,
 }
 #endif
 
+/*
+ * See also commit ff9fb72bc077 ("debugfs: return error values,
+ * not NULL") # v5.0.
+ */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 0, 0)
+static inline struct dentry *debugfs_create_dir_backport(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry;
+
+	dentry = debugfs_create_dir(name, parent);
+	if (!dentry)
+		return ERR_PTR(-ENOMEM);
+
+	return dentry;
+}
+
+static inline struct dentry *debugfs_create_file_backport(const char *name, umode_t mode,
+							  struct dentry *parent, void *data,
+							  const struct file_operations *fops)
+{
+	struct dentry *dentry;
+
+	dentry = debugfs_create_file(name, mode, parent, data, fops);
+	if (!dentry)
+		return ERR_PTR(-ENOMEM);
+
+	return dentry;
+}
+
+#define debugfs_create_dir debugfs_create_dir_backport
+#define debugfs_create_file debugfs_create_file_backport
+#endif
+
 /* <linux/device.h> */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0)