[RFC PATCH mtd-utils 021/110] ubifs-utils: Add linux kernel error conversion definitions

[Zhihao Cheng]

Add linux kernel error conversion definitions, because there are
many error type conversions(eg. PTR_ERR, ERR_PTR) used in UBIFS
linux kernel libs.

This is a preparation for replacing implementation of UBIFS utils with
linux kernel libs.

Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
---
 ubifs-utils/Makemodule.am      |  1 +
 ubifs-utils/common/linux_err.h | 62 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 ubifs-utils/common/linux_err.h

diff --git a/ubifs-utils/Makemodule.am b/ubifs-utils/Makemodule.am
index 0f9c0fa6..69192ffd 100644
--- a/ubifs-utils/Makemodule.am
+++ b/ubifs-utils/Makemodule.am
@@ -1,6 +1,7 @@
 common_SOURCES = \
 	ubifs-utils/common/compiler_attributes.h \
 	ubifs-utils/common/linux_types.h \
+	ubifs-utils/common/linux_err.h \
 	ubifs-utils/common/defs.h \
 	ubifs-utils/common/crc16.h \
 	ubifs-utils/common/crc16.c \
diff --git a/ubifs-utils/common/linux_err.h b/ubifs-utils/common/linux_err.h
new file mode 100644
index 00000000..5c6ddc3f
--- /dev/null
+++ b/ubifs-utils/common/linux_err.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ERR_H
+#define _LINUX_ERR_H
+
+/* Adapted from include/linux/err.h */
+
+#include <stdbool.h>
+
+/*
+ * Kernel pointers have redundant information, so we can use a
+ * scheme where we can return either an error code or a normal
+ * pointer with the same return value.
+ *
+ * This should be a per-architecture thing, to allow different
+ * error and pointer decisions.
+ */
+#define MAX_ERRNO	4095
+
+#define IS_ERR_VALUE(x) ((unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO)
+
+static inline void * ERR_PTR(long error)
+{
+	return (void *) error;
+}
+
+static inline long PTR_ERR(const void *ptr)
+{
+	return (long) ptr;
+}
+
+static inline bool IS_ERR(const void *ptr)
+{
+	return IS_ERR_VALUE((unsigned long)ptr);
+}
+
+static inline bool IS_ERR_OR_NULL(const void *ptr)
+{
+	return !ptr || IS_ERR_VALUE((unsigned long)ptr);
+}
+
+/**
+ * ERR_CAST - Explicitly cast an error-valued pointer to another pointer type
+ * @ptr: The pointer to cast.
+ *
+ * Explicitly cast an error-valued pointer to another pointer type in such a
+ * way as to make it clear that's what's going on.
+ */
+static inline void * ERR_CAST(const void *ptr)
+{
+	/* cast away the const */
+	return (void *) ptr;
+}
+
+static inline int PTR_ERR_OR_ZERO(const void *ptr)
+{
+	if (IS_ERR(ptr))
+		return PTR_ERR(ptr);
+	else
+		return 0;
+}
+
+#endif /* _LINUX_ERR_H */
-- 
2.13.6