[Concept,04/19] linux: Add mm_types.h header with VM stubs

diff --git a/fs/ext4l/ext4_uboot.h b/fs/ext4l/ext4_uboot.h
index d04a843175b..6a06805329f 100644
--- a/fs/ext4l/ext4_uboot.h
+++ b/fs/ext4l/ext4_uboot.h
@@ -456,29 +456,15 @@  struct name_snapshot {
 	struct qstr name;
 };
 
-/* vm_fault_t - stub */
-typedef unsigned int vm_fault_t;
-
-/* VM flags */
-#define VM_SHARED		0x00000008
-#define VM_WRITE		0x00000002
-#define VM_HUGEPAGE		0x01000000
-#define FAULT_FLAG_WRITE	0x01
+/* VM types - use linux/mm_types.h */
+#include <linux/mm_types.h>
 
 /* pipe_inode_info - forward declaration */
 struct pipe_inode_info;
 
-/* vm_area_desc - for mmap_prepare */
-struct vm_area_desc {
-	struct file *file;
-	unsigned long vm_flags;
-	const struct vm_operations_struct *vm_ops;
-};
-
-/* Forward declarations for function prototypes */
+/* Forward declarations for function prototypes (vm_fault is in linux/mm_types.h) */
 struct kstat;
 struct path;
-struct vm_fault;
 struct file_kattr;
 struct dir_context;
 struct readahead_control;
@@ -592,10 +578,7 @@  static inline int bdev_read_only(struct block_device *bdev)
 #define STATX_ATTR_ENCRYPTED	0x00000800
 #define STATX_ATTR_VERITY	0x00100000
 
-/* VM fault return values */
-#define VM_FAULT_SIGBUS		0x0002
-#define VM_FAULT_NOPAGE		0x0010
-#define VM_FAULT_LOCKED		0x0200
+/* VM fault return values are in linux/mm_types.h */
 
 /* struct path is defined in linux/fs.h */
 
@@ -625,44 +608,11 @@  struct kstat {
 	u32 atomic_write_segments_max;
 };
 
-/* struct vm_area_struct - virtual memory area */
-struct vm_area_struct {
-	unsigned long vm_start;
-	unsigned long vm_end;
-	struct file *vm_file;
-	unsigned long vm_flags;
-};
-
-/* struct page - minimal stub */
-struct page {
-	unsigned long flags;
-};
-
-/* struct vm_fault - virtual memory fault info */
-struct vm_fault {
-	struct vm_area_struct *vma;
-	unsigned long address;
-	unsigned int flags;
-	pgoff_t pgoff;
-	struct folio *folio;
-	struct page *page;
-};
-
-/* vm_operations_struct - virtual memory area operations */
-struct vm_operations_struct {
-	vm_fault_t (*fault)(struct vm_fault *vmf);
-	vm_fault_t (*huge_fault)(struct vm_fault *vmf, unsigned int order);
-	vm_fault_t (*page_mkwrite)(struct vm_fault *vmf);
-	vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf);
-	vm_fault_t (*map_pages)(struct vm_fault *vmf, pgoff_t start, pgoff_t end);
-};
+/* VM structs (vm_area_struct, page, vm_fault, vm_operations_struct) are in linux/mm_types.h */
 
 /* Forward declaration for swap */
 struct swap_info_struct;
 
-/* MAX_PAGECACHE_ORDER - maximum order for page cache allocations */
-#define MAX_PAGECACHE_ORDER	12
-
 /* Process flags */
 #define PF_MEMALLOC		0x00000800
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
new file mode 100644
index 00000000000..57a52769b05
--- /dev/null
+++ b/include/linux/mm_types.h
@@ -0,0 +1,116 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Memory management types stub for U-Boot
+ *
+ * U-Boot doesn't have virtual memory management, so these are stubs.
+ */
+#ifndef _LINUX_MM_TYPES_H
+#define _LINUX_MM_TYPES_H
+
+#include <linux/types.h>
+
+/* Forward declarations */
+struct file;
+struct folio;
+struct address_space;
+
+/**
+ * struct page - minimal stub for page structure
+ * @flags: page flags
+ *
+ * U-Boot stub - only the flags field is provided.
+ */
+struct page {
+	unsigned long flags;
+};
+
+/**
+ * typedef vm_fault_t - return type for page fault handlers
+ *
+ * Encodes the result of a page fault.
+ */
+typedef unsigned int vm_fault_t;
+
+/* VM flags for vm_area_struct */
+#define VM_SHARED		0x00000008
+#define VM_WRITE		0x00000002
+#define VM_HUGEPAGE		0x01000000
+
+/* Fault flags */
+#define FAULT_FLAG_WRITE	0x01
+
+/* VM fault return values */
+#define VM_FAULT_SIGBUS		0x0002
+#define VM_FAULT_NOPAGE		0x0010
+#define VM_FAULT_LOCKED		0x0200
+
+/* Maximum order for page cache allocations */
+#define MAX_PAGECACHE_ORDER	12
+
+struct vm_operations_struct;
+
+/**
+ * struct vm_area_struct - virtual memory area
+ * @vm_start: start address
+ * @vm_end: end address
+ * @vm_file: file this vma is associated with
+ * @vm_flags: VM flags
+ *
+ * U-Boot stub.
+ */
+struct vm_area_struct {
+	unsigned long vm_start;
+	unsigned long vm_end;
+	struct file *vm_file;
+	unsigned long vm_flags;
+};
+
+/**
+ * struct vm_fault - virtual memory fault info
+ * @vma: virtual memory area
+ * @address: faulting address
+ * @flags: fault flags
+ * @pgoff: page offset
+ * @folio: folio being faulted
+ * @page: page being faulted
+ *
+ * U-Boot stub.
+ */
+struct vm_fault {
+	struct vm_area_struct *vma;
+	unsigned long address;
+	unsigned int flags;
+	pgoff_t pgoff;
+	struct folio *folio;
+	struct page *page;
+};
+
+/**
+ * struct vm_operations_struct - virtual memory area operations
+ *
+ * Callbacks for VM operations. U-Boot stub.
+ */
+struct vm_operations_struct {
+	vm_fault_t (*fault)(struct vm_fault *vmf);
+	vm_fault_t (*huge_fault)(struct vm_fault *vmf, unsigned int order);
+	vm_fault_t (*page_mkwrite)(struct vm_fault *vmf);
+	vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf);
+	vm_fault_t (*map_pages)(struct vm_fault *vmf, pgoff_t start,
+				pgoff_t end);
+};
+
+/**
+ * struct vm_area_desc - for mmap_prepare
+ * @file: associated file
+ * @vm_flags: VM flags
+ * @vm_ops: VM operations
+ *
+ * U-Boot stub.
+ */
+struct vm_area_desc {
+	struct file *file;
+	unsigned long vm_flags;
+	const struct vm_operations_struct *vm_ops;
+};
+
+#endif /* _LINUX_MM_TYPES_H */