1 files changed, 56 insertions, 8 deletions
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 59ce712f082d..1cefcf87a694 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -50,17 +50,65 @@ extern asmlinkage int swsusp_arch_resume(void);
 extern unsigned int count_data_pages(void);
+/**
+ *      Auxiliary structure used for reading the snapshot image data and
+ *      metadata from and writing them to the list of page backup entries
+ *      (PBEs) which is the main data structure of swsusp.
+ *
+ *      Using struct snapshot_handle we can transfer the image, including its
+ *      metadata, as a continuous sequence of bytes with the help of
+ *      snapshot_read_next() and snapshot_write_next().
+ *
+ *      The code that writes the image to a storage or transfers it to
+ *      the user land is required to use snapshot_read_next() for this
+ *      purpose and it should not make any assumptions regarding the internal
+ *      structure of the image.  Similarly, the code that reads the image from
+ *      a storage or transfers it from the user land is required to use
+ *      snapshot_write_next().
+ *
+ *      This may allow us to change the internal structure of the image
+ *      in the future with considerably less effort.
+ */
 struct snapshot_handle {
-        loff_t          offset;
+        loff_t          offset; /* number of the last byte ready for reading
-        unsigned int    page;
+                                 * or writing in the sequence
-        unsigned int    page_offset;
+                                 */
-        unsigned int    prev;
+        unsigned int    cur;    /* number of the block of PAGE_SIZE bytes the
-        struct pbe      *pbe, *last_pbe;
+                                 * next operation will refer to (ie. current)
-        void            *buffer;
+                                 */
-        unsigned int    buf_offset;
+        unsigned int    cur_offset;     /* offset with respect to the current
-        int             sync_read;
+                                         * block (for the next operation)
+                                         */
+        unsigned int    prev;   /* number of the block of PAGE_SIZE bytes that
+                                 * was the current one previously
+                                 */
+        struct pbe      *pbe;   /* PBE that corresponds to 'buffer' */
+        struct pbe      *last_pbe;      /* When the image is restored (eg. read
+                                         * from disk) we can store some image
+                                         * data directly in the page frames
+                                         * in which they were before suspend.
+                                         * In such a case the PBEs that
+                                         * correspond to them will be unused.
+                                         * This is the last PBE, so far, that
+                                         * does not correspond to such data.
+                                         */
+        void            *buffer;        /* address of the block to read from
+                                         * or write to
+                                         */
+        unsigned int    buf_offset;     /* location to read from or write to,
+                                         * given as a displacement from 'buffer'
+                                         */
+        int             sync_read;      /* Set to one to notify the caller of
+                                         * snapshot_write_next() that it may
+                                         * need to call wait_on_bio_chain()
+                                         */
 };
+/* This macro returns the address from/to which the caller of
+ * snapshot_read_next()/snapshot_write_next() is allowed to
+ * read/write data after the function returns
+ */
 #define data_of(handle) ((handle).buffer + (handle).buf_offset)
 extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);

diff --git a/kernel/power/power.h b/kernel/power/power.h index 59ce712f082d..1cefcf87a694 100644 --- a/kernel/power/power.h +++ b/kernel/power/power.h
@@ -50,17 +50,65 @@ extern asmlinkage int swsusp_arch_resume(void);
50		50
51	extern unsigned int count_data_pages(void);	51	extern unsigned int count_data_pages(void);
52		52
		53	/**
		54	* Auxiliary structure used for reading the snapshot image data and
		55	* metadata from and writing them to the list of page backup entries
		56	* (PBEs) which is the main data structure of swsusp.
		57	*
		58	* Using struct snapshot_handle we can transfer the image, including its
		59	* metadata, as a continuous sequence of bytes with the help of
		60	* snapshot_read_next() and snapshot_write_next().
		61	*
		62	* The code that writes the image to a storage or transfers it to
		63	* the user land is required to use snapshot_read_next() for this
		64	* purpose and it should not make any assumptions regarding the internal
		65	* structure of the image. Similarly, the code that reads the image from
		66	* a storage or transfers it from the user land is required to use
		67	* snapshot_write_next().
		68	*
		69	* This may allow us to change the internal structure of the image
		70	* in the future with considerably less effort.
		71	*/
		72
53	struct snapshot_handle {	73	struct snapshot_handle {
54	loff_t offset;	74	loff_t offset; /* number of the last byte ready for reading
55	unsigned int page;	75	* or writing in the sequence
56	unsigned int page_offset;	76	*/
57	unsigned int prev;	77	unsigned int cur; /* number of the block of PAGE_SIZE bytes the
58	struct pbe pbe, last_pbe;	78	* next operation will refer to (ie. current)
59	void *buffer;	79	*/
60	unsigned int buf_offset;	80	unsigned int cur_offset; /* offset with respect to the current
61	int sync_read;	81	* block (for the next operation)
		82	*/
		83	unsigned int prev; /* number of the block of PAGE_SIZE bytes that
		84	* was the current one previously
		85	*/
		86	struct pbe pbe; / PBE that corresponds to 'buffer' */
		87	struct pbe last_pbe; / When the image is restored (eg. read
		88	* from disk) we can store some image
		89	* data directly in the page frames
		90	* in which they were before suspend.
		91	* In such a case the PBEs that
		92	* correspond to them will be unused.
		93	* This is the last PBE, so far, that
		94	* does not correspond to such data.
		95	*/
		96	void buffer; / address of the block to read from
		97	* or write to
		98	*/
		99	unsigned int buf_offset; /* location to read from or write to,
		100	* given as a displacement from 'buffer'
		101	*/
		102	int sync_read; /* Set to one to notify the caller of
		103	* snapshot_write_next() that it may
		104	* need to call wait_on_bio_chain()
		105	*/
62	};	106	};
63		107
		108	/* This macro returns the address from/to which the caller of
		109	* snapshot_read_next()/snapshot_write_next() is allowed to
		110	* read/write data after the function returns
		111	*/
64	#define data_of(handle) ((handle).buffer + (handle).buf_offset)	112	#define data_of(handle) ((handle).buffer + (handle).buf_offset)
65		113
66	extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);	114	extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);