[MTD] Rework the out of band handling completely

Hopefully the last iteration on this!

The handling of out of band data on NAND was accompanied by tons of fruitless
discussions and halfarsed patches to make it work for a particular
problem. Sufficiently annoyed by I all those "I know it better" mails and the
resonable amount of discarded "it solves my problem" patches, I finally decided
to go for the big rework. After removing the _ecc variants of mtd read/write
functions the solution to satisfy the various requirements was to refactor the
read/write _oob functions in mtd.

The major change is that read/write_oob now takes a pointer to an operation
descriptor structure "struct mtd_oob_ops".instead of having a function with at
least seven arguments.

read/write_oob which should probably renamed to a more descriptive name, can do
the following tasks:

- read/write out of band data
- read/write data content and out of band data
- read/write raw data content and out of band data (ecc disabled)

struct mtd_oob_ops has a mode field, which determines the oob handling mode.

Aside of the MTD_OOB_RAW mode, which is intended to be especially for
diagnostic purposes and some internal functions e.g. bad block table creation,
the other two modes are for mtd clients:

MTD_OOB_PLACE puts/gets the given oob data exactly to/from the place which is
described by the ooboffs and ooblen fields of the mtd_oob_ops strcuture. It's
up to the caller to make sure that the byte positions are not used by the ECC
placement algorithms.

MTD_OOB_AUTO puts/gets the given oob data automaticaly to/from the places in
the out of band area which are described by the oobfree tuples in the ecclayout
data structre which is associated to the devicee.

The decision whether data plus oob or oob only handling is done depends on the
setting of the datbuf member of the data structure. When datbuf == NULL then
the internal read/write_oob functions are selected, otherwise the read/write
data routines are invoked.

Tested on a few platforms with all variants. Please be aware of possible
regressions for your particular device / application scenario

Disclaimer: Any whining will be ignored from those who just contributed "hot
air blurb" and never sat down to tackle the underlying problem of the mess in
the NAND driver grown over time and the big chunk of work to fix up the
existing users. The problem was not the holiness of the existing MTD
interfaces. The problems was the lack of time to go for the big overhaul. It's
easy to add more mess to the existing one, but it takes alot of effort to go
for a real solution.

Improvements and bugfixes are welcome!

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 48 insertions, 2 deletions

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 4970c2e96fbf..e75bb584e80b 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -67,6 +67,50 @@ struct mtd_ecc_stats {
 	unsigned long failed;
 };
 
+/*
+ * oob operation modes
+ *
+ * MTD_OOB_PLACE:	oob data are placed at the given offset
+ * MTD_OOB_AUTO:	oob data are automatically placed at the free areas
+ *			which are defined by the ecclayout
+ * MTD_OOB_RAW:		mode to read raw data+oob in one chunk. The oob data
+ *			is inserted into the data. Thats a raw image of the
+ *			flash contents.
+ */
+typedef enum {
+	MTD_OOB_PLACE,
+	MTD_OOB_AUTO,
+	MTD_OOB_RAW,
+} mtd_oob_mode_t;
+
+/**
+ * struct mtd_oob_ops - oob operation operands
+ * @mode:	operation mode
+ *
+ * @len:	number of bytes to write/read. When a data buffer is given
+ *		(datbuf != NULL) this is the number of data bytes. When
+ +		no data buffer is available this is the number of oob bytes.
+ *
+ * @retlen:	number of bytes written/read. When a data buffer is given
+ *		(datbuf != NULL) this is the number of data bytes. When
+ +		no data buffer is available this is the number of oob bytes.
+ *
+ * @ooblen:	number of oob bytes per page
+ * @ooboffs:	offset of oob data in the oob area (only relevant when
+ *		mode = MTD_OOB_PLACE)
+ * @datbuf:	data buffer - if NULL only oob data are read/written
+ * @oobbuf:	oob data buffer
+ */
+struct mtd_oob_ops {
+	mtd_oob_mode_t	mode;
+	size_t		len;
+	size_t		retlen;
+	size_t		ooblen;
+	uint32_t	ooboffs;
+	uint8_t		*datbuf;
+	uint8_t		*oobbuf;
+};
+
 struct mtd_info {
 	u_char type;
 	u_int32_t flags;
@@ -125,8 +169,10 @@ struct mtd_info {
 	int (*read) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
 	int (*write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf);
 
-	int (*read_oob) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
-	int (*write_oob) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf);
+	int (*read_oob) (struct mtd_info *mtd, loff_t from,
+			 struct mtd_oob_ops *ops);
+	int (*write_oob) (struct mtd_info *mtd, loff_t to,
+			 struct mtd_oob_ops *ops);
 
 	/*
 	 * Methods to access the protection register area, present in some