mtd: edit comments on deprecation of ioctl ECCGETLAYOUT

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=0ceacf36e9c41859a6072342d27cf6e60776c523
Commit:     0ceacf36e9c41859a6072342d27cf6e60776c523
Parent:     cc26c3cd3d1cf40a07f2b19ac4c53d517bee52a5
Author:     Brian Norris <computersforpeace at gmail.com>
AuthorDate: Sun Sep 19 23:57:12 2010 -0700
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Sun Oct 24 23:37:27 2010 +0100

    mtd: edit comments on deprecation of ioctl ECCGETLAYOUT
    
    There were some improvements and additions necessary in the
    comments explaining of the expansion of nand_ecclayout, the
    introduction of nand_ecclayout_user, and the deprecation of the
    ioctl ECCGETLAYOUT.
    
    Also, I found a better placement for the macro MTD_MAX_ECCPOS_ENTRIES;
    next to the definition of MTD_MAX_OOBFREE_ENTRIES in mtd-abi.h. The macro
    is really only important for the ioctl code (found in drivers/mtd/mtdchar.c)
    but since there are small edits being made to the user-space header, I
    figured this is a better location.
    
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
    Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/mtdchar.c   |    2 +-
 include/linux/mtd/mtd.h |    8 ++++----
 include/mtd/mtd-abi.h   |   11 ++++++++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 24d35ba..1d981a5 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -495,7 +495,7 @@ static int shrink_ecclayout(const struct nand_ecclayout *from,
 
 	memset(to, 0, sizeof(*to));
 
-	to->eccbytes = min((int)from->eccbytes, MTD_MAX_ECCPOS_ENTRIES_OLD);
+	to->eccbytes = min((int)from->eccbytes, MTD_MAX_ECCPOS_ENTRIES);
 	for (i = 0; i < to->eccbytes; i++)
 		to->eccpos[i] = from->eccpos[i];
 
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 03a1e95..fe8d77e 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -112,11 +112,11 @@ struct mtd_oob_ops {
 
 #define MTD_MAX_OOBFREE_ENTRIES_LARGE	32
 #define MTD_MAX_ECCPOS_ENTRIES_LARGE	448
-#define MTD_MAX_ECCPOS_ENTRIES_OLD	64	/* Previous maximum */
 /*
- * Correct ECC layout control structure. This replaces old nand_ecclayout
- * (mtd-abi.h) that is exported via ECCGETLAYOUT ioctl. It should be expandable
- *  in the future simply by the above macros.
+ * Internal ECC layout control structure. For historical reasons, there is a
+ * similar, smaller struct nand_ecclayout_user (in mtd-abi.h) that is retained
+ * for export to user-space via the ECCGETLAYOUT ioctl.
+ * nand_ecclayout should be expandable in the future simply by the above macros.
  */
 struct nand_ecclayout {
 	__u32 eccbytes;
diff --git a/include/mtd/mtd-abi.h b/include/mtd/mtd-abi.h
index 5bce083..a57c4cb 100644
--- a/include/mtd/mtd-abi.h
+++ b/include/mtd/mtd-abi.h
@@ -144,13 +144,18 @@ struct nand_oobfree {
 };
 
 #define MTD_MAX_OOBFREE_ENTRIES	8
+#define MTD_MAX_ECCPOS_ENTRIES	64
 /*
- * ECC layout control structure. Exported to userspace for
- * diagnosis and to allow creation of raw images
+ * OBSOLETE: ECC layout control structure. Exported to user-space via ioctl
+ * ECCGETLAYOUT for backwards compatbility and should not be mistaken as a
+ * complete set of ECC information. The ioctl truncates the larger internal
+ * structure to retain binary compatibility with the static declaration of the
+ * ioctl. Note that the "MTD_MAX_..._ENTRIES" macros represent the max size of
+ * the user struct, not the MAX size of the internal struct nand_ecclayout.
  */
 struct nand_ecclayout_user {
 	__u32 eccbytes;
-	__u32 eccpos[64];
+	__u32 eccpos[MTD_MAX_ECCPOS_ENTRIES];
 	__u32 oobavail;
 	struct nand_oobfree oobfree[MTD_MAX_OOBFREE_ENTRIES];
 };