mtd: nand: expand nand_ecc_layout, deprecate ioctl ECCGETLAYOUT

struct nand_ecclayout is too small for many new chips; OOB regions can be as
large as 448 bytes and may increase more in the future. Thus, copying that
struct to user-space with the ECCGETLAYOUT ioctl is not a good idea; the ioctl
would have to be updated every time there's a change to the current largest
size.

Instead, the old nand_ecclayout is renamed to nand_ecclayout_user and a
new struct nand_ecclayout is created that can accomodate larger sizes and
expand without affecting the user-space. struct nand_ecclayout can still
be used in board drivers without modification -- at least for now.

A new function is provided to convert from the new to the old in order to
allow the deprecated ioctl to continue to work with truncated data. Perhaps
the ioctl, the conversion process, and the struct nand_ecclayout_user can be
removed altogether in the future.

Note: There are comments in nand/davinci_nand.c::nand_davinci_probe()
regarding this issue; this driver (and maybe others) can be updated to
account for extra space. All kernel drivers can use the expanded
nand_ecclayout as a drop-in replacement and ignore its benefits.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index a825002123c84bc0a24ce26e00400be277b09c22..24d35ba62b84166fd964673f713b1a1852212abf 100644 (file)
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -477,6 +477,39 @@ static int mtd_do_readoob(struct mtd_info *mtd, uint64_t start,
        return ret;
 }
 
+/*
+ * Copies (and truncates, if necessary) data from the larger struct,
+ * nand_ecclayout, to the smaller, deprecated layout struct,
+ * nand_ecclayout_user. This is necessary only to suppport the deprecated
+ * API ioctl ECCGETLAYOUT while allowing all new functionality to use
+ * nand_ecclayout flexibly (i.e. the struct may change size in new
+ * releases without requiring major rewrites).
+ */
+static int shrink_ecclayout(const struct nand_ecclayout *from,
+               struct nand_ecclayout_user *to)
+{
+       int i;
+
+       if (!from || !to)
+               return -EINVAL;
+
+       memset(to, 0, sizeof(*to));
+
+       to->eccbytes = min((int)from->eccbytes, MTD_MAX_ECCPOS_ENTRIES_OLD);
+       for (i = 0; i < to->eccbytes; i++)
+               to->eccpos[i] = from->eccpos[i];
+
+       for (i = 0; i < MTD_MAX_OOBFREE_ENTRIES; i++) {
+               if (from->oobfree[i].length == 0 &&
+                               from->oobfree[i].offset == 0)
+                       break;
+               to->oobavail += from->oobfree[i].length;
+               to->oobfree[i] = from->oobfree[i];
+       }
+
+       return 0;
+}
+
 static int mtd_ioctl(struct file *file, u_int cmd, u_long arg)
 {
        struct mtd_file_info *mfi = file->private_data;
@@ -812,14 +845,23 @@ static int mtd_ioctl(struct file *file, u_int cmd, u_long arg)
        }
 #endif
 
+       /* This ioctl is being deprecated - it truncates the ecc layout */
        case ECCGETLAYOUT:
        {
+               struct nand_ecclayout_user *usrlay;
+
                if (!mtd->ecclayout)
                        return -EOPNOTSUPP;
 
-               if (copy_to_user(argp, mtd->ecclayout,
-                                sizeof(struct nand_ecclayout)))
-                       return -EFAULT;
+               usrlay = kmalloc(sizeof(*usrlay), GFP_KERNEL);
+               if (!usrlay)
+                       return -ENOMEM;
+
+               shrink_ecclayout(mtd->ecclayout, usrlay);
+
+               if (copy_to_user(argp, usrlay, sizeof(*usrlay)))
+                       ret = -EFAULT;
+               kfree(usrlay);
                break;
        }
 

diff --git a/drivers/mtd/nand/davinci_nand.c b/drivers/mtd/nand/davinci_nand.c
index 2ac7367afe77c26c2a209469218c928db3f6140c..70698e86e4371f41edbaa6c3ba4345289b835bd2 100644 (file)
--- a/drivers/mtd/nand/davinci_nand.c
+++ b/drivers/mtd/nand/davinci_nand.c
@@ -749,6 +749,9 @@ static int __init nand_davinci_probe(struct platform_device *pdev)
                 * breaks userspace ioctl interface with mtd-utils. Once we
                 * resolve this issue, NAND_ECC_HW_OOB_FIRST mode can be used
                 * for the 4KiB page chips.
+                *
+                * TODO: Note that nand_ecclayout has now been expanded and can
+                *  hold plenty of OOB entries.
                 */
                dev_warn(&pdev->dev, "no 4-bit ECC support yet "
                                "for 4KiB-page NAND\n");

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 8485e42a9b092327e797383d7de8848dfb4d36cb..03a1e954c586ca3233ce78bfc2e1b6216539e5de 100644 (file)
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -110,6 +110,21 @@ struct mtd_oob_ops {
        uint8_t         *oobbuf;
 };
 
+#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.
+ */
+struct nand_ecclayout {
+       __u32 eccbytes;
+       __u32 eccpos[MTD_MAX_ECCPOS_ENTRIES_LARGE];
+       __u32 oobavail;
+       struct nand_oobfree oobfree[MTD_MAX_OOBFREE_ENTRIES_LARGE];
+};
+
 struct mtd_info {
        u_char type;
        uint32_t flags;

diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index 274b6196091df019e9e2fb65214a8fdbeafeca15..930c8ac198dbca6c1dc62fadbba8cb8c2bdec6d0 100644 (file)
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -39,7 +39,7 @@ struct mtd_partition {
        uint64_t size;                  /* partition size */
        uint64_t offset;                /* offset within the master MTD space */
        uint32_t mask_flags;            /* master MTD flags to mask out for this partition */
-       struct nand_ecclayout *ecclayout;       /* out of band layout for this partition (NAND only)*/
+       struct nand_ecclayout *ecclayout;       /* out of band layout for this partition (NAND only) */
 };
 
 #define MTDPART_OFS_NXTBLK     (-2)

diff --git a/include/mtd/mtd-abi.h b/include/mtd/mtd-abi.h
index 4debb451463474a30da023f25161b4077e58f6c0..5bce08384345083c110f1c7da60174b512794f44 100644 (file)
--- a/include/mtd/mtd-abi.h
+++ b/include/mtd/mtd-abi.h
@@ -119,7 +119,7 @@ struct otp_info {
 #define OTPGETREGIONCOUNT      _IOW('M', 14, int)
 #define OTPGETREGIONINFO       _IOW('M', 15, struct otp_info)
 #define OTPLOCK                        _IOR('M', 16, struct otp_info)
-#define ECCGETLAYOUT           _IOR('M', 17, struct nand_ecclayout)
+#define ECCGETLAYOUT           _IOR('M', 17, struct nand_ecclayout_user)
 #define ECCGETSTATS            _IOR('M', 18, struct mtd_ecc_stats)
 #define MTDFILEMODE            _IO('M', 19)
 #define MEMERASE64             _IOW('M', 20, struct erase_info_user64)
@@ -148,7 +148,7 @@ struct nand_oobfree {
  * ECC layout control structure. Exported to userspace for
  * diagnosis and to allow creation of raw images
  */
-struct nand_ecclayout {
+struct nand_ecclayout_user {
        __u32 eccbytes;
        __u32 eccpos[64];
        __u32 oobavail;

diff --git a/include/mtd/mtd-user.h b/include/mtd/mtd-user.h
index aa3c2f86a91335e2e755d54399c852d954771141..83327c808c861938dfa36f6b7d7762656b811309 100644 (file)
--- a/include/mtd/mtd-user.h
+++ b/include/mtd/mtd-user.h
@@ -29,6 +29,6 @@ typedef struct mtd_info_user mtd_info_t;
 typedef struct erase_info_user erase_info_t;
 typedef struct region_info_user region_info_t;
 typedef struct nand_oobinfo nand_oobinfo_t;
-typedef struct nand_ecclayout nand_ecclayout_t;
+typedef struct nand_ecclayout_user nand_ecclayout_t;
 
 #endif /* __MTD_USER_H__ */