[PATCH v4 0/4] mtdchar: add MEMREAD ioctl

[PATCH v4 0/4] mtdchar: add MEMREAD ioctl

[Michał Kępień]

This patch series adds a new mtdchar ioctl, MEMREAD.  Its purpose is to
serve as a read counterpart of the MEMWRITE ioctl, exposing a broader
set of capabilities for read operations (e.g. use of MTD_OPS_AUTO_OOB,
access to ECC statistics) to user-space applications making use of MTD
devices via /dev/mtd* character devices.

Changes from v3:

  - Fixed two issues found by Richard Weinberger [1]:

      - prevent integer overflow,
      - use kvmalloc() for potentially large allocations.

    (Identical fixes have already been applied to mtdchar_write_ioctl(),
    i.e. the write counterpart of the ioctl proposed in this patch
    series, in mtd/next. [2] [3])

Changes from v2:

  - Squashed patch 1/5 into patch 5/5 to prevent breaking bisectability
    due to an incompatible ABI change between those two patches.
    Revised commit messages accordingly.

Changes from v1:

  - Added patches 2-5 which enable the new MEMREAD ioctl to report ECC
    statistics for the read operation back to user space.  (There are
    obviously different ways these changes can be split up into separate
    commits; I was aiming for maximum ease of review.)

  - The 'retlen' and 'oobretlen' fields were not set in the struct
    mtd_read_req returned to userspace.  This was done properly in
    Boris' original draft patch [1], but I missed it in my v1.

  - Invalid IS_ERR() checks were replaced with NULL checks.  This was an
    artifact of copy-pasting mtdchar_write_ioctl() in v1: unlike
    memdup_user() used therein, kmalloc() always returns NULL on error.

  - Minor subject prefix adjustment for patch 1/5 ("mtd" -> "mtdchar").

[1] http://lists.infradead.org/pipermail/linux-mtd/2022-February/091276.html
[2] http://lists.infradead.org/pipermail/linux-mtd/2022-June/093829.html
[3] http://lists.infradead.org/pipermail/linux-mtd/2022-June/093828.html

Michał Kępień (4):
  mtd: track maximum number of bitflips for each read request
  mtd: always initialize 'stats' in struct mtd_oob_ops
  mtd: add ECC error accounting for each read request
  mtdchar: add MEMREAD ioctl

 drivers/mtd/devices/docg3.c             |   8 ++
 drivers/mtd/inftlcore.c                 |   6 +-
 drivers/mtd/mtdchar.c                   | 139 ++++++++++++++++++++++++
 drivers/mtd/mtdcore.c                   |   5 +
 drivers/mtd/mtdswap.c                   |   6 +-
 drivers/mtd/nand/onenand/onenand_base.c |  16 ++-
 drivers/mtd/nand/onenand/onenand_bbt.c  |   2 +-
 drivers/mtd/nand/raw/nand_base.c        |  10 ++
 drivers/mtd/nand/raw/nand_bbt.c         |   8 +-
 drivers/mtd/nand/raw/sm_common.c        |   2 +-
 drivers/mtd/nand/spi/core.c             |  10 ++
 drivers/mtd/nftlcore.c                  |   6 +-
 drivers/mtd/sm_ftl.c                    |   4 +-
 drivers/mtd/ssfdc.c                     |   2 +-
 drivers/mtd/tests/nandbiterrs.c         |   2 +-
 drivers/mtd/tests/oobtest.c             |   8 +-
 drivers/mtd/tests/readtest.c            |   2 +-
 fs/jffs2/wbuf.c                         |   6 +-
 include/linux/mtd/mtd.h                 |   7 ++
 include/uapi/mtd/mtd-abi.h              |  64 ++++++++++-
 20 files changed, 279 insertions(+), 34 deletions(-)

-- 
2.37.0



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[PATCH v4 1/4] mtd: track maximum number of bitflips for each read request

[Michał Kępień]

mtd_read_oob() callers are currently oblivious to the details of ECC
errors detected during the read operation - they only learn (through the
return value) whether any corrected bitflips or uncorrectable errors
occurred.  More detailed ECC information can be useful to user-space
applications for making better-informed choices about moving data
around.

Extend struct mtd_oob_ops with a pointer to a newly-introduced struct
mtd_req_stats and set its 'max_bitflips' field to the maximum number of
bitflips found in a single ECC step during the read operation performed
by mtd_read_oob().  This is a prerequisite for ultimately passing that
value back to user space.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
 drivers/mtd/mtdcore.c   | 5 +++++
 include/linux/mtd/mtd.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 6fafea80fd98..80c98e546d72 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1622,6 +1622,9 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 	if (!master->_read_oob && (!master->_read || ops->oobbuf))
 		return -EOPNOTSUPP;
 
+	if (ops->stats)
+		memset(ops->stats, 0, sizeof(*ops->stats));
+
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ret_code = mtd_io_emulated_slc(mtd, from, true, ops);
 	else
@@ -1639,6 +1642,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 		return ret_code;
 	if (mtd->ecc_strength == 0)
 		return 0;	/* device lacks ecc */
+	if (ops->stats)
+		ops->stats->max_bitflips = ret_code;
 	return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
 }
 EXPORT_SYMBOL_GPL(mtd_read_oob);
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 955aee14b0f7..fccad1766458 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -40,6 +40,10 @@ struct mtd_erase_region_info {
 	unsigned long *lockmap;		/* If keeping bitmap of locks */
 };
 
+struct mtd_req_stats {
+	unsigned int max_bitflips;
+};
+
 /**
  * struct mtd_oob_ops - oob operation operands
  * @mode:	operation mode
@@ -70,6 +74,7 @@ struct mtd_oob_ops {
 	uint32_t	ooboffs;
 	uint8_t		*datbuf;
 	uint8_t		*oobbuf;
+	struct mtd_req_stats *stats;
 };
 
 /**
-- 
2.37.0



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http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 2/4] mtd: always initialize 'stats' in struct mtd_oob_ops

[Michał Kępień]

As the 'stats' field in struct mtd_oob_ops is used in conditional
expressions, ensure it is always zero-initialized in all such structures
to prevent random stack garbage from being interpreted as a pointer.

Strictly speaking, this problem currently only needs to be fixed for
struct mtd_oob_ops structures subsequently passed to mtd_read_oob().
However, this commit goes a step further and makes all instances of
struct mtd_oob_ops in the tree zero-initialized, in hope of preventing
future problems, e.g. if struct mtd_req_stats gets extended with write
statistics at some point.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
Obviously this objective can be achieved in various ways.  I was aiming
for a minimal diff which does the job.

 drivers/mtd/inftlcore.c                 | 6 +++---
 drivers/mtd/mtdswap.c                   | 6 +++---
 drivers/mtd/nand/onenand/onenand_base.c | 4 ++--
 drivers/mtd/nand/onenand/onenand_bbt.c  | 2 +-
 drivers/mtd/nand/raw/nand_bbt.c         | 8 ++++----
 drivers/mtd/nand/raw/sm_common.c        | 2 +-
 drivers/mtd/nftlcore.c                  | 6 +++---
 drivers/mtd/sm_ftl.c                    | 4 ++--
 drivers/mtd/ssfdc.c                     | 2 +-
 drivers/mtd/tests/nandbiterrs.c         | 2 +-
 drivers/mtd/tests/oobtest.c             | 8 ++++----
 drivers/mtd/tests/readtest.c            | 2 +-
 fs/jffs2/wbuf.c                         | 6 +++---
 13 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/drivers/mtd/inftlcore.c b/drivers/mtd/inftlcore.c
index 6b48397c750c..58ca1c21ebe6 100644
--- a/drivers/mtd/inftlcore.c
+++ b/drivers/mtd/inftlcore.c
@@ -136,7 +136,7 @@ static void inftl_remove_dev(struct mtd_blktrans_dev *dev)
 int inftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 		   size_t *retlen, uint8_t *buf)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
@@ -156,7 +156,7 @@ int inftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 int inftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 		    size_t *retlen, uint8_t *buf)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
@@ -176,7 +176,7 @@ int inftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 static int inftl_write(struct mtd_info *mtd, loff_t offs, size_t len,
 		       size_t *retlen, uint8_t *buf, uint8_t *oob)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
diff --git a/drivers/mtd/mtdswap.c b/drivers/mtd/mtdswap.c
index dc7f1532a37f..680366616da2 100644
--- a/drivers/mtd/mtdswap.c
+++ b/drivers/mtd/mtdswap.c
@@ -323,7 +323,7 @@ static int mtdswap_read_markers(struct mtdswap_dev *d, struct swap_eb *eb)
 	struct mtdswap_oobdata *data, *data2;
 	int ret;
 	loff_t offset;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	offset = mtdswap_eb_offset(d, eb);
 
@@ -370,7 +370,7 @@ static int mtdswap_write_marker(struct mtdswap_dev *d, struct swap_eb *eb,
 	struct mtdswap_oobdata n;
 	int ret;
 	loff_t offset;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	ops.ooboffs = 0;
 	ops.oobbuf = (uint8_t *)&n;
@@ -878,7 +878,7 @@ static unsigned int mtdswap_eblk_passes(struct mtdswap_dev *d,
 	loff_t base, pos;
 	unsigned int *p1 = (unsigned int *)d->page_buf;
 	unsigned char *p2 = (unsigned char *)d->oob_buf;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int ret;
 
 	ops.mode = MTD_OPS_AUTO_OOB;
diff --git a/drivers/mtd/nand/onenand/onenand_base.c b/drivers/mtd/nand/onenand/onenand_base.c
index 958bac54b190..5810104420a2 100644
--- a/drivers/mtd/nand/onenand/onenand_base.c
+++ b/drivers/mtd/nand/onenand/onenand_base.c
@@ -2935,7 +2935,7 @@ static int do_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
 	struct onenand_chip *this = mtd->priv;
 	unsigned char *pbuf = buf;
 	int ret;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	/* Force buffer page aligned */
 	if (len < mtd->writesize) {
@@ -2977,7 +2977,7 @@ static int do_otp_lock(struct mtd_info *mtd, loff_t from, size_t len,
 		size_t *retlen, u_char *buf)
 {
 	struct onenand_chip *this = mtd->priv;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int ret;
 
 	if (FLEXONENAND(this)) {
diff --git a/drivers/mtd/nand/onenand/onenand_bbt.c b/drivers/mtd/nand/onenand/onenand_bbt.c
index b17315f8e1d4..d7fe35bc45cb 100644
--- a/drivers/mtd/nand/onenand/onenand_bbt.c
+++ b/drivers/mtd/nand/onenand/onenand_bbt.c
@@ -61,7 +61,7 @@ static int create_bbt(struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr
 	int startblock;
 	loff_t from;
 	size_t readlen;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int rgn;
 
 	printk(KERN_INFO "Scanning device for bad blocks\n");
diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
index a3723da2e0a0..e4664fa6fd9e 100644
--- a/drivers/mtd/nand/raw/nand_bbt.c
+++ b/drivers/mtd/nand/raw/nand_bbt.c
@@ -313,7 +313,7 @@ static int scan_read_oob(struct nand_chip *this, uint8_t *buf, loff_t offs,
 			 size_t len)
 {
 	struct mtd_info *mtd = nand_to_mtd(this);
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res, ret = 0;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
@@ -354,7 +354,7 @@ static int scan_write_bbt(struct nand_chip *this, loff_t offs, size_t len,
 			  uint8_t *buf, uint8_t *oob)
 {
 	struct mtd_info *mtd = nand_to_mtd(this);
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	ops.mode = MTD_OPS_PLACE_OOB;
 	ops.ooboffs = 0;
@@ -416,7 +416,7 @@ static int scan_block_fast(struct nand_chip *this, struct nand_bbt_descr *bd,
 {
 	struct mtd_info *mtd = nand_to_mtd(this);
 
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int ret, page_offset;
 
 	ops.ooblen = mtd->oobsize;
@@ -756,7 +756,7 @@ static int write_bbt(struct nand_chip *this, uint8_t *buf,
 	uint8_t rcode = td->reserved_block_code;
 	size_t retlen, len = 0;
 	loff_t to;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	ops.ooblen = mtd->oobsize;
 	ops.ooboffs = 0;
diff --git a/drivers/mtd/nand/raw/sm_common.c b/drivers/mtd/nand/raw/sm_common.c
index ba24cb36d0b9..6df33e8d77df 100644
--- a/drivers/mtd/nand/raw/sm_common.c
+++ b/drivers/mtd/nand/raw/sm_common.c
@@ -99,7 +99,7 @@ static const struct mtd_ooblayout_ops oob_sm_small_ops = {
 static int sm_block_markbad(struct nand_chip *chip, loff_t ofs)
 {
 	struct mtd_info *mtd = nand_to_mtd(chip);
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	struct sm_oob oob;
 	int ret;
 
diff --git a/drivers/mtd/nftlcore.c b/drivers/mtd/nftlcore.c
index 913db0dd6a8d..64d319e959b2 100644
--- a/drivers/mtd/nftlcore.c
+++ b/drivers/mtd/nftlcore.c
@@ -124,7 +124,7 @@ int nftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 		  size_t *retlen, uint8_t *buf)
 {
 	loff_t mask = mtd->writesize - 1;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
@@ -145,7 +145,7 @@ int nftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
 		   size_t *retlen, uint8_t *buf)
 {
 	loff_t mask = mtd->writesize - 1;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
@@ -168,7 +168,7 @@ static int nftl_write(struct mtd_info *mtd, loff_t offs, size_t len,
 		      size_t *retlen, uint8_t *buf, uint8_t *oob)
 {
 	loff_t mask = mtd->writesize - 1;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int res;
 
 	ops.mode = MTD_OPS_PLACE_OOB;
diff --git a/drivers/mtd/sm_ftl.c b/drivers/mtd/sm_ftl.c
index 7f955fade838..4cfec3b7b446 100644
--- a/drivers/mtd/sm_ftl.c
+++ b/drivers/mtd/sm_ftl.c
@@ -239,7 +239,7 @@ static int sm_read_sector(struct sm_ftl *ftl,
 			  uint8_t *buffer, struct sm_oob *oob)
 {
 	struct mtd_info *mtd = ftl->trans->mtd;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	struct sm_oob tmp_oob;
 	int ret = -EIO;
 	int try = 0;
@@ -323,7 +323,7 @@ static int sm_write_sector(struct sm_ftl *ftl,
 			   int zone, int block, int boffset,
 			   uint8_t *buffer, struct sm_oob *oob)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	struct mtd_info *mtd = ftl->trans->mtd;
 	int ret;
 
diff --git a/drivers/mtd/ssfdc.c b/drivers/mtd/ssfdc.c
index 1d05c121904c..04da685c36be 100644
--- a/drivers/mtd/ssfdc.c
+++ b/drivers/mtd/ssfdc.c
@@ -163,7 +163,7 @@ static int read_physical_sector(struct mtd_info *mtd, uint8_t *sect_buf,
 /* Read redundancy area (wrapper to MTD_READ_OOB */
 static int read_raw_oob(struct mtd_info *mtd, loff_t offs, uint8_t *buf)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int ret;
 
 	ops.mode = MTD_OPS_RAW;
diff --git a/drivers/mtd/tests/nandbiterrs.c b/drivers/mtd/tests/nandbiterrs.c
index 08084c018a59..98d7508f95b1 100644
--- a/drivers/mtd/tests/nandbiterrs.c
+++ b/drivers/mtd/tests/nandbiterrs.c
@@ -99,7 +99,7 @@ static int write_page(int log)
 static int rewrite_page(int log)
 {
 	int err = 0;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	if (log)
 		pr_info("rewrite page\n");
diff --git a/drivers/mtd/tests/oobtest.c b/drivers/mtd/tests/oobtest.c
index 532997e10e29..13fed398937e 100644
--- a/drivers/mtd/tests/oobtest.c
+++ b/drivers/mtd/tests/oobtest.c
@@ -56,7 +56,7 @@ static void do_vary_offset(void)
 static int write_eraseblock(int ebnum)
 {
 	int i;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int err = 0;
 	loff_t addr = (loff_t)ebnum * mtd->erasesize;
 
@@ -165,7 +165,7 @@ static size_t memffshow(loff_t addr, loff_t offset, const void *cs,
 static int verify_eraseblock(int ebnum)
 {
 	int i;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int err = 0;
 	loff_t addr = (loff_t)ebnum * mtd->erasesize;
 	size_t bitflips;
@@ -260,7 +260,7 @@ static int verify_eraseblock(int ebnum)
 
 static int verify_eraseblock_in_one_go(int ebnum)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int err = 0;
 	loff_t addr = (loff_t)ebnum * mtd->erasesize;
 	size_t len = mtd->oobavail * pgcnt;
@@ -338,7 +338,7 @@ static int __init mtd_oobtest_init(void)
 	int err = 0;
 	unsigned int i;
 	uint64_t tmp;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	loff_t addr = 0, addr0;
 
 	printk(KERN_INFO "\n");
diff --git a/drivers/mtd/tests/readtest.c b/drivers/mtd/tests/readtest.c
index e70d588083a3..99670ef91f2b 100644
--- a/drivers/mtd/tests/readtest.c
+++ b/drivers/mtd/tests/readtest.c
@@ -47,7 +47,7 @@ static int read_eraseblock_by_page(int ebnum)
 				err = ret;
 		}
 		if (mtd->oobsize) {
-			struct mtd_oob_ops ops;
+			struct mtd_oob_ops ops = { };
 
 			ops.mode      = MTD_OPS_PLACE_OOB;
 			ops.len       = 0;
diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
index c6821a509481..4061e0ba7010 100644
--- a/fs/jffs2/wbuf.c
+++ b/fs/jffs2/wbuf.c
@@ -1035,7 +1035,7 @@ int jffs2_check_oob_empty(struct jffs2_sb_info *c,
 {
 	int i, ret;
 	int cmlen = min_t(int, c->oobavail, OOB_CM_SIZE);
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 
 	ops.mode = MTD_OPS_AUTO_OOB;
 	ops.ooblen = NR_OOB_SCAN_PAGES * c->oobavail;
@@ -1076,7 +1076,7 @@ int jffs2_check_oob_empty(struct jffs2_sb_info *c,
 int jffs2_check_nand_cleanmarker(struct jffs2_sb_info *c,
 				 struct jffs2_eraseblock *jeb)
 {
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int ret, cmlen = min_t(int, c->oobavail, OOB_CM_SIZE);
 
 	ops.mode = MTD_OPS_AUTO_OOB;
@@ -1101,7 +1101,7 @@ int jffs2_write_nand_cleanmarker(struct jffs2_sb_info *c,
 				 struct jffs2_eraseblock *jeb)
 {
 	int ret;
-	struct mtd_oob_ops ops;
+	struct mtd_oob_ops ops = { };
 	int cmlen = min_t(int, c->oobavail, OOB_CM_SIZE);
 
 	ops.mode = MTD_OPS_AUTO_OOB;
-- 
2.37.0



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Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 3/4] mtd: add ECC error accounting for each read request

[Michał Kępień]

Extend struct mtd_req_stats with two new fields holding the number of
corrected bitflips and uncorrectable errors detected during a read
operation.  This is a prerequisite for ultimately passing those counters
to user space, where they can be useful to applications for making
better-informed choices about moving data around.

Unlike 'max_bitflips' (which is set - in a common code path - to the
return value of a function called while the MTD device's mutex is held),
these counters have to be maintained in each MTD driver which defines
the '_read_oob' callback because the statistics need to be calculated
while the MTD device's mutex is held.

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
 drivers/mtd/devices/docg3.c             |  8 ++++++++
 drivers/mtd/nand/onenand/onenand_base.c | 12 ++++++++++++
 drivers/mtd/nand/raw/nand_base.c        | 10 ++++++++++
 drivers/mtd/nand/spi/core.c             | 10 ++++++++++
 include/linux/mtd/mtd.h                 |  2 ++
 5 files changed, 42 insertions(+)

diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index 5b0ae5ddad74..3783ae5c6d23 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -871,6 +871,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 	u8 *buf = ops->datbuf;
 	size_t len, ooblen, nbdata, nboob;
 	u8 hwecc[DOC_ECC_BCH_SIZE], eccconf1;
+	struct mtd_ecc_stats old_stats;
 	int max_bitflips = 0;
 
 	if (buf)
@@ -895,6 +896,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 	ret = 0;
 	skip = from % DOC_LAYOUT_PAGE_SIZE;
 	mutex_lock(&docg3->cascade->lock);
+	old_stats = mtd->ecc_stats;
 	while (ret >= 0 && (len > 0 || ooblen > 0)) {
 		calc_block_sector(from - skip, &block0, &block1, &page, &ofs,
 			docg3->reliable);
@@ -966,6 +968,12 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 	}
 
 out:
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
 	mutex_unlock(&docg3->cascade->lock);
 	return ret;
 err_in_read:
diff --git a/drivers/mtd/nand/onenand/onenand_base.c b/drivers/mtd/nand/onenand/onenand_base.c
index 5810104420a2..f66385faf631 100644
--- a/drivers/mtd/nand/onenand/onenand_base.c
+++ b/drivers/mtd/nand/onenand/onenand_base.c
@@ -1440,6 +1440,7 @@ static int onenand_read_oob(struct mtd_info *mtd, loff_t from,
 			    struct mtd_oob_ops *ops)
 {
 	struct onenand_chip *this = mtd->priv;
+	struct mtd_ecc_stats old_stats;
 	int ret;
 
 	switch (ops->mode) {
@@ -1453,12 +1454,23 @@ static int onenand_read_oob(struct mtd_info *mtd, loff_t from,
 	}
 
 	onenand_get_device(mtd, FL_READING);
+
+	old_stats = mtd->ecc_stats;
+
 	if (ops->datbuf)
 		ret = ONENAND_IS_4KB_PAGE(this) ?
 			onenand_mlc_read_ops_nolock(mtd, from, ops) :
 			onenand_read_ops_nolock(mtd, from, ops);
 	else
 		ret = onenand_read_oob_nolock(mtd, from, ops);
+
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	onenand_release_device(mtd);
 
 	return ret;
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 6b67b7dfe7ce..3e20de1e145c 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -3818,6 +3818,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 			 struct mtd_oob_ops *ops)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct mtd_ecc_stats old_stats;
 	int ret;
 
 	ops->retlen = 0;
@@ -3829,11 +3830,20 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 
 	nand_get_device(chip);
 
+	old_stats = mtd->ecc_stats;
+
 	if (!ops->datbuf)
 		ret = nand_do_read_oob(chip, from, ops);
 	else
 		ret = nand_do_read_ops(chip, from, ops);
 
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	nand_release_device(chip);
 	return ret;
 }
diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index d5b685d1605e..90d8a88c9326 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -635,6 +635,7 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 {
 	struct spinand_device *spinand = mtd_to_spinand(mtd);
 	struct nand_device *nand = mtd_to_nanddev(mtd);
+	struct mtd_ecc_stats old_stats;
 	unsigned int max_bitflips = 0;
 	struct nand_io_iter iter;
 	bool disable_ecc = false;
@@ -646,6 +647,8 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 
 	mutex_lock(&spinand->lock);
 
+	old_stats = mtd->ecc_stats;
+
 	nanddev_io_for_each_page(nand, NAND_PAGE_READ, from, ops, &iter) {
 		if (disable_ecc)
 			iter.req.mode = MTD_OPS_RAW;
@@ -668,6 +671,13 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 		ops->oobretlen += iter.req.ooblen;
 	}
 
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	mutex_unlock(&spinand->lock);
 
 	if (ecc_failed && !ret)
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index fccad1766458..c12a5930f32c 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -41,6 +41,8 @@ struct mtd_erase_region_info {
 };
 
 struct mtd_req_stats {
+	unsigned int uncorrectable_errors;
+	unsigned int corrected_bitflips;
 	unsigned int max_bitflips;
 };
 
-- 
2.37.0



______________________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 4/4] mtdchar: add MEMREAD ioctl

[Michał Kępień]

User-space applications making use of MTD devices via /dev/mtd*
character devices currently have limited capabilities for reading data:

  - only deprecated methods of accessing OOB layout information exist,

  - there is no way to explicitly specify MTD operation mode to use; it
    is auto-selected based on the MTD file mode (MTD_FILE_MODE_*) set
    for the character device; in particular, this prevents using
    MTD_OPS_AUTO_OOB for reads,

  - all existing user-space interfaces which cause mtd_read() or
    mtd_read_oob() to be called (via mtdchar_read() and
    mtdchar_read_oob(), respectively) return success even when those
    functions return -EUCLEAN or -EBADMSG; this renders user-space
    applications using these interfaces unaware of any corrected
    bitflips or uncorrectable ECC errors detected during reads.

Note that the existing MEMWRITE ioctl allows the MTD operation mode to
be explicitly set, allowing user-space applications to write page data
and OOB data without requiring them to know anything about the OOB
layout of the MTD device they are writing to (MTD_OPS_AUTO_OOB).  Also,
the MEMWRITE ioctl does not mangle the return value of mtd_write_oob().

Add a new ioctl, MEMREAD, which addresses the above issues.  It is
intended to be a read-side counterpart of the existing MEMWRITE ioctl.
Similarly to the latter, the read operation is performed in a loop which
processes at most mtd->erasesize bytes in each iteration.  This is done
to prevent unbounded memory allocations caused by calling kmalloc() with
the 'size' argument taken directly from the struct mtd_read_req provided
by user space.  However, the new ioctl is implemented so that the values
it returns match those that would have been returned if just a single
mtd_read_oob() call was issued to handle the entire read operation in
one go.

Note that while just returning -EUCLEAN or -EBADMSG to user space would
already be a valid and useful indication of the ECC algorithm detecting
errors during a read operation, that signal would not be granular enough
to cover all use cases.  For example, knowing the maximum number of
bitflips detected in a single ECC step during a read operation performed
on a given page may be useful when dealing with an MTD partition whose
ECC layout varies across pages (e.g. a partition consisting of a
bootloader area using a "custom" ECC layout followed by data pages using
a "standard" ECC layout).  To address that, include ECC statistics in
the structure returned to user space by the new MEMREAD ioctl.

Link: https://www.infradead.org/pipermail/linux-mtd/2016-April/067085.html

Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
 drivers/mtd/mtdchar.c      | 139 +++++++++++++++++++++++++++++++++++++
 include/uapi/mtd/mtd-abi.h |  64 +++++++++++++++--
 2 files changed, 198 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 05860288a7af..01f1c6792df9 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -688,6 +688,137 @@ static int mtdchar_write_ioctl(struct mtd_info *mtd,
 	return ret;
 }
 
+static int mtdchar_read_ioctl(struct mtd_info *mtd,
+		struct mtd_read_req __user *argp)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	struct mtd_read_req req;
+	void __user *usr_data, *usr_oob;
+	uint8_t *datbuf = NULL, *oobbuf = NULL;
+	size_t datbuf_len, oobbuf_len;
+	size_t orig_len, orig_ooblen;
+	int ret = 0;
+
+	if (copy_from_user(&req, argp, sizeof(req)))
+		return -EFAULT;
+
+	orig_len = req.len;
+	orig_ooblen = req.ooblen;
+
+	usr_data = (void __user *)(uintptr_t)req.usr_data;
+	usr_oob = (void __user *)(uintptr_t)req.usr_oob;
+
+	if (!master->_read_oob)
+		return -EOPNOTSUPP;
+
+	if (!usr_data)
+		req.len = 0;
+
+	if (!usr_oob)
+		req.ooblen = 0;
+
+	req.ecc_stats.uncorrectable_errors = 0;
+	req.ecc_stats.corrected_bitflips = 0;
+	req.ecc_stats.max_bitflips = 0;
+
+	req.len &= 0xffffffff;
+	req.ooblen &= 0xffffffff;
+
+	if (req.start + req.len > mtd->size) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	datbuf_len = min_t(size_t, req.len, mtd->erasesize);
+	if (datbuf_len > 0) {
+		datbuf = kvmalloc(datbuf_len, GFP_KERNEL);
+		if (!datbuf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	oobbuf_len = min_t(size_t, req.ooblen, mtd->erasesize);
+	if (oobbuf_len > 0) {
+		oobbuf = kvmalloc(oobbuf_len, GFP_KERNEL);
+		if (!oobbuf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	while (req.len > 0 || (!usr_data && req.ooblen > 0)) {
+		struct mtd_req_stats stats;
+		struct mtd_oob_ops ops = {
+			.mode = req.mode,
+			.len = min_t(size_t, req.len, datbuf_len),
+			.ooblen = min_t(size_t, req.ooblen, oobbuf_len),
+			.datbuf = datbuf,
+			.oobbuf = oobbuf,
+			.stats = &stats,
+		};
+
+		/*
+		 * Shorten non-page-aligned, eraseblock-sized reads so that the
+		 * read ends on an eraseblock boundary.  This is necessary in
+		 * order to prevent OOB data for some pages from being
+		 * duplicated in the output of non-page-aligned reads requiring
+		 * multiple mtd_read_oob() calls to be completed.
+		 */
+		if (ops.len == mtd->erasesize)
+			ops.len -= mtd_mod_by_ws(req.start + ops.len, mtd);
+
+		ret = mtd_read_oob(mtd, (loff_t)req.start, &ops);
+
+		req.ecc_stats.uncorrectable_errors +=
+			stats.uncorrectable_errors;
+		req.ecc_stats.corrected_bitflips += stats.corrected_bitflips;
+		req.ecc_stats.max_bitflips =
+			max(req.ecc_stats.max_bitflips, stats.max_bitflips);
+
+		if (ret && !mtd_is_bitflip_or_eccerr(ret))
+			break;
+
+		if (copy_to_user(usr_data, ops.datbuf, ops.retlen) ||
+		    copy_to_user(usr_oob, ops.oobbuf, ops.oobretlen)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		req.start += ops.retlen;
+		req.len -= ops.retlen;
+		usr_data += ops.retlen;
+
+		req.ooblen -= ops.oobretlen;
+		usr_oob += ops.oobretlen;
+	}
+
+	/*
+	 * As multiple iterations of the above loop (and therefore multiple
+	 * mtd_read_oob() calls) may be necessary to complete the read request,
+	 * adjust the final return code to ensure it accounts for all detected
+	 * ECC errors.
+	 */
+	if (!ret || mtd_is_bitflip(ret)) {
+		if (req.ecc_stats.uncorrectable_errors > 0)
+			ret = -EBADMSG;
+		else if (req.ecc_stats.corrected_bitflips > 0)
+			ret = -EUCLEAN;
+	}
+
+out:
+	req.len = orig_len - req.len;
+	req.ooblen = orig_ooblen - req.ooblen;
+
+	if (copy_to_user(argp, &req, sizeof(req)))
+		ret = -EFAULT;
+
+	kvfree(datbuf);
+	kvfree(oobbuf);
+
+	return ret;
+}
+
 static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 {
 	struct mtd_file_info *mfi = file->private_data;
@@ -710,6 +841,7 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 	case MEMGETINFO:
 	case MEMREADOOB:
 	case MEMREADOOB64:
+	case MEMREAD:
 	case MEMISLOCKED:
 	case MEMGETOOBSEL:
 	case MEMGETBADBLOCK:
@@ -884,6 +1016,13 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 		break;
 	}
 
+	case MEMREAD:
+	{
+		ret = mtdchar_read_ioctl(mtd,
+		      (struct mtd_read_req __user *)arg);
+		break;
+	}
+
 	case MEMLOCK:
 	{
 		struct erase_info_user einfo;
diff --git a/include/uapi/mtd/mtd-abi.h b/include/uapi/mtd/mtd-abi.h
index 890d9e5b76d7..714d55b49d2a 100644
--- a/include/uapi/mtd/mtd-abi.h
+++ b/include/uapi/mtd/mtd-abi.h
@@ -55,9 +55,9 @@ struct mtd_oob_buf64 {
  * @MTD_OPS_RAW:	data are transferred as-is, with no error correction;
  *			this mode implies %MTD_OPS_PLACE_OOB
  *
- * These modes can be passed to ioctl(MEMWRITE) and are also used internally.
- * See notes on "MTD file modes" for discussion on %MTD_OPS_RAW vs.
- * %MTD_FILE_MODE_RAW.
+ * These modes can be passed to ioctl(MEMWRITE) and ioctl(MEMREAD); they are
+ * also used internally. See notes on "MTD file modes" for discussion on
+ * %MTD_OPS_RAW vs. %MTD_FILE_MODE_RAW.
  */
 enum {
 	MTD_OPS_PLACE_OOB = 0,
@@ -91,6 +91,53 @@ struct mtd_write_req {
 	__u8 padding[7];
 };
 
+/**
+ * struct mtd_read_req_ecc_stats - ECC statistics for a read operation
+ *
+ * @uncorrectable_errors: the number of uncorrectable errors that happened
+ *			  during the read operation
+ * @corrected_bitflips: the number of bitflips corrected during the read
+ *			operation
+ * @max_bitflips: the maximum number of bitflips detected in any single ECC
+ *		  step for the data read during the operation; this information
+ *		  can be used to decide whether the data stored in a specific
+ *		  region of the MTD device should be moved somewhere else to
+ *		  avoid data loss.
+ */
+struct mtd_read_req_ecc_stats {
+	__u32 uncorrectable_errors;
+	__u32 corrected_bitflips;
+	__u32 max_bitflips;
+};
+
+/**
+ * struct mtd_read_req - data structure for requesting a read operation
+ *
+ * @start:	start address
+ * @len:	length of data buffer (only lower 32 bits are used)
+ * @ooblen:	length of OOB buffer (only lower 32 bits are used)
+ * @usr_data:	user-provided data buffer
+ * @usr_oob:	user-provided OOB buffer
+ * @mode:	MTD mode (see "MTD operation modes")
+ * @padding:	reserved, must be set to 0
+ * @ecc_stats:	ECC statistics for the read operation
+ *
+ * This structure supports ioctl(MEMREAD) operations, allowing data and/or OOB
+ * reads in various modes. To read from OOB-only, set @usr_data == NULL, and to
+ * read data-only, set @usr_oob == NULL. However, setting both @usr_data and
+ * @usr_oob to NULL is not allowed.
+ */
+struct mtd_read_req {
+	__u64 start;
+	__u64 len;
+	__u64 ooblen;
+	__u64 usr_data;
+	__u64 usr_oob;
+	__u8 mode;
+	__u8 padding[7];
+	struct mtd_read_req_ecc_stats ecc_stats;
+};
+
 #define MTD_ABSENT		0
 #define MTD_RAM			1
 #define MTD_ROM			2
@@ -207,6 +254,12 @@ struct otp_info {
 #define MEMWRITE		_IOWR('M', 24, struct mtd_write_req)
 /* Erase a given range of user data (must be in mode %MTD_FILE_MODE_OTP_USER) */
 #define OTPERASE		_IOW('M', 25, struct otp_info)
+/*
+ * Most generic read interface; can read in-band and/or out-of-band in various
+ * modes (see "struct mtd_read_req"). This ioctl is not supported for flashes
+ * without OOB, e.g., NOR flash.
+ */
+#define MEMREAD			_IOWR('M', 26, struct mtd_read_req)
 
 /*
  * Obsolete legacy interface. Keep it in order not to break userspace
@@ -270,8 +323,9 @@ struct mtd_ecc_stats {
  * Note: %MTD_FILE_MODE_RAW provides the same functionality as %MTD_OPS_RAW -
  * raw access to the flash, without error correction or autoplacement schemes.
  * Wherever possible, the MTD_OPS_* mode will override the MTD_FILE_MODE_* mode
- * (e.g., when using ioctl(MEMWRITE)), but in some cases, the MTD_FILE_MODE is
- * used out of necessity (e.g., `write()', ioctl(MEMWRITEOOB64)).
+ * (e.g., when using ioctl(MEMWRITE) or ioctl(MEMREAD)), but in some cases, the
+ * MTD_FILE_MODE is used out of necessity (e.g., `write()',
+ * ioctl(MEMWRITEOOB64)).
  */
 enum mtd_file_modes {
 	MTD_FILE_MODE_NORMAL = MTD_OTP_OFF,
-- 
2.37.0



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http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: [PATCH v4 4/4] mtdchar: add MEMREAD ioctl

[Richard Weinberger]

----- Ursprüngliche Mail -----
> Von: "Michał Kępień" <kernel@kempniu.pl>
> An: "Miquel Raynal" <miquel.raynal@bootlin.com>, "richard" <richard@nod.at>, "Vignesh Raghavendra" <vigneshr@ti.com>
> CC: "Boris Brezillon" <boris.brezillon@collabora.com>, "linux-mtd" <linux-mtd@lists.infradead.org>, "linux-kernel"
> <linux-kernel@vger.kernel.org>
> Gesendet: Mittwoch, 29. Juni 2022 14:57:37
> Betreff: [PATCH v4 4/4] mtdchar: add MEMREAD ioctl

> User-space applications making use of MTD devices via /dev/mtd*
> character devices currently have limited capabilities for reading data:
> 
>  - only deprecated methods of accessing OOB layout information exist,
> 
>  - there is no way to explicitly specify MTD operation mode to use; it
>    is auto-selected based on the MTD file mode (MTD_FILE_MODE_*) set
>    for the character device; in particular, this prevents using
>    MTD_OPS_AUTO_OOB for reads,
> 
>  - all existing user-space interfaces which cause mtd_read() or
>    mtd_read_oob() to be called (via mtdchar_read() and
>    mtdchar_read_oob(), respectively) return success even when those
>    functions return -EUCLEAN or -EBADMSG; this renders user-space
>    applications using these interfaces unaware of any corrected
>    bitflips or uncorrectable ECC errors detected during reads.
> 
> Note that the existing MEMWRITE ioctl allows the MTD operation mode to
> be explicitly set, allowing user-space applications to write page data
> and OOB data without requiring them to know anything about the OOB
> layout of the MTD device they are writing to (MTD_OPS_AUTO_OOB).  Also,
> the MEMWRITE ioctl does not mangle the return value of mtd_write_oob().
> 
> Add a new ioctl, MEMREAD, which addresses the above issues.  It is
> intended to be a read-side counterpart of the existing MEMWRITE ioctl.
> Similarly to the latter, the read operation is performed in a loop which
> processes at most mtd->erasesize bytes in each iteration.  This is done
> to prevent unbounded memory allocations caused by calling kmalloc() with
> the 'size' argument taken directly from the struct mtd_read_req provided
> by user space.  However, the new ioctl is implemented so that the values
> it returns match those that would have been returned if just a single
> mtd_read_oob() call was issued to handle the entire read operation in
> one go.
> 
> Note that while just returning -EUCLEAN or -EBADMSG to user space would
> already be a valid and useful indication of the ECC algorithm detecting
> errors during a read operation, that signal would not be granular enough
> to cover all use cases.  For example, knowing the maximum number of
> bitflips detected in a single ECC step during a read operation performed
> on a given page may be useful when dealing with an MTD partition whose
> ECC layout varies across pages (e.g. a partition consisting of a
> bootloader area using a "custom" ECC layout followed by data pages using
> a "standard" ECC layout).  To address that, include ECC statistics in
> the structure returned to user space by the new MEMREAD ioctl.
> 
> Link: https://www.infradead.org/pipermail/linux-mtd/2016-April/067085.html
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Michał Kępień <kernel@kempniu.pl>
> ---
> drivers/mtd/mtdchar.c      | 139 +++++++++++++++++++++++++++++++++++++
> include/uapi/mtd/mtd-abi.h |  64 +++++++++++++++--
> 2 files changed, 198 insertions(+), 5 deletions(-)

Acked-by: Richard Weinberger <richard@nod.at>

Thanks,
//richard

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Re: [PATCH v4 4/4] mtdchar: add MEMREAD ioctl

[Miquel Raynal]

On Wed, 2022-06-29 at 12:57:37 UTC, =?utf-8?b?TWljaGHFgiBLxJlwaWXFhA==?= wrote:
> User-space applications making use of MTD devices via /dev/mtd*
> character devices currently have limited capabilities for reading data:
> 
>   - only deprecated methods of accessing OOB layout information exist,
> 
>   - there is no way to explicitly specify MTD operation mode to use; it
>     is auto-selected based on the MTD file mode (MTD_FILE_MODE_*) set
>     for the character device; in particular, this prevents using
>     MTD_OPS_AUTO_OOB for reads,
> 
>   - all existing user-space interfaces which cause mtd_read() or
>     mtd_read_oob() to be called (via mtdchar_read() and
>     mtdchar_read_oob(), respectively) return success even when those
>     functions return -EUCLEAN or -EBADMSG; this renders user-space
>     applications using these interfaces unaware of any corrected
>     bitflips or uncorrectable ECC errors detected during reads.
> 
> Note that the existing MEMWRITE ioctl allows the MTD operation mode to
> be explicitly set, allowing user-space applications to write page data
> and OOB data without requiring them to know anything about the OOB
> layout of the MTD device they are writing to (MTD_OPS_AUTO_OOB).  Also,
> the MEMWRITE ioctl does not mangle the return value of mtd_write_oob().
> 
> Add a new ioctl, MEMREAD, which addresses the above issues.  It is
> intended to be a read-side counterpart of the existing MEMWRITE ioctl.
> Similarly to the latter, the read operation is performed in a loop which
> processes at most mtd->erasesize bytes in each iteration.  This is done
> to prevent unbounded memory allocations caused by calling kmalloc() with
> the 'size' argument taken directly from the struct mtd_read_req provided
> by user space.  However, the new ioctl is implemented so that the values
> it returns match those that would have been returned if just a single
> mtd_read_oob() call was issued to handle the entire read operation in
> one go.
> 
> Note that while just returning -EUCLEAN or -EBADMSG to user space would
> already be a valid and useful indication of the ECC algorithm detecting
> errors during a read operation, that signal would not be granular enough
> to cover all use cases.  For example, knowing the maximum number of
> bitflips detected in a single ECC step during a read operation performed
> on a given page may be useful when dealing with an MTD partition whose
> ECC layout varies across pages (e.g. a partition consisting of a
> bootloader area using a "custom" ECC layout followed by data pages using
> a "standard" ECC layout).  To address that, include ECC statistics in
> the structure returned to user space by the new MEMREAD ioctl.
> 
> Link: https://www.infradead.org/pipermail/linux-mtd/2016-April/067085.html
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Michał Kępień <kernel@kempniu.pl>
> Acked-by: Richard Weinberger <richard@nod.at>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel

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Re: [PATCH v4 3/4] mtd: add ECC error accounting for each read request

[Miquel Raynal]

On Wed, 2022-06-29 at 12:57:36 UTC, =?utf-8?b?TWljaGHFgiBLxJlwaWXFhA==?= wrote:
> Extend struct mtd_req_stats with two new fields holding the number of
> corrected bitflips and uncorrectable errors detected during a read
> operation.  This is a prerequisite for ultimately passing those counters
> to user space, where they can be useful to applications for making
> better-informed choices about moving data around.
> 
> Unlike 'max_bitflips' (which is set - in a common code path - to the
> return value of a function called while the MTD device's mutex is held),
> these counters have to be maintained in each MTD driver which defines
> the '_read_oob' callback because the statistics need to be calculated
> while the MTD device's mutex is held.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Michał Kępień <kernel@kempniu.pl>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel

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Re: [PATCH v4 2/4] mtd: always initialize 'stats' in struct mtd_oob_ops

[Miquel Raynal]

On Wed, 2022-06-29 at 12:57:35 UTC, =?utf-8?b?TWljaGHFgiBLxJlwaWXFhA==?= wrote:
> As the 'stats' field in struct mtd_oob_ops is used in conditional
> expressions, ensure it is always zero-initialized in all such structures
> to prevent random stack garbage from being interpreted as a pointer.
> 
> Strictly speaking, this problem currently only needs to be fixed for
> struct mtd_oob_ops structures subsequently passed to mtd_read_oob().
> However, this commit goes a step further and makes all instances of
> struct mtd_oob_ops in the tree zero-initialized, in hope of preventing
> future problems, e.g. if struct mtd_req_stats gets extended with write
> statistics at some point.
> 
> Signed-off-by: Michał Kępień <kernel@kempniu.pl>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel

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Re: [PATCH v4 1/4] mtd: track maximum number of bitflips for each read request

[Miquel Raynal]

On Wed, 2022-06-29 at 12:57:34 UTC, =?utf-8?b?TWljaGHFgiBLxJlwaWXFhA==?= wrote:
> mtd_read_oob() callers are currently oblivious to the details of ECC
> errors detected during the read operation - they only learn (through the
> return value) whether any corrected bitflips or uncorrectable errors
> occurred.  More detailed ECC information can be useful to user-space
> applications for making better-informed choices about moving data
> around.
> 
> Extend struct mtd_oob_ops with a pointer to a newly-introduced struct
> mtd_req_stats and set its 'max_bitflips' field to the maximum number of
> bitflips found in a single ECC step during the read operation performed
> by mtd_read_oob().  This is a prerequisite for ultimately passing that
> value back to user space.
> 
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Michał Kępień <kernel@kempniu.pl>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel

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