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Subject[PATCH v2 2/5] mtd: track maximum number of bitflips for each read request
Date
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 70f492dce158..9423af6db385 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1575,6 +1575,9 @@ 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
@@ -1592,6 +1595,8 @@ 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 1ffa933121f6..f976aabcb378 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;
};

/**
--
2.34.1
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