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From:   =?UTF-8?q?Micha=C5=82=20K=C4=99pie=C5=84?= <kernel@kempniu.pl>
To:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>
Cc:     Boris Brezillon <boris.brezillon@collabora.com>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Message-ID: <20220629125737.14418-2-kernel@kempniu.pl>
Subject: [PATCH v4 1/4] mtd: track maximum number of bitflips for each read request
Date:   Wed, 29 Jun 2022 14:57:34 +0200
In-Reply-To: <20220629125737.14418-1-kernel@kempniu.pl>
References: <20220629125737.14418-1-kernel@kempniu.pl>
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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: Micha=C5=82 K=C4=99pie=C5=84 <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, s=
truct mtd_oob_ops *ops)
 =09if (!master->_read_oob && (!master->_read || ops->oobbuf))
 =09=09return -EOPNOTSUPP;
=20
+=09if (ops->stats)
+=09=09memset(ops->stats, 0, sizeof(*ops->stats));
+
 =09if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 =09=09ret_code =3D mtd_io_emulated_slc(mtd, from, true, ops);
 =09else
@@ -1639,6 +1642,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, s=
truct mtd_oob_ops *ops)
 =09=09return ret_code;
 =09if (mtd->ecc_strength =3D=3D 0)
 =09=09return 0;=09/* device lacks ecc */
+=09if (ops->stats)
+=09=09ops->stats->max_bitflips =3D ret_code;
 =09return ret_code >=3D 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 {
 =09unsigned long *lockmap;=09=09/* If keeping bitmap of locks */
 };
=20
+struct mtd_req_stats {
+=09unsigned int max_bitflips;
+};
+
 /**
  * struct mtd_oob_ops - oob operation operands
  * @mode:=09operation mode
@@ -70,6 +74,7 @@ struct mtd_oob_ops {
 =09uint32_t=09ooboffs;
 =09uint8_t=09=09*datbuf;
 =09uint8_t=09=09*oobbuf;
+=09struct mtd_req_stats *stats;
 };
=20
 /**
--=20
2.37.0