[PATCH v2 06/29] mtd: Add support for reading MTD devices via the nvmem API

Bartosz Golaszewski
2018-08-10T08:05:03Z

From: Alban Bedel <albeu@free.fr>

Allow drivers that use the nvmem API to read data stored on MTD devices.
For this the mtd devices are registered as read-only NVMEM providers.

Signed-off-by: Alban Bedel <albeu@free.fr>
[Bartosz:
- use the managed variant of nvmem_register(),
- set the nvmem name]
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/mtd/Kconfig | 1 +
drivers/mtd/mtdcore.c | 50 +++++++++++++++++++++++++++++++++++++++++
include/linux/mtd/mtd.h | 2 ++
3 files changed, 53 insertions(+)

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index 46ab7feec6b6..f5549482d0df 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -1,5 +1,6 @@
menuconfig MTD
tristate "Memory Technology Device (MTD) support"
+ imply NVMEM
help
Memory Technology Devices are flash, RAM and similar chips, often
used for solid state file systems on embedded devices. This option
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 42395df06be9..a57302eaceb5 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -488,6 +488,49 @@ int mtd_pairing_groups(struct mtd_info *mtd)
}
EXPORT_SYMBOL_GPL(mtd_pairing_groups);

+static int mtd_nvmem_reg_read(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct mtd_info *mtd = priv;
+ size_t retlen;
+ int err;
+
+ err = mtd_read(mtd, offset, bytes, &retlen, val);
+ if (err && err != -EUCLEAN)
+ return err;
+
+ return retlen == bytes ? 0 : -EIO;
+}
+
+static int mtd_nvmem_add(struct mtd_info *mtd)
+{
+ struct nvmem_config config = { };
+
+ config.dev = &mtd->dev;
+ config.owner = THIS_MODULE;
+ config.name = mtd->name;
+ config.reg_read = mtd_nvmem_reg_read;
+ config.size = mtd->size;
+ config.word_size = 1;
+ config.stride = 1;
+ config.read_only = true;
+ config.root_only = true;
+ config.priv = mtd;
+
+ mtd->nvmem = devm_nvmem_register(&mtd->dev, &config);
+ if (IS_ERR(mtd->nvmem)) {
+ /* Just ignore if there is no NVMEM support in the kernel */
+ if (PTR_ERR(mtd->nvmem) == -ENOSYS) {
+ mtd->nvmem = NULL;
+ } else {
+ dev_err(&mtd->dev, "Failed to register NVMEM device\n");
+ return PTR_ERR(mtd->nvmem);
+ }
+ }
+
+ return 0;
+}
+
static struct dentry *dfs_dir_mtd;

/**
@@ -570,6 +613,11 @@ int add_mtd_device(struct mtd_info *mtd)
if (error)
goto fail_added;

+ /* Add the nvmem provider */
+ error = mtd_nvmem_add(mtd);
+ if (error)
+ goto fail_nvmem_add;
+
if (!IS_ERR_OR_NULL(dfs_dir_mtd)) {
mtd->dbg.dfs_dir = debugfs_create_dir(dev_name(&mtd->dev), dfs_dir_mtd);
if (IS_ERR_OR_NULL(mtd->dbg.dfs_dir)) {
@@ -595,6 +643,8 @@ int add_mtd_device(struct mtd_info *mtd)
__module_get(THIS_MODULE);
return 0;

+fail_nvmem_add:
+ device_unregister(&mtd->dev);
fail_added:
of_node_put(mtd_get_of_node(mtd));
idr_remove(&mtd_idr, i);
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index a86c4fa93115..8121c6582285 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -25,6 +25,7 @@
#include <linux/notifier.h>
#include <linux/device.h>
#include <linux/of.h>
+#include <linux/nvmem-provider.h>

#include <mtd/mtd-abi.h>

@@ -339,6 +340,7 @@ struct mtd_info {
struct device dev;
int usecount;
struct mtd_debug_info dbg;
+ struct nvmem_device *nvmem;
};

int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
--
2.18.0