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

Boris Brezillon
2018-08-17T16:27:20Z

Hi Bartosz,

On Fri, 10 Aug 2018 10:05:03 +0200
Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> 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>

What happened to the 2 other patches of Alban's series? I'd really like
the DT case to be handled/agreed on in the same patchset, but IIRC,
Alban and Srinivas disagreed on how this should be represented. I
hope this time we'll come to an agreement, because the MTD <-> NVMEM
glue has been floating around for quite some time...

Regards,

Boris

> ---
> 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,