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Date: Tue, 7 Mar 2017 19:52:57 +0100
From: Boris Brezillon <boris.brezillon@...e-electrons.com>
To: Alban <albeu@...e.fr>
Cc: linux-kernel@...r.kernel.org,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
David Woodhouse <dwmw2@...radead.org>,
Brian Norris <computersforpeace@...il.com>,
Marek Vasut <marek.vasut@...il.com>,
Richard Weinberger <richard@....at>,
Cyrille Pitchen <cyrille.pitchen@...el.com>,
devicetree@...r.kernel.org, linux-mtd@...ts.infradead.org,
Moritz Fischer <moritz.fischer@...us.com>
Subject: Re: [PATCH v2 2/2] mtd: Add support for reading MTD devices via the
nvmem API
On Tue, 7 Mar 2017 09:26:04 +0100
Alban <albeu@...e.fr> wrote:
> Allow drivers that use the nvmem API to read data stored on MTD devices.
> Add an option to the MTD core that allow registering the MTD as
> read-only NVMEM providers.
>
> Signed-off-by: Alban <albeu@...e.fr>
> ---
> Changelog:
> v2: * Moved to the MTD core instead of using notifiers
> * Fixed the Kconfig description
> ---
> drivers/mtd/Kconfig | 9 +++++++
> drivers/mtd/Makefile | 1 +
> drivers/mtd/mtdcore.c | 13 +++++++++
> drivers/mtd/mtdnvmem.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++
> drivers/mtd/mtdnvmem.h | 25 +++++++++++++++++
> include/linux/mtd/mtd.h | 4 +++
> 6 files changed, 124 insertions(+)
> create mode 100644 drivers/mtd/mtdnvmem.c
> create mode 100644 drivers/mtd/mtdnvmem.h
>
> diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
> index e83a279..5a34c6a 100644
> --- a/drivers/mtd/Kconfig
> +++ b/drivers/mtd/Kconfig
> @@ -322,6 +322,15 @@ config MTD_PARTITIONED_MASTER
> the parent of the partition device be the master device, rather than
> what lies behind the master.
>
> +config MTD_NVMEM
> + bool "Register MTD devices as NVMEM providers"
> + default y
> + depends on NVMEM || COMPILE_TEST
> + help
> + Provides support for reading config data from MTD devices. This can
> + be used by drivers to read device specific data such as MAC addresses
> + or calibration results.
> +
> source "drivers/mtd/chips/Kconfig"
>
> source "drivers/mtd/maps/Kconfig"
> diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
> index 99bb9a1..879a542 100644
> --- a/drivers/mtd/Makefile
> +++ b/drivers/mtd/Makefile
> @@ -5,6 +5,7 @@
> # Core functionality.
> obj-$(CONFIG_MTD) += mtd.o
> mtd-y := mtdcore.o mtdsuper.o mtdconcat.o mtdpart.o mtdchar.o
> +mtd-$(CONFIG_MTD_NVMEM) += mtdnvmem.o
>
> obj-$(CONFIG_MTD_OF_PARTS) += ofpart.o
> obj-$(CONFIG_MTD_REDBOOT_PARTS) += redboot.o
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 66a9ded..bb88997 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -45,6 +45,7 @@
> #include <linux/mtd/partitions.h>
>
> #include "mtdcore.h"
> +#include "mtdnvmem.h"
>
> static struct backing_dev_info *mtd_bdi;
>
> @@ -554,6 +555,11 @@ 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;
> +
> device_create(&mtd_class, mtd->dev.parent, MTD_DEVT(i) + 1, NULL,
> "mtd%dro", i);
>
> @@ -571,6 +577,8 @@ 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);
> @@ -611,6 +619,11 @@ int del_mtd_device(struct mtd_info *mtd)
> mtd->index, mtd->name, mtd->usecount);
> ret = -EBUSY;
> } else {
> + /* Try to remove the NVMEM provider */
> + ret = mtd_nvmem_remove(mtd);
> + if (ret)
> + goto out_error;
> +
> device_unregister(&mtd->dev);
>
> idr_remove(&mtd_idr, mtd->index);
> diff --git a/drivers/mtd/mtdnvmem.c b/drivers/mtd/mtdnvmem.c
> new file mode 100644
> index 0000000..d6bc402
> --- /dev/null
> +++ b/drivers/mtd/mtdnvmem.c
> @@ -0,0 +1,72 @@
> +/*
> + * Copyright (C) 2017 Alban Bedel <albeu@...e.fr>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/of.h>
> +
> +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;
> +}
> +
> +int mtd_nvmem_add(struct mtd_info *mtd)
> +{
> + struct device_node *np = dev_of_node(&mtd->dev);
> + struct nvmem_config config = {};
> +
> + /* OF devices must have the nvmem-provider property */
> + if (np && !of_property_read_bool(np, "nvmem-provider"))
> + return 0;
> +
> + config.dev = &mtd->dev;
> + config.owner = THIS_MODULE;
> + config.reg_read = mtd_nvmem_reg_read;
> + config.size = mtd->size;
> + config.word_size = 1;
> + config.stride = 1;
> + config.read_only = true;
> + config.priv = mtd;
> +
> + mtd->nvmem = nvmem_register(&config);
> + if (IS_ERR(mtd->nvmem)) {
> + dev_err(&mtd->dev, "Failed to register NVMEM device\n");
> + return PTR_ERR(mtd->nvmem);
> + }
> +
> + return 0;
> +}
> +
> +int mtd_nvmem_remove(struct mtd_info *mtd)
> +{
> + int ret;
> +
> + if (!mtd->nvmem)
> + return 0;
> +
> + ret = nvmem_unregister(mtd->nvmem);
> + if (ret)
> + dev_err(&mtd->dev, "Failed to unregister NVMEM device\n");
> +
> + return ret;
> +}
Given the amount of code I wonder if this shouldn't be integrated in
mtdcore.c and unconditionally compiled in.
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Alban Bedel <albeu@...e.fr>");
> +MODULE_DESCRIPTION("Driver to read config data from MTD devices");
> diff --git a/drivers/mtd/mtdnvmem.h b/drivers/mtd/mtdnvmem.h
> new file mode 100644
> index 0000000..a49d8bd
> --- /dev/null
> +++ b/drivers/mtd/mtdnvmem.h
> @@ -0,0 +1,25 @@
> +/*
> + * Copyright (C) 2017 Alban Bedel <albeu@...e.fr>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +#ifndef MTD_NVMEM_H
> +#define MTD_NVMEM_H 1
> +
> +struct mtd_info;
> +
> +#ifdef CONFIG_MTD_NVMEM
> +int mtd_nvmem_add(struct mtd_info *mtd);
> +int mtd_nvmem_remove(struct mtd_info *mtd);
> +#else
> +static inline int mtd_nvmem_add(struct mtd_info *mtd)
> +{ return 0; }
> +
> +static inline int mtd_nvmem_remove(struct mtd_info *mtd)
> +{ return 0; }
> +#endif
> +
> +#endif /* MTD_NVMEM_H */
> diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
> index eebdc63..e06c6e6 100644
> --- a/include/linux/mtd/mtd.h
> +++ b/include/linux/mtd/mtd.h
> @@ -205,6 +205,7 @@ struct mtd_pairing_scheme {
> };
>
> struct module; /* only needed for owner field in mtd_info */
> +struct nvmem_device;
Include nvmem-provider.h instead of re-defining struct nvmem_device
here.
>
> struct mtd_info {
> u_char type;
> @@ -351,6 +352,9 @@ struct mtd_info {
> struct module *owner;
> struct device dev;
> int usecount;
> +#if IS_ENABLED(CONFIG_MTD_NVMEM)
> + struct nvmem_device *nvmem;
> +#endif
Hm, I don't see any #if IS_ENABLED() or #ifdef CONFIG_ statements in
this file. I know it adds an extra 32/64 bits field for nothing if the
feature is disabled, but how about keeping the struct definition simple
by unconditionally adding the nvmem field.
> };
>
> int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
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