mtd: add support for reading MTD devices via the nvmem API

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.

We don't support device tree systems for now.

Signed-off-by: Alban Bedel <albeu@free.fr>
[Bartosz:
  - include linux/nvmem-provider.h
  - set the name of the nvmem provider
  - set no_of_node to true in nvmem_config
  - don't check the return value of nvmem_unregister() - it cannot fail
  - tweaked the commit message]
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index c77f537323ecb371d1be527df650bf6fb8ca4713..efbe7a6f1d8ff3e5c5f98b86003da69234d0f44a 100644 (file)
--- 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 97ac219c082e7ef78993084ffcc8c9e98abaaac4..5f1053d995b083f43e203efd691c5011a286c27d 100644 (file)
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -41,6 +41,7 @@
 #include <linux/reboot.h>
 #include <linux/leds.h>
 #include <linux/debugfs.h>
+#include <linux/nvmem-provider.h>
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
@@ -488,6 +489,50 @@ 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.name = mtd->name;
+       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.root_only = true;
+       config.no_of_node = true;
+       config.priv = mtd;
+
+       mtd->nvmem = nvmem_register(&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 +615,11 @@ 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 +645,8 @@ 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);
@@ -637,6 +689,10 @@ int del_mtd_device(struct mtd_info *mtd)
                       mtd->index, mtd->name, mtd->usecount);
                ret = -EBUSY;
        } else {
+               /* Try to remove the NVMEM provider */
+               if (mtd->nvmem)
+                       nvmem_unregister(mtd->nvmem);
+
                device_unregister(&mtd->dev);
 
                idr_remove(&mtd_idr, mtd->index);

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index cd0be91bdefa55f568253904c7d374751fffac52..545070c2ee6473b2d395c69716df0198b6b0d4f1 100644 (file)
--- 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>
 
@@ -341,6 +342,7 @@ 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,