[06/28] mtd: Add support for reading MTD devices via the nvmem API

Message ID 20180808153150.23444-7-brgl@bgdev.pl
State Superseded
Headers show
Series
  • at24: remove at24_platform_data
Related show

Commit Message

Bartosz Golaszewski Aug. 8, 2018, 3:31 p.m.
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.
On OF systems only devices that have the 'nvmem-provider' property
are registered, on non-OF system all MTD devices are registered.

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(+)

Comments

Andrew Lunn Aug. 8, 2018, 4:20 p.m. | #1
On Wed, Aug 08, 2018 at 05:31:28PM +0200, Bartosz Golaszewski 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.
> On OF systems only devices that have the 'nvmem-provider' property
> are registered, on non-OF system all MTD devices are registered.
> @@ -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;
> +

Hi Bartosz

Maybe it is hiding somewhere, but i don't see any code looking into
device tree looking for the 'nvmem-provider' property.

       Andrew
Bartosz Golaszewski Aug. 8, 2018, 4:26 p.m. | #2
2018-08-08 18:20 GMT+02:00 Andrew Lunn <andrew@lunn.ch>:
> On Wed, Aug 08, 2018 at 05:31:28PM +0200, Bartosz Golaszewski 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.
>> On OF systems only devices that have the 'nvmem-provider' property
>> are registered, on non-OF system all MTD devices are registered.
>> @@ -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;
>> +
>
> Hi Bartosz
>
> Maybe it is hiding somewhere, but i don't see any code looking into
> device tree looking for the 'nvmem-provider' property.
>
>        Andrew

Ugh, I copied the commit message from Alban's patch. For the moment
there's no such thing, you're right. I'll fix it for v2.

Bart

Patch

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,