[PATCH v2 1/4] nvmem: Replace spaces with tab in documentation

[PATCH v2 1/4] nvmem: Replace spaces with tab in documentation

[Marek Vasut]

Replace two spaces with tab in the sysfs attribute documentation.
No functional change.

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: linux-i2c@vger.kernel.org
---
V2: - New patch
---
 Documentation/ABI/stable/sysfs-bus-nvmem | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
index c399323f37de3..854bd11d72ac4 100644
--- a/Documentation/ABI/stable/sysfs-bus-nvmem
+++ b/Documentation/ABI/stable/sysfs-bus-nvmem
@@ -1,6 +1,6 @@
 What:		/sys/bus/nvmem/devices/.../nvmem
 Date:		July 2015
-KernelVersion:  4.2
+KernelVersion:	4.2
 Contact:	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
 Description:
 		This file allows user to read/write the raw NVMEM contents.
-- 
2.43.0

[PATCH v2 2/4] nvmem: Document type attribute

[Marek Vasut]

Document a type attribute used by userspace to discern different types of
NVMEM devices. The implementation is already present, the ABI document is
missing, add it.

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: linux-i2c@vger.kernel.org
---
V2: - New patch
---
 Documentation/ABI/stable/sysfs-bus-nvmem | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
index 854bd11d72ac4..0e3a8492a1082 100644
--- a/Documentation/ABI/stable/sysfs-bus-nvmem
+++ b/Documentation/ABI/stable/sysfs-bus-nvmem
@@ -20,3 +20,14 @@ Description:
 		  ...
 		  *
 		  0001000
+
+What:		/sys/bus/nvmem/devices/.../type
+Date:		November 2018
+KernelVersion:	5.0
+Contact:	Alexandre Belloni <alexandre.belloni@bootlin.com>
+Description:
+		This read-only attribute allows user to read the NVMEM
+		device type. Supported types are "Unknown", "EEPROM",
+		"OTP", "Battery backed", "FRAM".
+		Note: This file is only present if CONFIG_NVMEM_SYSFS
+		is enabled
-- 
2.43.0

Re: [PATCH v2 2/4] nvmem: Document type attribute

[Alexandre Belloni]

On 23/06/2024 05:15:45+0200, Marek Vasut wrote:
> Document a type attribute used by userspace to discern different types of
> NVMEM devices. The implementation is already present, the ABI document is
> missing, add it.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>

Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> Cc: linux-i2c@vger.kernel.org
> ---
> V2: - New patch
> ---
>  Documentation/ABI/stable/sysfs-bus-nvmem | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
> index 854bd11d72ac4..0e3a8492a1082 100644
> --- a/Documentation/ABI/stable/sysfs-bus-nvmem
> +++ b/Documentation/ABI/stable/sysfs-bus-nvmem
> @@ -20,3 +20,14 @@ Description:
>  		  ...
>  		  *
>  		  0001000
> +
> +What:		/sys/bus/nvmem/devices/.../type
> +Date:		November 2018
> +KernelVersion:	5.0
> +Contact:	Alexandre Belloni <alexandre.belloni@bootlin.com>
> +Description:
> +		This read-only attribute allows user to read the NVMEM
> +		device type. Supported types are "Unknown", "EEPROM",
> +		"OTP", "Battery backed", "FRAM".
> +		Note: This file is only present if CONFIG_NVMEM_SYSFS
> +		is enabled
> -- 
> 2.43.0
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[PATCH v2 3/4] nvmem: Use sysfs_emit() for type attribute

[Marek Vasut]

Use sysfs_emit() instead of sprintf() to follow best practice per
Documentation/filesystems/sysfs.rst
"
show() should only use sysfs_emit()...
"

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: linux-i2c@vger.kernel.org
---
V2: - New patch
---
 drivers/nvmem/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index e1ec3b7200d7b..b31abffcdfc00 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -179,7 +179,7 @@ static ssize_t type_show(struct device *dev,
 {
 	struct nvmem_device *nvmem = to_nvmem_device(dev);
 
-	return sprintf(buf, "%s\n", nvmem_type_str[nvmem->type]);
+	return sysfs_emit(buf, "%s\n", nvmem_type_str[nvmem->type]);
 }
 
 static DEVICE_ATTR_RO(type);
-- 
2.43.0

[PATCH v2 4/4] nvmem: core: Implement force_ro sysfs attribute

[Marek Vasut]

Implement "force_ro" sysfs attribute to allow users to set read-write
devices as read-only and back to read-write from userspace. The choice
of the name is based on MMC core 'force_ro' attribute.

This solves a situation where an AT24 I2C EEPROM with GPIO based nWP
signal may have to be occasionally updated. Such I2C EEPROM device is
usually set as read-only during most of the regular system operation,
but in case it has to be updated in a controlled manner, it could be
unlocked using this new "force_ro" sysfs attribute and then re-locked
again.

The "read-only" DT property and config->read_only configuration is
respected and is used to set default state of the device, read-only
or read-write, for devices which do implement .reg_write function.
For devices which do not implement .reg_write function, the device
is unconditionally read-only and the "force_ro" attribute is not
visible.

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: linux-i2c@vger.kernel.org
---
V2: - Document the force_ro attribute
    - Use sysfs_emit()
---
 Documentation/ABI/stable/sysfs-bus-nvmem | 13 +++++++
 drivers/nvmem/core.c                     | 44 ++++++++++++++++++++++++
 drivers/nvmem/internals.h                |  1 +
 3 files changed, 58 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
index 0e3a8492a1082..c713c4e6cecb1 100644
--- a/Documentation/ABI/stable/sysfs-bus-nvmem
+++ b/Documentation/ABI/stable/sysfs-bus-nvmem
@@ -1,3 +1,16 @@
+What:		/sys/bus/nvmem/devices/.../force_ro
+Date:		June 2024
+KernelVersion:	6.11
+Contact:	Marek Vasut <marex@denx.de>
+Description:
+		This read/write attribute allows users to set read-write
+		devices as read-only and back to read-write from userspace.
+		This can be used to unlock and relock write-protection of
+		devices which are generally locked, except during sporadic
+		programming operation.
+		Note: This file is only present if CONFIG_NVMEM_SYSFS
+		is enabled
+
 What:		/sys/bus/nvmem/devices/.../nvmem
 Date:		July 2015
 KernelVersion:	4.2
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index b31abffcdfc00..2321fb7da1e92 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -184,7 +184,30 @@ static ssize_t type_show(struct device *dev,
 
 static DEVICE_ATTR_RO(type);
 
+static ssize_t force_ro_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	return sysfs_emit(buf, "%d\n", nvmem->read_only);
+}
+
+static ssize_t force_ro_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+	int ret = kstrtobool(buf, &nvmem->read_only);
+
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(force_ro);
+
 static struct attribute *nvmem_attrs[] = {
+	&dev_attr_force_ro.attr,
 	&dev_attr_type.attr,
 	NULL,
 };
@@ -299,6 +322,25 @@ static umode_t nvmem_bin_attr_is_visible(struct kobject *kobj,
 	return nvmem_bin_attr_get_umode(nvmem);
 }
 
+static umode_t nvmem_attr_is_visible(struct kobject *kobj,
+				     struct attribute *attr, int i)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+	/*
+	 * If the device has no .reg_write operation, do not allow
+	 * configuration as read-write.
+	 * If the device is set as read-only by configuration, it
+	 * can be forced into read-write mode using the 'force_ro'
+	 * attribute.
+	 */
+	if (attr == &dev_attr_force_ro.attr && !nvmem->reg_write)
+		return 0;	/* Attribute not visible */
+
+	return attr->mode;
+}
+
 static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry,
 					    const char *id, int index);
 
@@ -355,6 +397,7 @@ static const struct attribute_group nvmem_bin_group = {
 	.bin_attrs	= nvmem_bin_attributes,
 	.attrs		= nvmem_attrs,
 	.is_bin_visible = nvmem_bin_attr_is_visible,
+	.is_visible	= nvmem_attr_is_visible,
 };
 
 /* Cell attributes will be dynamically allocated */
@@ -971,6 +1014,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 
 	nvmem->read_only = device_property_present(config->dev, "read-only") ||
 			   config->read_only || !nvmem->reg_write;
+	nvmem->default_read_only = nvmem->read_only;
 
 #ifdef CONFIG_NVMEM_SYSFS
 	nvmem->dev.groups = nvmem_dev_groups;
diff --git a/drivers/nvmem/internals.h b/drivers/nvmem/internals.h
index 18fed57270e5e..0667937ebb86b 100644
--- a/drivers/nvmem/internals.h
+++ b/drivers/nvmem/internals.h
@@ -16,6 +16,7 @@ struct nvmem_device {
 	int			id;
 	struct kref		refcnt;
 	size_t			size;
+	bool			default_read_only;
 	bool			read_only;
 	bool			root_only;
 	int			flags;
-- 
2.43.0

Re: [PATCH v2 4/4] nvmem: core: Implement force_ro sysfs attribute

[Greg Kroah-Hartman]

On Sun, Jun 23, 2024 at 05:15:47AM +0200, Marek Vasut wrote:
> Implement "force_ro" sysfs attribute to allow users to set read-write
> devices as read-only and back to read-write from userspace. The choice
> of the name is based on MMC core 'force_ro' attribute.
> 
> This solves a situation where an AT24 I2C EEPROM with GPIO based nWP
> signal may have to be occasionally updated. Such I2C EEPROM device is
> usually set as read-only during most of the regular system operation,
> but in case it has to be updated in a controlled manner, it could be
> unlocked using this new "force_ro" sysfs attribute and then re-locked
> again.
> 
> The "read-only" DT property and config->read_only configuration is
> respected and is used to set default state of the device, read-only
> or read-write, for devices which do implement .reg_write function.
> For devices which do not implement .reg_write function, the device
> is unconditionally read-only and the "force_ro" attribute is not
> visible.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> ---
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> Cc: linux-i2c@vger.kernel.org
> ---
> V2: - Document the force_ro attribute
>     - Use sysfs_emit()
> ---
>  Documentation/ABI/stable/sysfs-bus-nvmem | 13 +++++++
>  drivers/nvmem/core.c                     | 44 ++++++++++++++++++++++++
>  drivers/nvmem/internals.h                |  1 +
>  3 files changed, 58 insertions(+)
> 
> diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
> index 0e3a8492a1082..c713c4e6cecb1 100644
> --- a/Documentation/ABI/stable/sysfs-bus-nvmem
> +++ b/Documentation/ABI/stable/sysfs-bus-nvmem
> @@ -1,3 +1,16 @@
> +What:		/sys/bus/nvmem/devices/.../force_ro
> +Date:		June 2024
> +KernelVersion:	6.11
> +Contact:	Marek Vasut <marex@denx.de>
> +Description:
> +		This read/write attribute allows users to set read-write
> +		devices as read-only and back to read-write from userspace.
> +		This can be used to unlock and relock write-protection of
> +		devices which are generally locked, except during sporadic
> +		programming operation.
> +		Note: This file is only present if CONFIG_NVMEM_SYSFS
> +		is enabled

And what exactly are the values that can be read or written here?

thanks,

greg k-h

Re: [PATCH v2 4/4] nvmem: core: Implement force_ro sysfs attribute

[Marek Vasut]

On 6/23/24 8:13 AM, Greg Kroah-Hartman wrote:
> On Sun, Jun 23, 2024 at 05:15:47AM +0200, Marek Vasut wrote:
>> Implement "force_ro" sysfs attribute to allow users to set read-write
>> devices as read-only and back to read-write from userspace. The choice
>> of the name is based on MMC core 'force_ro' attribute.
>>
>> This solves a situation where an AT24 I2C EEPROM with GPIO based nWP
>> signal may have to be occasionally updated. Such I2C EEPROM device is
>> usually set as read-only during most of the regular system operation,
>> but in case it has to be updated in a controlled manner, it could be
>> unlocked using this new "force_ro" sysfs attribute and then re-locked
>> again.
>>
>> The "read-only" DT property and config->read_only configuration is
>> respected and is used to set default state of the device, read-only
>> or read-write, for devices which do implement .reg_write function.
>> For devices which do not implement .reg_write function, the device
>> is unconditionally read-only and the "force_ro" attribute is not
>> visible.
>>
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> ---
>> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> Cc: linux-i2c@vger.kernel.org
>> ---
>> V2: - Document the force_ro attribute
>>      - Use sysfs_emit()
>> ---
>>   Documentation/ABI/stable/sysfs-bus-nvmem | 13 +++++++
>>   drivers/nvmem/core.c                     | 44 ++++++++++++++++++++++++
>>   drivers/nvmem/internals.h                |  1 +
>>   3 files changed, 58 insertions(+)
>>
>> diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
>> index 0e3a8492a1082..c713c4e6cecb1 100644
>> --- a/Documentation/ABI/stable/sysfs-bus-nvmem
>> +++ b/Documentation/ABI/stable/sysfs-bus-nvmem
>> @@ -1,3 +1,16 @@
>> +What:		/sys/bus/nvmem/devices/.../force_ro
>> +Date:		June 2024
>> +KernelVersion:	6.11
>> +Contact:	Marek Vasut <marex@denx.de>
>> +Description:
>> +		This read/write attribute allows users to set read-write
>> +		devices as read-only and back to read-write from userspace.
>> +		This can be used to unlock and relock write-protection of
>> +		devices which are generally locked, except during sporadic
>> +		programming operation.
>> +		Note: This file is only present if CONFIG_NVMEM_SYSFS
>> +		is enabled
> 
> And what exactly are the values that can be read or written here?

I expanded it to this:

  This read/write attribute allows users to set read-write
  devices as read-only and back to read-write from userspace.
  This can be used to unlock and relock write-protection of
  devices which are generally locked, except during sporadic
  programming operation.
+Read returns '0' or '1' for read-write or read-only modes
+respectively.
+Write parses one of 'YyTt1NnFf0', or [oO][NnFf] for "on"
+and "off", i.e. what kstrbool() supports.
  Note: This file is only present if CONFIG_NVMEM_SYSFS
  is enabled.

But I wonder, wouldn't it be better if write only supported '0' and '1' 
too, instead of the whole list of stuff that kstrbool() supports ?