@@ -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 snprintf(buf, PAGE_SIZE, "%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;
@@ -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;
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: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Cc: Bartosz Golaszewski <brgl@bgdev.pl> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-i2c@vger.kernel.org --- drivers/nvmem/core.c | 44 +++++++++++++++++++++++++++++++++++++++ drivers/nvmem/internals.h | 1 + 2 files changed, 45 insertions(+)