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nvmem: core: add NVMEM_SYSFS Kconfig
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Many nvmem providers are not very keen on having default sysfs
nvmem entry, as most of the usecases for them are inside kernel
itself. And in some cases read/writes to some areas in nvmem are
restricted and trapped at secure monitor level, so accessing them
from userspace would result in board reboots.

This patch adds new NVMEM_SYSFS Kconfig to make binary sysfs entry
an optional one. This provision will give more flexibility to users.
This patch also moves existing sysfs code to a new file so that its
not compiled in when its not really required.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Gaurav Kohli <gkohli@codeaurora.org>
Tested-by: Gaurav Kohli <gkohli@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Srinivas Kandagatla authored and Greg Kroah-Hartman committed Apr 25, 2019
1 parent fc1eb6e commit ae0c2d7
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Showing 6 changed files with 337 additions and 260 deletions.
2 changes: 2 additions & 0 deletions Documentation/ABI/stable/sysfs-bus-nvmem
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@ Description:
This file allows user to read/write the raw NVMEM contents.
Permissions for write to this file depends on the nvmem
provider configuration.
Note: This file is only present if CONFIG_NVMEM_SYSFS
is enabled

ex:
hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
Expand Down
10 changes: 10 additions & 0 deletions drivers/nvmem/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,16 @@ menuconfig NVMEM

if NVMEM

config NVMEM_SYSFS
bool "/sys/bus/nvmem/devices/*/nvmem (sysfs interface)"
depends on SYSFS
default y
help
Say Y here to add a sysfs interface for NVMEM.

This interface is mostly used by userspace applications to
read/write directly into nvmem.

config NVMEM_IMX_IIM
tristate "i.MX IC Identification Module support"
depends on ARCH_MXC || COMPILE_TEST
Expand Down
3 changes: 3 additions & 0 deletions drivers/nvmem/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,9 @@
obj-$(CONFIG_NVMEM) += nvmem_core.o
nvmem_core-y := core.o

obj-$(CONFIG_NVMEM_SYSFS) += nvmem_sysfs.o
nvmem_sysfs-y := nvmem-sysfs.o

# Devices
obj-$(CONFIG_NVMEM_BCM_OCOTP) += nvmem-bcm-ocotp.o
nvmem-bcm-ocotp-y := bcm-ocotp.o
Expand Down
264 changes: 4 additions & 260 deletions drivers/nvmem/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,27 +17,7 @@
#include <linux/nvmem-provider.h>
#include <linux/of.h>
#include <linux/slab.h>

struct nvmem_device {
struct module *owner;
struct device dev;
int stride;
int word_size;
int id;
struct kref refcnt;
size_t size;
bool read_only;
int flags;
enum nvmem_type type;
struct bin_attribute eeprom;
struct device *base_dev;
struct list_head cells;
nvmem_reg_read_t reg_read;
nvmem_reg_write_t reg_write;
void *priv;
};

#define FLAG_COMPAT BIT(0)
#include "nvmem.h"

struct nvmem_cell {
const char *name;
Expand All @@ -61,18 +41,7 @@ static LIST_HEAD(nvmem_lookup_list);

static BLOCKING_NOTIFIER_HEAD(nvmem_notifier);

static const char * const nvmem_type_str[] = {
[NVMEM_TYPE_UNKNOWN] = "Unknown",
[NVMEM_TYPE_EEPROM] = "EEPROM",
[NVMEM_TYPE_OTP] = "OTP",
[NVMEM_TYPE_BATTERY_BACKED] = "Battery backed",
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key eeprom_lock_key;
#endif

#define to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
void *val, size_t bytes)
{
Expand All @@ -91,187 +60,6 @@ static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
return -EINVAL;
}

static ssize_t type_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct nvmem_device *nvmem = to_nvmem_device(dev);

return sprintf(buf, "%s\n", nvmem_type_str[nvmem->type]);
}

static DEVICE_ATTR_RO(type);

static struct attribute *nvmem_attrs[] = {
&dev_attr_type.attr,
NULL,
};

static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *attr,
char *buf, loff_t pos, size_t count)
{
struct device *dev;
struct nvmem_device *nvmem;
int rc;

if (attr->private)
dev = attr->private;
else
dev = container_of(kobj, struct device, kobj);
nvmem = to_nvmem_device(dev);

/* Stop the user from reading */
if (pos >= nvmem->size)
return 0;

if (count < nvmem->word_size)
return -EINVAL;

if (pos + count > nvmem->size)
count = nvmem->size - pos;

count = round_down(count, nvmem->word_size);

rc = nvmem_reg_read(nvmem, pos, buf, count);

if (rc)
return rc;

return count;
}

static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *attr,
char *buf, loff_t pos, size_t count)
{
struct device *dev;
struct nvmem_device *nvmem;
int rc;

if (attr->private)
dev = attr->private;
else
dev = container_of(kobj, struct device, kobj);
nvmem = to_nvmem_device(dev);

/* Stop the user from writing */
if (pos >= nvmem->size)
return -EFBIG;

if (count < nvmem->word_size)
return -EINVAL;

if (pos + count > nvmem->size)
count = nvmem->size - pos;

count = round_down(count, nvmem->word_size);

rc = nvmem_reg_write(nvmem, pos, buf, count);

if (rc)
return rc;

return count;
}

/* default read/write permissions */
static struct bin_attribute bin_attr_rw_nvmem = {
.attr = {
.name = "nvmem",
.mode = 0644,
},
.read = bin_attr_nvmem_read,
.write = bin_attr_nvmem_write,
};

static struct bin_attribute *nvmem_bin_rw_attributes[] = {
&bin_attr_rw_nvmem,
NULL,
};

static const struct attribute_group nvmem_bin_rw_group = {
.bin_attrs = nvmem_bin_rw_attributes,
.attrs = nvmem_attrs,
};

static const struct attribute_group *nvmem_rw_dev_groups[] = {
&nvmem_bin_rw_group,
NULL,
};

/* read only permission */
static struct bin_attribute bin_attr_ro_nvmem = {
.attr = {
.name = "nvmem",
.mode = 0444,
},
.read = bin_attr_nvmem_read,
};

static struct bin_attribute *nvmem_bin_ro_attributes[] = {
&bin_attr_ro_nvmem,
NULL,
};

static const struct attribute_group nvmem_bin_ro_group = {
.bin_attrs = nvmem_bin_ro_attributes,
.attrs = nvmem_attrs,
};

static const struct attribute_group *nvmem_ro_dev_groups[] = {
&nvmem_bin_ro_group,
NULL,
};

/* default read/write permissions, root only */
static struct bin_attribute bin_attr_rw_root_nvmem = {
.attr = {
.name = "nvmem",
.mode = 0600,
},
.read = bin_attr_nvmem_read,
.write = bin_attr_nvmem_write,
};

static struct bin_attribute *nvmem_bin_rw_root_attributes[] = {
&bin_attr_rw_root_nvmem,
NULL,
};

static const struct attribute_group nvmem_bin_rw_root_group = {
.bin_attrs = nvmem_bin_rw_root_attributes,
.attrs = nvmem_attrs,
};

static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
&nvmem_bin_rw_root_group,
NULL,
};

/* read only permission, root only */
static struct bin_attribute bin_attr_ro_root_nvmem = {
.attr = {
.name = "nvmem",
.mode = 0400,
},
.read = bin_attr_nvmem_read,
};

static struct bin_attribute *nvmem_bin_ro_root_attributes[] = {
&bin_attr_ro_root_nvmem,
NULL,
};

static const struct attribute_group nvmem_bin_ro_root_group = {
.bin_attrs = nvmem_bin_ro_root_attributes,
.attrs = nvmem_attrs,
};

static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
&nvmem_bin_ro_root_group,
NULL,
};

static void nvmem_release(struct device *dev)
{
struct nvmem_device *nvmem = to_nvmem_device(dev);
Expand Down Expand Up @@ -422,43 +210,6 @@ static int nvmem_add_cells(struct nvmem_device *nvmem,
return rval;
}

/*
* nvmem_setup_compat() - Create an additional binary entry in
* drivers sys directory, to be backwards compatible with the older
* drivers/misc/eeprom drivers.
*/
static int nvmem_setup_compat(struct nvmem_device *nvmem,
const struct nvmem_config *config)
{
int rval;

if (!config->base_dev)
return -EINVAL;

if (nvmem->read_only)
nvmem->eeprom = bin_attr_ro_root_nvmem;
else
nvmem->eeprom = bin_attr_rw_root_nvmem;
nvmem->eeprom.attr.name = "eeprom";
nvmem->eeprom.size = nvmem->size;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
nvmem->eeprom.attr.key = &eeprom_lock_key;
#endif
nvmem->eeprom.private = &nvmem->dev;
nvmem->base_dev = config->base_dev;

rval = device_create_bin_file(nvmem->base_dev, &nvmem->eeprom);
if (rval) {
dev_err(&nvmem->dev,
"Failed to create eeprom binary file %d\n", rval);
return rval;
}

nvmem->flags |= FLAG_COMPAT;

return 0;
}

/**
* nvmem_register_notifier() - Register a notifier block for nvmem events.
*
Expand Down Expand Up @@ -651,14 +402,7 @@ 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;

if (config->root_only)
nvmem->dev.groups = nvmem->read_only ?
nvmem_ro_root_dev_groups :
nvmem_rw_root_dev_groups;
else
nvmem->dev.groups = nvmem->read_only ?
nvmem_ro_dev_groups :
nvmem_rw_dev_groups;
nvmem->dev.groups = nvmem_sysfs_get_groups(nvmem, config);

device_initialize(&nvmem->dev);

Expand All @@ -669,7 +413,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
goto err_put_device;

if (config->compat) {
rval = nvmem_setup_compat(nvmem, config);
rval = nvmem_sysfs_setup_compat(nvmem, config);
if (rval)
goto err_device_del;
}
Expand All @@ -696,7 +440,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
nvmem_device_remove_all_cells(nvmem);
err_teardown_compat:
if (config->compat)
device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
nvmem_sysfs_remove_compat(nvmem, config);
err_device_del:
device_del(&nvmem->dev);
err_put_device:
Expand Down
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