nvmem: core: add NVMEM_SYSFS Kconfig

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>

6 files changed, 337 insertions, 260 deletions

diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem
index 5923ab4620c5..9ffba8576f7b 100644
--- a/Documentation/ABI/stable/sysfs-bus-nvmem
+++ b/Documentation/ABI/stable/sysfs-bus-nvmem
@@ -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
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index a90e9a1ebe55..6b2c4254c2fb 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -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
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 4c7ba12a7005..c1fe4768dfef 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -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
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 5abebf2128b8..c7892c3da91f 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -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;
@@ -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)
 {
@@ -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);
@@ -422,43 +210,6 @@ err:
         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.
  *
@@ -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);
 
@@ -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;
         }
@@ -696,7 +440,7 @@ err_remove_cells:
         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:
diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c
new file mode 100644
index 000000000000..6f303b91f6e7
--- /dev/null
+++ b/drivers/nvmem/nvmem-sysfs.c
@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, Linaro Limited
+ */
+#include "nvmem.h"
+
+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
+
+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->priv, 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->priv, 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,
+};
+
+const struct attribute_group **nvmem_sysfs_get_groups(
+                                        struct nvmem_device *nvmem,
+                                        const struct nvmem_config *config)
+{
+        if (config->root_only)
+                return nvmem->read_only ?
+                        nvmem_ro_root_dev_groups :
+                        nvmem_rw_root_dev_groups;
+
+        return nvmem->read_only ? nvmem_ro_dev_groups : nvmem_rw_dev_groups;
+}
+
+/*
+ * nvmem_setup_compat() - Create an additional binary entry in
+ * drivers sys directory, to be backwards compatible with the older
+ * drivers/misc/eeprom drivers.
+ */
+int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
+                              const struct nvmem_config *config)
+{
+        int rval;
+
+        if (!config->compat)
+                return 0;
+
+        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;
+}
+
+void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
+                              const struct nvmem_config *config)
+{
+        if (config->compat)
+                device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
+}
diff --git a/drivers/nvmem/nvmem.h b/drivers/nvmem/nvmem.h
new file mode 100644
index 000000000000..eb8ed7121fa3
--- /dev/null
+++ b/drivers/nvmem/nvmem.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _DRIVERS_NVMEM_H
+#define _DRIVERS_NVMEM_H
+
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.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 to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
+#define FLAG_COMPAT             BIT(0)
+
+#ifdef CONFIG_NVMEM_SYSFS
+const struct attribute_group **nvmem_sysfs_get_groups(
+                                        struct nvmem_device *nvmem,
+                                        const struct nvmem_config *config);
+int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
+                              const struct nvmem_config *config);
+void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
+                              const struct nvmem_config *config);
+#else
+static inline const struct attribute_group **nvmem_sysfs_get_groups(
+                                        struct nvmem_device *nvmem,
+                                        const struct nvmem_config *config)
+{
+        return NULL;
+}
+
+static inline int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
+                                      const struct nvmem_config *config)
+{
+        return -ENOSYS;
+}
+static inline void nvmem_sysfs_remove_compat(struct nvmem_device *nvmem,
+                              const struct nvmem_config *config)
+{
+}
+#endif /* CONFIG_NVMEM_SYSFS */
+
+#endif /* _DRIVERS_NVMEM_H */