[PATCH] arm64: Skip apply SSBS call for non SSBS system

[PATCH] arm64: Skip apply SSBS call for non SSBS system

[Gaurav Kohli]

In a system where no cpu's implement SSBS, for
them no need to set pstate. This might help to save
few cpu cycles during context switch.

Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6089638..79f80f1 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next)
 	struct pt_regs *regs = task_pt_regs(next);
 
 	/*
+	 * For Targets which don't have SSBS support, they
+	 * can return from here.
+	 */
+	if (!IS_ENABLED(CONFIG_ARM64_SSBD))
+		return;
+
+	/*
 	 * Nothing to do for kernel threads, but 'regs' may be junk
 	 * (e.g. idle task) so check the flags and bail early.
 	 */
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project


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[PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY

[Gaurav Kohli]

From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

Some users might not want to expose nvmem entry to sysfs and
only intend to use kernel interface so add such provision.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
  Documentation/ABI/stable/sysfs-bus-nvmem |  2 ++
  drivers/nvmem/Kconfig                    |  5 +++++
  drivers/nvmem/core.c                     | 11 ++++++-----
  3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem 
b/Documentation/ABI/stable/sysfs-bus-nvmem
index 5923ab4620c5..12aab0a85fea 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 not present if CONFIG_NVMEM_NO_SYSFS_ENTRY
+		is enabled

  		ex:
  		hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 0a7a470ee859..6ab3276d287c 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -192,4 +192,9 @@ config SC27XX_EFUSE
  	  This driver can also be built as a module. If so, the module
  	  will be called nvmem-sc27xx-efuse.

+config NVMEM_NO_SYSFS_ENTRY
+	bool "No nvmem sysfs entry"
+
+	help
+	  Say Yes if you do not want to add nvmem entry to sysfs.
  endif
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index b9a0270883a0..c70f183fe379 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -216,7 +216,7 @@ static const struct attribute_group 
nvmem_bin_rw_group = {
	.attrs		= nvmem_attrs,
  };

-static const struct attribute_group *nvmem_rw_dev_groups[] = {
+static const __maybe_unused struct attribute_group 
*nvmem_rw_dev_groups[] = {
  	&nvmem_bin_rw_group,
  	NULL,
  };
@@ -240,7 +240,7 @@ static const struct attribute_group 
nvmem_bin_ro_group = {
  	.attrs		= nvmem_attrs,
  };

-static const struct attribute_group *nvmem_ro_dev_groups[] = {
+static const __maybe_unused struct attribute_group 
*nvmem_ro_dev_groups[] = {
  	&nvmem_bin_ro_group,
  	NULL,
  };
@@ -265,7 +265,7 @@ static const struct attribute_group 
nvmem_bin_rw_root_group = {
  	.attrs		= nvmem_attrs,
  };

-static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
+static const __maybe_unused struct attribute_group 
*nvmem_rw_root_dev_groups[] = {
  	&nvmem_bin_rw_root_group,
  	NULL,
  };
@@ -289,7 +289,7 @@ static const struct attribute_group 
nvmem_bin_ro_root_group = {
  	.attrs		= nvmem_attrs,
  };

-static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
+static const __maybe_unused struct attribute_group 
*nvmem_ro_root_dev_groups[] = {
  	&nvmem_bin_ro_root_group,
  	NULL,
  };
@@ -688,6 +688,7 @@ struct nvmem_device *nvmem_register(const struct 
nvmem_config *config)
  	nvmem->read_only = device_property_present(config->dev, "read-only") |
  			   config->read_only;

+#if !defined(CONFIG_NVMEM_NO_SYSFS_ENTRY)
  	if (config->root_only)
  		nvmem->dev.groups = nvmem->read_only ?
  			nvmem_ro_root_dev_groups :
@@ -696,7 +697,7 @@ struct nvmem_device *nvmem_register(const struct 
nvmem_config *config)
  		nvmem->dev.groups = nvmem->read_only ?
  			nvmem_ro_dev_groups :
  			nvmem_rw_dev_groups;
-
+#endif
  	device_initialize(&nvmem->dev);

  	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
-- 
2.21.0

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Re: [PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY

[Gaurav Kohli]

Please ignore this patch, some problem in my git send mail.
Apologies for the spam.


On 8/4/2020 7:44 PM, Gaurav Kohli wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> 
> Some users might not want to expose nvmem entry to sysfs and
> only intend to use kernel interface so add such provision.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>    Documentation/ABI/stable/sysfs-bus-nvmem |  2 ++
>    drivers/nvmem/Kconfig                    |  5 +++++
>    drivers/nvmem/core.c                     | 11 ++++++-----
>    3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem
> b/Documentation/ABI/stable/sysfs-bus-nvmem
> index 5923ab4620c5..12aab0a85fea 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 not present if CONFIG_NVMEM_NO_SYSFS_ENTRY
> +		is enabled
> 
>    		ex:
>    		hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 0a7a470ee859..6ab3276d287c 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -192,4 +192,9 @@ config SC27XX_EFUSE
>    	  This driver can also be built as a module. If so, the module
>    	  will be called nvmem-sc27xx-efuse.
> 
> +config NVMEM_NO_SYSFS_ENTRY
> +	bool "No nvmem sysfs entry"
> +
> +	help
> +	  Say Yes if you do not want to add nvmem entry to sysfs.
>    endif
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index b9a0270883a0..c70f183fe379 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -216,7 +216,7 @@ static const struct attribute_group
> nvmem_bin_rw_group = {
> 	.attrs		= nvmem_attrs,
>    };
> 
> -static const struct attribute_group *nvmem_rw_dev_groups[] = {
> +static const __maybe_unused struct attribute_group
> *nvmem_rw_dev_groups[] = {
>    	&nvmem_bin_rw_group,
>    	NULL,
>    };
> @@ -240,7 +240,7 @@ static const struct attribute_group
> nvmem_bin_ro_group = {
>    	.attrs		= nvmem_attrs,
>    };
> 
> -static const struct attribute_group *nvmem_ro_dev_groups[] = {
> +static const __maybe_unused struct attribute_group
> *nvmem_ro_dev_groups[] = {
>    	&nvmem_bin_ro_group,
>    	NULL,
>    };
> @@ -265,7 +265,7 @@ static const struct attribute_group
> nvmem_bin_rw_root_group = {
>    	.attrs		= nvmem_attrs,
>    };
> 
> -static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
> +static const __maybe_unused struct attribute_group
> *nvmem_rw_root_dev_groups[] = {
>    	&nvmem_bin_rw_root_group,
>    	NULL,
>    };
> @@ -289,7 +289,7 @@ static const struct attribute_group
> nvmem_bin_ro_root_group = {
>    	.attrs		= nvmem_attrs,
>    };
> 
> -static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
> +static const __maybe_unused struct attribute_group
> *nvmem_ro_root_dev_groups[] = {
>    	&nvmem_bin_ro_root_group,
>    	NULL,
>    };
> @@ -688,6 +688,7 @@ struct nvmem_device *nvmem_register(const struct
> nvmem_config *config)
>    	nvmem->read_only = device_property_present(config->dev, "read-only") |
>    			   config->read_only;
> 
> +#if !defined(CONFIG_NVMEM_NO_SYSFS_ENTRY)
>    	if (config->root_only)
>    		nvmem->dev.groups = nvmem->read_only ?
>    			nvmem_ro_root_dev_groups :
> @@ -696,7 +697,7 @@ struct nvmem_device *nvmem_register(const struct
> nvmem_config *config)
>    		nvmem->dev.groups = nvmem->read_only ?
>    			nvmem_ro_dev_groups :
>    			nvmem_rw_dev_groups;
> -
> +#endif
>    	device_initialize(&nvmem->dev);
> 
>    	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
> 

-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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[PATCH] nvmem: core: add NVMEM_SYSFS Kconfig

[Gaurav Kohli]

From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

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>
---
 Documentation/ABI/stable/sysfs-bus-nvmem |   2 +
 drivers/nvmem/Kconfig                    |   9 +
 drivers/nvmem/Makefile                   |   3 +
 drivers/nvmem/core.c                     | 264 +----------------------
 drivers/nvmem/nvmem-sysfs.c              | 256 ++++++++++++++++++++++
 drivers/nvmem/nvmem.h                    |  62 ++++++
 6 files changed, 336 insertions(+), 260 deletions(-)
 create mode 100644 drivers/nvmem/nvmem-sysfs.c
 create mode 100644 drivers/nvmem/nvmem.h

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..e316811e9c04 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -13,6 +13,15 @@ menuconfig NVMEM
 
 if NVMEM
 
+config NVMEM_SYSFS
+	bool "/sys/bus/nvmem/devices/*/nvmem (sysfs interface)"
+	depends on SYSFS
+	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 @@ 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.
  *
@@ -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 @@ 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:
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 */

_______________________________________________
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Re: [PATCH] nvmem: core: add NVMEM_SYSFS Kconfig

[Gaurav Kohli]

Please ignore this patch also, sent due to git send mistake.
Apologies for the spam.


On 8/4/2020 7:44 PM, Gaurav Kohli wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> 
> 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>
> ---
>   Documentation/ABI/stable/sysfs-bus-nvmem |   2 +
>   drivers/nvmem/Kconfig                    |   9 +
>   drivers/nvmem/Makefile                   |   3 +
>   drivers/nvmem/core.c                     | 264 +----------------------
>   drivers/nvmem/nvmem-sysfs.c              | 256 ++++++++++++++++++++++
>   drivers/nvmem/nvmem.h                    |  62 ++++++
>   6 files changed, 336 insertions(+), 260 deletions(-)
>   create mode 100644 drivers/nvmem/nvmem-sysfs.c
>   create mode 100644 drivers/nvmem/nvmem.h
> 
> 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..e316811e9c04 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -13,6 +13,15 @@ menuconfig NVMEM
>   
>   if NVMEM
>   
> +config NVMEM_SYSFS
> +	bool "/sys/bus/nvmem/devices/*/nvmem (sysfs interface)"
> +	depends on SYSFS
> +	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 @@ 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.
>    *
> @@ -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 @@ 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:
> 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 */
> 

-- 
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Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system

[Gaurav Kohli]

Hi,

Please let us know, is below patch good to have
or not for non ssbs systems.

On 8/4/2020 7:44 PM, Gaurav Kohli wrote:
> In a system where no cpu's implement SSBS, for
> them no need to set pstate. This might help to save
> few cpu cycles during context switch.
> 
> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
> 
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 6089638..79f80f1 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next)
>   	struct pt_regs *regs = task_pt_regs(next);
>   
>   	/*
> +	 * For Targets which don't have SSBS support, they
> +	 * can return from here.
> +	 */
> +	if (!IS_ENABLED(CONFIG_ARM64_SSBD))
> +		return;
> +
> +	/*
>   	 * Nothing to do for kernel threads, but 'regs' may be junk
>   	 * (e.g. idle task) so check the flags and bail early.
>   	 */
> 

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a Linux Foundation Collaborative Project.

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Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system

[Will Deacon]

On Tue, Aug 04, 2020 at 07:44:42PM +0530, Gaurav Kohli wrote:
> In a system where no cpu's implement SSBS, for
> them no need to set pstate. This might help to save
> few cpu cycles during context switch.
> 
> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
> 
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 6089638..79f80f1 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next)
>  	struct pt_regs *regs = task_pt_regs(next);
>  
>  	/*
> +	 * For Targets which don't have SSBS support, they
> +	 * can return from here.
> +	 */
> +	if (!IS_ENABLED(CONFIG_ARM64_SSBD))
> +		return;

Does this actually make a measurable difference?

Will

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Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system

[Gaurav Kohli]

On 8/12/2020 7:00 PM, Will Deacon wrote:
> On Tue, Aug 04, 2020 at 07:44:42PM +0530, Gaurav Kohli wrote:
>> In a system where no cpu's implement SSBS, for
>> them no need to set pstate. This might help to save
>> few cpu cycles during context switch.
>>
>> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
>>
>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
>> index 6089638..79f80f1 100644
>> --- a/arch/arm64/kernel/process.c
>> +++ b/arch/arm64/kernel/process.c
>> @@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next)
>>   	struct pt_regs *regs = task_pt_regs(next);
>>   
>>   	/*
>> +	 * For Targets which don't have SSBS support, they
>> +	 * can return from here.
>> +	 */
>> +	if (!IS_ENABLED(CONFIG_ARM64_SSBD))
>> +		return;
> 
> Does this actually make a measurable difference?
> 
> Will
> 

Hi Will,

While doing code review between older kernel and latest kernel for 
context switch case, there i have found this and thought it is good to 
have for non-ssbs system to return early(as this might improve).

Please let me know if you want to run some tests.

Regards
Gaurav

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