[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

From: Lee Jones <lee.jones@linaro.org>

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/base/Kconfig    |    3 +
 drivers/base/Makefile   |    1 +
 drivers/base/soc.c      |   96 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sys_soc.h |   29 ++++++++++++++
 4 files changed, 129 insertions(+), 0 deletions(-)
 create mode 100644 drivers/base/soc.c
 create mode 100644 include/linux/sys_soc.h

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index e9e5238..f381fcc 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -168,6 +168,9 @@ config SYS_HYPERVISOR
 	bool
 	default n
 
+config SYS_SOC
+	bool
+
 config ARCH_NO_SYSDEV_OPS
 	bool
 	---help---
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4c5701c..a0d246d 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
 endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_SYS_SOC) += soc.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
diff --git a/drivers/base/soc.c b/drivers/base/soc.c
new file mode 100644
index 0000000..1a409e2
--- /dev/null
+++ b/drivers/base/soc.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+static char *soc_names[] = {"1", "2", "3", "4", "5", "6", "7", "8" };
+static struct device parent_soc = { .init_name = "soc", };
+struct device *soc[MAX_SOCS];
+
+static int soc_device_create_files(struct device *soc,
+                                   struct device_attribute soc_attrs[]);
+
+static void soc_device_remove_files(struct device *soc,
+                                    struct device_attribute soc_attrs[]);
+
+static int __init soc_device_create_files(struct device *soc,
+                                          struct device_attribute soc_attrs[])
+{
+	int ret = 0;
+	int i = 0;
+
+	while (soc_attrs[i].attr.name != NULL) {
+		ret = device_create_file(soc, &soc_attrs[i++]);
+		if (ret)
+			goto out;
+	}
+	return ret;
+
+out:
+	soc_device_remove_files(soc, soc_attrs);
+	return ret;
+}
+
+static void __exit soc_device_remove_files(struct device *soc,
+                                           struct device_attribute soc_attrs[])
+{
+	int i = 0;
+
+	while (soc_attrs[i++].attr.name != NULL)
+		device_remove_file(soc, &soc_attrs[i]);
+}
+
+int __init soc_device_register(struct device_attribute *soc_attrs[],
+                               int soc_count)
+{
+	int ret, i;
+
+	/* Register top-level SoC device '/sys/devices/soc' */
+	ret = device_register(&parent_soc);
+	if (ret)
+		return ret;
+
+	/* Register each SoC and populate sysfs with requested attributes */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc[i] = kmalloc(sizeof(struct device), GFP_KERNEL);
+		if (!soc[i])
+			return -ENOMEM;
+
+		memset(soc[i], 0, sizeof(struct device));
+		soc[i]->init_name = soc_names[i];
+		soc[i]->parent = &parent_soc;
+
+		ret = device_register(soc[i]);
+		if (ret)
+			return ret;
+
+		soc_device_create_files(soc[i], soc_attrs[i]);
+	}
+
+	return ret;
+}
+
+void __exit soc_device_unregister(struct device_attribute *soc_attrs[],
+                                  int soc_count)
+{
+	int i;
+
+	/* Unregister and free all SoC from sysfs */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc_device_remove_files(soc[i], soc_attrs[i]);
+		device_unregister(soc[i]);
+		kfree(soc[i]);
+	}
+
+	/* Unregister top-level SoC device '/sys/devices/soc' */
+	device_unregister(&parent_soc);
+}
diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
new file mode 100644
index 0000000..072cd39
--- /dev/null
+++ b/include/linux/sys_soc.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+#ifndef __SYS_SOC_H
+#define __SYS_SOC_H
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+
+#define MAX_SOCS 8
+
+/**
+ * soc_device_register - register SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @soc: Parent node '/sys/devices/soc'
+ */
+int soc_device_register(struct device_attribute *soc_attrs[],
+                        int num_socs);
+/**
+ *  soc_device_unregister - unregister SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @soc: Parent node '/sys/devices/soc'
+ */
+void soc_device_unregister(struct device_attribute *soc_attrs[],
+                           int num_socs);
+
+#endif /* __SYS_SOC_H */
-- 
1.7.4.1

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Jamie Iles]

Hi Lee,

Works fine on my platform, but I have a couple of questions.

On Mon, Apr 11, 2011 at 07:01:16PM +0100, Lee Jones wrote:
> From: Lee Jones <lee.jones@linaro.org>
> 
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/base/Kconfig    |    3 +
>  drivers/base/Makefile   |    1 +
>  drivers/base/soc.c      |   96 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/sys_soc.h |   29 ++++++++++++++
>  4 files changed, 129 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/base/soc.c
>  create mode 100644 include/linux/sys_soc.h
> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index e9e5238..f381fcc 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -168,6 +168,9 @@ config SYS_HYPERVISOR
>  	bool
>  	default n
>  
> +config SYS_SOC
> +	bool
> +
>  config ARCH_NO_SYSDEV_OPS
>  	bool
>  	---help---
> diff --git a/drivers/base/Makefile b/drivers/base/Makefile
> index 4c5701c..a0d246d 100644
> --- a/drivers/base/Makefile
> +++ b/drivers/base/Makefile
> @@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
>  obj-$(CONFIG_MODULES)	+= module.o
>  endif
>  obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
> +obj-$(CONFIG_SYS_SOC) += soc.o
>  
>  ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
>  
> diff --git a/drivers/base/soc.c b/drivers/base/soc.c
> new file mode 100644
> index 0000000..1a409e2
> --- /dev/null
> +++ b/drivers/base/soc.c
> @@ -0,0 +1,96 @@
> +/*
> + * Copyright (C) ST-Ericsson SA 2011
> + *
> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +
> +#include <linux/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/stat.h>
> +#include <linux/slab.h>
> +#include <linux/sys_soc.h>
> +
> +static char *soc_names[] = {"1", "2", "3", "4", "5", "6", "7", "8" };

Could this be made const?  Actually, could we just use dev_set_name() 
and do it at runtime?

> +static struct device parent_soc = { .init_name = "soc", };

I don't think this device can be statically allocated.

> +struct device *soc[MAX_SOCS];
> +
> +static int soc_device_create_files(struct device *soc,
> +                                   struct device_attribute soc_attrs[]);
> +
> +static void soc_device_remove_files(struct device *soc,
> +                                    struct device_attribute soc_attrs[]);

If you move soc_device_remove_files() above soc_device_create_files() 
then I don't think you need these prototypes.

> +
> +static int __init soc_device_create_files(struct device *soc,
> +                                          struct device_attribute soc_attrs[])
> +{
> +	int ret = 0;
> +	int i = 0;
> +
> +	while (soc_attrs[i].attr.name != NULL) {
> +		ret = device_create_file(soc, &soc_attrs[i++]);
> +		if (ret)
> +			goto out;
> +	}
> +	return ret;
> +
> +out:
> +	soc_device_remove_files(soc, soc_attrs);
> +	return ret;
> +}
> +
> +static void __exit soc_device_remove_files(struct device *soc,
> +                                           struct device_attribute soc_attrs[])

This is used in the cleanup path of soc_device_create_files() so can't 
be annotated with __exit:

`soc_device_remove_files' referenced in section `.init.text' of 
drivers/built-in.o: defined in discarded section `.exit.text' of 
drivers/built-in.o

> +{
> +	int i = 0;
> +
> +	while (soc_attrs[i++].attr.name != NULL)
> +		device_remove_file(soc, &soc_attrs[i]);
> +}
> +
> +int __init soc_device_register(struct device_attribute *soc_attrs[],
> +                               int soc_count)
> +{
> +	int ret, i;

Shouldn't this check that soc_count < MAX_SOCS?

> +
> +	/* Register top-level SoC device '/sys/devices/soc' */
> +	ret = device_register(&parent_soc);
> +	if (ret)
> +		return ret;

I think that this device needs to be dynamically allocated and have a 
release function that does a kfree() on it.

> +
> +	/* Register each SoC and populate sysfs with requested attributes */
> +	for (i = 0; i < soc_count - 1; i++) {
> +		soc[i] = kmalloc(sizeof(struct device), GFP_KERNEL);
> +		if (!soc[i])
> +			return -ENOMEM;
> +
> +		memset(soc[i], 0, sizeof(struct device));

kzalloc() and remove the memset()?

> +		soc[i]->init_name = soc_names[i];

It would be good to use dev_set_name() here, but I wonder if perhaps the 
devices should be called soc1, soc2 etc rather than 1, 2?

> +		soc[i]->parent = &parent_soc;
> +
> +		ret = device_register(soc[i]);
> +		if (ret)
> +			return ret;
> +
> +		soc_device_create_files(soc[i], soc_attrs[i]);
> +	}
> +
> +	return ret;
> +}
> +
> +void __exit soc_device_unregister(struct device_attribute *soc_attrs[],
> +                                  int soc_count)
> +{
> +	int i;
> +
> +	/* Unregister and free all SoC from sysfs */
> +	for (i = 0; i < soc_count - 1; i++) {
> +		soc_device_remove_files(soc[i], soc_attrs[i]);
> +		device_unregister(soc[i]);
> +		kfree(soc[i]);

The kfree() should be done in the .release() method otherwise the device 
could be freed whilst someone still holds a reference.

> +	}
> +
> +	/* Unregister top-level SoC device '/sys/devices/soc' */
> +	device_unregister(&parent_soc);
> +}
> diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
> new file mode 100644
> index 0000000..072cd39
> --- /dev/null
> +++ b/include/linux/sys_soc.h
> @@ -0,0 +1,29 @@
> +/*
> + * Copyright (C) ST-Ericsson SA 2011
> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +#ifndef __SYS_SOC_H
> +#define __SYS_SOC_H
> +
> +#include <linux/kobject.h>
> +#include <linux/device.h>
> +
> +#define MAX_SOCS 8
> +
> +/**
> + * soc_device_register - register SoC as a device
> + * @soc_attr: Array of sysfs file attributes
> + * @soc: Parent node '/sys/devices/soc'
> + */
> +int soc_device_register(struct device_attribute *soc_attrs[],
> +                        int num_socs);
> +/**
> + *  soc_device_unregister - unregister SoC as a device
> + * @soc_attr: Array of sysfs file attributes
> + * @soc: Parent node '/sys/devices/soc'
> + */
> +void soc_device_unregister(struct device_attribute *soc_attrs[],
> +                           int num_socs);
> +
> +#endif /* __SYS_SOC_H */
> -- 
> 1.7.4.1
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Hi James,

Firstly, thank you for taking the time to review my patch.

I hope this is more to your liking:

--------------------------------------------------------------------------------

From: Lee Jones <lee.jones@linaro.org>

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/base/Kconfig    |    3 +
 drivers/base/Makefile   |    1 +
 drivers/base/soc.c      |  127 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sys_soc.h |   29 +++++++++++
 4 files changed, 160 insertions(+), 0 deletions(-)
 create mode 100644 drivers/base/soc.c
 create mode 100644 include/linux/sys_soc.h

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index e9e5238..f381fcc 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -168,6 +168,9 @@ config SYS_HYPERVISOR
 	bool
 	default n
 
+config SYS_SOC
+	bool
+
 config ARCH_NO_SYSDEV_OPS
 	bool
 	---help---
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4c5701c..a0d246d 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
 endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_SYS_SOC) += soc.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
diff --git a/drivers/base/soc.c b/drivers/base/soc.c
new file mode 100644
index 0000000..9862a7e
--- /dev/null
+++ b/drivers/base/soc.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+struct device *parent_soc;
+struct device *soc[MAX_SOCS];
+
+static void soc_device_remove_files(struct device *soc,
+                                    struct device_attribute soc_attrs[])
+{
+	int i = 0;
+
+	while (soc_attrs[i++].attr.name != NULL)
+		device_remove_file(soc, &soc_attrs[i]);
+}
+
+static int __init soc_device_create_files(struct device *soc,
+                                          struct device_attribute soc_attrs[])
+{
+	int ret = 0;
+	int i = 0;
+
+	while (soc_attrs[i].attr.name != NULL) {
+		ret = device_create_file(soc, &soc_attrs[i++]);
+		if (ret)
+			goto out;
+	}
+	return ret;
+
+out:
+	soc_device_remove_files(soc, soc_attrs);
+	return ret;
+}
+
+void soc_device_release(struct device *soc)
+{
+	kfree(soc);
+}
+
+int __init soc_device_register(struct device_attribute *soc_attrs[],
+                               int soc_count)
+{
+	int ret, i;
+
+	if (!soc_attrs || soc_count > MAX_SOCS)
+		return -EINVAL;
+
+	/* Register top-level SoC device '/sys/devices/soc'. */
+	parent_soc = kzalloc(sizeof(struct device), GFP_KERNEL);
+	if (!parent_soc)
+		return -ENOMEM;
+
+	ret = dev_set_name(parent_soc, "soc");
+	if (ret)
+		goto soc_parent_free;
+
+	parent_soc->release = soc_device_release;
+
+	ret = device_register(parent_soc);
+	if (ret)
+		goto soc_parent_free;
+
+	/* Register each SoC and populate sysfs with requested attributes. */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc[i] = kzalloc(sizeof(struct device), GFP_KERNEL);
+		if (!soc[i]) {
+			ret = -ENOMEM;
+			goto soc_out_of_memory;
+		}
+
+		ret = dev_set_name(soc[i], "soc%d", i);
+		if (ret)
+			goto soc_free_unreg;
+
+		soc[i]->parent = parent_soc;
+		soc[i]->release = soc_device_release;
+
+		ret = device_register(soc[i]);
+		if (ret)
+			goto soc_free_unreg;
+
+		ret = soc_device_create_files(soc[i], soc_attrs[i]);
+		if (ret)
+			goto soc_free_unreg;
+	}
+	return ret;
+
+soc_free_unreg:
+	kfree(soc[i]);
+soc_out_of_memory:
+	/* Unregister only previously registered SoCs. */
+	soc_device_unregister(soc_attrs, i);
+	return ret;
+
+soc_parent_free:
+	/* Free unregisterable parent SoC device. */
+	kfree(parent_soc);
+	return ret;
+}
+
+void soc_device_unregister(struct device_attribute *soc_attrs[],
+                           int soc_count)
+{
+	int i;
+
+	if (!soc_attrs || soc_count > MAX_SOCS)
+		return;
+
+	/* Unregister and free all SoC from sysfs */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc_device_remove_files(soc[i], soc_attrs[i]);
+		device_unregister(soc[i]);
+	}
+
+	/* Unregister top-level SoC device '/sys/devices/soc'. */
+	device_unregister(parent_soc);
+}
diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
new file mode 100644
index 0000000..529a798
--- /dev/null
+++ b/include/linux/sys_soc.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+#ifndef __SYS_SOC_H
+#define __SYS_SOC_H
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+
+#define MAX_SOCS 8
+
+/**
+ * soc_device_register - register SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @num_socs: Amount of SoCs we're attempting to register
+ */
+int soc_device_register(struct device_attribute *soc_attrs[],
+                        int num_socs);
+/**
+ * soc_device_unregister - unregister SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @num_socs: Amount of SoCs we're attempting to register
+ */
+void soc_device_unregister(struct device_attribute *soc_attrs[],
+                           int num_socs);
+
+#endif /* __SYS_SOC_H */
-- 
1.7.4.1

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Arnd Bergmann]

On Tuesday 12 July 2011, Lee Jones wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/base/Kconfig    |   10 +++++
>  drivers/base/Makefile   |    1 +
>  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/sys_soc.h |   45 +++++++++++++++++++++

After looking at the patch again, I do have some important comments
after all. I had only looked at the documentation you posted, not
at the actual patch.

> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index d57e8d0..2feab2b 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -168,4 +168,14 @@ config SYS_HYPERVISOR
>  	bool
>  	default n
>  
> +config ARCH_NO_SYSDEV_OPS
> +	bool
> +	---help---
> +	  To be selected by architectures that don't use sysdev class or
> +	  sysdev driver power management (suspend/resume) and shutdown
> +	  operations.

You don't seem to be using this anywhere. What is this for?

> diff --git a/drivers/base/soc.c b/drivers/base/soc.c
> new file mode 100644
> index 0000000..30659f4
> --- /dev/null
> +++ b/drivers/base/soc.c
> @@ -0,0 +1,98 @@
> +/*
> + * Copyright (C) ST-Ericsson SA 2011
> + *
> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +
> +#include <linux/sysfs.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/stat.h>
> +#include <linux/slab.h>
> +#include <linux/sys_soc.h>
> +
> +struct device_attribute soc_attrs[] = {
> +	__ATTR(machine,  S_IRUGO, NULL, NULL),
> +	__ATTR(family,   S_IRUGO, NULL, NULL),
> +	__ATTR(soc_id,   S_IRUGO, NULL, NULL),
> +	__ATTR(revision, S_IRUGO, NULL, NULL),
> +	__ATTR_NULL,
> +};

This method does not work. You only set the function pointers
when you call soc_device_register, but they will end up overwriting
the existing function pointers when you have multiple callers of that
function.

It would be better to define a 'struct soc_device' derived from 'struct 
device' that holds a pointer to the actual strings (or operations, if
you insist) and provide a single soc_info_get() function that is used
for all the attributes.

> +const char *soc_names[] = { "1", "2", "3", "4", "5", "6", "7", "8" };
> +static int soc_count = 0;

This is a bit silly and artificially limits the number of SoC devices.
It's much simpler to just use dev_set_name().

> +static struct device soc_grandparent = {
> +	.init_name = "soc",
> +};
>
> +static int soc_device_create_files(struct device *soc);
> +static void soc_device_remove_files(struct device *soc);

No forward declarations for static functions please.

> +int __init soc_device_register(struct device *soc_parent,
> +			struct soc_callback_functions *soc_callbacks)
> +{
> +	int ret;
> +
> +	soc_attrs[MACHINE].show = soc_callbacks->get_machine_fn;
> +	soc_attrs[FAMILY].show = soc_callbacks->get_family_fn;
> +	soc_attrs[SOCID].show = soc_callbacks->get_soc_id_fn;
> +	soc_attrs[REVISION].show = soc_callbacks->get_revision_fn;

It's better to allocate the device here, so you don't have to
do it in each caller.

> +	soc_parent->init_name = soc_names[soc_count];
> +	soc_parent->parent = &soc_grandparent;
> +
> +	ret = device_register(soc_parent);
> +	if (ret)
> +		return ret;
> +
> +	soc_device_create_files(soc_parent);
> +
> +	soc_count++;

This needs some locking to ensure that you don't try to register
two devices with the same number.

> +
> +void __exit soc_device_unregister(struct device *soc_parent)
> +{
> +	/* Unregister and free SoC from sysfs */
> +	soc_device_remove_files(soc_parent);
> +	device_unregister(soc_parent);
> +
> +	if (--soc_count == 0)
> +		/* Unregister top-level SoC device '/sys/devices/soc' */
> +	device_unregister(&soc_grandparent);
> +}

The exit function does not make any sense if you cannot build the soc
support itself as a module, which in turn makes no sense at all.

> +
> +#define MAX_SOCS 8
> +#define MACHINE  0
> +#define FAMILY   1
> +#define SOCID    2
> +#define REVISION 3
> +

I think these defines are used nowhere by the individual drivers, so they
need not be in the header file. More importantly, the names are not put
in a proper namespace, so they can easily collide with other macros
or enums.

	Arnd

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

On 13/07/11 08:53, Greg KH wrote:
> On Wed, Jul 13, 2011 at 08:16:05AM +0100, Lee Jones wrote:
>> On 12/07/11 17:08, Greg KH wrote:
>>> On Tue, Jul 12, 2011 at 05:13:39PM +0300, Baruch Siach wrote:
>>>> Hi Lee,
>>>>
>>>> On Tue, Jul 12, 2011 at 02:08:08PM +0100, Lee Jones wrote:
>>>>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>>>>> ---
>>>>>  drivers/base/Kconfig    |   10 +++++
>>>>>  drivers/base/Makefile   |    1 +
>>>>>  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>>  include/linux/sys_soc.h |   45 +++++++++++++++++++++
>>>>>  4 files changed, 154 insertions(+), 0 deletions(-)
>>>>>  create mode 100644 drivers/base/soc.c
>>>>>  create mode 100644 include/linux/sys_soc.h
>>>>
>>>> I guess you should Cc Greg Kroah-Hartman <gregkh@suse.de> on this series.
>>
>> Yes, of course. Thanks Baruch.
>>
>>> Only if the submitter wants it applied, obviously, they don't :)
>>>
>>> Why do we have things like the MAINTAINERS file and
>>> scripts/get_maintainer.pl if no one uses them...
>>
>> Doh! Sorry Greg. I'm playing around with my new send-patches.sh and I've
>> neglected to add functionality to apply bespoke To, CC and BCC fields on
>> sending. I'll make the amendments to the script for next time.
> 
> Do you really need another 'send-patches.sh' type script?  What's wrong
> with the built in ones from git or quilt that requires a custom one?

Yes, I really am that lazy. :)

Firstly, I don't send enough patches upstream to enable me to learn then
retain the knowledge to quickly type out a `git send-email` command. If
I write a script just once and keep it centrally located, it will
inevitably save me time in the long-term. Also, when I draft patches I
may do so from a different email address depending on the hat I'm
wearing at any given moment. Supplying an account flag "--can" or
"--lin" is somewhat easier than typing out different credentials each
time. "--smtp-server", "--smtp-server-port", "--smtp-encryption",
"--smtp-user", "--smtp-pass" and "--from" all differ from account to
account.

With this script I dump the patch-set into a directory and issue
"send-patches.sh --lin --arm <patchdir>" and off goes the patch-set to
the Arm ML. However, as Baruch and yourself kindly noticed, I omitted
functionality to add the maintainer and interested party email address -
I'll fix that now.

Sorry for any inconvenience this may have caused.

Kind regards,
Lee

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Greg KH]

On Wed, Jul 13, 2011 at 08:16:05AM +0100, Lee Jones wrote:
> On 12/07/11 17:08, Greg KH wrote:
> > On Tue, Jul 12, 2011 at 05:13:39PM +0300, Baruch Siach wrote:
> >> Hi Lee,
> >>
> >> On Tue, Jul 12, 2011 at 02:08:08PM +0100, Lee Jones wrote:
> >>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> >>> ---
> >>>  drivers/base/Kconfig    |   10 +++++
> >>>  drivers/base/Makefile   |    1 +
> >>>  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
> >>>  include/linux/sys_soc.h |   45 +++++++++++++++++++++
> >>>  4 files changed, 154 insertions(+), 0 deletions(-)
> >>>  create mode 100644 drivers/base/soc.c
> >>>  create mode 100644 include/linux/sys_soc.h
> >>
> >> I guess you should Cc Greg Kroah-Hartman <gregkh@suse.de> on this series.
> 
> Yes, of course. Thanks Baruch.
> 
> > Only if the submitter wants it applied, obviously, they don't :)
> > 
> > Why do we have things like the MAINTAINERS file and
> > scripts/get_maintainer.pl if no one uses them...
> 
> Doh! Sorry Greg. I'm playing around with my new send-patches.sh and I've
> neglected to add functionality to apply bespoke To, CC and BCC fields on
> sending. I'll make the amendments to the script for next time.

Do you really need another 'send-patches.sh' type script?  What's wrong
with the built in ones from git or quilt that requires a custom one?

greg k-h

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

On 12/07/11 17:08, Greg KH wrote:
> On Tue, Jul 12, 2011 at 05:13:39PM +0300, Baruch Siach wrote:
>> Hi Lee,
>>
>> On Tue, Jul 12, 2011 at 02:08:08PM +0100, Lee Jones wrote:
>>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>>> ---
>>>  drivers/base/Kconfig    |   10 +++++
>>>  drivers/base/Makefile   |    1 +
>>>  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
>>>  include/linux/sys_soc.h |   45 +++++++++++++++++++++
>>>  4 files changed, 154 insertions(+), 0 deletions(-)
>>>  create mode 100644 drivers/base/soc.c
>>>  create mode 100644 include/linux/sys_soc.h
>>
>> I guess you should Cc Greg Kroah-Hartman <gregkh@suse.de> on this series.

Yes, of course. Thanks Baruch.

> Only if the submitter wants it applied, obviously, they don't :)
> 
> Why do we have things like the MAINTAINERS file and
> scripts/get_maintainer.pl if no one uses them...

Doh! Sorry Greg. I'm playing around with my new send-patches.sh and I've
neglected to add functionality to apply bespoke To, CC and BCC fields on
sending. I'll make the amendments to the script for next time.

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Greg KH]

On Tue, Jul 12, 2011 at 05:13:39PM +0300, Baruch Siach wrote:
> Hi Lee,
> 
> On Tue, Jul 12, 2011 at 02:08:08PM +0100, Lee Jones wrote:
> > Signed-off-by: Lee Jones <lee.jones@linaro.org>
> > ---
> >  drivers/base/Kconfig    |   10 +++++
> >  drivers/base/Makefile   |    1 +
> >  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/sys_soc.h |   45 +++++++++++++++++++++
> >  4 files changed, 154 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/base/soc.c
> >  create mode 100644 include/linux/sys_soc.h
> 
> I guess you should Cc Greg Kroah-Hartman <gregkh@suse.de> on this series.

Only if the submitter wants it applied, obviously, they don't :)

Why do we have things like the MAINTAINERS file and
scripts/get_maintainer.pl if no one uses them...

greg k-h

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Baruch Siach]

Hi Lee,

On Tue, Jul 12, 2011 at 02:08:08PM +0100, Lee Jones wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/base/Kconfig    |   10 +++++
>  drivers/base/Makefile   |    1 +
>  drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/sys_soc.h |   45 +++++++++++++++++++++
>  4 files changed, 154 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/base/soc.c
>  create mode 100644 include/linux/sys_soc.h

I guess you should Cc Greg Kroah-Hartman <gregkh@suse.de> on this series.

baruch

[snip]

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/base/Kconfig    |   10 +++++
 drivers/base/Makefile   |    1 +
 drivers/base/soc.c      |   98 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sys_soc.h |   45 +++++++++++++++++++++
 4 files changed, 154 insertions(+), 0 deletions(-)
 create mode 100644 drivers/base/soc.c
 create mode 100644 include/linux/sys_soc.h

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index d57e8d0..2feab2b 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -168,4 +168,14 @@ config SYS_HYPERVISOR
 	bool
 	default n
 
+config ARCH_NO_SYSDEV_OPS
+	bool
+	---help---
+	  To be selected by architectures that don't use sysdev class or
+	  sysdev driver power management (suspend/resume) and shutdown
+	  operations.
+
+config SYS_SOC
+	bool
+
 endmenu
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4c5701c..a0d246d 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
 endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_SYS_SOC) += soc.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
diff --git a/drivers/base/soc.c b/drivers/base/soc.c
new file mode 100644
index 0000000..30659f4
--- /dev/null
+++ b/drivers/base/soc.c
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+struct device_attribute soc_attrs[] = {
+	__ATTR(machine,  S_IRUGO, NULL, NULL),
+	__ATTR(family,   S_IRUGO, NULL, NULL),
+	__ATTR(soc_id,   S_IRUGO, NULL, NULL),
+	__ATTR(revision, S_IRUGO, NULL, NULL),
+	__ATTR_NULL,
+};
+
+const char *soc_names[] = { "1", "2", "3", "4", "5", "6", "7", "8" };
+static int soc_count = 0;
+
+static struct device soc_grandparent = {
+	.init_name = "soc",
+};
+
+static int soc_device_create_files(struct device *soc);
+static void soc_device_remove_files(struct device *soc);
+
+static int __init soc_device_create_files(struct device *soc)
+{
+	int ret = 0;
+	int i   = 0;
+
+	while (soc_attrs[i].attr.name != NULL) {
+		ret = device_create_file(soc, &soc_attrs[i++]);
+		if (ret)
+			goto out;
+	}
+	return ret;
+
+out:
+	soc_device_remove_files(soc);
+	return ret;
+}
+
+static void __exit soc_device_remove_files(struct device *soc)
+{
+	int i = 0;
+
+	while (soc_attrs[i++].attr.name != NULL)
+		device_remove_file(soc, &soc_attrs[i]);
+}
+
+int __init soc_device_register(struct device *soc_parent,
+			struct soc_callback_functions *soc_callbacks)
+{
+	int ret;
+
+	soc_attrs[MACHINE].show = soc_callbacks->get_machine_fn;
+	soc_attrs[FAMILY].show = soc_callbacks->get_family_fn;
+	soc_attrs[SOCID].show = soc_callbacks->get_soc_id_fn;
+	soc_attrs[REVISION].show = soc_callbacks->get_revision_fn;
+
+	if (!soc_count) {
+		/* Register top-level SoC device '/sys/devices/soc' */
+		ret = device_register(&soc_grandparent);
+		if (ret)
+			return ret;
+	}
+
+	soc_parent->init_name = soc_names[soc_count];
+	soc_parent->parent = &soc_grandparent;
+
+	ret = device_register(soc_parent);
+	if (ret)
+		return ret;
+
+	soc_device_create_files(soc_parent);
+
+	soc_count++;
+
+	return ret;
+}
+
+void __exit soc_device_unregister(struct device *soc_parent)
+{
+	/* Unregister and free SoC from sysfs */
+	soc_device_remove_files(soc_parent);
+	device_unregister(soc_parent);
+
+	if (--soc_count == 0)
+		/* Unregister top-level SoC device '/sys/devices/soc' */
+	device_unregister(&soc_grandparent);
+}
diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
new file mode 100644
index 0000000..94d5707
--- /dev/null
+++ b/include/linux/sys_soc.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+#ifndef __SYS_SOC_H
+#define __SYS_SOC_H
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+
+#define MAX_SOCS 8
+#define MACHINE  0
+#define FAMILY   1
+#define SOCID    2
+#define REVISION 3
+
+struct soc_callback_functions {
+	ssize_t (*get_machine_fn)(struct device *dev,
+				struct device_attribute *attr, char *buf);
+	ssize_t (*get_family_fn)(struct device *dev,
+				struct device_attribute *attr, char *buf);
+	ssize_t (*get_soc_id_fn)(struct device *dev,
+				struct device_attribute *attr, char *buf);
+	ssize_t (*get_revision_fn)(struct device *dev,
+				struct device_attribute *attr, char *buf);
+};
+
+/**
+ * soc_device_register - register SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @soc: Parent node '/sys/devices/soc'
+ */
+int soc_device_register(struct device *soc_parent,
+			struct soc_callback_functions *soc_callbacks);
+
+/**
+ *  soc_device_unregister - unregister SoC as a device
+ * @soc_attr: Array of sysfs file attributes
+ * @soc: Parent node '/sys/devices/soc'
+ */
+void soc_device_unregister(struct device *soc_parent);
+
+#endif /* __SYS_SOC_H */
-- 
1.7.4.1

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Hi Russell,

>>> Ok, in that case, I'd suggest you use your ST-Ericsson address for
>>> Signed-off-by and the author statement above.
>>
>> I'm not an ST-Ericsson employee, thus do not have an associated address.
>>
>> I work for Linaro, currently on assignment to ST-Ericsson.
> 
> It was my understanding gained last week was that Linaro is a separate
> organization, and that while folk are working for Linaro, stuff they
> create belongs to Linaro and not the company whose office they happen
> to be sitting in.
> 
> I also thought Linaro was supposed to be an organization for solving
> the _common_ problems being experienced by each member organization,
> rather than being a contracting house to any one particular
> organization.  Am I mistaken?

You are not mistaken for the most part. However, you are referring to
the engineering work carried out by the engineers contained in the
Linaro Working Groups. The role I occupy within the company is slightly
different. I lead a group of individuals called a "Landing Team". There
are currently four of these within Linaro; ST-Ericsson (mine), Texas
Instruments, Samsung and Freescale, with a view on increasing that
number over the upcoming months. The Landing Team's main purpose is to
upstream as much code as possible for a previously specified SoC, in our
case the u8500. How the Landing Team spends their time is my
responsibility and as such (unless Linaro or ST-Ericsson management have
a special request) is depicted by me.

With regards to the Copyright label, I will endeavor to find a
definitive answer. We came to the conclusion of "Written by Linaro for
ST-Ericsson" some time ago in a Landing Team meeting we held some months
ago. If you or Arnd see this as an issue clearly we need to have more
meetings and involve more senior people from Linaro to chase a
conclusive answer.

Thanks for your time and input Russell and Arnd, it is appreciated.

Kind regards,
Lee Jones
Team Lead, Linaro ST-Ericsson Landing Team

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Russell King - ARM Linux]

On Thu, Apr 21, 2011 at 12:56:07PM +0100, Lee Jones wrote:
> Hi Arnd,
> 
> </snip>
> 
> >>> (I believe this would be Copyright Linaro Ltd, not ST-Ericsson SA,
> >>> but better ask internally in ST-Ericsson about what your rules are)
> >>
> >> We've had internal discussions about this. I believe this is the correct
> >> thing to do. The Copyright should stay with ST-Ericsson.
> > 
> > Ok, in that case, I'd suggest you use your ST-Ericsson address for
> > Signed-off-by and the author statement above.
> 
> I'm not an ST-Ericsson employee, thus do not have an associated address.
> 
> I work for Linaro, currently on assignment to ST-Ericsson.

It was my understanding gained last week was that Linaro is a separate
organization, and that while folk are working for Linaro, stuff they
create belongs to Linaro and not the company whose office they happen
to be sitting in.

I also thought Linaro was supposed to be an organization for solving
the _common_ problems being experienced by each member organization,
rather than being a contracting house to any one particular
organization.  Am I mistaken?

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Hi Arnd,

</snip>

>>> (I believe this would be Copyright Linaro Ltd, not ST-Ericsson SA,
>>> but better ask internally in ST-Ericsson about what your rules are)
>>
>> We've had internal discussions about this. I believe this is the correct
>> thing to do. The Copyright should stay with ST-Ericsson.
> 
> Ok, in that case, I'd suggest you use your ST-Ericsson address for
> Signed-off-by and the author statement above.

I'm not an ST-Ericsson employee, thus do not have an associated address.

I work for Linaro, currently on assignment to ST-Ericsson.

</snip>

> I would prefer to standardise the attributes as much as possible. Ideally,
> all SOCs should export the same set of attributes, and in no case should
> there be multiple SOCs that have the same attribute name but with a
> slightly different interface (e.g. one writable, or one root-only readable),
> or the same contents in attributes of different names.
> 
> The best way to ensure this is to give less flexiblity to the person
> implementing the individual SOC code. All attributes that are documented
> to be available across SOCs can simply be automatically created and
> filled with the data provided by the platform.
> 
> Having interfaces specific to one SOC should be the absolute exception,
> so I'd try to make that as hard as possible.

Well your word overrides mine.

I'll completely rewrite the driver again. It may be some time before
it's complete (post-UDS/LDS), as I have a lot on 'till then. I would
like to see this to the end though, so leave it with me.

Kind regards,
Lee

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Arnd Bergmann]

On Thursday 21 April 2011, Lee Jones wrote:

> >> diff --git a/drivers/base/soc.c b/drivers/base/soc.c
> >> new file mode 100644
> >> index 0000000..5e4d6ef
> >> --- /dev/null
> >> +++ b/drivers/base/soc.c
> >> @@ -0,0 +1,127 @@
> >> +/*
> >> + * Copyright (C) ST-Ericsson SA 2011
> >> + *
> >> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> >> + * License terms:  GNU General Public License (GPL), version 2
> >> + */
> > 
> > (I believe this would be Copyright Linaro Ltd, not ST-Ericsson SA,
> > but better ask internally in ST-Ericsson about what your rules are)
> 
> We've had internal discussions about this. I believe this is the correct
> thing to do. The Copyright should stay with ST-Ericsson.

Ok, in that case, I'd suggest you use your ST-Ericsson address for
Signed-off-by and the author statement above.

> >> +int __init soc_device_register(struct device_attribute *soc_attrs[],
> >> +                               int soc_count)
> > 
> > This needs to return the soc device, otherwise there is nothing that
> > a platform can do with the device.
> 
> What do you think the platform would want to do with the device?

Add the child devices, or add more attributes.

> > Passing the soc_count the way you do won't work when you have different
> > SoCs, 
> 
> Why won't the platform know how many SoCs are on a given platform?
>
> > so better require the user to call the register function repeatedly.
> 
> ... and if it truly doesn't know, how will it know how many times to
> call the register function?

You could have a platform that has several SOCs, some of which are optional,
E.g. one SoC for that contains the main CPU, and then another SOC of
a different vendor plugged into an external bus.

> > I think a nicer interface would be to pass a data structure into it
> > with the data you always want to export, and then have the soc
> > core create the necessary attributes, instead of requiring every
> > user to duplicate that code.
> > 
> > A possible interface might be
> > 
> > struct soc_device {
> > 	const char *machine;
> > 	const char *family;
> > 	/* ... */
> > 	struct device dev;
> > };
> 
> Either way, the probing functions would have to be called in order to
> populate the structure. Why is using the struct device_attribute
> show|store callbacks to call them a bad thing to do in this case?

Code is more complex than data, and we want to have the complexity
in a central location, not copied over all subarchitectures. When
you use a flattened device tree, the strings can simply point to
properties of the root device, so there would be very little to
do other than assign them.

> > struct soc_device *soc_device_register(const char *machine, const char *family);
> > 
> > For the nonstandard attributes, I would recommend having the individual
> > drivers call device_create_file, in order to discourage the use of 
> > device specific attribute names.
> 
> I'm not entirely sure what you mean here. I'm assuming you mean calling
> device_create_file from platform code once the device has been
> registered and a pointer passed back.

Right.

> If that's the case then surely the
> driver could set the attribute names to _any_ value still?
> 
> I really like the:
> 
> struct device_attribute soc_one_attrs[] = {
> 	__ATTR(machine,  S_IRUGO, ux500_get_machine,  NULL),
> 	__ATTR(family,   S_IRUGO, ux500_get_family,   NULL),
> 	__ATTR(soc_id,   S_IRUGO, ux500_get_soc_id,   NULL),
> 	/* ... */
> 	__ATTR_NULL,
> };

> ... interface. I think it's neat, and easy to read. Are you suggesting I
> should remove this altogether and replace it with passing const
> arguments for common attributes and insisting the platform code calls
> device_create_file for all non-standard ones? If so, if you would be
> kind enough to explain why this is better, I'd appreciate it.

I would prefer to standardise the attributes as much as possible. Ideally,
all SOCs should export the same set of attributes, and in no case should
there be multiple SOCs that have the same attribute name but with a
slightly different interface (e.g. one writable, or one root-only readable),
or the same contents in attributes of different names.

The best way to ensure this is to give less flexiblity to the person
implementing the individual SOC code. All attributes that are documented
to be available across SOCs can simply be automatically created and
filled with the data provided by the platform.

Having interfaces specific to one SOC should be the absolute exception,
so I'd try to make that as hard as possible.

	Arnd

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Hi Arnd,

> On Thursday 14 April 2011, Lee Jones wrote:
>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>> ---
> 
> This definitely needs a changelog, explaining what the code is there for,
> and why you chose this interface and not the alternatives we discussed
> earlier.

No problem.

>> diff --git a/drivers/base/soc.c b/drivers/base/soc.c
>> new file mode 100644
>> index 0000000..5e4d6ef
>> --- /dev/null
>> +++ b/drivers/base/soc.c
>> @@ -0,0 +1,127 @@
>> +/*
>> + * Copyright (C) ST-Ericsson SA 2011
>> + *
>> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
>> + * License terms:  GNU General Public License (GPL), version 2
>> + */
> 
> (I believe this would be Copyright Linaro Ltd, not ST-Ericsson SA,
> but better ask internally in ST-Ericsson about what your rules are)

We've had internal discussions about this. I believe this is the correct
thing to do. The Copyright should stay with ST-Ericsson.

>> +struct device *parent_soc;
>> +struct device *soc[MAX_SOCS];
> 
> The array should not be needed here, you can simply iterate all soc
> devices using device_for_each_child() if required.

Joy, another re-write.

(I think you are correct however)

> Global variables should really not have such generic names. Better
> make all variables static and make sure that the code using them
> can at there properly.

Agreed.

>> +int __init soc_device_register(struct device_attribute *soc_attrs[],
>> +                               int soc_count)
> 
> This needs to return the soc device, otherwise there is nothing that
> a platform can do with the device.

What do you think the platform would want to do with the device?

> Passing the soc_count the way you do won't work when you have different
> SoCs, 

Why won't the platform know how many SoCs are on a given platform?

> so better require the user to call the register function repeatedly.

... and if it truly doesn't know, how will it know how many times to
call the register function?

> I think a nicer interface would be to pass a data structure into it
> with the data you always want to export, and then have the soc
> core create the necessary attributes, instead of requiring every
> user to duplicate that code.
> 
> A possible interface might be
> 
> struct soc_device {
> 	const char *machine;
> 	const char *family;
> 	/* ... */
> 	struct device dev;
> };

Either way, the probing functions would have to be called in order to
populate the structure. Why is using the struct device_attribute
show|store callbacks to call them a bad thing to do in this case?

> struct soc_device *soc_device_register(const char *machine, const char *family);
> 
> For the nonstandard attributes, I would recommend having the individual
> drivers call device_create_file, in order to discourage the use of 
> device specific attribute names.

I'm not entirely sure what you mean here. I'm assuming you mean calling
device_create_file from platform code once the device has been
registered and a pointer passed back. If that's the case then surely the
driver could set the attribute names to _any_ value still?

I really like the:

struct device_attribute soc_one_attrs[] = {
	__ATTR(machine,  S_IRUGO, ux500_get_machine,  NULL),
	__ATTR(family,   S_IRUGO, ux500_get_family,   NULL),
	__ATTR(soc_id,   S_IRUGO, ux500_get_soc_id,   NULL),
	/* ... */
	__ATTR_NULL,
};

... interface. I think it's neat, and easy to read. Are you suggesting I
should remove this altogether and replace it with passing const
arguments for common attributes and insisting the platform code calls
device_create_file for all non-standard ones? If so, if you would be
kind enough to explain why this is better, I'd appreciate it.

>> diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
>> new file mode 100644
>> index 0000000..988cf6f
>> --- /dev/null
>> +++ b/include/linux/sys_soc.h
>> @@ -0,0 +1,29 @@
>> +/*
>> + * Copyright (C) ST-Ericsson SA 2011
>> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
>> + * License terms:  GNU General Public License (GPL), version 2
>> + */
>> +#ifndef __SYS_SOC_H
>> +#define __SYS_SOC_H
>> +
>> +#include <linux/kobject.h>
>> +#include <linux/device.h>
>> +
>> +#define MAX_SOCS 8
> 
> No need to hardcode the maximum.

No problem.

Kind regards,
Lee

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Arnd Bergmann]

Hi Lee,

On Thursday 14 April 2011, Lee Jones wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---

This definitely needs a changelog, explaining what the code is there for,
and why you chose this interface and not the alternatives we discussed
earlier.

> diff --git a/drivers/base/soc.c b/drivers/base/soc.c
> new file mode 100644
> index 0000000..5e4d6ef
> --- /dev/null
> +++ b/drivers/base/soc.c
> @@ -0,0 +1,127 @@
> +/*
> + * Copyright (C) ST-Ericsson SA 2011
> + *
> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> + * License terms:  GNU General Public License (GPL), version 2
> + */

(I believe this would be Copyright Linaro Ltd, not ST-Ericsson SA,
but better ask internally in ST-Ericsson about what your rules are)

> +struct device *parent_soc;
> +struct device *soc[MAX_SOCS];

The array should not be needed here, you can simply iterate all soc
devices using device_for_each_child() if required.

Global variables should really not have such generic names. Better
make all variables static and make sure that the code using them
can at there properly.

> +int __init soc_device_register(struct device_attribute *soc_attrs[],
> +                               int soc_count)

This needs to return the soc device, otherwise there is nothing that
a platform can do with the device.

Passing the soc_count the way you do won't work when you have different
SoCs, so better require the user to call the register function repeatedly.


I think a nicer interface would be to pass a data structure into it
with the data you always want to export, and then have the soc
core create the necessary attributes, instead of requiring every
user to duplicate that code.

A possible interface might be

struct soc_device {
	const char *machine;
	const char *family;
	/* ... */
	struct device dev;
};

struct soc_device *soc_device_register(const char *machine, const char *family);

For the nonstandard attributes, I would recommend having the individual
drivers call device_create_file, in order to discourage the use of 
device specific attribute names.

> diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
> new file mode 100644
> index 0000000..988cf6f
> --- /dev/null
> +++ b/include/linux/sys_soc.h
> @@ -0,0 +1,29 @@
> +/*
> + * Copyright (C) ST-Ericsson SA 2011
> + * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +#ifndef __SYS_SOC_H
> +#define __SYS_SOC_H
> +
> +#include <linux/kobject.h>
> +#include <linux/device.h>
> +
> +#define MAX_SOCS 8

No need to hardcode the maximum.

	Arnd

[PATCH 1/3] Framework for exporting System-on-Chip information via sysfs

[Lee Jones]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/base/Kconfig    |    3 +
 drivers/base/Makefile   |    1 +
 drivers/base/soc.c      |  127 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sys_soc.h |   29 +++++++++++
 4 files changed, 160 insertions(+), 0 deletions(-)
 create mode 100644 drivers/base/soc.c
 create mode 100644 include/linux/sys_soc.h

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index e9e5238..f381fcc 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -168,6 +168,9 @@ config SYS_HYPERVISOR
 	bool
 	default n
 
+config SYS_SOC
+	bool
+
 config ARCH_NO_SYSDEV_OPS
 	bool
 	---help---
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4c5701c..a0d246d 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -18,6 +18,7 @@ ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
 endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_SYS_SOC) += soc.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
diff --git a/drivers/base/soc.c b/drivers/base/soc.c
new file mode 100644
index 0000000..5e4d6ef
--- /dev/null
+++ b/drivers/base/soc.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+struct device *parent_soc;
+struct device *soc[MAX_SOCS];
+
+static void soc_device_remove_files(struct device *soc,
+                                    struct device_attribute soc_attrs[])
+{
+	int i = 0;
+
+	while (soc_attrs[i++].attr.name != NULL)
+		device_remove_file(soc, &soc_attrs[i]);
+}
+
+static int __init soc_device_create_files(struct device *soc,
+                                          struct device_attribute soc_attrs[])
+{
+	int ret = 0;
+	int i = 0;
+
+	while (soc_attrs[i].attr.name != NULL) {
+		ret = device_create_file(soc, &soc_attrs[i++]);
+		if (ret)
+			goto out;
+	}
+	return ret;
+
+out:
+	soc_device_remove_files(soc, soc_attrs);
+	return ret;
+}
+
+void soc_device_release(struct device *soc)
+{
+	kfree(soc);
+}
+
+int __init soc_device_register(struct device_attribute *soc_attrs[],
+                               int soc_count)
+{
+	int ret, i;
+
+	if (!soc_attrs || soc_count > MAX_SOCS)
+		return -EINVAL;
+
+	/* Register top-level SoC device '/sys/devices/soc'. */
+	parent_soc = kzalloc(sizeof(struct device), GFP_KERNEL);
+	if (!parent_soc)
+		return -ENOMEM;
+
+	ret = dev_set_name(parent_soc, "soc");
+	if (ret)
+		goto soc_parent_free;
+
+	parent_soc->release = soc_device_release;
+
+	ret = device_register(parent_soc);
+	if (ret)
+		goto soc_parent_free;
+
+	/* Register each SoC and populate sysfs with requested attributes. */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc[i] = kzalloc(sizeof(struct device), GFP_KERNEL);
+		if (!soc[i]) {
+			ret = -ENOMEM;
+			goto soc_out_of_memory;
+		}
+
+		ret = dev_set_name(soc[i], "soc%d", i);
+		if (ret)
+			goto soc_free_unreg;
+
+		soc[i]->parent = parent_soc;
+		soc[i]->release = soc_device_release;
+
+		ret = device_register(soc[i]);
+		if (ret)
+			goto soc_free_unreg;
+
+		ret = soc_device_create_files(soc[i], soc_attrs[i]);
+		if (ret)
+			goto soc_free_unreg;
+	}
+	return ret;
+
+soc_free_unreg:
+	kfree(soc[i]);
+soc_out_of_memory:
+	/* Unregister only previously registered SoCs. */
+	soc_device_unregister(soc_attrs, i);
+	return ret;
+
+soc_parent_free:
+	/* Free unregisterable parent SoC device. */
+	kfree(parent_soc);
+	return ret;
+}
+
+void soc_device_unregister(struct device_attribute *soc_attrs[],
+                           int soc_count)
+{
+	int i;
+
+	if (!soc_attrs || soc_count > MAX_SOCS)
+		return;
+
+	/* Unregister and free all SoC from sysfs. */
+	for (i = 0; i < soc_count - 1; i++) {
+		soc_device_remove_files(soc[i], soc_attrs[i]);
+		device_unregister(soc[i]);
+	}
+
+	/* Unregister top-level SoC device '/sys/devices/soc'. */
+	device_unregister(parent_soc);
+}
diff --git a/include/linux/sys_soc.h b/include/linux/sys_soc.h
new file mode 100644
index 0000000..988cf6f
--- /dev/null
+++ b/include/linux/sys_soc.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ * Author: Lee Jones <lee.jones@linaro.org> for ST-Ericsson.
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+#ifndef __SYS_SOC_H
+#define __SYS_SOC_H
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+
+#define MAX_SOCS 8
+
+/**
+ * soc_device_register - register SoC as a device
+ * @soc_attrs: Multiple arrays of sysfs file attributes
+ * @num_socs: Amount of SoCs we're attempting to register
+ */
+int soc_device_register(struct device_attribute *soc_attrs[],
+                        int num_socs);
+/**
+ * soc_device_unregister - unregister SoC as a device
+ * @soc_attrs: Multiple arrays of sysfs file attributes
+ * @num_socs: Amount of SoCs we're attempting to register
+ */
+void soc_device_unregister(struct device_attribute *soc_attrs[],
+                           int num_socs);
+
+#endif /* __SYS_SOC_H */
-- 
1.7.4.1