[PATCH] drivers: base: add cpu_device_create to support per-cpu devices

[Sudeep Holla <sudeep.holla@arm.com>]

From: Sudeep Holla <sudeep.holla@arm.com>

This patch adds a new function to create per-cpu devices.
This helps in:
1. reusing the device infrastructure to create any cpu related
   attributes and corresponding sysfs instead of creating and
   dealing with raw kobjects directly
2. retaining the legacy path(/sys/devices/system/cpu/..) to support
   existing sysfs ABI
3. avoiding to create links in the bus directory pointing to the
   device as there would be per-cpu instance of these devices with
   the same name since dev->bus is not populated to cpu_sysbus on
   purpose

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/base/cpu.c  | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/cpu.h |  4 ++++
 2 files changed, 58 insertions(+)

Hi Greg,

Here is the alternate solution I could come up with instead of
creating cpu class. cpu_device_create is very similar to
device_create_groups_vargs w/o class support, but I could not
reuse anything else to avoid creating similar function.

Let me know your thoughts/suggestions on this.

Regards,
Sudeep


diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 277a9cfa9040..53f0c4141d05 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -363,6 +363,60 @@ struct device *get_cpu_device(unsigned cpu)
 }
 EXPORT_SYMBOL_GPL(get_cpu_device);
 
+static void device_create_release(struct device *dev)
+{
+	kfree(dev);
+}
+
+static struct device *
+__cpu_device_create(struct device *parent, void *drvdata,
+		    const struct attribute_group **groups,
+		    const char *fmt, va_list args)
+{
+	struct device *dev = NULL;
+	int retval = -ENODEV;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	device_initialize(dev);
+	dev->parent = parent;
+	dev->groups = groups;
+	dev->release = device_create_release;
+	dev_set_drvdata(dev, drvdata);
+
+	retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
+	if (retval)
+		goto error;
+
+	retval = device_add(dev);
+	if (retval)
+		goto error;
+
+	return dev;
+
+error:
+	put_device(dev);
+	return ERR_PTR(retval);
+}
+
+struct device *cpu_device_create(struct device *parent, void *drvdata,
+				 const struct attribute_group **groups,
+				 const char *fmt, ...)
+{
+	va_list vargs;
+	struct device *dev;
+
+	va_start(vargs, fmt);
+	dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
+	va_end(vargs);
+	return dev;
+}
+EXPORT_SYMBOL_GPL(cpu_device_create);
+
 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 #endif
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 95978ad7fcdd..bb790a5621c0 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -19,6 +19,7 @@
 
 struct device;
 struct device_node;
+struct attribute_group;
 
 struct cpu {
 	int node_id;		/* The node which contains the CPU */
@@ -39,6 +40,9 @@ extern void cpu_remove_dev_attr(struct device_attribute *attr);
 extern int cpu_add_dev_attr_group(struct attribute_group *attrs);
 extern void cpu_remove_dev_attr_group(struct attribute_group *attrs);
 
+extern struct device *cpu_device_create(struct device *parent, void *drvdata,
+					const struct attribute_group **groups,
+					const char *fmt, ...);
 #ifdef CONFIG_HOTPLUG_CPU
 extern void unregister_cpu(struct cpu *cpu);
 extern ssize_t arch_cpu_probe(const char *, size_t);
-- 
1.8.3.2