diff mbox

[v2,1/9] drivers: base: add new class "cpu" to group cpu devices

Message ID 1406306692-7135-2-git-send-email-sudeep.holla@arm.com
State New
Headers show

Commit Message

Sudeep Holla July 25, 2014, 4:44 p.m. UTC 
From: Sudeep Holla <sudeep.holla@arm.com>

This patch creates a new class called "cpu" and assigns it to all the
cpu devices. This helps in grouping all the cpu devices and associated
child devices under the same class.

This patch also:
1. modifies the get_parent_device to return the legacy path
   (/sys/devices/system/cpu/..) for the cpu class devices to support
   existing sysfs ABI
2. avoids creating link in the class directory pointing to the device as
   there would be per-cpu instance of these devices with the same name
3. makes sure subsystem symlink continues pointing to cpu bus instead of
   cpu class for cpu devices

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/base/core.c | 39 +++++++++++++++++++++++++++++++++------
 drivers/base/cpu.c  |  7 +++++++
 include/linux/cpu.h |  2 ++
 3 files changed, 42 insertions(+), 6 deletions(-)

Comments

Stephen Boyd July 25, 2014, 7:09 p.m. UTC | #1 
On 07/25/14 09:44, Sudeep Holla wrote:
> From: Sudeep Holla <sudeep.holla@arm.com>
>
> This patch creates a new class called "cpu" and assigns it to all the
> cpu devices. This helps in grouping all the cpu devices and associated
> child devices under the same class.
>
> This patch also:
> 1. modifies the get_parent_device to return the legacy path
>    (/sys/devices/system/cpu/..) for the cpu class devices to support
>    existing sysfs ABI
> 2. avoids creating link in the class directory pointing to the device as
>    there would be per-cpu instance of these devices with the same name
> 3. makes sure subsystem symlink continues pointing to cpu bus instead of
>    cpu class for cpu devices
>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Why can't we make a 'cache' bus that the cache devices hang off of? It
doesn't make sense to me why we would want to have cache devices living
on the cpu bus.
Sudeep Holla July 28, 2014, 1:37 p.m. UTC | #2 
On 25/07/14 20:09, Stephen Boyd wrote:
> On 07/25/14 09:44, Sudeep Holla wrote:
>> From: Sudeep Holla <sudeep.holla@arm.com>
>>
>> This patch creates a new class called "cpu" and assigns it to all the
>> cpu devices. This helps in grouping all the cpu devices and associated
>> child devices under the same class.
>>
>> This patch also:
>> 1. modifies the get_parent_device to return the legacy path
>>     (/sys/devices/system/cpu/..) for the cpu class devices to support
>>     existing sysfs ABI
>> 2. avoids creating link in the class directory pointing to the device as
>>     there would be per-cpu instance of these devices with the same name
>> 3. makes sure subsystem symlink continues pointing to cpu bus instead of
>>     cpu class for cpu devices
>>
>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> Why can't we make a 'cache' bus that the cache devices hang off of? It
> doesn't make sense to me why we would want to have cache devices living
> on the cpu bus.
>

Yes we can group them under cache, but to support legacy sysfs path
under which various cpu related information including caches, we need
to have a workaround as in this patch.

Instead of having this fixup for each class like cache, having them
grouped under cpu is better IMO and hence I added caches to cpu class.
It also helps to move few other cpu related subsystems using raw
kobjects to the device attribute groups and corresponding APIs.

Regards,
Sudeep

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diff mbox

Patch

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 20da3ad1696b..fe622e2a48d0 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -10,6 +10,7 @@ 
  *
  */
 
+#include <linux/cpu.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -742,6 +743,12 @@  static struct kobject *get_device_parent(struct device *dev,
 			return &block_class.p->subsys.kobj;
 		}
 #endif
+		/*
+		 * if the device is in cpu class, then use the default/legacy
+		 * /sys/devices/system/cpu/.. path
+		 */
+		if (dev->class == cpu_class)
+			return &parent->kobj;
 
 		/*
 		 * If we have no parent, we live in "virtual".
@@ -808,11 +815,17 @@  static int device_add_class_symlinks(struct device *dev)
 	if (!dev->class)
 		return 0;
 
-	error = sysfs_create_link(&dev->kobj,
-				  &dev->class->p->subsys.kobj,
-				  "subsystem");
-	if (error)
-		goto out;
+	/*
+	 * the subsystem symlink in each cpu device needs to continue
+	 * pointing to cpu bus
+	 */
+	if (dev->bus != &cpu_subsys) {
+		error = sysfs_create_link(&dev->kobj,
+					  &dev->class->p->subsys.kobj,
+					  "subsystem");
+		if (error)
+			goto out;
+	}
 
 	if (dev->parent && device_is_not_partition(dev)) {
 		error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
@@ -826,6 +839,13 @@  static int device_add_class_symlinks(struct device *dev)
 	if (sysfs_deprecated && dev->class == &block_class)
 		return 0;
 #endif
+	/*
+	 * don't create a link in the cpu class directory pointing to the
+	 * device as there would be per-cpu instance of these devices with
+	 * the same name
+	 */
+	if (dev->class == cpu_class)
+		return 0;
 
 	/* link in the class directory pointing to the device */
 	error = sysfs_create_link(&dev->class->p->subsys.kobj,
@@ -851,11 +871,18 @@  static void device_remove_class_symlinks(struct device *dev)
 
 	if (dev->parent && device_is_not_partition(dev))
 		sysfs_remove_link(&dev->kobj, "device");
-	sysfs_remove_link(&dev->kobj, "subsystem");
+
+	/* if subsystem points to cpu bus, bus_remove_device will remove it */
+	if (dev->bus != &cpu_subsys)
+		sysfs_remove_link(&dev->kobj, "subsystem");
 #ifdef CONFIG_BLOCK
 	if (sysfs_deprecated && dev->class == &block_class)
 		return;
 #endif
+	/* symlinks are not created for cpu class devices, nothing to remove */
+	if (dev->class == cpu_class)
+		return;
+
 	sysfs_delete_link(&dev->class->p->subsys.kobj, &dev->kobj, dev_name(dev));
 }
 
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 006b1bc5297d..056b8854e4fb 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -322,6 +322,7 @@  static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)
 }
 #endif
 
+struct class *cpu_class;
 /*
  * register_cpu - Setup a sysfs device for a CPU.
  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
@@ -338,6 +339,8 @@  int register_cpu(struct cpu *cpu, int num)
 	memset(&cpu->dev, 0x00, sizeof(struct device));
 	cpu->dev.id = num;
 	cpu->dev.bus = &cpu_subsys;
+	cpu->dev.parent = cpu_subsys.dev_root;
+	cpu->dev.class = cpu_class;
 	cpu->dev.release = cpu_device_release;
 	cpu->dev.offline_disabled = !cpu->hotpluggable;
 	cpu->dev.offline = !cpu_online(num);
@@ -423,5 +426,9 @@  void __init cpu_dev_init(void)
 	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 		panic("Failed to register CPU subsystem");
 
+	cpu_class = class_create(THIS_MODULE, "cpu");
+	if (IS_ERR(cpu_class))
+		panic("Failed to register CPU class");
+
 	cpu_dev_register_generic();
 }
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 95978ad7fcdd..8c0fc9b0acad 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -39,6 +39,8 @@  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 class *cpu_class;
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern void unregister_cpu(struct cpu *cpu);
 extern ssize_t arch_cpu_probe(const char *, size_t);