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Date:   Fri, 18 Jan 2019 09:39:23 +0800
From:   Wei Yang <richardw.yang@linux.intel.com>
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Wei Yang <richardw.yang@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] driver core: move device->knode_class to device_private
Message-ID: <20190118013923.GA8975@richard>
Reply-To: Wei Yang <richardw.yang@linux.intel.com>
References: <20190117055719.6161-1-richardw.yang@linux.intel.com>
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On Thu, Jan 17, 2019 at 10:38:13AM +0100, Rafael J. Wysocki wrote:
>On Thu, Jan 17, 2019 at 6:57 AM Wei Yang <richardw.yang@linux.intel.com> wrote:
>>
>> As the description of struct device_private says, it stores data which
>> is private to driver core. And it already has similar fields like:
>> knode_parent, knode_driver, knode_driver and knode_bus. This look it is
>> more proper to put knode_class together with those fields to make it
>> private to driver core.
>>
>> This patch move device->knode_class to device_private to make it comply
>> with code convention.
>>
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
>As a rule, I'm not a big fan of changes like this, because the only
>reason for doing it seems to be aesthetics and it may be problematic
>for people doing various types of backports, live patching etc, but
>this particular one makes sense to me.

Rafael,

Thanks for your comment. 

To be honest, I didn't realized the trouble it will introduce to backport and
live patching. :-)

>
>> ---
>>  drivers/base/base.h    |  4 ++++
>>  drivers/base/class.c   | 12 ++++++++----
>>  drivers/base/core.c    |  4 ++--
>>  include/linux/device.h |  1 -
>>  4 files changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/base/base.h b/drivers/base/base.h
>> index 7a419a7a6235..37329a668935 100644
>> --- a/drivers/base/base.h
>> +++ b/drivers/base/base.h
>> @@ -60,6 +60,7 @@ struct driver_private {
>>   * @knode_parent - node in sibling list
>>   * @knode_driver - node in driver list
>>   * @knode_bus - node in bus list
>> + * @knode_class - node in class list
>>   * @deferred_probe - entry in deferred_probe_list which is used to retry the
>>   *     binding of drivers which were unable to get all the resources needed by
>>   *     the device; typically because it depends on another driver getting
>> @@ -74,6 +75,7 @@ struct device_private {
>>         struct klist_node knode_parent;
>>         struct klist_node knode_driver;
>>         struct klist_node knode_bus;
>> +       struct klist_node knode_class;
>>         struct list_head deferred_probe;
>>         struct device *device;
>>  };
>> @@ -83,6 +85,8 @@ struct device_private {
>>         container_of(obj, struct device_private, knode_driver)
>>  #define to_device_private_bus(obj)     \
>>         container_of(obj, struct device_private, knode_bus)
>> +#define to_device_private_class(obj)   \
>> +       container_of(obj, struct device_private, knode_class)
>>
>>  /* initialisation functions */
>>  extern int devices_init(void);
>> diff --git a/drivers/base/class.c b/drivers/base/class.c
>> index 54def4e02f00..df7fde599407 100644
>> --- a/drivers/base/class.c
>> +++ b/drivers/base/class.c
>> @@ -119,14 +119,16 @@ static void class_put(struct class *cls)
>>
>>  static void klist_class_dev_get(struct klist_node *n)
>>  {
>> -       struct device *dev = container_of(n, struct device, knode_class);
>> +       struct device_private *p = to_device_private_class(n);
>> +       struct device *dev = p->device;
>
>the
>
>p = to_device_private_class(n)
>dev = p->device
>
>pattern is repeated below for at least a couple of times.
>
>Care to add a static helper for this to reduce the code duplication somewhat?
>

Yep, this is reasonable. Let me put them in a helper.

>>
>>         get_device(dev);
>>  }
>>
>>  static void klist_class_dev_put(struct klist_node *n)
>>  {
>> -       struct device *dev = container_of(n, struct device, knode_class);
>> +       struct device_private *p = to_device_private_class(n);
>> +       struct device *dev = p->device;
>>
>>         put_device(dev);
>>  }
>> @@ -277,7 +279,7 @@ void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
>>         struct klist_node *start_knode = NULL;
>>
>>         if (start)
>> -               start_knode = &start->knode_class;
>> +               start_knode = &start->p->knode_class;
>>         klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
>>         iter->type = type;
>>  }
>> @@ -298,13 +300,15 @@ EXPORT_SYMBOL_GPL(class_dev_iter_init);
>>  struct device *class_dev_iter_next(struct class_dev_iter *iter)
>>  {
>>         struct klist_node *knode;
>> +       struct device_private *p;
>>         struct device *dev;
>>
>>         while (1) {
>>                 knode = klist_next(&iter->ki);
>>                 if (!knode)
>>                         return NULL;
>> -               dev = container_of(knode, struct device, knode_class);
>> +               p = to_device_private_class(knode);
>> +               dev = p->device;
>>                 if (!iter->type || iter->type == dev->type)
>>                         return dev;
>>         }
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index 04bbcd779e11..a624d27d11c0 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -1932,7 +1932,7 @@ int device_add(struct device *dev)
>>         if (dev->class) {
>>                 mutex_lock(&dev->class->p->mutex);
>>                 /* tie the class to the device */
>> -               klist_add_tail(&dev->knode_class,
>> +               klist_add_tail(&dev->p->knode_class,
>>                                &dev->class->p->klist_devices);
>>
>>                 /* notify any interfaces that the device is here */
>> @@ -2069,7 +2069,7 @@ void device_del(struct device *dev)
>>                         if (class_intf->remove_dev)
>>                                 class_intf->remove_dev(dev, class_intf);
>>                 /* remove the device from the class list */
>> -               klist_del(&dev->knode_class);
>> +               klist_del(&dev->p->knode_class);
>>                 mutex_unlock(&dev->class->p->mutex);
>>         }
>>         device_remove_file(dev, &dev_attr_uevent);
>> diff --git a/include/linux/device.h b/include/linux/device.h
>> index 1b25c7a43f4c..040e97669f94 100644
>> --- a/include/linux/device.h
>> +++ b/include/linux/device.h
>> @@ -1035,7 +1035,6 @@ struct device {
>>         spinlock_t              devres_lock;
>>         struct list_head        devres_head;
>>
>> -       struct klist_node       knode_class;
>>         struct class            *class;
>>         const struct attribute_group **groups;  /* optional groups */
>>
>> --
>> 2.19.1
>>

-- 
Wei Yang
Help you, Help me