linux-kernel - Re: [Update 4][PATCH 2/7] ACPI / scan: Introduce common code for ACPI-based device hotplug

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Date:	Tue, 26 Feb 2013 11:02:56 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Toshi Kani <toshi.kani@...com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>
Subject: Re: [Update 4][PATCH 2/7] ACPI / scan: Introduce common code for
 ACPI-based device hotplug

2013/02/26 10:09, Toshi Kani wrote:
> On Tue, 2013-02-26 at 09:40 +0900, Yasuaki Ishimatsu wrote:
>> 2013/02/26 8:39, Rafael J. Wysocki wrote:
>>> On Monday, February 25, 2013 11:07:52 AM Toshi Kani wrote:
>>>> On Sat, 2013-02-23 at 22:38 +0000, Rafael J. Wysocki wrote:
>>>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>>>
>>>>> Multiple drivers handling hotplug-capable ACPI device nodes install
>>>>> notify handlers covering the same types of events in a very similar
>>>>> way.  Moreover, those handlers are installed in separate namespace
>>>>> walks, although that really should be done during namespace scans
>>>>> carried out by acpi_bus_scan().  This leads to substantial code
>>>>> duplication, unnecessary overhead and behavior that is hard to
>>>>> follow.
>>>>>
>>>>> For this reason, introduce common code in drivers/acpi/scan.c for
>>>>> handling hotplug-related notification and carrying out device
>>>>> insertion and eject operations in a generic fashion, such that it
>>>>> may be used by all of the relevant drivers in the future.  To cover
>>>>> the existing differences between those drivers introduce struct
>>>>> acpi_hotplug_profile for representing collections of hotplug
>>>>> settings associated with different ACPI scan handlers that can be
>>>>> used by the drivers to make the common code reflect their current
>>>>> behavior.
>>>>>
>>>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>>> ---
>>>>>
>>>>> This update causes acpi_bus_device_eject() to only emit KOBJ_OFFLINE uevent if
>>>>> autoexec is unset for the given scan handler.
>>>>>
>>>>> This will require the doc in patch [5/7] to be updated which I'm going to do if
>>>>> everyone is OK with the $subject patch.
>>>>>
>>>>> Thanks,
>>>>> Rafael
>>>>    :
>>>>> +
>>>>> +static void acpi_scan_bus_device_check(acpi_handle handle, u32 ost_source)
>>>>> +{
>>>>> +	struct acpi_device *device = NULL;
>>>>> +	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
>>>>> +	int error;
>>>>> +
>>>>> +	mutex_lock(&acpi_scan_lock);
>>>>> +
>>>>> +	acpi_bus_get_device(handle, &device);
>>>>> +	if (device) {
>>>>> +		dev_warn(&device->dev, "Attempt to re-insert\n");
>>>>> +		goto out;
>>>>> +	}
>>>>> +	acpi_evaluate_hotplug_ost(handle, ost_source,
>>>>> +				  ACPI_OST_SC_INSERT_IN_PROGRESS, NULL);
>>>>> +	error = acpi_bus_scan(handle);
>>>>> +	if (error) {
>>>>> +		acpi_handle_warn(handle, "Namespace scan failure\n");
>>>>> +		goto out;
>>>>> +	}
>>>>> +	error = acpi_bus_get_device(handle, &device);
>>>>> +	if (error) {
>>>>> +		acpi_handle_warn(handle, "Missing device node object\n");
>>>>> +		goto out;
>>>>> +	}
>>>>> +	ost_code = ACPI_OST_SC_SUCCESS;
>>>>> +	if (device->handler && device->handler->hotplug.uevents)
>>>>> +		kobject_uevent(&device->dev.kobj, KOBJ_ONLINE);
>>>>
>>
>>>> I confirmed that the uevent crash issue was solved.  Thinking further, I
>>>> wonder if we need to emit KOBJ_ONLINE here.  This behavior is asymmetric
>>>> since we do not emit KOBJ_OFFLINE when autoeject is set.
>>>
>>> Well, I put that in there only to be able to make the container driver behave
>>> in a backwards compatible way (which is to emit KOBJ_ONLINE at this point).
>>>
>>> If the container driver doesn't need to emit KOBJ_ONLINE at all, I agree with
>>> your suggestion.
>>>
>>>> The definition of ONLINE/OFFLINE event to an ACPI device object seems also
>>>> bogus since there is no online/offline operation to the ACPI device object
>>>> itself.
>>>> Online/offline operation is only possible to actual device, such as
>>>> system/cpu/cpu% and system/memory/memory%.
>>>
>>> That's correct, but I don't know what the user space expectations are
>>> currently.
>>
>> My system expects this event to be notified when hot adding container device.
>> My container device has cpu and memory. As Toshi said, these devices are
>> offline when hot adding container device. So in my system, when notifying
>> container device's KOBJ_ONLINE event, my application runs for onlining these
>> devices. If this event is not notified to user land, we cannot online these
>> devices  automatically.
>

> Thanks for the info.  Can your application listen KOBJ_ADD to a
> container device, instead of KOBJ_ONLINE?  IOW, does it distinguish
> between ADD and ONLINE events to a container device?

My application does not distinguish between ADD and ONLINE events
currently. But if the event is changed from ONLINE to ADD, I will
change my application.

Thanks,
Yasuaki Ishimatsu

>
> -Toshi
>
>


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