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

[Rafael J. Wysocki]

On Tuesday, February 26, 2013 12:40:22 PM Yasuaki Ishimatsu wrote:
> 2013/02/26 12:11, Rafael J. Wysocki wrote:
> > On Tuesday, February 26, 2013 11:02:56 AM Yasuaki Ishimatsu wrote:
> >> 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@xxxxxxxxx>
> >>>>>>>
> >>>>>>> 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@xxxxxxxxx>
> >>>>>>> ---
> >>>>>>>
> >>>>>>> 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.
> >
> > KOBJ_ADD is emitted for every struct acpi_device being registered, including
> > container devices, by acpi_device_add_finalize().  Can your application listen
> > to those events?
> 
> Ah O.K. I understood. Even if the ONLINE event disappers, my application can get
> ADD event from acpi_device_add_finalize(). Of course, I need to change my
> application.
> If the ADD event of container device is notified after hot adding devices which
> are contained into container device, there is no reason to leave ONLINE event.

If they are located below the container device in the namespace, then the
container's ADD will happen before they are added, so if the ONLINE event is
supposed to mean that all devices under the container have been added, we need
to keep it as is.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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