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

[Yasuaki Ishimatsu]

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.

Thanks,
Yasuaki Ishimatsu

> -Toshi


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