Re: [Xen-devel] [PATCH 3/8] ACPI: processor: add __acpi_processor_[un]register_driver helpers.

[Konrad Rzeszutek Wilk]

On Mon, Dec 19, 2011 at 01:48:01PM +0800, Tian, Kevin wrote:
> > From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> > Sent: Saturday, December 17, 2011 6:04 AM
> > 
> > On Wed, Nov 30, 2011 at 12:20:59PM -0500, Konrad Rzeszutek Wilk wrote:
> > > From: Tang Liang <liang.tang@xxxxxxxxxx>
> > >
> > > This patch implement __acpi_processor_[un]register_driver helper,
> > > so we can registry override processor driver function. Specifically
> > > the Xen processor driver.
> > 
> > Liang,
> > 
> > Is the reason we are doing this b/c we need to call acpi_bus_register_driver
> > and inhibit the registration of 'acpi_processor_driver' ?
> > 
> > And the reason we don't want 'acpi_processor_driver' to run is b/c of what?
> > If the cpuidle is disabled what is the harm of running the
> > 'acpi_processor_driver'
> > driver?
> 
> IIRC, the reason why we want a Xen specific driver is because current driver
> is integrated with OS logic too tightly, e.g. the various checks on VCPU related
> structures. Long time ago the 1st version in Xen was to use same driver, by
> adding various tweaking lines inside which makes it completely messed. Then
> later it's found that it's clearer to create a Xen specific wrapping driver, by 
> invoking some exported functions from existing one.

What I am asking is does it matter "if the current driver is integrated
with OS logic to tighly" - as it is not running anyhow (b/c cpuidle is
disabled).

And if Xen specific driver can run along-side the generic one - since
the generic one is not doing any work (b/c cpuidle is disabled).

That is what I am trying to figure out - since this patch purpose is to
thwart the generic driver from running and allowing the xen one to run.
> 
> Thanks
> Kevin
> 
> > 
> > >
> > > By default the values are set to the native one.
> > >
> > > Signed-off-by: Tang Liang <liang.tang@xxxxxxxxxx>
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > > ---
> > >  drivers/acpi/processor_driver.c |   35
> > +++++++++++++++++++++++++++++------
> > >  include/acpi/processor.h        |    6 +++++-
> > >  2 files changed, 34 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> > > index 211c078..55f0b89 100644
> > > --- a/drivers/acpi/processor_driver.c
> > > +++ b/drivers/acpi/processor_driver.c
> > > @@ -90,6 +90,11 @@ static const struct acpi_device_id
> > processor_device_ids[] = {
> > >  };
> > >  MODULE_DEVICE_TABLE(acpi, processor_device_ids);
> > >
> > > +int (*__acpi_processor_register_driver)(void) =
> > acpi_processor_register_driver;
> > > +void (*__acpi_processor_unregister_driver)(void) \
> > > +	= acpi_processor_unregister_driver;
> > > +
> > > +
> > >  static struct acpi_driver acpi_processor_driver = {
> > >  	.name = "processor",
> > >  	.class = ACPI_PROCESSOR_CLASS,
> > > @@ -779,6 +784,22 @@ void acpi_processor_uninstall_hotplug_notify(void)
> > >  	unregister_hotcpu_notifier(&acpi_cpu_notifier);
> > >  }
> > >
> > > +int acpi_processor_register_driver(void)
> > > +{
> > > +	int result = 0;
> > > +
> > > +	result = acpi_bus_register_driver(&acpi_processor_driver);
> > > +	return result;
> > > +}
> > > +
> > > +void acpi_processor_unregister_driver(void)
> > > +{
> > > +	acpi_bus_unregister_driver(&acpi_processor_driver);
> > > +
> > > +	cpuidle_unregister_driver(&acpi_idle_driver);
> > > +
> > > +	return;
> > > +}
> > >  /*
> > >   * We keep the driver loaded even when ACPI is not running.
> > >   * This is needed for the powernow-k8 driver, that works even without
> > > @@ -794,9 +815,11 @@ static int __init acpi_processor_init(void)
> > >
> > >  	memset(&errata, 0, sizeof(errata));
> > >
> > > -	result = acpi_bus_register_driver(&acpi_processor_driver);
> > > -	if (result < 0)
> > > -		return result;
> > > +	if (__acpi_processor_register_driver) {
> > > +		result = __acpi_processor_register_driver();
> > > +		if (result < 0)
> > > +			return result;
> > > +	}
> > >
> > >  	acpi_processor_install_hotplug_notify();
> > >
> > > @@ -809,6 +832,7 @@ static int __init acpi_processor_init(void)
> > >  	return 0;
> > >  }
> > >
> > > +
> > >  static void __exit acpi_processor_exit(void)
> > >  {
> > >  	if (acpi_disabled)
> > > @@ -820,9 +844,8 @@ static void __exit acpi_processor_exit(void)
> > >
> > >  	acpi_processor_uninstall_hotplug_notify();
> > >
> > > -	acpi_bus_unregister_driver(&acpi_processor_driver);
> > > -
> > > -	cpuidle_unregister_driver(&acpi_idle_driver);
> > > +	if (__acpi_processor_unregister_driver)
> > > +		__acpi_processor_unregister_driver();
> > >
> > >  	return;
> > >  }
> > > diff --git a/include/acpi/processor.h b/include/acpi/processor.h
> > > index bd99fb6..969cbc9 100644
> > > --- a/include/acpi/processor.h
> > > +++ b/include/acpi/processor.h
> > > @@ -225,6 +225,9 @@ struct acpi_processor_errata {
> > >  	} piix4;
> > >  };
> > >
> > > +extern int (*__acpi_processor_register_driver)(void);
> > > +extern void (*__acpi_processor_unregister_driver)(void);
> > > +
> > >  extern int acpi_processor_preregister_performance(struct
> > >  						  acpi_processor_performance
> > >  						  __percpu *performance);
> > > @@ -242,7 +245,8 @@ int acpi_processor_notify_smm(struct module
> > *calling_module);
> > >
> > >  void acpi_processor_install_hotplug_notify(void);
> > >  void acpi_processor_uninstall_hotplug_notify(void);
> > > -
> > > +int acpi_processor_register_driver(void);
> > > +void acpi_processor_unregister_driver(void);
> > >  int acpi_processor_add(struct acpi_device *device);
> > >  int acpi_processor_remove(struct acpi_device *device, int type);
> > >  void acpi_processor_notify(struct acpi_device *device, u32 event);
> > > --
> > > 1.7.7.3
> 
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