Subject: Re: [RFC PATCH v2 02/12] ACPI: Add sys_hotplug.h for system device hotplug framework

From: Toshi Kani <[email-masked]>
Date: Mon, 14 Jan 2013 08:53:53 -0700

On Fri, 2013-01-11 at 22:25 +0100, Rafael J. Wysocki wrote:
> On Thursday, January 10, 2013 04:40:20 PM Toshi Kani wrote:
> > Added include/acpi/sys_hotplug.h, which is ACPI-specific system
> > device hotplug header and defines the order values of ACPI-specific
> > handlers.
> > 
> > Signed-off-by: Toshi Kani <[email-masked]>
> > ---
> >  include/acpi/sys_hotplug.h |   48 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> >  create mode 100644 include/acpi/sys_hotplug.h
> > 
> > diff --git a/include/acpi/sys_hotplug.h b/include/acpi/sys_hotplug.h
> > new file mode 100644
> > index 0000000..ad80f61
> > --- /dev/null
> > +++ b/include/acpi/sys_hotplug.h
> > @@ -0,0 +1,48 @@
> > +/*
> > + * sys_hotplug.h - ACPI System device hot-plug framework
> > + *
> > + * Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
> > + *	Toshi Kani <[email-masked]>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#ifndef _ACPI_SYS_HOTPLUG_H
> > +#define _ACPI_SYS_HOTPLUG_H
> > +
> > +#include <linux/list.h>
> > +#include <linux/device.h>
> > +#include <linux/sys_hotplug.h>
> > +
> > +/*
> > + * System device hot-plug operation proceeds in the following order.
> > + *   Validate phase -> Execute phase -> Commit phase
> > + *
> > + * The order values below define the calling sequence of ACPI-specific
> > + * handlers for each phase in ascending order.  The order value of
> > + * platform-neutral handlers are defined in <linux/sys_hotplug.h>.
> > + */
> > +
> > +/* Add Validate order values */
> > +#define SHP_ACPI_BUS_ADD_VALIDATE_ORDER		0	/* must be first */
> > +
> > +/* Add Execute order values */
> > +#define SHP_ACPI_BUS_ADD_EXECUTE_ORDER		10
> > +#define SHP_ACPI_RES_ADD_EXECUTE_ORDER		20
> > +
> > +/* Add Commit order values */
> > +#define SHP_ACPI_BUS_ADD_COMMIT_ORDER		10
> > +
> > +/* Delete Validate order values */
> > +#define SHP_ACPI_BUS_DEL_VALIDATE_ORDER		0	/* must be first */
> > +#define SHP_ACPI_RES_DEL_VALIDATE_ORDER		10
> > +
> > +/* Delete Execute order values */
> > +#define SHP_ACPI_BUS_DEL_EXECUTE_ORDER		100
> > +
> > +/* Delete Commit order values */
> > +#define SHP_ACPI_BUS_DEL_COMMIT_ORDER		100
> > +
> > +#endif	/* _ACPI_SYS_HOTPLUG_H */
> > --
> 
> Why did you use the particular values above?

The ordering values above are used to define the relative order among
handlers.  For instance, the 100 for SHP_ACPI_BUS_DEL_EXECUTE_ORDER can
potentially be 21 since it is still larger than 20 for
SHP_MEM_DEL_EXECUTE_ORDER defined in linux/sys_hotplug.h.  I picked 100
so that more platform-neutral handlers can be added in between 20 and
100 in future.

Thanks,
-Toshi