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

[Toshi Kani]

On Tue, 2013-01-29 at 23:51 -0500, Greg KH wrote:
> On Mon, Jan 14, 2013 at 12:21:30PM -0700, Toshi Kani wrote:
> > On Mon, 2013-01-14 at 20:07 +0100, Rafael J. Wysocki wrote:
> > > On Monday, January 14, 2013 11:42:09 AM Toshi Kani wrote:
> > > > On Mon, 2013-01-14 at 19:47 +0100, Rafael J. Wysocki wrote:
> > > > > On Monday, January 14, 2013 08:53:53 AM Toshi Kani wrote:
> > > > > > 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 <toshi.kani at hp.com>
> > > > > > > > ---
> > > > > > > >  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 <toshi.kani at hp.com>
> > > > > > > > + *
> > > > > > > > + * 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.
> > > > > 
> > > > > I thought so, but I don't think it's a good idea to add gaps like this.
> > > > 
> > > > OK, I will use an equal gap of 10 for all values.  So, the 100 in the
> > > > above example will be changed to 30.  
> > > 
> > > I wonder why you want to have those gaps at all.
> > 
> > Oh, I see.  I think some gap is helpful since it allows a new handler to
> > come between without recompiling other modules.  For instance, OEM
> > vendors may want to add their own handlers with loadable modules after
> > the kernel is distributed.
> 
> No, we don't support such a model, sorry, just make it a sequence of
> numbers and go from there.  If a vendor wants to modify the kernel to
> add new values, they can rebuild the core code as well.
> 
> I really don't like the whole idea of values in the first place, can't
> we just do things in the correct order in the code, and not be driven by
> random magic values?

OK, I will define all the values with enum, which is something like
below.  I think it is more manageable in this way as we do not have to
define magic values.

enum shp_add_order {
    /* Validate Phase */
    SHP_FW_BUS_ADD_VALIDATE_ORDER,

    /* Execute Phase */
    SHP_FW_BUS_ADD_EXECUTE_ORDER,
    SHP_FW_RES_ADD_EXECUTE_ORDER,
    SHP_MEM_ADD_EXECUTE_ORDER,
    SHP_CPU_ADD_EXECUTE_ORDER,

    /* Commit Phase */
    SHP_ADD_COMMIT_BASE_ORDER,
    SHP_FW_BUS_ADD_COMMIT_ORDER,
};

Thanks,
-Toshi