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

From: Greg KH <[email-masked]>
Date: Mon, 14 Jan 2013 11:21:34 -0800

On Mon, Jan 14, 2013 at 08:07:35PM +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 <[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.
> > > 
> > > 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.
> 
> Anyway, this is just a small detail and it doesn't mean I don't have more
> comments.  I just need some more time to get the big picture idea of how this
> is supposed to work and perhaps Greg will have some remarks too.

Yes, give me a few days to catch up on other patches before I get the
chance to review these.

greg k-h