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

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Date:	Mon, 14 Jan 2013 19:47:36 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	lenb@...nel.org, gregkh@...uxfoundation.org,
	akpm@...ux-foundation.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	bhelgaas@...gle.com, isimatu.yasuaki@...fujitsu.com,
	jiang.liu@...wei.com, wency@...fujitsu.com, guohanjun@...wei.com,
	yinghai@...nel.org, srivatsa.bhat@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH v2 02/12] ACPI: Add sys_hotplug.h for system device hotplug framework

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@...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@...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.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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