linux-kernel - Re: [linux-pm] [RFC][PATCH] Add late pm notifiers for hibernate

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Date:	Thu, 9 Apr 2009 14:17:41 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
cc:	linux-pm@...ts.linux-foundation.org, <schwidefsky@...ibm.com>,
	<ubraun@...ux.vnet.ibm.com>, <heiko.carstens@...ibm.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [RFC][PATCH] Add late pm notifiers for hibernate

On Wed, 8 Apr 2009, Michael Holzheu wrote:

> From: Michael Holzheu <holzheu at linux.vnet.ibm.com>
> 
> This patch is a suggestion to solve the issue reported by Ursula Braun:
> https://lists.linux-foundation.org/pipermail/linux-pm/2009-March/020443.html
> 
> On s390 we have device drivers that don't belong to a Linux bus. Therefore
> we can't use the PM device callbacks (dev_pm_ops). The only way to get
> informed that we hibernate or resume is the pm_notifier_call_chain.

I'm curious to know what device drivers these are that don't have a 
bus.  Could they use the platform bus?  That's more or less what it's 
intended for -- devices that don't fit anywhere else.

> Unfortunately some of our drivers need a frozen userspace to do their
> hibernate actions and the current notifiers are called before userspace is
> frozen. Another point is that we want our console driver to suspend as late
> as possible so that we can see all the hibernate progress messages on the
> console.

It's possible to avoid suspending the console at all if you boot with
"no_console_suspend" as a kernel parameter.

Alan Stern

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