Re: NAK new drivers without proper power management?

From: Pavel Machek <pavel@ucw.cz>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
	Arjan van de Ven <arjan@infradead.org>,
	nigel@nigel.suspend2.net, LKML <linux-kernel@vger.kernel.org>
Subject: Re: NAK new drivers without proper power management?
Date: Mon, 12 Feb 2007 17:55:01 +0100	[thread overview]
Message-ID: <20070212165501.GA18101@elf.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.62.0702121653160.2928@pademelon.sonytel.be>

Hi!

> > > > "If the device requires that, implement .suspend and .resume or at least
> > >                                                                   ^^^^^^^^
> > > > define .suspend that will always return -ENOSYS (then people will know they
> > >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > whether or not the device requires .suspend and .resume, define .suspend that
> > >                                                            ^^^^^^^^^^^^^^^^^^^^
> > > > will always return -ENOSYS."
> > >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
> > > It's nicer if you don't have to implement dummy functions at all.
> > 
> > Unfortunately, drivers currently assume "NULL == nothing is needed",
> > so we'd have t do big search & replace... 
> 
> Which means you also cannot easily keep track of which driver supports
> suspend/resume and which doesn't, as there will always be drivers where a
> missing suspend/resume function is correct.
> 
> Wouldn't it be more sensible to have
> 
>     .suspend = suspend_nothing_to_do
> 
> instead, and reserve NULL for `not yet implemented'?

It would be. Patch would be welcome :-).
								Pavel
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