linux-kernel - Re: NAK new drivers without proper power management?

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Message-ID: <20070212165501.GA18101@elf.ucw.cz>
Date:	Mon, 12 Feb 2007 17:55:01 +0100
From:	Pavel Machek <pavel@....cz>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Arjan van de Ven <arjan@...radead.org>,
	nigel@...el.suspend2.net, LKML <linux-kernel@...r.kernel.org>
Subject: Re: NAK new drivers without proper power management?

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
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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