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

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Message-ID: <Pine.LNX.4.62.0702121653160.2928@pademelon.sonytel.be>
Date:	Mon, 12 Feb 2007 16:57:35 +0100 (CET)
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Pavel Machek <pavel@....cz>
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?

On Mon, 12 Feb 2007, Pavel Machek wrote:
> > > "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'?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds
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