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

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Date:	Tue, 13 Feb 2007 11:02:51 +0100
From:	Tilman Schmidt <tilman@...p.cc>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Pavel Machek <pavel@....cz>, "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?

Geert Uytterhoeven schrieb:
> On Mon, 12 Feb 2007, Pavel Machek wrote:

>> > 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",

More often than not they assume nothing of the kind.

>> 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.

I think those are rare exceptions. They could and should be
asked to make this statement explicit, as you propose:

> Wouldn't it be more sensible to have
> 
>     .suspend = suspend_nothing_to_do
> 
> instead, and reserve NULL for `not yet implemented'?

NULL is already taken for 'don't know'. So *two* new values
are needed, one for "nothing to do" and one for "not supported".

-- 
Tilman Schmidt                    E-Mail: tilman@...p.cc
Bonn, Germany
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