linux-kernel - Re: [PATCH] PCMCIA: prevent auto insert during resume.

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Date:	Mon, 29 Oct 2007 19:24:15 +0000
From:	Pavel Machek <pavel@....cz>
To:	Rodolfo Giometti <giometti@...eenne.com>
Cc:	linux-pcmcia@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCMCIA: prevent auto insert during resume.

On Fri 2007-10-26 19:18:57, Rodolfo Giometti wrote:
> On Fri, Oct 26, 2007 at 06:00:31PM +0100, Russell King wrote:
> 
> > > > > Also if you didn't eject the socket, at resume the device will be
> > > > > powered up again, my patch just prevents that a pre-powered off device
> > > > > to be turned on at resume time.
> > > > > 
> > > > > However you should consider that some embedded systems have fixed
> > > > > PCMCIA devices that can't be removed so there are no reasons to detect
> > > > > them after resume, nobody can change them. :)
> > > > > 
> > > > > Also battery powered devices can go very frequently to sleep and the
> > > > > current behavior force the user to switch off the unused device each
> > > > > time the system resumes from sleep.
> > > > 
> > > > I realise that.  I do work on embedded devices, and this behaviour is
> > > > explicitly there to support embedded devices.
> > > > 
> > > > I've suggested a workable solution to you which allows both of us to
> > > > have the behaviour we both desire from the system.  That sounds like
> > > > a negotiated solution to me...
> > > 
> > > Do you mean to switch off the socket from userland? It could be a
> > > solution but in this case the device is powered on each time even if
> > > for a short delay...
> > 
> > If it's a permanent device, and you've powered it down via pccardctl,
> > then you've powered it down from userland.  So record that it's been
> > powered down from userland.  Then, on resume, if it's been powered down
> > from userland, don't try to re-power it on resume.
> 
> But the userland doesn't re-power it on resume... it's the kernel
> itself whos re-powers the device on resume. So the userland can only
> power down the device again.

I think Russell means: at a flag into kernel. If user powers down the
device, set the flag. If flag is set during resume, avoid powering up
the device.

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