Date: Thu, 1 Nov 2007 18:56:29 +0000
From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Rodolfo Giometti <giometti@enneenne.com>, Pavel Machek <pavel@ucw.cz>,
       linux-pcmcia@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PCMCIA: prevent auto insert during resume.
Message-ID: <20071101185629.GA3136@flint.arm.linux.org.uk>
Mail-Followup-To: Rodolfo Giometti <giometti@enneenne.com>,
	Pavel Machek <pavel@ucw.cz>, linux-pcmcia@lists.infradead.org,
	linux-kernel@vger.kernel.org
References: <20071026154705.GY19019@enneenne.com> <20071026160206.GC4321@flint.arm.linux.org.uk> <20071026162705.GZ19019@enneenne.com> <20071026163651.GD4321@flint.arm.linux.org.uk> <20071026165400.GA19019@enneenne.com> <20071026170030.GE4321@flint.arm.linux.org.uk> <20071026171857.GC19019@enneenne.com> <20071029192414.GC7742@ucw.cz> <20071101145359.GH5548@enneenne.com> <20071101183741.GA27621@flint.arm.linux.org.uk>
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On Thu, Nov 01, 2007 at 06:37:41PM +0000, Russell King wrote:
> On Thu, Nov 01, 2007 at 03:53:59PM +0100, Rodolfo Giometti wrote:
> > On Mon, Oct 29, 2007 at 07:24:15PM +0000, Pavel Machek wrote:
> > > 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.
> > 
> > That's exactly what my patch does! :)
> > 
> > If the user does 'eject' the device is not powered on at resume.
> > 
> > Currently, with out the patch, if you do an 'eject' to power down the
> > device, then you go to sleep and resume, the device is powered up
> > again and you have to do a new 'eject' to power it down.
> > 
> > My patch fixes this behaviour.
> 
> Let's be absolutely clear about this.  The patch in your original post
> does *NOT* do that.  It *completely* removes the possibility of powering
> up a device inserted into the PCMCIA slot before resuming without
> unplugging and replugging it by removing the code which detects an
> inserted card on resume.
> 
> And let's also be clear about something else.  You _were_ crystal clear
> on that aspect of it from your last mail on the subject since you were
> asking for names of attributes to set and clear such a flag.  I didn't
> respond because I'm not going to hold your hand with such obvious
> issues - if you need that level of support, it will be far faster for
> me to write the damned patch myself.

Oh, and I'd like to make another thing clear - let's get the roles of
responsibility right.

I'm the ex-PCMCIA maintainer who had a requirement for the current
behaviour on my embedded ARM devices with classical PCMCIA sockets.

Dominik is the current PCMCIA maintainer who gets to say what goes in,
how things should be designed, etc.

You're the guy coming along with a different requirement for a device
using the PCMCIA subsystem in a non-classical way (non-pluggable PCMCIA)
and finding that the subsystem doesn't work in a good way with that
setup, and suggesting we break classical PCMCIA setups to make it
work.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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