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

[Rodolfo Giometti <giometti@enneenne.com>]

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.

Current status without the patch:

   hostname:~# pccardctl status
   Socket 0:
     3.3V 16-bit PC Card
     Subdevice 0 (function 0) [unbound]
   hostname:~# pccardctl eject
   pccard: card ejected from slot 0
   hostname:~# pccardctl status
   Socket 0:
     no card
   hostname:~# apm -s
   Stopping tasks ... done.
   Suspending console(s)
   <<RESUME>>
   hostname:~# usb0: full speed config #1: 100 mA, Ethernet Gadget, using CDC Ethernet Subset
   pccard: PCMCIA card inserted into slot 0
   pcmcia: registering new device pcmcia0.0
   Restarting tasks ... done.
   hostname:~# pccardctl status
   Socket 0:
     3.3V 16-bit PC Card
     Subdevice 0 (function 0) [unbound]

The device into PCMCIA slot 0 is _auto_ powered up again.

(Possible) future status with the patch:

   hostname:~# pccardctl status
   Socket 0:
     3.3V 16-bit PC Card
     Subdevice 0 (function 0) [unbound]
   hostname:~# pccardctl eject 
   pccard: card ejected from slot 0
   hostname:~# pccardctl status
   Socket 0:
     no card
   hostname:~# apm -s
   Stopping tasks ... done.
   Suspending console(s)
   <<RESUME>>
   hostname:~# usb0: full speed config #1: 100 mA, Ethernet Gadget, using CDC Ethernet Subset
   Restarting tasks ... done.
   pccardctl status
   Socket 0:
     no card
   hostname:~# pccardctl insert
   pccard: PCMCIA card inserted into slot 0
   pcmcia: registering new device pcmcia0.0
   hostname:~# pccardctl status
   Socket 0:
     3.3V 16-bit PC Card
     Subdevice 0 (function 0) [unbound]

The device into PCMCIA slot 0 is _not_ powered up and the user should
use "pccardctl insert" to do that (on my battery powered device this
behaviour saves the battery a lot).

If you like current behaviour don't apply the patch. :)

> 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.

In the past I did some "obvious" patches and the maintainer told me:
"plase change this name" or "modify the default behaviour",
etc.. That's why I asked for. I thought it could be less time
consuming ask before then modify again after...

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail:    giometti@enneenne.com
Linux Device Driver                             giometti@gnudd.com
Embedded Systems                     		giometti@linux.it
UNIX programming                     phone:     +39 349 2432127
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/