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Re: Bug#167009: Proper creation of /dev/apm_bios

On Fre, 2002-11-01 at 13:09, Simon Richter wrote:
> On Fri, Nov 01, 2002 at 02:46:29PM +0000, J.D. Hood wrote:
> > The question was: Why does X need APM support in order
> > to recover from a suspend-and-resume cycle?
> Yes, and the short answer to this is that this is actually pointless. X
> already receives VT_ACTIVATE and VT_DEACTIVATE events,

I don't think it does, at least 'on PPC'. That's (part of) the problem.

> > If the OS lacks APM support, then it is completely
> > unaware of APM events such as suspending and resuming,
> There are still the other PM standards, like ACPI on i386/ia64, the Mac
> standard on PowerPC etc. That's why APM support will not help the
> PowerPC people (in fact, nothing will; see below).

Wrong, see below.

> > which is implemented in firmware.  The OS can't switch
> > from X to the console, because nothing tells it that
> > a suspend is about to happen, or has happened.  So far
> > as the OS is concerned, all that happens is that the
> > real time clock jumps ahead.
> Actually we have unified PM in the kernel now, which means that we have
> a single routine which all PM modules will call on suspend. I'm going to
> check back with the kernel code whether the VT switch still happens or
> if that got lost in the transition to unified PM and if necessary, lobby
> for its re-inclusion.

It shouldn't be necessary, X can handle this internally for the PM
standards it supports (currently only APM).

> > Of course, because firmware rarely restores everything
> > exactly to its pre-suspend state, some other things
> > are different too ... and herein lies the cause of the
> > hangs.
> Which is the PowerPC problem. The init sequence for the graphics
> hardware is a well-kept secret, so in fact the kernel would have to call
> the firmware init, but for some reason (I'm not too deep into that) this
> doesn't work.

This isn't needed normally 'on PPC'.

> > To cure the problem on powerpc it will not suffice
> > to install the powermgmt-base package.  All that
> > does (after getting the administrator's permission) is
> > create /dev/apm_bios (via MAKEDEV) if the node doesn't
> > exist already exist.  It also configures modutils 
> > and devfs for APM.  But powermgmt-base doesn't add APM
> > support to a kernel that lacks it.
> Which would be complete and utter BS, since PPC doesn't have APM.

We do have APM emulation for Macs, /dev/apm_bios works if that's enabled
in the kernel.

Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member   /  CS student, Free Software enthusiast

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