linux-kernel - Re: CONFIG_APM_POWER

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Date:	Sun, 2 Jan 2011 21:16:57 +0200
From:	Yotam Medini <yotam.medini@...il.com>
To:	Randy Dunlap <rdunlap@...otime.net>
Cc:	linux-kernel@...r.kernel.org, Avery Pennarun <apenwarr@...mnit.ca>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: CONFIG_APM_POWER - still possible?

Using the hints I got here, I realized that /proc/apm
is supposed to be created (for x86) by:
   apm_init() @ arch/x86/kernel/apm_32.c
I added some debug printk messages in some places I considered related.
>From these I learned the following:

1. In setup_arch(...) @ arch/x86/kernel/setup.c:
	apm_info.bios = boot_params.apm_bios_info;
   it has the value:
        apm_info.bios.version == 0

2. In apm_init() @ arch/x86/kernel/apm_32.c:
  if (apm_info.bios.version == 0 || paravirt_enabled() || machine_is_olpc()) {
    printk(KERN_INFO "apm: BIOS not found.\n");
    return -ENODEV;
  }

  It gets here with
     apm_info.bios.version == 0
  This is why 'dmesg' shows:
     apm: BIOS not found
  and thus /proc/apm is not created.

3. In  query_apm_bios() @ arch/x86/boot/apm.c
   I added debug puts messages.
   But 'dmesg' showed none of them.

Could it be that some boot-command line parameters are not well passed
to the kernel?
Is the 'initrd' involved in this? I am not familiar with the 'black art' of
constructing 'initrd'. I am using mkinitramfs for this.
The initrd I get does manage to bring up the kernel, the file-systems
and a essentially - a running system.

I still have not tried compiling apm directly into the kernel.
I may try it later, but I believe the problem lies elsewhere.

Thanks for all the tips -- yotam


On Fri, 31 Dec 2010 14:23:35 -0800
Randy Dunlap <rdunlap@...otime.net> wrote:

> On Fri, 31 Dec 2010 23:40:10 +0200 Yotam Medini wrote:
>
> > ....
> >   $ sudo modprobe apm
> >   FATAL: Error inserting apm
> >     (/lib/modules/2.6.32.yumax/kernel/arch/x86/kernel/apm.ko): No such device
> > ....
> > Also the "/proc/apm" is created in
> >   drivers/char/Makefile:71
> >     obj-$(CONFIG_APM_EMULATION)	+= apm-emulation.o
> >   drivers/char/apm-emulation.c:668-670
>
> Hint: This is not the only place that /proc/apm is created.
> ....
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