[poky] [PATCH 1/1] meta-yocto: remove apm from beagleboard MACHINE_FEATURES

[Richard Purdie]

On Thu, 2011-08-11 at 20:51 -0400, Bruce Ashfield wrote:
> On 11-08-11 7:47 PM, Richard Purdie wrote:
> > On Thu, 2011-08-11 at 15:16 -0400, Bruce Ashfield wrote:
> >> Fixes [YOCTO: #916]
> >>
> >> apm is not something that we require in our yocto reference beagleboard
> >> BSP. It currently is listed in the MACHINE_FEATURES for the board, which
> >> leads to the runtime message:
> >>
> >>    Starting advanced power management daemon: No APM support in kernel
> >>
> >> Since "/proc/apm" is not present. The board config we are targeting does
> >> not have the hardware to back this, so adding the emulation support
> >> wouldn't yield useful data. We'll leave this extended functionality for
> >> other more appropriate beagleboard configs.
> >
> > On arm it used to be the case that this was the only way to expose user
> > interface to suspend/resume the machine. Its not so much about their
> > being hardware present for it as the whole kernel side was emulation of
> > the user space notification part.
> >
> > Has something changed in recent kernels in this area?
> 
> I won't claim to be an expert here .. but I haven't used apmd
> on many machines in quite a while. Assuming suspend_ops is
> implemented, it is typically just something ike this:
> 
>   echo mem > /sys/power/state
> 
>     or
> 
>   echo standby > /sys/power/state
> 
> With a wakeup via the rtc, or whatever the board offers. I'm
> cc'ing Liming on this, since he's been poking at the board recently
> and may have more hands on information to share.
> 
> If we ARE removing this capability, then we'll take the other option
> that we had for this case and enable the emulation.

I have a suspicion that certain parts of the sato code do
assume /dev/apm_bios device emulation is present to get userspace
notification of suspend/resume events which the above doesn't provide
last I checked.

Likely this isn't an issue and I think that code in sato (matchbox panel
app iirc) is toggled by the MACHINE_FEATURES but its certainly worth
keeping in mind...

Cheers,

Richard