Messages in this thread | | | Date | Wed, 19 Jan 2000 13:28:55 -0800 (PST) | From | Andy Henroid <> | Subject | Re: 2.3.40-5 -- "apm" no longer recognizes that I have an APM-ena bled kernel. |
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> -----Original Message----- > From: Jamie Lokier > [mailto:lkd@tantalophile.demon.co.uk] > Sent: Tuesday, January 18, 2000 3:18 PM > To: Miles Lane > Cc: Linux Kernel > Subject: Re: 2.3.40-5 -- "apm" no longer recognizes > that I have an > APM-enabled kernel. > > > Miles Lane wrote: >> When I run the command "apm", I receive an error >> stating: >> No APM support in kernel >> This in spite of having APM enabled in my .config >> file: > > That's because you've got ACPI enabled too. ACPI > now overrides APM if it is compiled in. > > I don't know why it does that -- APM seems to work > fine with ACPI in earlier kernels, and now suspend > takes longer and the clock isn't restored properly > after a suspend.
APM is disabled by ACPI as both can not be enabled at once. On some platforms you can get away with APM engaged (the most common reason is to compensate for a non-working S5 implementation and fallback to APM power off) but it's not safe to do. If you want to use APM, turn off or disable (kernel command line "acpi=off") ACPI.
> The solution: turn off ACPI. I can't see what the > point in using the ACPI support is at the moment.
On systems with working ACPI implementations, ACPI gets you CPU power states (saves power when CPU is idle), S5 (soft off), and power/sleep button support. APM additionally provides suspend and battery status and these features are currently incomplete for ACPI but on the way.
> If the ACPI user space tools (e.g. acpid) do > anything useful, it isn't documented.
acpid reads the ACPI tables and uploads important information about how to do CPU power states, S-states, and handles power/sleep button presses. If acpid does not run, the ACPI driver won't do much useful.
> For me the only effect of acpid is to prevent > suspends from suspending at all. Nothing useful > like battery life estimation, clock updating, > that sort of thing.
Battery support is coming. It's a bit more complicated to do than APM, hence the delay. You have to have a completely working AML interpreter and, for many systems, an embedded controller driver.
> A lot of work is obviously going into the kernel > ACPI driver. Of course I'd like to minimise power > consumption on my laptop. So I'm wondering, how > is that kernel driver getting tested? Is there a > user space tool I haven't found?
Most of the problems we are seeing are just discovered by people running with ACPI on various systems. There is really no better way to test things like C-states, S-states, and buttons other than by hand.
-Andy
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