Userspace ACPI interpreter ( was [ACPI] [RFC] dev_acpi: support for userspace access to acpi)

On IA64 platform, ACPI interpreter seems to be mandatory for those
stuff, but IA32 is not.  So, the ram disk is the generic solution 
for loading user space interpreter for boot. 


Yes, it needs a lot of work.  If we want to continue, we should find out
what's the benefit of doing so. The biggest benefit could be that kernel
will be less complex, thus kernel will be more stable.  At least, some
ACPI operation (like information query) is not needed to be handled in
kernel in synchronous manner, which is kernel invoking ACPI interpreter
like calling a C function. On laptop, I DO get many bug reports that
kernel 
crashes, or hang for a while ,or input event lost..., just due to AML
call executed
by ACPI interpreter running in the kernel.  I expect all this symptom
will
be gone, if interpreter is running in user space.

Thanks,
Luming
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In two sentences: If you want to play with moving the interpreter
to user-space, please do so, and do it on ia64, so you have to
deal with the interesting problems.

And this whole thing is a gigantic tangent that is only distracting
attention from the real question at hand, namely, Alex's dev_acpi
patch, which exists today and enables some very interesting new
functionality.
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Is there a significant advantage to doing having a user-mode ACPI
interpreter?  The only advantage I can think of is that the ACPI
interpreter could now live in pageable memory.  Are there any others?

					- Ted
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>



One reason for kernel-mode interpreter is to live in unpageable memory.

User-mode ACPI interpreter advantages:

1. Without losing platform functionality, user-mode interpreter
can make kernel less complex, thus more stronger.

2. Kernel can release from AML issues.
...

Thanks,
Luming
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  Yes, I agree Alex's dev_acpi is interesting, which could result in 
the removal of some acpi specific drive such as battery.c, button.c,
fan.c, thermal.c ....   So, I raised the question of userspace ACPI 
interpreter.  Intuitively, userspace is the right place for interpreter.

Thanks,
Luming

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> [ It would be sort of neat if we could built the core ACPI support in

It would be possible with some Makefile hacks. Basically you would need
to objcopy the ACPI object files and rename .text*/.data* to 
a different acpi specific name. Then you can give it an special 
area in the vmlinux.lds and possibly free it.

I agree with you that it's better kept in the kernel.


Hmm, this used to be smaller, no? Perhaps someone going over
bloat-o-meter[1] output to an older version would be useful.
There is probably some low{*filter*} fruit.

-Andi

[1] ftp://ftp.firstfloor.org/pub/ak/perl/bloat-o-meter

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Hi!


I do not think you want to put thermal/fan into userspace. If you boot
machine with init=/bin/bash, you should have working system. System
without fan fail... fast.

Plus you want to do suspend/resume.
								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
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