Messages in this thread | | | Date | Tue, 12 May 2009 08:02:31 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] Acer Aspire One Fan Control |
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Hi,
On Mon, May 11, 2009 at 08:05:07PM +0200, Peter Feuerer wrote: > Hello, > > Borislav Petkov writes: >> >> the more I'm looking at the driver, the more I get annoyed by that >> user/kernel mode operation split. Remind me again why the driver should >> be loaded and not started automatically but the user should be required >> to activate it explicitly? > > The idea of not starting the module in kernel mode was from Matthew. And > he stated that it could harm the hardware when software controls the fan > instead of the BIOS. It may also be possible, that the warranty gets > invalid when you do that. Not sure about how acer would handle a defect > which could be caused by overheating and when they detect that software > was controlling the fan. That's why I think Matthew is right.
We actually don't have any reliable source for the temperature envelope of the surrounding hardware, right? Quick search didn't reveal anything here. I only came across a bunch of freeware tools which do fan control of the aspire ones but all the temperature trip points for the fan in those were ranging from 50 - 63° which leads to think that those all are kinda "common sense"-settings the authors came up with without any hard data from the manufacturer.
For example, mine has a Seagate Momentum ATA-8 ST9160310AS hdd and its spec[¹] says:
"2.10.1 Ambient temperature
Ambient temperature is defined as the temperature of the environment immediately surrounding the drive. Actual drive case temperature should not exceed 65°C (149°F) within the operating ambient conditions."
From what I could measure here empirically, the fan starts in low RPM mode at around 37°C and and gets cranked up to max when the temp reaches ~55°C. This envelope in the BIOS code is taking surrounding devices into consideration, I guess and am wondering whether the 67°C setting in your driver is still within safe limits, hmmm?
[..]
>> What is more, if the userspace program would fail, there's no way >> for the module to get activated again and jump in instead of the >> userspace program to the rescue. Which goes more to show that you >> don't need userspace control _at_ _all_ and the only two agents >> controlling the fan should be the BIOS or the kernel module. > > After reading and thinking about all this a while, I agree with you. > In the next patch I won't allow the user to switch on/off the fan > anymore.
Cool.
>> So I think that the kernel module should take over fan control >> upon load. This way you'll be able to get rid of all that needless >> complexity around kernelmode/disable_kernelmode and have a simple >> clean design. > > I would really like to do that, but what do you think about the >hardware damage / warranty things written above?
It seems that the BIOS setting is lower/safer so, yes, you're right, we don't want to void any warranties, so the BIOS control _should_ actually be the default since we are not at all sure whether moving the envelope up the temperature scale won't hurt the hardware.
/me would love to see some reliable info on that from the manufacturer...
[..]
Thanks for your work.
¹http://www.seagate.com/staticfiles/support/disc/manuals/notebook/momentus/5400.4/SATA/100468842a.pdf
-- Regards/Gruss, Boris. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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