Date: Mon, 15 Mar 1999 12:41:41 -0700 (MST) From: "Kenneth D. Merry" <ken@plutotech.com> To: dillon@apollo.backplane.com (Matthew Dillon) Cc: smp@csn.net, hackers@FreeBSD.ORG Subject: Re: power-off without halt Message-ID: <199903151941.MAA20523@panzer.plutotech.com> In-Reply-To: <199903151844.KAA01410@apollo.backplane.com> from Matthew Dillon at "Mar 15, 1999 10:44: 1 am"
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Matthew Dillon wrote... > :Hi, > : > : We are looking at using FreeBSD as an "embedded OS" inside a line > :of instruments we are building. I think I have a handle on all the > :issues except how to cleanly handle shutdown where there is no > :console, and thus no way to send a 'halt' command. The requirement > :is that the user can merely turn off the power, nothing more required. > : > : I can modify the disk setup, kernel/util code as needed, I just need some > :idea for a workable solution. Has anyone delt with this problem before? > : > :-- > :Steve Passe | powered by > :smp@csn.net | Symmetric MultiProcessor FreeBSD > > Well, physically speaking you can't power off a machine that may > be writing to its disk. If it is in the middle of a write, you > *will* lose sectors to hard errors. > > So, typically, the best way to deal with this sort of situation is > to mount the disk read-only and never write to it. Or to not have a > disk at all. Or to use a pcmcia type flash disk. SGI boxes have a neat feature (or at least they did when I did IRIX work a few years ago). They have a "soft" power off switch. You hit the switch, and it safely shuts down the machine. Don't ATX power supplies have some sort of soft power-off capability? How about tying a "power" button on the front panel of this device to a switch that would tell the machine to halt itself and then power off? From looking at the ATX power supply specs: http://www.teleport.com/~atx/spec/atxps09.pdf It looks like there is a signal that tells the power supply to power itself off. However, there's also a "standby" 5V power lead that is always active when the power supply is plugged in. That's what allows things like wake on LAN to work. It looks like the pieces are there. What you want, I suppose, is a motherboard that can intercept the power switch signal, generate an interrupt, and then wait for some feedback from the OS before sending the signal on to shut down the power. Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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