Date: Tue, 03 May 2011 22:11:45 +0200 From: David Demelier <demelier.david@gmail.com> To: Roland Smith <rsmith@xs4all.nl> Cc: freebsd-questions@freebsd.org Subject: Re: Get the dev.cpu.0.temperature from sysctl(3) Message-ID: <4DC06181.1070500@gmail.com> In-Reply-To: <20110503194009.GA63997@slackbox.erewhon.net> References: <4DBFB8F1.4050504@gmail.com> <20110503194009.GA63997@slackbox.erewhon.net>
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On 03/05/2011 21:40, Roland Smith wrote: > On Tue, May 03, 2011 at 10:12:33AM +0200, David Demelier wrote: >> Hello, >> >> I would like to get the dev.cpu.0.temperature node from sysctlbyname(). >> It seems this node is an opaque type but how to check it and store it to >> the appropriate variable type ? > > The best way to determine this is to read the source. I did that some time ago > to fix the temperature display in sysutils/conky. > > The sysctl dev.cpu.0.temperature returns an integer, see > /sys/dev/coretemp/coretemp.c (look for the string "temperature"), and you'll see: > > /* > * Add the "temperature" MIB to dev.cpu.N. > */ > sc->sc_oid = SYSCTL_ADD_PROC(device_get_sysctl_ctx(pdev), > SYSCTL_CHILDREN(device_get_sysctl_tree(pdev)), > OID_AUTO, "temperature", > CTLTYPE_INT | CTLFLAG_RD, > dev, 0, coretemp_get_temp_sysctl, "IK", > "Current temperature"); > > If you look at the definition of coretemp_get_temp_sysctl in the same file: > > coretemp_get_temp_sysctl(SYSCTL_HANDLER_ARGS) > { > device_t dev = (device_t) arg1; > int temp; > > temp = coretemp_get_temp(dev) * 10 + TZ_ZEROC; > > return (sysctl_handle_int(oidp,&temp, 0, req)); > } > > So the returned value is an 'int'. Note that TZ_ZEROC is #defined as 2732 at > the beginning of the file. The returned value is therefore the temperature > in Kelvin times ten. > > On my machine, it gives e.g.: > > sysctl dev.cpu.0.temperature > dev.cpu.0.temperature: 46.0C > > If we check the 'raw' return value; > > sysctl -b dev.cpu.0.temperature|hd > 00000000 78 0c 00 00 |x...| > 00000004 > > Running this value with the abovementioned algorithm in reverse through a > calculator, we get > > (0x0c78-2732)/10 = 46°C > > Hope this helps. > > > Roland Thanks a lot! I had a look into the src and I saw the format "IK" used to register the sysctl node but I was also surprised that "IK" was not defined in man sysctl(9) But I finally understood that K should means Kelvin :) Cheers, -- David Demelier
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