Date: Tue, 3 May 2011 21:40:10 +0200 From: Roland Smith <rsmith@xs4all.nl> To: David Demelier <demelier.david@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: Get the dev.cpu.0.temperature from sysctl(3) Message-ID: <20110503194009.GA63997@slackbox.erewhon.net> In-Reply-To: <4DBFB8F1.4050504@gmail.com> References: <4DBFB8F1.4050504@gmail.com>
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On Tue, May 03, 2011 at 10:12:33AM +0200, David Demelier wrote:
> Hello,
>=20
> I would like to get the dev.cpu.0.temperature node from sysctlbyname().=
=20
> It seems this node is an opaque type but how to check it and store it to=
=20
> 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.=20
The sysctl dev.cpu.0.temperature returns an integer, see
/sys/dev/coretemp/coretemp.c (look for the string "temperature"), and you'l=
l see:
/*
* Add the "temperature" MIB to dev.cpu.N.
*/
sc->sc_oid =3D 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 =3D (device_t) arg1;
int temp;
temp =3D 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 =3D 46=B0C
Hope this helps.
Roland
--=20
R.F.Smith http://www.xs4all.nl/~rsmith/
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