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
78 0c 00 00 |x...|
0004
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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