[lm-sensors] Single Sensor Check

[lm-sensors] Single Sensor Check

[sensored]

[-- Attachment #1.1: Type: text/plain, Size: 743 bytes --]

Hello, all!  I need to add a check for an alarm to a single sensor in my C
program, and I'd like to do so without the overhead of calling out to an
external program and parsing its output (plus all the error-checking, etc.).
I have been having some issues compiling lm-sensors (so that I can step
through with a debugger), so perhaps you can help me short-circuit this
process a little: 

Is there a way to read the value of a sensor (all it throws is ALARM or
nothing) from somewhere (e.g. in a protected area of memory)? For example,
dmidecode finds an SMBIOS table at a particular memory location, copies it,
and just navigates the table to find the values for the DMI info... Are
sensors accessible in a similar manner?

Thanks!

-Ken

 


[-- Attachment #1.2: Type: text/html, Size: 5009 bytes --]

[-- Attachment #2: Type: text/plain, Size: 153 bytes --]

_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [lm-sensors] Single Sensor Check

[Matt Roberds]

On Fri, 15 Aug 2008, sensored@CubicC.com wrote:
> Hello, all!  I need to add a check for an alarm to a single sensor in
> my C program, and I'd like to do so without the overhead of calling
> out to an external program and parsing its output (plus all the
> error-checking, etc.).

Assuming a Unix-ish environment: write a script (in shell, Perl, etc)
that calls sensors for you, parses the output, and creates a short file
with the information you need.  Put the script in cron, and/or have it
run continuously.  In your C program, read in the short file (whose
format you control) and act on it appropriately.  Add checking to avoid
race conditions, etc, but also remember that most sensors and alarms
don't update all that fast; if it really does matter if you catch the
alarm now or 2 seconds from now, you need a different approach.

> I have been having some issues compiling lm-sensors (so that I can
> step through with a debugger), so perhaps you can help me short-circuit
> this process a little:

You should be able to run the sensors-detect script in the lm-sensors
package without compiling the entire package; this should at least tell
you if the sensor chip you have is supported.

> Is there a way to read the value of a sensor (all it throws is ALARM or
> nothing) from somewhere (e.g. in a protected area of memory)?

Yes.  This is 100% dependent on the hardware you are using and will even
change between different revisions of a particular motherboard.  If you
have control over what hardware is used, then get the data sheet for the
sensor/monitoring chip being used and read it; it should describe how to
access the chip.  If there is an lm-sensors driver for that chip, look
at it as well to see what you need to do.

Matt Roberds


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [lm-sensors] Single Sensor Check

[sensored]

Thanks, Matt -- I appreciate the time you took to respond.  I *do* have
control over the motherboard, so I went looking for documentation on the
chipset & sensors, but there was nothing offered other than basic "How to
configure the BIOS" information.  Do you have any suggestions of what,
specifically, I could ask the manufacturer for (if they'll even oblige me).

I dug deeper into the lm-sensors code, and determined that lm-sensors is
parsing a file in /sys/devices/platform/i2c-9191/9191-0290/ (and responding
accordingly).  Can you help me understand how this file got created there,
and how it is updated (I assume the data needs to be updated in close to
real-time)?

Thanks again.

-Ken

-----Original Message-----
From: Matt Roberds [mailto:mattroberds@cox.net] 
Sent: Friday, August 15, 2008 8:17 PM
To: sensored@CubicC.com
Cc: lm-sensors@lm-sensors.org
Subject: Re: [lm-sensors] Single Sensor Check

On Fri, 15 Aug 2008, sensored@CubicC.com wrote:
> Hello, all!  I need to add a check for an alarm to a single sensor in
> my C program, and I'd like to do so without the overhead of calling
> out to an external program and parsing its output (plus all the
> error-checking, etc.).

Assuming a Unix-ish environment: write a script (in shell, Perl, etc)
that calls sensors for you, parses the output, and creates a short file
with the information you need.  Put the script in cron, and/or have it
run continuously.  In your C program, read in the short file (whose
format you control) and act on it appropriately.  Add checking to avoid
race conditions, etc, but also remember that most sensors and alarms
don't update all that fast; if it really does matter if you catch the
alarm now or 2 seconds from now, you need a different approach.

> I have been having some issues compiling lm-sensors (so that I can
> step through with a debugger), so perhaps you can help me short-circuit
> this process a little:

You should be able to run the sensors-detect script in the lm-sensors
package without compiling the entire package; this should at least tell
you if the sensor chip you have is supported.

> Is there a way to read the value of a sensor (all it throws is ALARM or
> nothing) from somewhere (e.g. in a protected area of memory)?

Yes.  This is 100% dependent on the hardware you are using and will even
change between different revisions of a particular motherboard.  If you
have control over what hardware is used, then get the data sheet for the
sensor/monitoring chip being used and read it; it should describe how to
access the chip.  If there is an lm-sensors driver for that chip, look
at it as well to see what you need to do.

Matt Roberds


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [lm-sensors] Single Sensor Check

[Jean Delvare]

Hi Ken,

On Tue, 2 Sep 2008 17:31:53 -0400, sensored@CubicC.com wrote:
> Thanks, Matt -- I appreciate the time you took to respond.  I *do* have
> control over the motherboard, so I went looking for documentation on the
> chipset & sensors, but there was nothing offered other than basic "How to
> configure the BIOS" information.  Do you have any suggestions of what,
> specifically, I could ask the manufacturer for (if they'll even oblige me).
> 
> I dug deeper into the lm-sensors code, and determined that lm-sensors is
> parsing a file in /sys/devices/platform/i2c-9191/9191-0290/ (and responding
> accordingly).  Can you help me understand how this file got created there,
> and how it is updated (I assume the data needs to be updated in close to
> real-time)?

You must be using a relatively old kernel to have such a device name...

Anyway, the files in question are created by whatever hardware
monitoring driver your system is using. To find out which it is, look
at the "driver" link in this directory.

The data in these files are updated only when you read from them, and
are cached for a short period of time (1 to 2 seconds, depends on the
driver) to prevent a given user from causing too much I/O traffic to
the monitoring chip.

To answer your question more generically: you can ask libsensors for a
specific input value, however the sensors command-line tool doesn't
offer any interface for this so you would have to either add it or
write your own little program interfacing with libsensors. The
alternative is to read from /sys directly, as you already found out,
but then you lose the labelling and scaling facilities of libsensors.

-- 
Jean Delvare

_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors