Introduction

The vt1211 is a sensor chip used for instance on the EPIA-CL Mini-ITX board which I have. The board has a fan-less VIA-eden processor, and I have not connected the fan in the box. I am worried about the temperature, so I want to monitor it.

The driver for vt1211 has not been ported to kernel version 2.6 by the lm_sensors project yet. The port has been listed as in progress for several months so I decided to port it myself and hopefully give something back to the open source community.

News

Fri Dec 31 12:08:49 CET 2004: Added a new patch for the 2.6.10 kernel. The vt1211.c file is not altered at all, just a new kernel patch.
Fri Oct 22 17:12:42 CEST 2004: Added another sensors.conf for EPIA-M 10000N.
Tue Oct 5 17:19:28 CEST 2004: Corrected a bug in show_temp_hyst that Simon found, he also sent a new sensors.conf . Made a note about i2c-isa.ko .
Sun Sep 26 19:54:48 CEST 2004: Changed to IN_MULTIPLIER=10 (was 1) to get correct voltage readings. Large changes in this doc. (it has been a busy day)
Sun Sep 26 17:05:36 CEST 2004: Got an updated kernel patch from Stefan, and got a sensors.conf for EPIA-M 10000N from Simon. My thanks for their help and contributions.
Sun Sep 26 07:45:29 CEST 2004: The driver was updated. The in-driver register converions was made optional. The Conversion Confusion paragraph was added. This is important so please read it.
Tue Sep 21 08:01:19 CEST 2004: Added the Patches and packages chapter with useful related items provided by Stefan Plattner.

The module

Here it is (there is also a kernel-patch further below);

vt1211.c

Download it to you work directory and build it with;

        echo "obj-m := vt1211.o" > Makefile
        make -C /path/to/your/kernel2.6/source/dir SUBDIRS=$PWD modules

Read the Documentation/kbuild/modules.txt in your kernel directory for more info about how to build modules.

Install it with the usual module-init-tools;

        insmod i2c-sensor.ko
        insmod vt1211.ko

The example is my commands. You may use modprobe , or require more or less modules to be loaded before vt1211.ko.

NOTE: The i2c-isa.ko module is required, else the 0-6000 directories will be missing. It seems like modprobe can miss this. A user had this problem on Fedora Core 3 test2.

Check the result by examining the /sys files;

# cd /sys/devices/platform/i2c-0/0-6000/
# ls
alarms           fan2_pwm         in4_max          temp3_input
detach_state     fan2_pwm_enable  in4_min          temp3_max
fan1_div         in0_ref          in5_input        temp3_max_hyst
fan1_input       in2_input        in5_max          temp4_input
fan1_min         in2_max          in5_min          temp4_max
fan1_pwm         in2_min          name             temp4_max_hyst
fan1_pwm_enable  in3_input        power            vrm
fan2_div         in3_max          temp2_input
fan2_input       in3_min          temp2_max
fan2_min         in4_input        temp2_max_hyst
# cat temp3_input in?_input
99250
1190
1900
2090
2020

The i2c-0/0-6000 is an address and may differ on your system. The example shows raw un-converted register values. These will be converted to readable values by some program like sensors . Or you can check the formulas in sensors.conf and convert them yourself;

        # compute temp3  (@ - 65) / 0.9686,  (@ * 0.9686) + 65
        echo "scale=2; (99.250-65)/0.9686" | bc -q
        35.36

So the register value 99250 is converted to 35.36 degree Celsius. The example uses bc for the computation. Note that the value from the driver is divided by the multiplier (described below).

The possibility to configure some sensors to either temp or voltage ( in ) has been removed. Instead the configuration has been setup like the default in /etc/sensors.conf ;

    label in2 "VCore1"
    label in3 "+5V"
    label in4 "+12V"
    label in5 "+3.3V"

    label temp2 "MB1 Temp"
    label temp3 "Proc Temp"
    label temp4 "MB2 Temp"

The driver can be compiled with an option (ALL_SENSORS) that enables all sensor files. This also adds the non-standard uch_config file for configuring the sensors.

Patches and packages

Stefan Plattner has provided alternative ways of installing the vt1211 driver. These are easier than the instruction above for most Linux users.

First the vt1211 driver as a patch to the kernel instead of a stand-alone module.

patch-vt1211-2.6.txt

And a ready to use debian package of kernel 2.6.8 with all the relevant epia patches plus supermount is available here.

My thanks to Stefan for providing these packages.

On request I have made a kernel path for the 2.6.10 kernel. The module is not altered at all;

patch-vt1211-2.6.10.txt

Conversion Confusion

When I made the port i read these documents in the Documentation/i2c/ directory in the kernel source;

porting-clients
sysfs-interface

The examples below is taken from kernel 2.6.8.1. In the porting-clients you can read;

        "Use the file names specified in Documentation/i2c/sysfs-interface
         for the individual files. Also convert the units these files read 
         and write to the specified ones."

The units in sysfs-interface is for instance instance;

        temp[1-4]_input Temperature input value.
                Unit: millidegree Celcius
                Read only value.

From this I concluded that the conversions should be done inside the driver. This is also done in the other VIA driver, the via686a.c . But I was wrong ...

I got a mail from Simon who owns a new EPIA-M 10000N board. On his board the register conversions are different. For instance;

        temp3 (@*@*0.0046)-(@*0.088)-0.748, (@*0.9686)+65

Here is the sensors.conf for the EPIA-M 10000N board from Simon;

sensors.conf.txt

Here is another contributed sensors.conf for the EPIA-M 10000N, found at VIAARENA about 12 month ago (Oct 2003);

sensors2.conf.txt

For other (older) boards the sensors.conf in the lm_sensors package will probably do nicely.

Reading the sysfs-interface again more carefully I found;

        ... the conversions cannot be hard coded into the driver and
        have to be done in user space.

        For this reason, even if we aim at a chip-independant
        libsensors, it will still require a configuration file
        (e.g. /etc/sensors.conf) for proper values conversion,
        labeling of inputs and hiding of unused inputs.

So the register values should not be converted by the driver. But the register values should still be multiplied by a factor inside the driver.

Register multipliers
Multiplier	2.4 kernel	2.6 kernel
TEMP_MULTIPLIER	10	1000
IN_MULTIPLIER (volt)	1(?)	10(?)

The IN_MULTIPLIER I think is incorrect in my 2.4 version (from lm_sensors-2.8.5) it should be 10 to fit the sensors.conf formulas. Further I think the the value should really be 1000 in the 2.6 version. Here is an example with IN_MULTIPLIER=10;

        # compute in4 ((@ * 100) - 3) / (0.1754 * 95.8), ...
        > cat /sys/devices/platform/i2c-0/0-6000/in4_input
        2080
        > echo "((2080*100)-3)/(0.1754*95.8)" | bc -q
        12378

This is the 12V in milli-volt, so it looks OK. But the formula contains (@*100) which no other sensor-chip driver has. So I really think that IN_MULTIPLIER=1000 should be used, and the formula should be;

        compute in4 (@ - 3) / (0.1754 * 95.8),

As you might understand I am a bit confused about this, but is is clear that the conversion should not be done by the driver. So The internal register conversion is disabled by default, but can be re-enabled. The register multipliers are macros and easy to alter.

It shouldn't be very hard to alter the driver and the translation files (e.g /etc/sensors.conf) to get correct values, but if anybody knows the correct way, please let me know.

Testing

I know there are tools for reading the sensors, but I have only tested this by printing the files under /sys. My Mini-ITX system is a primitive diskless system so installing tools (especially perl based) requires too much job.

I have tried to compare the CPU temperature and the voltages towards the PC Health Status menu on the BIOS screen. The voltage values are about the same. The CPU temperature from the vt1211 module seems a bit (~4 degrees) higher than the BIOS value. I do not know why or which is most correct, but I think its the same if you run the original 2.4 version of the module.

The fan_pwm is supposed to control the fan speed. I connected the fan in my system but could not control it. I read something on the viaarena forum that the fan on my board is connected to 12V always, so this is not necessarily a fault. I think the value is written ok by the driver, but the HW refuses to accept it. Example;

# echo 1 > fan2_pwm_enable
# echo 50 > fan2_pwm; cat fan2_pwm
50
# cat fan2_pwm
255

The value 50 seems to be written, but when the HW value is re-read by the driver it is back to 255 (100% fan speed).

The thermistor sensors (temp2 and temp4) are not used on my board so I can not test them. The translation formula is again taken from /etc/sensors.conf and seems a bit simplified compared to via686a.