Hi > I have a Thinkpad T42, and as far as I can tell, it has an Intel 82801 > SMBus (which I gather from the output of lspci), and a National > Semiconductor PC87591 sensors chip (which I read at > http://archives.andrew.net.au/lm-sensors/msg31277.html). I think we do not have the driver for this chip yet. > I'm not completely new to Linux, but I don't know much about I2C, > although I've read some of the basics. From what I understand, I2C can > be used by lm-sensors, and possibly by ACPI. Lm-sensors talk to chips directly. ACPI is a framework between operation system and hardware. It used for powermanagent and also temps/fans control in notebooks. > I've read ominous things about lm-sensors in regards to Thinkpads (at > http://www.thinkwiki.org/wiki/Problem_with_lm-sensors), but I don't know > if this means that I should abandon trying to get any benefit from the > I2C bus. There is a security EEPROM connected to i2c which will be corrupted if you scan the bus. BIOS will disallow to start the notebook and your motherboard will need to be replaced. > Here's a few questions I have: > > 1. Do I need to have the kernel configured for /both/ hardware bus > support /and/ sensors chip support to get any value out of I2C, or > is it possible there are other devices on the bus that might be of > service? You need the bus driver to talk to devices connected to a bus. You can just abstract the I2C bus as a network connected chips every chip with some address. Each chip has some accessible registers which chip drivers understand. > 2. Is there any great way to confirm that Thinkpad T42's actually > have a NS PC87591 sensors chip? I was hesitant to run the > sensors-detect on my Thinkpad because of sharp warnings I found > on-line. This is EXTREMLY DANGEROUS !!!!!!!!!!!! I think you can run it ONLY IF you delete i2c-i801 module AND DO NOT ALLOW to SCAN i2c/SMBUS. (or compile kernel WITHOUT i2c bus drivers support) **************************************** If you will ALLOW it YOUR MOTHERBOARD IS LIKELY needed to be replaced ant it will COST you a LOT of money. **************************************** DO NOT TRY IT if ACPI works for you. acpi -V should show the temps. And that is what you need ;) > 3. If I can't use lm-sensors on a Thinkpad, does ACPI rely at all on > I2C? If so, what kind of configuration do I need to set that up > (kernel-wise or user-space-wise)? It may use I2C to get battery status etc... If you want to use ACPI you should configure your kernel see ACPI-HOWTO for details. > 4. How should I test that I2C is working when everything's all set up? Do not try to play with I2C on you thinkpad. > I appreciate any feedback you can provide, even if just pointing me > towards other resources. Try google to find something about I2C you can start at Philips web site. Regards Rudolf
