lm_sensors2/kernel/chips lm75.c

Jean Delvare khali at linux-fr.org
Sun Feb 20 11:24:06 CET 2005


> Modified Files:
> 	lm75.c 
> Log Message:
> (mds) only initialize CMP/INT bit, and only if necessary

I am not happy with that change.

For one thing, if the chip was in shutdown mode, you leave it there.
This means that the temperature will never be updated, making the driver
useless.

For another, changing the CMP/INT bit is NOT a good idea. It's fine to
change the mode when it only affects alarm bits. However in this case
what it affects is the OS output, and you don't know what is wired to
that output. If the chip was programmed to INT mode, which is not the
default, there must be a reason, and that reason must be that whatever
is wired to the OS output expects interrupts and not comparator mode. By
arbitrarily changing the mode (and with no reason at that) you probably
screw the hardware overtemperature control mechanism.

The second point is no worse than what we had before (which obviously
means that most hardware designs don't use the interrupt mode, or we
would have had bad feedback), but the first one is a regression.

Thanks,
-- 
Jean Delvare



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