First, SCL low timeout is set to 25 milliseconds by default as opposed to 1
millisecond before. The new value is based on the SMBus specification.
The timeout can be changed on a per bus basis using
dev.iicbb.N.scl_low_timeout sysctl.
The driver uses DELAY to wait for high SCL up to 1 millisecond, then it
switches to pause_sbt(SBT_1MS) for the rest of the timeout.
While here I made a number of other changes.
'udelay' that's used for timing clock and data signals is now calculated
based on the requested bus frequency (dev.iicbus.N.frequency) instead of
being hardcoded to 10 microseconds. The calculations are done in such a
fashion that the default bus frequency of 100000 is converted to udelay of
10 us. This is for backward compatibility. The actual frequency will be
less than a quarter (I think) of the requested frequency.
Maybe I just should have let udelay to be set directly and ignored the bus
frequency as was the case before.
Also, I added detection of stuck low SCL in a few places.
Previously, the code would just carry on after the SCL low timeout and that
might potentially lead to misinterpreted bits.
Finally, I fixed several style issues near the code that I changed.
Many more are still remaining.