HEADS UP: Changes to bcm2835, Tegra, and Exynos i2c drivers

[Jason Thorpe <thorpej%me.com@localhost>]

Hey folks --

I just checked in a bunch of changes to the i2c code, and included in these changes were:

-- Rewrite of the bcm2835 "bsciic" driver as an interrupt-driven state machine.  This makes my single-core Pi boards feel a lot more responsive when transferring large amounts of data over i2c.

-- Fixed locking related bugs in the Tegra and Exynos i2c drivers.  In the Tegra case, doing so probably fixes a deadlock that previously necessitated forcing polled mode operation.  Someone who has the hardware should try disabling that line of code in tegra_i2c_exec() and using the i2c bus to talk to some devices.

I'll watch for any fallout over the coming days and try to quickly fix any issues that might crop up.

Cheers...

-- thorpej