This adds the possibility to open an I2C bus with O_NONBLOCK (or set it
later via fcntl) to get non-blocking transmissions. This means that if
the bus is busy, a read, write or transfer ioctl will return with a
EAGAIN errno.
- Remove the printf support leaving the direct printk support configured
with TESTS_USE_PRINTK and all other output goes via a buffered vsniprintf
call to printk.
- Control the test's single init for functions and global data with
TEST_INIT and not CONFIGURE_INIT. They are now separate.
Updates #3170.
This I2C driver framework has some major differences compared to libi2c.
* It is compatible to the Linux I2C user-space API.
* It uses generic IMFS nodes and thus reduces the levels of indirection.
* The drivers don't have to mess around with minor numbers to get their
state information.
* No arbitrary bus controller model is assumed. The main task of an I2C
bus controller driver is to process I2C messages. How this is done is
private to the driver.
* Scatter/gather operations are supported (I2C_M_NOSTART).
