linux-phytec-ti

drm/i2c: tda998x: allow sharing of the CEC device accesses

commit 14e5b5889d75894b633a393aff49d6583bce3b0d upstream.

cec_read() is non-atomic in the presence of other I2C bus transactions
to the same device.  This presents a problem when we add support for
the TDA9950 CEC engine part - both drivers can be trying to access the
device.

Avoid the inherent problems by switching to i2c_transfer() instead,
which allows us to perform more than one bus transaction atomically.

As this means we will be using I2C transactions rather than SMBUS, we
have to check that the host supports I2C functionality.

Tested-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>