Reinvent I2C ops

Do not use the global platform_i2c_transfer() function that can only be
implemented by a single driver. Instead, make a `struct device` aware
transfer() function the only interface function for I2C controller dri-
vers to implement.

To not force the slave device drivers to be implemented either above
generic I2C or specialized SMBus operations, we support SMBus control-
lers in the slave device interface too.

We start with four simple slave functions: i2c_readb(), i2c_writeb(),
i2c_readb_at() and i2c_writeb_at(). They are all compatible to respec-
tive SMBus functions. But we keep aliases because it would be weird to
force e.g. an I2C EEPROM driver to call smbus_read_byte().

Change-Id: I98386f91bf4799ba3df84ec8bc0f64edd4142818
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20846
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
diff --git a/src/soc/intel/common/block/i2c/i2c.c b/src/soc/intel/common/block/i2c/i2c.c
index aeb6d8f..625bb99 100644
--- a/src/soc/intel/common/block/i2c/i2c.c
+++ b/src/soc/intel/common/block/i2c/i2c.c
@@ -150,8 +150,14 @@
 	acpigen_pop_len();
 }
 
-static struct i2c_bus_operations i2c_bus_ops = {
-	.dev_to_bus			= &lpss_i2c_dev_to_bus,
+static int lpss_i2c_dev_transfer(struct device *dev,
+				 const struct i2c_msg *msg, size_t count)
+{
+	return lpss_i2c_transfer(lpss_i2c_dev_to_bus(dev), msg, count);
+}
+
+static const struct i2c_bus_operations i2c_bus_ops = {
+	.transfer = lpss_i2c_dev_transfer,
 };
 
 static struct device_operations i2c_dev_ops = {