i2c: slave: rework the slave API

After more discussion, brave users, and additional datasheet evaluation,
some API updates for the new I2C slave framework became imminent. The
slave events now get some easier to understand naming. Also, the event
handling has been simplified to only need a single call to the slave
callback when an action by the backend is required.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 71a6e07..5a84bea 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -382,11 +382,11 @@
 	if (ssr_filtered & SAR) {
 		/* read or write request */
 		if (ssr_raw & STM) {
-			i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_START, &value);
+			i2c_slave_event(priv->slave, I2C_SLAVE_READ_REQUESTED, &value);
 			rcar_i2c_write(priv, ICRXTX, value);
 			rcar_i2c_write(priv, ICSIER, SDE | SSR | SAR);
 		} else {
-			i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_START, &value);
+			i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
 			rcar_i2c_read(priv, ICRXTX);	/* dummy read */
 			rcar_i2c_write(priv, ICSIER, SDR | SSR | SAR);
 		}
@@ -406,17 +406,15 @@
 		int ret;
 
 		value = rcar_i2c_read(priv, ICRXTX);
-		ret = i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_END, &value);
+		ret = i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
 		/* Send NACK in case of error */
 		rcar_i2c_write(priv, ICSCR, SIE | SDBS | (ret < 0 ? FNA : 0));
-		i2c_slave_event(priv->slave, I2C_SLAVE_REQ_WRITE_START, &value);
 		rcar_i2c_write(priv, ICSSR, ~SDR & 0xff);
 	}
 
 	/* master wants to read from us */
 	if (ssr_filtered & SDE) {
-		i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_END, &value);
-		i2c_slave_event(priv->slave, I2C_SLAVE_REQ_READ_START, &value);
+		i2c_slave_event(priv->slave, I2C_SLAVE_READ_PROCESSED, &value);
 		rcar_i2c_write(priv, ICRXTX, value);
 		rcar_i2c_write(priv, ICSSR, ~SDE & 0xff);
 	}