serial: sc16is7xx: refactor FIFO access functions to increase commonality

Simplify FIFO access functions by avoiding to declare
a struct sc16is7xx_port *s variable within each function.

This is mainly done to have more commonality between the max310x and
sc16is7xx drivers.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20231221231823.2327894-15-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: hvilleneuvedoo

drivers/tty/serial/sc16is7xx.c

@@ -379,17 +379,15 @@ static void sc16is7xx_port_write(struct uart_port *port, u8 reg, u8 val)
 	regmap_write(one->regmap, reg, val);
 }
 
-static void sc16is7xx_fifo_read(struct uart_port *port, unsigned int rxlen)
+static void sc16is7xx_fifo_read(struct uart_port *port, u8 *rxbuf, unsigned int rxlen)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 
-	regmap_noinc_read(one->regmap, SC16IS7XX_RHR_REG, s->buf, rxlen);
+	regmap_noinc_read(one->regmap, SC16IS7XX_RHR_REG, rxbuf, rxlen);
 }
 
-static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send)
+static void sc16is7xx_fifo_write(struct uart_port *port, u8 *txbuf, u8 to_send)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 
 	/*
@@ -399,7 +397,7 @@ static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send)
 	if (unlikely(!to_send))
 		return;
 
-	regmap_noinc_write(one->regmap, SC16IS7XX_THR_REG, s->buf, to_send);
+	regmap_noinc_write(one->regmap, SC16IS7XX_THR_REG, txbuf, to_send);
 }
 
 static void sc16is7xx_port_update(struct uart_port *port, u8 reg,
@@ -575,7 +573,7 @@ static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 			s->buf[0] = sc16is7xx_port_read(port, SC16IS7XX_RHR_REG);
 			bytes_read = 1;
 		} else {
-			sc16is7xx_fifo_read(port, rxlen);
+			sc16is7xx_fifo_read(port, s->buf, rxlen);
 			bytes_read = rxlen;
 		}
 
@@ -664,7 +662,7 @@ static void sc16is7xx_handle_tx(struct uart_port *port)
 			uart_xmit_advance(port, 1);
 		}
 
-		sc16is7xx_fifo_write(port, to_send);
+		sc16is7xx_fifo_write(port, s->buf, to_send);
 	}
 
 	uart_port_lock_irqsave(port, &flags);