tty: serial: amba-pl011: replace TIOCMBIT macros by static functions

The driver uses two TIOCMBIT macros inside pl011_{get,set}_mctrl to
simplify the logic. Those look scary to checkpatch because they contain
ifs without do-while loops.

Avoid the macros by creating small equivalent static functions; that
lets the compiler do its type checking & avoids checkpatch errors.

For the second instance __assign_bit is not usable because it deals with
unsigned long pointers whereas we have an unsigned int in
pl011_set_mctrl.

This addresses the following checkpatch warnings:

    $ ./scripts/checkpatch.pl --strict --file \
        drivers/tty/serial/amba-pl011.c

    ERROR: Macros starting with if should be enclosed by a do -
           while loop to avoid possible if/else logic defects

    CHECK: Macro argument 'uartbit' may be better as '(uartbit)' to
           avoid precedence issues

    ERROR: Macros starting with if should be enclosed by a do - while
           loop to avoid possible if/else logic defects

    CHECK: Macro argument 'tiocmbit' may be better as '(tiocmbit)' to
           avoid precedence issues
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20231207-mbly-uart-v6-3-e384afa5e78c@bootlin.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/amba-pl011.c

@@ -1589,6 +1589,12 @@ static unsigned int pl011_tx_empty(struct uart_port *port)
 							0 : TIOCSER_TEMT;
 }
 
+static void pl011_maybe_set_bit(bool cond, unsigned int *ptr, unsigned int mask)
+{
+	if (cond)
+		*ptr |= mask;
+}
+
 static unsigned int pl011_get_mctrl(struct uart_port *port)
 {
 	struct uart_amba_port *uap =
@@ -1596,18 +1602,22 @@ static unsigned int pl011_get_mctrl(struct uart_port *port)
 	unsigned int result = 0;
 	unsigned int status = pl011_read(uap, REG_FR);
 
-#define TIOCMBIT(uartbit, tiocmbit)	\
-	if (status & uartbit)		\
-		result |= tiocmbit
+	pl011_maybe_set_bit(status & UART01x_FR_DCD, &result, TIOCM_CAR);
+	pl011_maybe_set_bit(status & uap->vendor->fr_dsr, &result, TIOCM_DSR);
+	pl011_maybe_set_bit(status & uap->vendor->fr_cts, &result, TIOCM_CTS);
+	pl011_maybe_set_bit(status & uap->vendor->fr_ri, &result, TIOCM_RNG);
 
-	TIOCMBIT(UART01x_FR_DCD, TIOCM_CAR);
-	TIOCMBIT(uap->vendor->fr_dsr, TIOCM_DSR);
-	TIOCMBIT(uap->vendor->fr_cts, TIOCM_CTS);
-	TIOCMBIT(uap->vendor->fr_ri, TIOCM_RNG);
-#undef TIOCMBIT
 	return result;
 }
 
+static void pl011_assign_bit(bool cond, unsigned int *ptr, unsigned int mask)
+{
+	if (cond)
+		*ptr |= mask;
+	else
+		*ptr &= ~mask;
+}
+
 static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
 	struct uart_amba_port *uap =
@@ -1616,23 +1626,16 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
 
 	cr = pl011_read(uap, REG_CR);
 
-#define	TIOCMBIT(tiocmbit, uartbit)		\
-	if (mctrl & tiocmbit)		\
-		cr |= uartbit;		\
-	else				\
-		cr &= ~uartbit
-
-	TIOCMBIT(TIOCM_RTS, UART011_CR_RTS);
-	TIOCMBIT(TIOCM_DTR, UART011_CR_DTR);
-	TIOCMBIT(TIOCM_OUT1, UART011_CR_OUT1);
-	TIOCMBIT(TIOCM_OUT2, UART011_CR_OUT2);
-	TIOCMBIT(TIOCM_LOOP, UART011_CR_LBE);
+	pl011_assign_bit(mctrl & TIOCM_RTS, &cr, UART011_CR_RTS);
+	pl011_assign_bit(mctrl & TIOCM_DTR, &cr, UART011_CR_DTR);
+	pl011_assign_bit(mctrl & TIOCM_OUT1, &cr, UART011_CR_OUT1);
+	pl011_assign_bit(mctrl & TIOCM_OUT2, &cr, UART011_CR_OUT2);
+	pl011_assign_bit(mctrl & TIOCM_LOOP, &cr, UART011_CR_LBE);
 
 	if (port->status & UPSTAT_AUTORTS) {
 		/* We need to disable auto-RTS if we want to turn RTS off */
-		TIOCMBIT(TIOCM_RTS, UART011_CR_RTSEN);
+		pl011_assign_bit(mctrl & TIOCM_RTS, &cr, UART011_CR_RTSEN);
 	}
-#undef TIOCMBIT
 
 	pl011_write(cr, uap, REG_CR);
 }