serial_core: Un-ifdef sysrq SUPPORT_SYSRQ

The SUPPORT_SYSRQ is messy: every .c source should define it before
including "serial_core.h" if sysrq is supported or struct uart_port will
differ in sizes. Also this prevents moving to serial_core.c functions:
uart_handle_sysrq_char(), uart_prepare_sysrq_char(),
uart_unlock_and_check_sysrq().

It doesn't save many bytes in the structure, and a better way to reduce
it's size would be making rs485 and iso7816 pointers.

Introduce `has_sysrq` member to be used by serial line drivers further.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-4-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/serial_core.h

@@ -240,14 +240,13 @@ struct uart_port {
 	resource_size_t		mapsize;
 	struct device		*dev;			/* parent device */
 
-#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
 	unsigned long		sysrq;			/* sysrq timeout */
 	unsigned int		sysrq_ch;		/* char for sysrq */
-#endif
+	unsigned char		has_sysrq;
 
 	unsigned char		hub6;			/* this should be in the 8250 driver */
 	unsigned char		suspended;
-	unsigned char		unused[2];
+	unsigned char		unused;
 	const char		*name;			/* port name */
 	struct attribute_group	*attr_group;		/* port specific attributes */
 	const struct attribute_group **tty_groups;	/* all attributes (serial core use only) */
@@ -461,31 +460,46 @@ extern void uart_handle_cts_change(struct uart_port *uport,
 extern void uart_insert_char(struct uart_port *port, unsigned int status,
 		 unsigned int overrun, unsigned int ch, unsigned int flag);
 
-#if defined(SUPPORT_SYSRQ) && defined(CONFIG_MAGIC_SYSRQ_SERIAL)
 static inline int
 uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
 {
-	if (port->sysrq) {
-		if (ch && time_before(jiffies, port->sysrq)) {
-			handle_sysrq(ch);
-			port->sysrq = 0;
-			return 1;
-		}
+	if (!IS_ENABLED(CONFIG_MAGIC_SYSRQ_SERIAL))
+		return 0;
+
+	if (!port->has_sysrq && !IS_ENABLED(SUPPORT_SYSRQ))
+		return 0;
+
+	if (!port->sysrq)
+		return 0;
+
+	if (ch && time_before(jiffies, port->sysrq)) {
+		handle_sysrq(ch);
 		port->sysrq = 0;
+		return 1;
 	}
+	port->sysrq = 0;
+
 	return 0;
 }
 static inline int
 uart_prepare_sysrq_char(struct uart_port *port, unsigned int ch)
 {
-	if (port->sysrq) {
-		if (ch && time_before(jiffies, port->sysrq)) {
-			port->sysrq_ch = ch;
-			port->sysrq = 0;
-			return 1;
-		}
+	if (!IS_ENABLED(CONFIG_MAGIC_SYSRQ_SERIAL))
+		return 0;
+
+	if (!port->has_sysrq && !IS_ENABLED(SUPPORT_SYSRQ))
+		return 0;
+
+	if (!port->sysrq)
+		return 0;
+
+	if (ch && time_before(jiffies, port->sysrq)) {
+		port->sysrq_ch = ch;
 		port->sysrq = 0;
+		return 1;
 	}
+	port->sysrq = 0;
+
 	return 0;
 }
 static inline void
@@ -493,6 +507,11 @@ uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
 {
 	int sysrq_ch;
 
+	if (!port->has_sysrq && !IS_ENABLED(SUPPORT_SYSRQ)) {
+		spin_unlock_irqrestore(&port->lock, irqflags);
+		return;
+	}
+
 	sysrq_ch = port->sysrq_ch;
 	port->sysrq_ch = 0;
 
@@ -501,17 +520,6 @@ uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
 	if (sysrq_ch)
 		handle_sysrq(sysrq_ch);
 }
-#else
-static inline int
-uart_handle_sysrq_char(struct uart_port *port, unsigned int ch) { return 0; }
-static inline int
-uart_prepare_sysrq_char(struct uart_port *port, unsigned int ch) { return 0; }
-static inline void
-uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
-{
-	spin_unlock_irqrestore(&port->lock, irqflags);
-}
-#endif
 
 /*
  * We do the SysRQ and SAK checking like this...
@@ -523,15 +531,16 @@ static inline int uart_handle_break(struct uart_port *port)
 	if (port->handle_break)
 		port->handle_break(port);
 
-#ifdef SUPPORT_SYSRQ
-	if (port->cons && port->cons->index == port->line) {
-		if (!port->sysrq) {
-			port->sysrq = jiffies + HZ*5;
-			return 1;
+	if (port->has_sysrq || IS_ENABLED(SUPPORT_SYSRQ)) {
+		if (port->cons && port->cons->index == port->line) {
+			if (!port->sysrq) {
+				port->sysrq = jiffies + HZ*5;
+				return 1;
+			}
+			port->sysrq = 0;
 		}
-		port->sysrq = 0;
 	}
-#endif
+
 	if (port->flags & UPF_SAK)
 		do_SAK(state->port.tty);
 	return 0;