[serial] Allow platform to specify mechanism for identifying console

Allow the platform configuration to provide a mechanism for
identifying the serial console UART.  Provide two globally available
mechanisms: "null" (i.e. no serial console), and "fixed" (i.e. use
whatever is specified by COMCONSOLE in config/serial.h).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/config/defaults/efi.h

@@ -28,6 +28,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define FDT_EFI
 #define MPAPI_EFI
 #define NAP_EFI
+#define SERIAL_FIXED
 
 #define	NET_PROTO_IPV6		/* IPv6 protocol */
 #define	NET_PROTO_LLDP		/* Link Layer Discovery protocol */

src/config/defaults/linux.h

@@ -24,6 +24,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define DMAAPI_FLAT
 #define ACPI_LINUX
 #define MPAPI_NULL
+#define SERIAL_NULL
 
 #define DRIVERS_LINUX
 

src/config/defaults/pcbios.h

@@ -26,6 +26,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define REBOOT_PCBIOS
 #define ACPI_RSDP
 #define MPAPI_PCBIOS
+#define SERIAL_FIXED
 
 #ifdef __x86_64__
 #define IOMAP_PAGES

src/config/defaults/sbi.h

@@ -25,6 +25,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define REBOOT_SBI
 #define UMALLOC_UHEAP
 #define MEMMAP_FDT
+#define SERIAL_NULL
 
 #define ACPI_NULL
 #define MPAPI_NULL

src/config/serial.h

@@ -13,6 +13,8 @@
 
 FILE_LICENCE ( GPL2_OR_LATER );
 
+#include <config/defaults.h>
+
 #define	COMCONSOLE	COM1		/* I/O port address */
 
 /* Keep settings from a previous user of the serial port (e.g. lilo or

src/core/serial.c

@@ -45,6 +45,12 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define CONSOLE_SERIAL ( CONSOLE_USAGE_ALL & ~CONSOLE_USAGE_LOG )
 #endif
 
+#ifdef SERIAL_FIXED
+#define SERIAL_PREFIX_fixed
+#else
+#define SERIAL_PREFIX_fixed __fixed_
+#endif
+
 /* Serial console UART */
 #ifndef COMCONSOLE
 #define COMCONSOLE NULL
@@ -55,12 +61,19 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define COMSPEED 0
 #endif
 
-/** Default serial console UART */
-static struct uart * const default_serial_console = COMCONSOLE;
-
 /** Active serial console UART */
 struct uart *serial_console;
 
+/**
+ * Get fixed serial console UART
+ *
+ * @ret uart		Serial console UART, or NULL
+ */
+static struct uart * serial_comconsole ( void ) {
+
+	return COMCONSOLE;
+}
+
 /**
  * Print a character to serial console
  *
@@ -128,10 +141,11 @@ struct console_driver serial_console_driver __console_driver = {
 
 /** Initialise serial console */
 static void serial_init ( void ) {
-	struct uart *uart = default_serial_console;
+	struct uart *uart;
 	int rc;
 
-	/* Do nothing if we have no default port */
+	/* Get default serial console, if any */
+	uart = default_serial_console();
 	if ( ! uart )
 		return;
 
@@ -174,3 +188,6 @@ struct startup_fn serial_startup_fn __startup_fn ( STARTUP_EARLY ) = {
 	.name = "serial",
 	.shutdown = serial_shutdown,
 };
+
+PROVIDE_SERIAL_INLINE ( null, default_serial_console );
+PROVIDE_SERIAL ( fixed, default_serial_console, serial_comconsole );

src/include/ipxe/serial.h

@@ -9,7 +9,61 @@
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
+#include <ipxe/api.h>
 #include <ipxe/uart.h>
+#include <config/serial.h>
+
+#ifdef SERIAL_NULL
+#define SERIAL_PREFIX_null
+#else
+#define SERIAL_PREFIX_null __null_
+#endif
+
+/**
+ * Calculate static inline serial API function name
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @ret _subsys_func	Subsystem API function
+ */
+#define SERIAL_INLINE( _subsys, _api_func ) \
+	SINGLE_API_INLINE ( SERIAL_PREFIX_ ## _subsys, _api_func )
+
+/**
+ * Provide a serial API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_SERIAL( _subsys, _api_func, _func ) \
+	PROVIDE_SINGLE_API ( SERIAL_PREFIX_ ## _subsys, _api_func, _func )
+
+/**
+ * Provide a static inline serial API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ */
+#define PROVIDE_SERIAL_INLINE( _subsys, _api_func ) \
+	PROVIDE_SINGLE_API_INLINE ( SERIAL_PREFIX_ ## _subsys, _api_func )
+
+/**
+ * Get null serial console UART
+ *
+ * @ret uart		Serial console UART, or NULL
+ */
+static inline __always_inline struct uart *
+SERIAL_INLINE ( null, default_serial_console ) ( void ) {
+	return NULL;
+}
+
+/**
+ * Get serial console UART
+ *
+ * @ret uart		Serial console UART, or NULL
+ */
+struct uart * default_serial_console ( void );
 
 extern struct uart *serial_console;