[console] Add concept of generic console configuration

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

src/arch/i386/image/bootsector.c

 #include <realmode.h>
 #include <biosint.h>
 #include <bootsector.h>
+#include <ipxe/console.h>
 
 /** Vector for storing original INT 18 handler
  *
 		      unsigned int drive ) {
 	int discard_b, discard_D, discard_d;
 
+	/* Reset console, since boot sector will probably use it */
+	console_reset();
+
 	DBG ( "Booting from boot sector at %04x:%04x\n", segment, offset );
 
 	/* Hook INTs 18 and 19 to capture failure paths */

src/arch/i386/image/pxe_image.c

 #include <ipxe/segment.h>
 #include <ipxe/netdevice.h>
 #include <ipxe/features.h>
+#include <ipxe/console.h>
 
 FEATURE ( FEATURE_IMAGE, "PXE", DHCP_EB_FEATURE_PXE, 1 );
 
 	/* Set PXE command line */
 	pxe_cmdline = image->cmdline;
 
+	/* Reset console since PXE NBP will probably use it */
+	console_reset();
+
 	/* Start PXE NBP */
 	rc = pxe_start_nbp();
 

src/core/console.c

 int iskey ( void ) {
 	return has_input() ? 1 : 0;
 }
+
+/**
+ * Configure console
+ *
+ * @v config		Console configuration
+ * @ret rc		Return status code
+ *
+ * The configuration is passed to all configurable consoles, including
+ * those which are currently disabled.  Consoles may choose to enable
+ * or disable themselves depending upon the configuration.
+ *
+ * If configuration fails, then all consoles will be reset.
+ */
+int console_configure ( struct console_configuration *config ) {
+	struct console_driver *console;
+	int rc;
+
+	/* Try to configure each console */
+	for_each_table_entry ( console, CONSOLES ) {
+		if ( ( console->configure ) &&
+		     ( ( rc = console->configure ( config ) ) != 0 ) )
+				goto err;
+	}
+
+	return 0;
+
+ err:
+	/* Reset all consoles, avoiding a potential infinite loop */
+	if ( config )
+		console_reset();
+	return rc;
+}

src/core/init.c

 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <ipxe/device.h>
+#include <ipxe/console.h>
 #include <ipxe/init.h>
 
 /** @file
 			startup_fn->shutdown ( flags );
 	}
 
+	/* Reset console */
+	console_reset();
+
 	started = 0;
 }

src/include/ipxe/console.h

 	 * will not block.
 	 */
 	int ( * iskey ) ( void );
+	/**
+	 * Configure console
+	 *
+	 * @v config		Console configuration, or NULL to reset
+	 * @ret rc		Return status code
+	 */
+	int ( * configure ) ( struct console_configuration *config );
 	/**
 	 * Console usage bitmask
 	 *
 
 extern int iskey ( void );
 extern int getkey ( unsigned long timeout );
+extern int console_configure ( struct console_configuration *config );
+
+/**
+ * Reset console
+ *
+ */
+static inline __attribute__ (( always_inline )) void console_reset ( void ) {
+
+	console_configure ( NULL );
+}
 
 #endif /* _IPXE_CONSOLE_H */