[hci] Continue processing while prompting for shell banner

Continue calling step() while displaying the shell banner.  This
potentially allows TCP connections to close gracefully after a failed
boot attempt.

Inspired-by: Guo-Fu Tseng <cooldavid@cooldavid.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/getkey.c

  * @v timeout		Timeout period, in ticks
  * @ret character	Character read from console
  */
-static int getchar_timeout ( unsigned long timeout ) {
+int getchar_timeout ( unsigned long timeout ) {
 	unsigned long expiry = ( currticks() + timeout );
 
 	while ( currticks() < expiry ) {

src/hci/shell_banner.c

 
 #include <stdio.h>
 #include <console.h>
-#include <unistd.h>
 #include <config/general.h>
 #include <ipxe/keys.h>
+#include <ipxe/timer.h>
 #include <ipxe/shell_banner.h>
 
 /** @file
  * @ret	enter_shell		User wants to enter shell
  */
 int shell_banner ( void ) {
-	int enter_shell = 0;
-	int wait_count;
 	int key;
 
 	/* Skip prompt if timeout is zero */
 	printf ( "\nPress Ctrl-B for the iPXE command line..." );
 
 	/* Wait for key */
-	for ( wait_count = 0 ; wait_count < BANNER_TIMEOUT ; wait_count++ ) {
-		if ( iskey() ) {
-			key = getchar();
-			if ( key == CTRL_B )
-				enter_shell = 1;
-			break;
-		}
-		mdelay(100);
-	}
+	key = getchar_timeout ( ( BANNER_TIMEOUT * TICKS_PER_SEC ) / 10 );
 
 	/* Clear the "Press Ctrl-B" line */
 	printf ( "\r                                         \r" );
 
-	return enter_shell;
+	return ( key == CTRL_B );
 }

src/include/console.h

 
 extern void putchar ( int character );
 extern int getchar ( void );
+extern int getchar_timeout ( unsigned long timeout );
 extern int iskey ( void );
 extern int getkey ( void );