[console] Support AltGr to access ASCII characters via remapping

Several keyboard layouts define ASCII characters as accessible only
via the AltGr modifier.  Add support for this modifier to ensure that
all ASCII characters are accessible.

Experiments suggest that the BIOS console is likely to fail to
generate ASCII characters when the AltGr key is pressed.  Work around
this limitation by accepting LShift+RShift (which will definitely
produce an ASCII character) as a synonym for AltGr.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/src/arch/x86/interface/pcbios/bios_console.c b/src/arch/x86/interface/pcbios/bios_console.c
index 2664ac8a5..0220c8564 100644
--- a/src/arch/x86/interface/pcbios/bios_console.c
+++ b/src/arch/x86/interface/pcbios/bios_console.c
@@ -362,6 +362,7 @@ static const char * bios_ansi_seq ( unsigned int scancode ) {
 static int bios_getchar ( void ) {
 	uint16_t keypress;
 	uint8_t kb0;
+	uint8_t kb2;
 	unsigned int scancode;
 	unsigned int character;
 	const char *ansi_seq;
@@ -387,6 +388,7 @@ static int bios_getchar ( void ) {
 	scancode = ( keypress >> 8 );
 	character = ( keypress & 0xff );
 	get_real ( kb0, BDA_SEG, BDA_KB0 );
+	get_real ( kb2, BDA_SEG, BDA_KB2 );
 
 	/* If it's a normal character, map (if applicable) and return it */
 	if ( character && ( character < 0x80 ) ) {
@@ -405,6 +407,16 @@ static int bios_getchar ( void ) {
 			character |= KEYMAP_CTRL;
 		if ( kb0 & BDA_KB0_CAPSLOCK )
 			character |= KEYMAP_CAPSLOCK_REDO;
+		if ( kb2 & BDA_KB2_RALT )
+			character |= KEYMAP_ALTGR;
+
+		/* Treat LShift+RShift as AltGr since many BIOSes will
+		 * not return ASCII characters when AltGr is pressed.
+		 */
+		if ( ( kb0 & ( BDA_KB0_LSHIFT | BDA_KB0_RSHIFT ) ) ==
+		     ( BDA_KB0_LSHIFT | BDA_KB0_RSHIFT ) ) {
+			character |= KEYMAP_ALTGR;
+		}
 
 		/* Map and return */
 		return key_remap ( character );