atkbd: Fix first keystroke force reset

mneumann · mneumann · commit f0dd2afff203 · 2025-06-02T00:24:49.000+02:00
Some i8042 falsely return KBD_ACK for ECHO command which cause the keyboard echo test to fail. Without passing echo test, the keyboard is considered as unconfigured. Although this is incorrect behavior, we still consider it correct to prevent the forced reset (a step to configure a keyboard) of the entire keyboard when the first key interrupt is reached. This should fix keyboard probing at least for Framework Laptop [1]. Taken-from: FreeBSD [2] (minus typos) [1]: https://reviews.freebsd.org/D50498 [2]: freebsd/freebsd-src@cba5d7a
diff --git a/sys/dev/misc/kbd/atkbd.c b/sys/dev/misc/kbd/atkbd.c
@@ -1305,14 +1305,26 @@ setup_kbd_port(KBDC kbdc, int port, int intr)
 static int
 get_kbd_echo(KBDC kbdc)
 {
+	int data;
 	/* enable the keyboard port, but disable the keyboard intr. */
 	if (setup_kbd_port(kbdc, TRUE, FALSE))
 		/* CONTROLLER ERROR: there is very little we can do... */
 		return ENXIO;
 
 	/* see if something is present */
 	write_kbd_command(kbdc, KBDC_ECHO);
-	if (read_kbd_data(kbdc) != KBD_ECHO) {
+	data = read_kbd_data(kbdc);
+
+	/*
+	 * Some i8042 falsely return KBD_ACK for ECHO command.
+	 * Though it is not correct behavior for AT keyboards, we accept
+	 * and consume it to prevent resetting the whole keyboard after the
+	 * first interrupt.
+	 */
+	if (data == KBD_ACK)
+		data = read_kbd_data(kbdc);
+
+	if (data != KBD_ECHO) {
 		empty_both_buffers(kbdc, 10);
 		test_controller(kbdc);
 		test_kbd_port(kbdc);
