The 8042 emulation found on Chromebooks does not support the RESET command,

for no good reason, and causes pckbc not to attach. However, sending a `get
keyboard id' works, so this can be used as a second check to give those
fawlty pieces of hardware a chance to work.

Based on a diff submitted by, and tested by,  Vladimir 'phcoder' Serbinenko.

2 files changed, 35 insertions, 8 deletions

diff --git a/sys/dev/pckbc/pckbd.c b/sys/dev/pckbc/pckbd.c
index 71ccf514758..50d523f395a 100644
--- a/sys/dev/pckbc/pckbd.c
+++ b/sys/dev/pckbc/pckbd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: pckbd.c,v 1.50 2023/07/25 10:00:44 miod Exp $ */
+/* $OpenBSD: pckbd.c,v 1.51 2023/08/13 21:54:02 miod Exp $ */
 /* $NetBSD: pckbd.c,v 1.24 2000/06/05 22:20:57 sommerfeld Exp $ */
 
 /*-
@@ -344,7 +344,7 @@ pckbdprobe(struct device *parent, void *match, void *aux)
 {
 	struct cfdata *cf = match;
 	struct pckbc_attach_args *pa = aux;
-	u_char cmd[1], resp[1];
+	u_char cmd[1], resp[2];
 	int res;
 
 	/*
@@ -363,10 +363,40 @@ pckbdprobe(struct device *parent, void *match, void *aux)
 	/* Reset the keyboard. */
 	cmd[0] = KBC_RESET;
 	res = pckbc_poll_cmd(pa->pa_tag, pa->pa_slot, cmd, 1, 1, resp, 1);
-	if (res) {
+	if (res != 0) {
 #ifdef DEBUG
 		printf("pckbdprobe: reset error %d\n", res);
 #endif
+	} else if (resp[0] != KBR_RSTDONE) {
+#ifdef DEBUG
+		printf("pckbdprobe: reset response 0x%x\n", resp[0]);
+#endif
+		res = EINVAL;
+	}
+#if defined(__i386__) || defined(__amd64__)
+	if (res) {
+		/*
+		 * The 8042 emulation on Chromebooks fails the reset
+		 * command but otherwise appears to work correctly.
+		 * Try a "get ID" command to give it a second chance.
+		 */
+		cmd[0] = KBC_GETID;
+		res = pckbc_poll_cmd(pa->pa_tag, pa->pa_slot,
+		    cmd, 1, 2, resp, 0);
+		if (res != 0) {
+#ifdef DEBUG
+			printf("pckbdprobe: getid error %d\n", res);
+#endif
+		} else if (resp[0] != 0xab || resp[1] != 0x83) {
+#ifdef DEBUG
+			printf("pckbdprobe: unexpected id 0x%x/0x%x\n",
+			    resp[0], resp[1]);
+#endif
+			res = EINVAL;
+		}
+	}
+#endif
+	if (res) {
 		/*
 		 * There is probably no keyboard connected.
 		 * Let the probe succeed if the keyboard is used
@@ -387,10 +417,6 @@ pckbdprobe(struct device *parent, void *match, void *aux)
 #endif
 		return (pckbd_is_console(pa->pa_tag, pa->pa_slot) ? 1 : 0);
 	}
-	if (resp[0] != KBR_RSTDONE) {
-		printf("pckbdprobe: reset response 0x%x\n", resp[0]);
-		return (0);
-	}
 
 	/*
 	 * Some keyboards seem to leave a second ack byte after the reset.
diff --git a/sys/dev/pckbc/pckbdreg.h b/sys/dev/pckbc/pckbdreg.h
index 6848f48f817..7acd4eb1703 100644
--- a/sys/dev/pckbc/pckbdreg.h
+++ b/sys/dev/pckbc/pckbdreg.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: pckbdreg.h,v 1.2 2003/10/22 09:44:22 jmc Exp $ */
+/* $OpenBSD: pckbdreg.h,v 1.3 2023/08/13 21:54:02 miod Exp $ */
 /* $NetBSD: pckbdreg.h,v 1.2 1998/04/07 13:43:16 hannken Exp $ */
 
 /*
@@ -12,6 +12,7 @@
 #define	KBC_DISABLE	0xF5	/* as per KBC_SETDEFAULT, but also disable key scanning */
 #define	KBC_ENABLE	0xF4	/* enable key scanning */
 #define	KBC_TYPEMATIC	0xF3	/* set typematic rate and delay */
+#define	KBC_GETID	0xF2	/* get keyboard ID (not supported on AT kbd) */
 #define	KBC_SETTABLE	0xF0	/* set scancode translation table */
 #define	KBC_MODEIND	0xED	/* set mode indicators (i.e. LEDs) */
 #define	KBC_ECHO	0xEE	/* request an echo from the keyboard */