svn commit: r305060 - head/sys/dev/kbdmux

[Bruce Evans]

Author: bde
Date: Tue Aug 30 12:36:14 2016
New Revision: 305060
URL: https://svnweb.freebsd.org/changeset/base/305060

Log:
  Fix keyboard polling "on/off" to support recursion.  vt depends on
  this, and sc will soon depend on it again.
  
  The on/off request is passed without modification to lower layers,
  so the bug was smaller in this layer than in in lower layers (the
  sequence on;on;off left polling off when it should be on, but the
  sequence on;on;off;on;off...  doesn't allow the interrupt handler
  to eat the input after an "off" that should't turn off polled mode,
  provided lower layers don't have the bug, since this layer is virtual.
  
  The bug was small in lower layers too.  Normally everything is Giant
  locked for keyboards, and this locks out the interrupt handler in
  on;on;off;on;off... sequences.  However, PR 211884 says that fixing
  this bug in ukbd in r303765 apparently causes the eating-by-interrupt
  behaviour that the fix is to prevent.
  
  Discussed with: emax

Modified:
  head/sys/dev/kbdmux/kbdmux.c

Modified: head/sys/dev/kbdmux/kbdmux.c
==============================================================================
--- head/sys/dev/kbdmux/kbdmux.c	Tue Aug 30 10:57:19 2016	(r305059)
+++ head/sys/dev/kbdmux/kbdmux.c	Tue Aug 30 12:36:14 2016	(r305060)
@@ -150,9 +150,9 @@ struct kbdmux_state
 
 	int			 ks_flags;	/* flags */
 #define COMPOSE			(1 << 0)	/* compose char flag */ 
-#define POLLING			(1 << 1)	/* polling */
 #define TASK			(1 << 2)	/* interrupt task queued */
 
+	int			 ks_polling;	/* poll nesting count */
 	int			 ks_mode;	/* K_XLATE, K_RAW, K_CODE */
 	int			 ks_state;	/* state */
 	int			 ks_accents;	/* accent key index (> 0) */
@@ -666,7 +666,7 @@ next_code:
 	/* see if there is something in the keyboard queue */
 	scancode = kbdmux_kbd_getc(state);
 	if (scancode == -1) {
-		if (state->ks_flags & POLLING) {
+		if (state->ks_polling != 0) {
 			kbdmux_kbd_t	*k;
 
 			SLIST_FOREACH(k, &state->ks_kbds, next) {
@@ -1244,7 +1244,8 @@ kbdmux_clear_state_locked(kbdmux_state_t
 {
 	KBDMUX_LOCK_ASSERT(state, MA_OWNED);
 
-	state->ks_flags &= ~(COMPOSE|POLLING);
+	state->ks_flags &= ~COMPOSE;
+	state->ks_polling = 0;
 	state->ks_state &= LOCK_MASK;	/* preserve locking key state */
 	state->ks_accents = 0;
 	state->ks_composed_char = 0;
@@ -1304,9 +1305,9 @@ kbdmux_poll(keyboard_t *kbd, int on)
 	KBDMUX_LOCK(state);
 
 	if (on)
-		state->ks_flags |= POLLING; 
+		state->ks_polling++;
 	else
-		state->ks_flags &= ~POLLING;
+		state->ks_polling--;
 
 	/* set poll on slave keyboards */
 	SLIST_FOREACH(k, &state->ks_kbds, next)