From 1f9799b68da9abaef19f7a9489e5bbd7acf58aae Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Wed, 3 Aug 2016 13:10:20 -0600
Subject: [PATCH] I/O Expanders:  Interrupt detection logic should not ignore
 the no-change case.  Still need to handle level interrupts even with no
 change.

---
 arch/sim/src/up_ioexpander.c | 14 +++++---------
 drivers/ioexpander/pcf8574.c | 12 ++----------
 drivers/ioexpander/tca64xx.c | 15 +++------------
 3 files changed, 10 insertions(+), 31 deletions(-)

diff --git a/arch/sim/src/up_ioexpander.c b/arch/sim/src/up_ioexpander.c
index 393fdd06e6..8eec0f9040 100644
--- a/arch/sim/src/up_ioexpander.c
+++ b/arch/sim/src/up_ioexpander.c
@@ -641,17 +641,13 @@ static ioe_pinset_t sim_int_update(FAR struct sim_dev_s *priv)
 
   input = priv->inval;
   diff  = priv->last ^ input;
-  if (diff == 0)
+  if (diff != 0)
     {
-      /* Nothing has changed */
-
-      return 0;
+      gpioinfo("toggles=%lx inval=%lx last=%lx diff=%lx\n",
+               (unsigned long)toggles, (unsigned long)priv->inval,
+               (unsigned long)priv->last, (unsigned long)diff);
     }
 
-  gpioinfo("toggles=%lx inval=%lx last=%lx diff=%lx\n",
-           (unsigned long)toggles, (unsigned long)priv->inval,
-           (unsigned long)priv->last, (unsigned long)diff);
-
   priv->last = input;
   intstat    = 0;
 
@@ -684,7 +680,7 @@ static ioe_pinset_t sim_int_update(FAR struct sim_dev_s *priv)
         }
       else /* if (SIM_LEVEL_SENSITIVE(priv, pin)) */
         {
-          /* Level triggered. Set intstat if in match level type. */
+          /* Level triggered. Set intstat if imatch in level type. */
 
           if ((pinval  && SIM_LEVEL_HIGH(priv, pin)) ||
               (!pinval && SIM_LEVEL_LOW(priv, pin)))
diff --git a/drivers/ioexpander/pcf8574.c b/drivers/ioexpander/pcf8574.c
index f28c2c9fff..b8eee535b9 100644
--- a/drivers/ioexpander/pcf8574.c
+++ b/drivers/ioexpander/pcf8574.c
@@ -797,15 +797,7 @@ static void pcf8574_int_update(void *handle, uint8_t input)
 
   /* Check the changed bits from last read */
 
-  diff = priv->input ^ input;
-  if (diff == 0)
-    {
-      /* Nothing has changed */
-
-      leave_critical_section(flags);
-      return;
-    }
-
+  diff        = priv->input ^ input;
   priv->input = input;
 
   /* PCF8574 doesn't support irq trigger, we have to do this in software. */
@@ -829,7 +821,7 @@ static void pcf8574_int_update(void *handle, uint8_t input)
         }
       else /* if (PCF8574_LEVEL_SENSITIVE(priv, pin)) */
         {
-          /* Level triggered. Set intstat if in match level type. */
+          /* Level triggered. Set intstat if match in level type. */
 
           if (((input & 1) != 0 && PCF8574_LEVEL_HIGH(priv, pin)) ||
               ((input & 1) == 0 && PCF8574_LEVEL_LOW(priv, pin)))
diff --git a/drivers/ioexpander/tca64xx.c b/drivers/ioexpander/tca64xx.c
index 49b57ddbb4..2b3b00cf05 100644
--- a/drivers/ioexpander/tca64xx.c
+++ b/drivers/ioexpander/tca64xx.c
@@ -1038,17 +1038,8 @@ static void tca64_int_update(FAR struct tca64_dev_s *priv, ioe_pinset_t input,
 
   /* Check the changed bits from last read */
 
-  input = (priv->input & ~mask) | (input & mask);
-  diff  = priv->input ^ input;
-
-  if (diff == 0)
-    {
-      /* Nothing has changed */
-
-      leave_critical_section(flags);
-      return;
-    }
-
+  input       = (priv->input & ~mask) | (input & mask);
+  diff        = priv->input ^ input;
   priv->input = input;
 
   /* TCA64XX doesn't support irq trigger, we have to do this in software. */
@@ -1072,7 +1063,7 @@ static void tca64_int_update(FAR struct tca64_dev_s *priv, ioe_pinset_t input,
         }
       else /* if (TCA64_LEVEL_SENSITIVE(priv, pin)) */
         {
-          /* Level triggered. Set intstat if in match level type. */
+          /* Level triggered. Set intstat bit if match in level type. */
 
           if (((input & 1) != 0 && TCA64_LEVEL_HIGH(priv, pin)) ||
               ((input & 1) == 0 && TCA64_LEVEL_LOW(priv, pin)))