[Qemu-devel] [PATCH v5 6/6] i8259: refactor pic_set_irq level logic

[Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>]

No change in functionality.

Clarify that the only difference between level triggered and
edge triggered interrupts is on the leading edge.

Signed-off-by: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>
---
 hw/i8259.c | 26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/hw/i8259.c b/hw/i8259.c
index c011787..1ba9b3a 100644
--- a/hw/i8259.c
+++ b/hw/i8259.c
@@ -140,26 +140,18 @@ static void pic_set_irq(void *opaque, int irq, int level)
     }
 #endif
 
-    if (s->elcr & mask) {
-        /* level triggered */
-        if (level) {
+    if (level) {
+        if ((s->last_irr & mask) == 0 ||  /* edge for edge triggered */
+            (s->elcr & mask)) {           /* or level triggered */
             s->irr |= mask;
-            s->last_irr |= mask;
-        } else {
-            s->irr &= ~mask;
-            s->last_irr &= ~mask;
         }
+        s->last_irr |= mask;
     } else {
-        /* edge triggered */
-        if (level) {
-            if ((s->last_irr & mask) == 0) {
-                s->irr |= mask;
-            }
-            s->last_irr |= mask;
-        } else {
-            s->irr &= ~mask;
-            s->last_irr &= ~mask;
-        }
+        /* Dropping level clears the interrupt regardless of edge trigger
+         * vs level trigger.
+         */
+        s->irr &= ~mask;
+        s->last_irr &= ~mask;
     }
     pic_update_irq(s);
 }
-- 
1.7.10.2.484.gcd07cc5