Whilst autopoll is enabled it is necessary to prevent the ADB buffer contents
from being overwritten until the host has read back the response in its
entirety.

Add adb_autopoll_block() and adb_autopoll_unblock() functions in preparation
for ensuring that the ADB buffer contents are protected for explicit ADB
requests.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200623204936.24064-16-mark.cave-ayland@ilande.co.uk>
---
 hw/input/adb.c         | 21 +++++++++++++++++++++
 include/hw/input/adb.h |  4 ++++
 2 files changed, 25 insertions(+)

diff --git a/hw/input/adb.c b/hw/input/adb.c
index b3ad7c5fca..70aa1f4570 100644
--- a/hw/input/adb.c
+++ b/hw/input/adb.c
@@ -157,6 +157,26 @@ void adb_set_autopoll_mask(ADBBusState *s, uint16_t mask)
     }
 }
 
+void adb_autopoll_block(ADBBusState *s)
+{
+    s->autopoll_blocked = true;
+
+    if (s->autopoll_enabled) {
+        timer_del(s->autopoll_timer);
+    }
+}
+
+void adb_autopoll_unblock(ADBBusState *s)
+{
+    s->autopoll_blocked = false;
+
+    if (s->autopoll_enabled) {
+        timer_mod(s->autopoll_timer,
+                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
+                  s->autopoll_rate_ms);
+    }
+}
+
 static void adb_autopoll(void *opaque)
 {
     ADBBusState *s = opaque;
@@ -184,6 +204,7 @@ static const VMStateDescription vmstate_adb_bus = {
         VMSTATE_BOOL(autopoll_enabled, ADBBusState),
         VMSTATE_UINT8(autopoll_rate_ms, ADBBusState),
         VMSTATE_UINT16(autopoll_mask, ADBBusState),
+        VMSTATE_BOOL(autopoll_blocked, ADBBusState),
         VMSTATE_END_OF_LIST()
     }
 };
diff --git a/include/hw/input/adb.h b/include/hw/input/adb.h
index cff264739c..bb75a7b1e3 100644
--- a/include/hw/input/adb.h
+++ b/include/hw/input/adb.h
@@ -86,6 +86,7 @@ struct ADBBusState {
 
     QEMUTimer *autopoll_timer;
     bool autopoll_enabled;
+    bool autopoll_blocked;
     uint8_t autopoll_rate_ms;
     uint16_t autopoll_mask;
     void (*autopoll_cb)(void *opaque);
@@ -96,6 +97,9 @@ int adb_request(ADBBusState *s, uint8_t *buf_out,
                 const uint8_t *buf, int len);
 int adb_poll(ADBBusState *s, uint8_t *buf_out, uint16_t poll_mask);
 
+void adb_autopoll_block(ADBBusState *s);
+void adb_autopoll_unblock(ADBBusState *s);
+
 void adb_set_autopoll_enabled(ADBBusState *s, bool enabled);
 void adb_set_autopoll_rate_ms(ADBBusState *s, int rate_ms);
 void adb_set_autopoll_mask(ADBBusState *s, uint16_t mask);
-- 
2.20.1