adb: add autopoll_blocked variable to block autopoll

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: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: NFinn Thain <fthain@telegraphics.com.au>
Acked-by: NLaurent Vivier <laurent@vivier.eu>
Message-Id: <20200623204936.24064-16-mark.cave-ayland@ilande.co.uk>

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()
     }
 };

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);