adb: fix adb-mouse read length and revert disable-reg3-direct-writes workaround

Commit 84051eb400 "adb: add property to disable direct reg 3 writes" introduced
a workaround for spurious writes to ADB register 3 when MacOS 9 enables
autopoll on the mouse device. Further analysis shows that the problem is that
only a partial request is sent, and since the len parameter is ignored then
stale data from the previous request is used causing the incorrect address
assignment.

Remove the disable-reg3-direct-writes workaround and instead check the length
parameter when the write is attempted, discarding the invalid request.

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: <20200623204936.24064-3-mark.cave-ayland@ilande.co.uk>

3 files changed, 40 insertions, 41 deletions

diff --git a/hw/input/adb-kbd.c b/hw/input/adb-kbd.c
index a6d5c9b7c9..027dd3e531 100644
--- a/hw/input/adb-kbd.c
+++ b/hw/input/adb-kbd.c
@@ -259,21 +259,19 @@ static int adb_kbd_request(ADBDevice *d, uint8_t *obuf,
                 trace_adb_kbd_request_change_addr(d->devaddr);
                 break;
             default:
-                if (!d->disable_direct_reg3_writes) {
-                    d->devaddr = buf[1] & 0xf;
-
-                    /* we support handlers:
-                     * 1: Apple Standard Keyboard
-                     * 2: Apple Extended Keyboard (LShift = RShift)
-                     * 3: Apple Extended Keyboard (LShift != RShift)
-                     */
-                    if (buf[2] == 1 || buf[2] == 2 || buf[2] == 3) {
-                        d->handler = buf[2];
-                    }
-
-                    trace_adb_kbd_request_change_addr_and_handler(d->devaddr,
-                                                                  d->handler);
+                d->devaddr = buf[1] & 0xf;
+                /*
+                 * we support handlers:
+                 * 1: Apple Standard Keyboard
+                 * 2: Apple Extended Keyboard (LShift = RShift)
+                 * 3: Apple Extended Keyboard (LShift != RShift)
+                 */
+                if (buf[2] == 1 || buf[2] == 2 || buf[2] == 3) {
+                    d->handler = buf[2];
                 }
+
+                trace_adb_kbd_request_change_addr_and_handler(d->devaddr,
+                                                              d->handler);
                 break;
             }
         }
diff --git a/hw/input/adb-mouse.c b/hw/input/adb-mouse.c
index aeba41bddd..78b6f5030c 100644
--- a/hw/input/adb-mouse.c
+++ b/hw/input/adb-mouse.c
@@ -135,6 +135,16 @@ static int adb_mouse_request(ADBDevice *d, uint8_t *obuf,
         case 2:
             break;
         case 3:
+            /*
+             * MacOS 9 has a bug in its ADB driver whereby after configuring
+             * the ADB bus devices it sends another write of invalid length
+             * to reg 3. Make sure we ignore it to prevent an address clash
+             * with the previous device.
+             */
+            if (len != 3) {
+                return 0;
+            }
+
             switch (buf[2]) {
             case ADB_CMD_SELF_TEST:
                 break;
@@ -145,27 +155,25 @@ static int adb_mouse_request(ADBDevice *d, uint8_t *obuf,
                 trace_adb_mouse_request_change_addr(d->devaddr);
                 break;
             default:
-                if (!d->disable_direct_reg3_writes) {
-                    d->devaddr = buf[1] & 0xf;
-
-                    /* we support handlers:
-                     * 0x01: Classic Apple Mouse Protocol / 100 cpi operations
-                     * 0x02: Classic Apple Mouse Protocol / 200 cpi operations
-                     * we don't support handlers (at least):
-                     * 0x03: Mouse systems A3 trackball
-                     * 0x04: Extended Apple Mouse Protocol
-                     * 0x2f: Microspeed mouse
-                     * 0x42: Macally
-                     * 0x5f: Microspeed mouse
-                     * 0x66: Microspeed mouse
-                     */
-                    if (buf[2] == 1 || buf[2] == 2) {
-                        d->handler = buf[2];
-                    }
-
-                    trace_adb_mouse_request_change_addr_and_handler(
-                        d->devaddr, d->handler);
+                d->devaddr = buf[1] & 0xf;
+                /*
+                 * we support handlers:
+                 * 0x01: Classic Apple Mouse Protocol / 100 cpi operations
+                 * 0x02: Classic Apple Mouse Protocol / 200 cpi operations
+                 * we don't support handlers (at least):
+                 * 0x03: Mouse systems A3 trackball
+                 * 0x04: Extended Apple Mouse Protocol
+                 * 0x2f: Microspeed mouse
+                 * 0x42: Macally
+                 * 0x5f: Microspeed mouse
+                 * 0x66: Microspeed mouse
+                 */
+                if (buf[2] == 1 || buf[2] == 2) {
+                    d->handler = buf[2];
                 }
+
+                trace_adb_mouse_request_change_addr_and_handler(d->devaddr,
+                                                                d->handler);
                 break;
             }
         }
diff --git a/hw/input/adb.c b/hw/input/adb.c
index bf1bc30d19..d85278a7b7 100644
--- a/hw/input/adb.c
+++ b/hw/input/adb.c
@@ -118,18 +118,11 @@ static void adb_device_realizefn(DeviceState *dev, Error **errp)
     bus->devices[bus->nb_devices++] = d;
 }
 
-static Property adb_device_properties[] = {
-    DEFINE_PROP_BOOL("disable-direct-reg3-writes", ADBDevice,
-                     disable_direct_reg3_writes, false),
-    DEFINE_PROP_END_OF_LIST(),
-};
-
 static void adb_device_class_init(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = adb_device_realizefn;
-    device_class_set_props(dc, adb_device_properties);
     dc->bus_type = TYPE_ADB_BUS;
 }