[Qemu-devel] [PATCH v2 2/2] hw/usb/dev-hid: add a usb-tablet Mac guest compatibility option

[Phil Dennis-Jordan <phil@philjordan.eu>]

Darwin/OS X/macOS's HID driver stack previously did not correctly drive Qemu's simulated USB Tablet. This adds a boolean option "mac_compat" to the device which subtly changes the device's report descriptor so it behaves in a way that Mac guests can handle.

Absolute pointing devices with HID Report Descriptor usage page of 0x01 (pointing) are handled by the macOS HID driver as analog sticks, and absolute coordinates are not directly translated to absolute mouse cursor positions.

The workaround is to report a usage page of 0x02 (mouse) instead. In combination with the previous commit's boot protocol fix, this allows the usb-tablet to correctly control the mouse cursor in OS X/macOS guest systems.

Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
---
 hw/usb/dev-hid.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/usb/dev-hid.c b/hw/usb/dev-hid.c
index a23e5d4..c4a0d22 100644
--- a/hw/usb/dev-hid.c
+++ b/hw/usb/dev-hid.c
@@ -51,6 +51,7 @@ typedef struct USBHIDState {
     uint32_t usb_version;
     char *display;
     uint32_t head;
+    bool mac_compat;
 } USBHIDState;
 
 #define TYPE_USB_HID "usb-hid"
@@ -599,6 +600,9 @@ static void usb_hid_handle_control(USBDevice *dev, USBPacket *p,
                 memcpy(data, qemu_tablet_hid_report_descriptor,
 		       sizeof(qemu_tablet_hid_report_descriptor));
                 p->actual_length = sizeof(qemu_tablet_hid_report_descriptor);
+                if (us->mac_compat) {
+                    data[3] = 0x02; /* Set usage to mouse, not pointing (1) */
+                }
             } else if (hs->kind == HID_KEYBOARD) {
                 memcpy(data, qemu_keyboard_hid_report_descriptor,
                        sizeof(qemu_keyboard_hid_report_descriptor));
@@ -801,6 +805,7 @@ static Property usb_tablet_properties[] = {
         DEFINE_PROP_UINT32("usb_version", USBHIDState, usb_version, 2),
         DEFINE_PROP_STRING("display", USBHIDState, display),
         DEFINE_PROP_UINT32("head", USBHIDState, head, 0),
+        DEFINE_PROP_BOOL("mac_compat", USBHIDState, mac_compat, false),
         DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.3.2 (Apple Git-55)