HID: apple: Disable Fn-key key-re-mapping on clone keyboards

The Maxxter KB-BT-001 Bluetooth keyboard, which looks somewhat like the
Apple Wireless Keyboard, is using the vendor and product IDs (05AC:0239)
of the Apple Wireless Keyboard (2009 ANSI version) <sigh>.

But its F1 - F10 keys are marked as sending F1 - F10, not the special
functions hid-apple.c maps them too; and since its descriptors do not
contain the HID_UP_CUSTOM | 0x0003 usage apple-hid looks for for the
Fn-key, apple_setup_input() never gets called, so F1 - F6 are mapped
to key-codes which have not been set in the keybit array causing them
to not send any events at all.

The lack of a usage code matching the Fn key in the clone is actually
useful as this allows solving this problem in a generic way.

This commits adds a fn_found flag and it adds a input_configured
callback which checks if this flag is set once all usages have been
mapped. If it is not set, then assume this is a clone and clear the
quirks bitmap so that the hid-apple code does not add any special
handling to this keyboard.

This fixes F1 - F6 not sending anything at all and F7 - F12 sending
the wrong codes on the Maxxter KB-BT-001 Bluetooth keyboard and on
similar clones.

Cc: Joao Moreno <mail@joaomoreno.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-apple.c

@@ -60,6 +60,7 @@ MODULE_PARM_DESC(swap_fn_leftctrl, "Swap the Fn and left Control keys. "
 struct apple_sc {
 	unsigned long quirks;
 	unsigned int fn_on;
+	unsigned int fn_found;
 	DECLARE_BITMAP(pressed_numlock, KEY_CNT);
 };
 
@@ -365,12 +366,15 @@ static int apple_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 		struct hid_field *field, struct hid_usage *usage,
 		unsigned long **bit, int *max)
 {
+	struct apple_sc *asc = hid_get_drvdata(hdev);
+
 	if (usage->hid == (HID_UP_CUSTOM | 0x0003) ||
 			usage->hid == (HID_UP_MSVENDOR | 0x0003) ||
 			usage->hid == (HID_UP_HPVENDOR2 | 0x0003)) {
 		/* The fn key on Apple USB keyboards */
 		set_bit(EV_REP, hi->input->evbit);
 		hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_FN);
+		asc->fn_found = true;
 		apple_setup_input(hi->input);
 		return 1;
 	}
@@ -397,6 +401,19 @@ static int apple_input_mapped(struct hid_device *hdev, struct hid_input *hi,
 	return 0;
 }
 
+static int apple_input_configured(struct hid_device *hdev,
+		struct hid_input *hidinput)
+{
+	struct apple_sc *asc = hid_get_drvdata(hdev);
+
+	if ((asc->quirks & APPLE_HAS_FN) && !asc->fn_found) {
+		hid_info(hdev, "Fn key not found (Apple Wireless Keyboard clone?), disabling Fn key handling\n");
+		asc->quirks = 0;
+	}
+
+	return 0;
+}
+
 static int apple_probe(struct hid_device *hdev,
 		const struct hid_device_id *id)
 {
@@ -611,6 +628,7 @@ static struct hid_driver apple_driver = {
 	.event = apple_event,
 	.input_mapping = apple_input_mapping,
 	.input_mapped = apple_input_mapped,
+	.input_configured = apple_input_configured,
 };
 module_hid_driver(apple_driver);