HID: apple: Swap the Fn and Left Control keys on Apple keyboards

This patch allows users to swap the Fn and left Control keys on all Apple
keyboards: internal (e.g. Macbooks) and external (both wired and wireless).
The patch adds a new hid-apple module param: swap_fn_leftctrl (off by default).

Signed-off-by: Zakhar Semenov <mail@free5lot.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-apple.c

@@ -51,6 +51,12 @@ MODULE_PARM_DESC(swap_opt_cmd, "Swap the Option (\"Alt\") and Command (\"Flag\")
 		"(For people who want to keep Windows PC keyboard muscle memory. "
 		"[0] = as-is, Mac layout. 1 = swapped, Windows layout.)");
 
+static unsigned int swap_fn_leftctrl;
+module_param(swap_fn_leftctrl, uint, 0644);
+MODULE_PARM_DESC(swap_fn_leftctrl, "Swap the Fn and left Control keys. "
+		"(For people who want to keep PC keyboard muscle memory. "
+		"[0] = as-is, Mac layout, 1 = swapped, PC layout)");
+
 struct apple_sc {
 	unsigned long quirks;
 	unsigned int fn_on;
@@ -162,6 +168,11 @@ static const struct apple_key_translation swapped_option_cmd_keys[] = {
 	{ }
 };
 
+static const struct apple_key_translation swapped_fn_leftctrl_keys[] = {
+	{ KEY_FN, KEY_LEFTCTRL },
+	{ }
+};
+
 static const struct apple_key_translation *apple_find_translation(
 		const struct apple_key_translation *table, u16 from)
 {
@@ -183,9 +194,11 @@ static int hidinput_apple_event(struct hid_device *hid, struct input_dev *input,
 	bool do_translate;
 	u16 code = 0;
 
-	if (usage->code == KEY_FN) {
+	u16 fn_keycode = (swap_fn_leftctrl) ? (KEY_LEFTCTRL) : (KEY_FN);
+
+	if (usage->code == fn_keycode) {
 		asc->fn_on = !!value;
-		input_event(input, usage->type, usage->code, value);
+		input_event(input, usage->type, KEY_FN, value);
 		return 1;
 	}
 
@@ -270,6 +283,14 @@ static int hidinput_apple_event(struct hid_device *hid, struct input_dev *input,
 		}
 	}
 
+	if (swap_fn_leftctrl) {
+		trans = apple_find_translation(swapped_fn_leftctrl_keys, usage->code);
+		if (trans) {
+			input_event(input, usage->type, trans->to, value);
+			return 1;
+		}
+	}
+
 	return 0;
 }
 
@@ -333,6 +354,11 @@ static void apple_setup_input(struct input_dev *input)
 
 	for (trans = apple_iso_keyboard; trans->from; trans++)
 		set_bit(trans->to, input->keybit);
+
+	if (swap_fn_leftctrl) {
+		for (trans = swapped_fn_leftctrl_keys; trans->from; trans++)
+			set_bit(trans->to, input->keybit);
+	}
 }
 
 static int apple_input_mapping(struct hid_device *hdev, struct hid_input *hi,