Input: Mac button emulation - implement as an input filter

Current implementation of Mac mouse button emulation plugs into legacy
keyboard driver, converts certain keys into button events on a separate
device, and suppresses the real events from reaching tty. This worked
well enough until user space started using evdev which was completely
unaware of this arrangement and kept sending original key presses to
its users. Change the implementation to use newly added input filter
framework so that original key presses are not transmitted to any
handlers.

As a bonus remove SYSCTL dependencies from the code and use Kconfig
instead; also do not create the emulated mouse device until user
activates emulation.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/char/keyboard.c

@@ -1185,11 +1185,6 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
 
 	rep = (down == 2);
 
-#ifdef CONFIG_MAC_EMUMOUSEBTN
-	if (mac_hid_mouse_emulate_buttons(1, keycode, down))
-		return;
-#endif /* CONFIG_MAC_EMUMOUSEBTN */
-
 	if ((raw_mode = (kbd->kbdmode == VC_RAW)) && !hw_raw)
 		if (emulate_raw(vc, keycode, !down << 7))
 			if (keycode < BTN_MISC && printk_ratelimit())

drivers/macintosh/Kconfig

@@ -172,6 +172,7 @@ config INPUT_ADBHID
 
 config MAC_EMUMOUSEBTN
 	bool "Support for mouse button 2+3 emulation"
+	depends on SYSCTL
 	select INPUT
 	help
 	  This provides generic support for emulating the 2nd and 3rd mouse

drivers/macintosh/mac_hid.c

@@ -13,17 +13,195 @@
 #include <linux/sysctl.h>
 #include <linux/input.h>
 #include <linux/module.h>
-#include <linux/kbd_kern.h>
 
-
-static struct input_dev *emumousebtn;
-static int emumousebtn_input_register(void);
 static int mouse_emulate_buttons;
 static int mouse_button2_keycode = KEY_RIGHTCTRL;	/* right control key */
 static int mouse_button3_keycode = KEY_RIGHTALT;	/* right option key */
-static int mouse_last_keycode;
 
-#if defined(CONFIG_SYSCTL)
+static struct input_dev *mac_hid_emumouse_dev;
+
+static int mac_hid_create_emumouse(void)
+{
+	static struct lock_class_key mac_hid_emumouse_dev_event_class;
+	static struct lock_class_key mac_hid_emumouse_dev_mutex_class;
+	int err;
+
+	mac_hid_emumouse_dev = input_allocate_device();
+	if (!mac_hid_emumouse_dev)
+		return -ENOMEM;
+
+	lockdep_set_class(&mac_hid_emumouse_dev->event_lock,
+			  &mac_hid_emumouse_dev_event_class);
+	lockdep_set_class(&mac_hid_emumouse_dev->mutex,
+			  &mac_hid_emumouse_dev_mutex_class);
+
+	mac_hid_emumouse_dev->name = "Macintosh mouse button emulation";
+	mac_hid_emumouse_dev->id.bustype = BUS_ADB;
+	mac_hid_emumouse_dev->id.vendor = 0x0001;
+	mac_hid_emumouse_dev->id.product = 0x0001;
+	mac_hid_emumouse_dev->id.version = 0x0100;
+
+	mac_hid_emumouse_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	mac_hid_emumouse_dev->keybit[BIT_WORD(BTN_MOUSE)] =
+		BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_MIDDLE) | BIT_MASK(BTN_RIGHT);
+	mac_hid_emumouse_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+
+	err = input_register_device(mac_hid_emumouse_dev);
+	if (err) {
+		input_free_device(mac_hid_emumouse_dev);
+		mac_hid_emumouse_dev = NULL;
+		return err;
+	}
+
+	return 0;
+}
+
+static void mac_hid_destroy_emumouse(void)
+{
+	input_unregister_device(mac_hid_emumouse_dev);
+	mac_hid_emumouse_dev = NULL;
+}
+
+static bool mac_hid_emumouse_filter(struct input_handle *handle,
+				    unsigned int type, unsigned int code,
+				    int value)
+{
+	unsigned int btn;
+
+	if (type != EV_KEY)
+		return false;
+
+	if (code == mouse_button2_keycode)
+		btn = BTN_MIDDLE;
+	else if (code == mouse_button3_keycode)
+		btn = BTN_RIGHT;
+	else
+		return false;
+
+	input_report_key(mac_hid_emumouse_dev, btn, value);
+	input_sync(mac_hid_emumouse_dev);
+
+	return true;
+}
+
+static int mac_hid_emumouse_connect(struct input_handler *handler,
+				    struct input_dev *dev,
+				    const struct input_device_id *id)
+{
+	struct input_handle *handle;
+	int error;
+
+	/* Don't bind to ourselves */
+	if (dev == mac_hid_emumouse_dev)
+		return -ENODEV;
+
+	handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL);
+	if (!handle)
+		return -ENOMEM;
+
+	handle->dev = dev;
+	handle->handler = handler;
+	handle->name = "mac-button-emul";
+
+	error = input_register_handle(handle);
+	if (error) {
+		printk(KERN_ERR
+			"mac_hid: Failed to register button emulation handle, "
+			"error %d\n", error);
+		goto err_free;
+	}
+
+	error = input_open_device(handle);
+	if (error) {
+		printk(KERN_ERR
+			"mac_hid: Failed to open input device, error %d\n",
+			error);
+		goto err_unregister;
+	}
+
+	return 0;
+
+ err_unregister:
+	input_unregister_handle(handle);
+ err_free:
+	kfree(handle);
+	return error;
+}
+
+static void mac_hid_emumouse_disconnect(struct input_handle *handle)
+{
+	input_close_device(handle);
+	input_unregister_handle(handle);
+	kfree(handle);
+}
+
+static const struct input_device_id mac_hid_emumouse_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+	},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(input, mac_hid_emumouse_ids);
+
+static struct input_handler mac_hid_emumouse_handler = {
+	.filter		= mac_hid_emumouse_filter,
+	.connect	= mac_hid_emumouse_connect,
+	.disconnect	= mac_hid_emumouse_disconnect,
+	.name		= "mac-button-emul",
+	.id_table	= mac_hid_emumouse_ids,
+};
+
+static int mac_hid_start_emulation(void)
+{
+	int err;
+
+	err = mac_hid_create_emumouse();
+	if (err)
+		return err;
+
+	err = input_register_handler(&mac_hid_emumouse_handler);
+	if (err) {
+		mac_hid_destroy_emumouse();
+		return err;
+	}
+
+	return 0;
+}
+
+static void mac_hid_stop_emulation(void)
+{
+	input_unregister_handler(&mac_hid_emumouse_handler);
+	mac_hid_destroy_emumouse();
+}
+
+static int mac_hid_toggle_emumouse(ctl_table *table, int write,
+				   void __user *buffer, size_t *lenp,
+				   loff_t *ppos)
+{
+	int *valp = table->data;
+	int old_val = *valp;
+	int rc;
+
+	rc = proc_dointvec(table, write, buffer, lenp, ppos);
+
+	if (rc == 0 && write && *valp != old_val) {
+		if (*valp == 1)
+			rc = mac_hid_start_emulation();
+		else if (*valp == 0)
+			mac_hid_stop_emulation();
+		else
+			rc = -EINVAL;
+	}
+
+	/* Restore the old value in case of error */
+	if (rc)
+		*valp = old_val;
+
+	return rc;
+}
+
 /* file(s) in /proc/sys/dev/mac_hid */
 static ctl_table mac_hid_files[] = {
 	{
@@ -31,7 +209,7 @@ static ctl_table mac_hid_files[] = {
 		.data		= &mouse_emulate_buttons,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= mac_hid_toggle_emumouse,
 	},
 	{
 		.procname	= "mouse_button2_keycode",
@@ -74,73 +252,12 @@ static ctl_table mac_hid_root_dir[] = {
 
 static struct ctl_table_header *mac_hid_sysctl_header;
 
-#endif /* endif CONFIG_SYSCTL */
-
-int mac_hid_mouse_emulate_buttons(int caller, unsigned int keycode, int down)
-{
-	switch (caller) {
-	case 1:
-		/* Called from keyboard.c */
-		if (mouse_emulate_buttons
-		    && (keycode == mouse_button2_keycode
-			|| keycode == mouse_button3_keycode)) {
-			if (mouse_emulate_buttons == 1) {
-				input_report_key(emumousebtn,
-						 keycode == mouse_button2_keycode ? BTN_MIDDLE : BTN_RIGHT,
-						 down);
-				input_sync(emumousebtn);
-				return 1;
-			}
-			mouse_last_keycode = down ? keycode : 0;
-		}
-		break;
-	}
-	return 0;
-}
-
-static struct lock_class_key emumousebtn_event_class;
-static struct lock_class_key emumousebtn_mutex_class;
-
-static int emumousebtn_input_register(void)
-{
-	int ret;
-
-	emumousebtn = input_allocate_device();
-	if (!emumousebtn)
-		return -ENOMEM;
-
-	lockdep_set_class(&emumousebtn->event_lock, &emumousebtn_event_class);
-	lockdep_set_class(&emumousebtn->mutex, &emumousebtn_mutex_class);
-
-	emumousebtn->name = "Macintosh mouse button emulation";
-	emumousebtn->id.bustype = BUS_ADB;
-	emumousebtn->id.vendor = 0x0001;
-	emumousebtn->id.product = 0x0001;
-	emumousebtn->id.version = 0x0100;
-
-	emumousebtn->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
-	emumousebtn->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
-		BIT_MASK(BTN_MIDDLE) | BIT_MASK(BTN_RIGHT);
-	emumousebtn->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
-
-	ret = input_register_device(emumousebtn);
-	if (ret)
-		input_free_device(emumousebtn);
-
-	return ret;
-}
 
 static int __init mac_hid_init(void)
 {
-	int err;
-
-	err = emumousebtn_input_register();
-	if (err)
-		return err;
-
-#if defined(CONFIG_SYSCTL)
 	mac_hid_sysctl_header = register_sysctl_table(mac_hid_root_dir);
-#endif /* CONFIG_SYSCTL */
+	if (!mac_hid_sysctl_header)
+		return -ENOMEM;
 
 	return 0;
 }

include/linux/kbd_kern.h

@@ -161,7 +161,4 @@ static inline void con_schedule_flip(struct tty_struct *t)
 	schedule_delayed_work(&t->buf.work, 0);
 }
 
-/* mac_hid.c */
-extern int mac_hid_mouse_emulate_buttons(int, unsigned int, int);
-
 #endif