[PATCH v12 12/17] HID: asus: add support for btn remapping

[Denis Benato <denis.benato@linux.dev>]

Add support for buttons remapping: the ability to assign different
button events to each one of the physical button on the device.

Each button exposes a remap_index sysfs attribute listing the valid
remap target names for the current gamepad mode: M1 and M2 can be
remapped to anything at any time, while other buttons may only be
remapped to gamepad codes in gamepad mode and keyboard/mouse/media
codes in desktop mode.

When the gamepad mode is changed the firmware automatically restores
its internal defaults, so the software cache is refreshed to reflect
the hardware state.

Co-developed-by: Luke Jones <luke@ljones.dev>
Signed-off-by: Luke Jones <luke@ljones.dev>
Signed-off-by: Denis Benato <denis.benato@linux.dev>
Signed-off-by: Jonathan LoBue <jlobue10@gmail.com>
---
 drivers/hid/hid-asus.c | 896 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 874 insertions(+), 22 deletions(-)

diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
index d20e433af574..b94cb8c50b28 100644
--- a/drivers/hid/hid-asus.c
+++ b/drivers/hid/hid-asus.c
@@ -41,6 +41,7 @@
 #include <linux/usb.h> /* For to_usb_interface for T100 touchpad intf check */
 #include <linux/power_supply.h>
 #include <linux/stddef.h>
+#include <linux/string.h>
 #include <linux/sysfs.h>
 #include <linux/leds.h>
 #include <linux/types.h>
@@ -108,6 +109,10 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
 #define ASUS_ALLY_TRIGGER_RANGE_UPPER_MIN 70
 #define ASUS_ALLY_TRIGGER_RANGE_UPPER_MAX 100
 
+#define ASUS_ALLY_BTN_CODE_LEN 0x2C
+
+#define ASUS_ALLY_BTN_FUNCTIONS_LEN 11
+
 /* Spurious HID codes sent by QUIRK_ROG_NKEY_KEYBOARD devices */
 #define ASUS_SPURIOUS_CODE_0XEA 0xea
 #define ASUS_SPURIOUS_CODE_0XEC 0xec
@@ -878,12 +883,215 @@ struct ally_turbo_config {
 	struct ally_btn_turbo_params btn_m1;
 };
 
+struct button_remap_attr {
+	struct device_attribute dev_attr;
+	enum ally_button_id button_id;
+	bool is_macro;
+};
+
+#define to_button_remap_attr(x) container_of(x, struct button_remap_attr, dev_attr)
+
 struct ally_btn_sysfs_entry {
 	struct attribute_group group;
-	struct attribute *attrs[5];
+	struct attribute *attrs[8];
 	enum ally_button_id btn;
 	struct device_attribute attr_turbo_period;
 	struct device_attribute attr_toggle_period;
+	struct button_remap_attr *remap_attr;
+	struct button_remap_attr *macro_attr;
+	struct device_attribute attr_remap_available;
+};
+
+enum btn_map_type {
+	BTN_TYPE_NONE = 0,
+	BTN_TYPE_PAD = 0x01,
+	BTN_TYPE_KB = 0x02,
+	BTN_TYPE_MOUSE = 0x03,
+	BTN_TYPE_MEDIA = 0x05,
+};
+
+struct btn_code_map {
+	unsigned char type;
+	unsigned char value;
+	const char *name;
+};
+
+static const struct btn_code_map ally_btn_codes[] = {
+	{ BTN_TYPE_NONE, 0x00, "NONE" },
+	/* Gamepad button codes */
+	{ BTN_TYPE_PAD, 0x01, "BTN_SOUTH" },
+	{ BTN_TYPE_PAD, 0x02, "BTN_EAST" },
+	{ BTN_TYPE_PAD, 0x03, "BTN_NORTH" },
+	{ BTN_TYPE_PAD, 0x04, "BTN_WEST" },
+	{ BTN_TYPE_PAD, 0x05, "BTN_TL" },
+	{ BTN_TYPE_PAD, 0x06, "BTN_TR" },
+	{ BTN_TYPE_PAD, 0x07, "BTN_THUMBL" },
+	{ BTN_TYPE_PAD, 0x08, "BTN_THUMBR" },
+	{ BTN_TYPE_PAD, 0x09, "ABS_HAT0Y_NEG" },
+	{ BTN_TYPE_PAD, 0x0A, "ABS_HAT0Y_POS" },
+	{ BTN_TYPE_PAD, 0x0B, "ABS_HAT0X_NEG" },
+	{ BTN_TYPE_PAD, 0x0C, "ABS_HAT0X_POS" },
+	{ BTN_TYPE_PAD, 0x0D, "ABS_Z" },
+	{ BTN_TYPE_PAD, 0x0E, "ABS_RZ" },
+	{ BTN_TYPE_PAD, 0x11, "BTN_SELECT" },
+	{ BTN_TYPE_PAD, 0x12, "BTN_START" },
+	{ BTN_TYPE_PAD, 0x13, "BTN_MODE" },
+
+	/* Keyboard button codes */
+	{ BTN_TYPE_KB, 0x8E, "FN_M2" },
+	{ BTN_TYPE_KB, 0x8F, "FN_M1" },
+	{ BTN_TYPE_KB, 0x76, "KEY_ESC" },
+	{ BTN_TYPE_KB, 0x05, "KEY_F1" },
+	{ BTN_TYPE_KB, 0x06, "KEY_F2" },
+	{ BTN_TYPE_KB, 0x04, "KEY_F3" },
+	{ BTN_TYPE_KB, 0x0C, "KEY_F4" },
+	{ BTN_TYPE_KB, 0x03, "KEY_F5" },
+	{ BTN_TYPE_KB, 0x0B, "KEY_F6" },
+	{ BTN_TYPE_KB, 0x80, "KEY_F7" },
+	{ BTN_TYPE_KB, 0x0A, "KEY_F8" },
+	{ BTN_TYPE_KB, 0x01, "KEY_F9" },
+	{ BTN_TYPE_KB, 0x09, "KEY_F10" },
+	{ BTN_TYPE_KB, 0x78, "KEY_F11" },
+	{ BTN_TYPE_KB, 0x07, "KEY_F12" },
+	{ BTN_TYPE_KB, 0x08, "KEY_F13" },
+	{ BTN_TYPE_KB, 0x10, "KEY_F14" },
+	{ BTN_TYPE_KB, 0x18, "KEY_F15" },
+	{ BTN_TYPE_KB, 0x0E, "KEY_GRAVE" }, /* backtick */
+	{ BTN_TYPE_KB, 0x16, "KEY_1" },
+	{ BTN_TYPE_KB, 0x1E, "KEY_2" },
+	{ BTN_TYPE_KB, 0x26, "KEY_3" },
+	{ BTN_TYPE_KB, 0x25, "KEY_4" },
+	{ BTN_TYPE_KB, 0x2E, "KEY_5" },
+	{ BTN_TYPE_KB, 0x36, "KEY_6" },
+	{ BTN_TYPE_KB, 0x3D, "KEY_7" },
+	{ BTN_TYPE_KB, 0x3E, "KEY_8" },
+	{ BTN_TYPE_KB, 0x46, "KEY_9" },
+	{ BTN_TYPE_KB, 0x45, "KEY_0" },
+	{ BTN_TYPE_KB, 0x4E, "KEY_MINUS" }, /* hyphen */
+	{ BTN_TYPE_KB, 0x55, "KEY_EQUAL" },
+	{ BTN_TYPE_KB, 0x66, "KEY_BACKSPACE" },
+	{ BTN_TYPE_KB, 0x0D, "KEY_TAB" },
+	{ BTN_TYPE_KB, 0x15, "KEY_Q" },
+	{ BTN_TYPE_KB, 0x1D, "KEY_W" },
+	{ BTN_TYPE_KB, 0x24, "KEY_E" },
+	{ BTN_TYPE_KB, 0x2D, "KEY_R" },
+	{ BTN_TYPE_KB, 0x2C, "KEY_T" },
+	{ BTN_TYPE_KB, 0x35, "KEY_Y" },
+	{ BTN_TYPE_KB, 0x3C, "KEY_U" },
+	{ BTN_TYPE_KB, 0x43, "KEY_I" },
+	{ BTN_TYPE_KB, 0x44, "KEY_O" },
+	{ BTN_TYPE_KB, 0x4D, "KEY_P" },
+	{ BTN_TYPE_KB, 0x54, "KEY_LEFTBRACE" },
+	{ BTN_TYPE_KB, 0x5B, "KEY_RIGHTBRACE" },
+	{ BTN_TYPE_KB, 0x5D, "KEY_BACKSLASH" },
+	{ BTN_TYPE_KB, 0x58, "KEY_CAPSLOCK" },
+	{ BTN_TYPE_KB, 0x1C, "KEY_A" },
+	{ BTN_TYPE_KB, 0x1B, "KEY_S" },
+	{ BTN_TYPE_KB, 0x23, "KEY_D" },
+	{ BTN_TYPE_KB, 0x2B, "KEY_F" },
+	{ BTN_TYPE_KB, 0x34, "KEY_G" },
+	{ BTN_TYPE_KB, 0x33, "KEY_H" },
+	{ BTN_TYPE_KB, 0x3B, "KEY_J" },
+	{ BTN_TYPE_KB, 0x42, "KEY_K" },
+	{ BTN_TYPE_KB, 0x4B, "KEY_L" },
+	{ BTN_TYPE_KB, 0x4C, "KEY_SEMICOLON" },
+	{ BTN_TYPE_KB, 0x52, "KEY_APOSTROPHE" },
+	{ BTN_TYPE_KB, 0x5A, "KEY_ENTER" },
+	{ BTN_TYPE_KB, 0x88, "KEY_LEFTSHIFT" },
+	{ BTN_TYPE_KB, 0x1A, "KEY_Z" },
+	{ BTN_TYPE_KB, 0x22, "KEY_X" },
+	{ BTN_TYPE_KB, 0x21, "KEY_C" },
+	{ BTN_TYPE_KB, 0x2A, "KEY_V" },
+	{ BTN_TYPE_KB, 0x32, "KEY_B" },
+	{ BTN_TYPE_KB, 0x31, "KEY_N" },
+	{ BTN_TYPE_KB, 0x3A, "KEY_M" },
+	{ BTN_TYPE_KB, 0x41, "KEY_COMMA" },
+	{ BTN_TYPE_KB, 0x49, "KEY_DOT" },
+	{ BTN_TYPE_KB, 0x4A, "KEY_SLASH" },
+	{ BTN_TYPE_KB, 0x89, "KEY_RIGHTSHIFT" },
+	{ BTN_TYPE_KB, 0x82, "KEY_LEFTMETA" },
+	{ BTN_TYPE_KB, 0x8A, "KEY_LEFTALT" },
+	{ BTN_TYPE_KB, 0x29, "KEY_SPACE" },
+	{ BTN_TYPE_KB, 0x8B, "KEY_RIGHTALT" },
+	{ BTN_TYPE_KB, 0x84, "KEY_COMPOSE" },
+	{ BTN_TYPE_KB, 0x8D, "KEY_RIGHTCTRL" },
+	{ BTN_TYPE_KB, 0xC3, "KEY_SYSRQ" },
+	{ BTN_TYPE_KB, 0x7E, "KEY_SCROLLLOCK" },
+	{ BTN_TYPE_KB, 0x91, "KEY_PAUSE" },
+	{ BTN_TYPE_KB, 0xC2, "KEY_INSERT" },
+	{ BTN_TYPE_KB, 0x94, "KEY_HOME" },
+	{ BTN_TYPE_KB, 0x96, "KEY_PAGEUP" },
+	{ BTN_TYPE_KB, 0xC0, "KEY_DELETE" },
+	{ BTN_TYPE_KB, 0x95, "KEY_END" },
+	{ BTN_TYPE_KB, 0x97, "KEY_PAGEDOWN" },
+	{ BTN_TYPE_KB, 0x98, "KEY_UP" },
+	{ BTN_TYPE_KB, 0x99, "KEY_DOWN" },
+	{ BTN_TYPE_KB, 0x9A, "KEY_LEFT" },
+	{ BTN_TYPE_KB, 0x9B, "KEY_RIGHT" },
+
+	/* Numpad button codes */
+	{ BTN_TYPE_KB, 0x77, "KEY_NUMLOCK" },
+	{ BTN_TYPE_KB, 0x90, "KEY_KPSLASH" },
+	{ BTN_TYPE_KB, 0x7C, "KEY_KPASTERISK" },
+	{ BTN_TYPE_KB, 0x7B, "KEY_KPMINUS" },
+	{ BTN_TYPE_KB, 0x70, "KEY_KP0" },
+	{ BTN_TYPE_KB, 0x69, "KEY_KP1" },
+	{ BTN_TYPE_KB, 0x72, "KEY_KP2" },
+	{ BTN_TYPE_KB, 0x7A, "KEY_KP3" },
+	{ BTN_TYPE_KB, 0x6B, "KEY_KP4" },
+	{ BTN_TYPE_KB, 0x73, "KEY_KP5" },
+	{ BTN_TYPE_KB, 0x74, "KEY_KP6" },
+	{ BTN_TYPE_KB, 0x6C, "KEY_KP7" },
+	{ BTN_TYPE_KB, 0x75, "KEY_KP8" },
+	{ BTN_TYPE_KB, 0x7D, "KEY_KP9" },
+	{ BTN_TYPE_KB, 0x79, "KEY_KPPLUS" },
+	{ BTN_TYPE_KB, 0x81, "KEY_KPENTER" },
+	{ BTN_TYPE_KB, 0x71, "KEY_KPDOT" },
+
+	/* Mouse button codes */
+	{ BTN_TYPE_MOUSE, 0x01, "BTN_LEFT" },
+	{ BTN_TYPE_MOUSE, 0x02, "BTN_RIGHT" },
+	{ BTN_TYPE_MOUSE, 0x03, "BTN_MIDDLE" },
+	{ BTN_TYPE_MOUSE, 0x04, "REL_WHEEL_HI_RES_UP" },
+	{ BTN_TYPE_MOUSE, 0x05, "REL_WHEEL_HI_RES_DOWN" },
+
+	/* Media button codes */
+	{ BTN_TYPE_MEDIA, 0x16, "MEDIA_SCREENSHOT" },
+	{ BTN_TYPE_MEDIA, 0x19, "MEDIA_SHOW_KEYBOARD" },
+	{ BTN_TYPE_MEDIA, 0x1C, "MEDIA_SHOW_DESKTOP" },
+	{ BTN_TYPE_MEDIA, 0x1E, "MEDIA_START_RECORDING" },
+	{ BTN_TYPE_MEDIA, 0x01, "MEDIA_MIC_OFF" },
+	{ BTN_TYPE_MEDIA, 0x02, "MEDIA_VOL_DOWN" },
+	{ BTN_TYPE_MEDIA, 0x03, "MEDIA_VOL_UP" },
+};
+
+/* Button pair indexes for mapping commands */
+enum btn_pair_index {
+	BTN_PAIR_DPAD_UPDOWN	= 0x01,
+	BTN_PAIR_DPAD_LEFTRIGHT	= 0x02,
+	BTN_PAIR_STICK_LR	= 0x03,
+	BTN_PAIR_BUMPER_LR	= 0x04,
+	BTN_PAIR_AB		= 0x05,
+	BTN_PAIR_XY		= 0x06,
+	BTN_PAIR_VIEW_MENU	= 0x07,
+	BTN_PAIR_M1M2		= 0x08,
+	BTN_PAIR_TRIGGER_LR	= 0x09,
+};
+
+struct button_map {
+	const struct btn_code_map *remap;
+	const struct btn_code_map *macro;
+};
+
+struct button_pair_map {
+	enum btn_pair_index pair_index;
+	struct button_map first;
+	struct button_map second;
+};
+
+/* Mappings the firmware is using. One set; a mode switch replaces it. */
+struct ally_button_mapping {
+	struct button_pair_map button_pairs[9];
 };
 
 static struct ally_prefs {
@@ -926,10 +1134,598 @@ static struct ally_prefs {
 
 	struct ally_turbo_config turbo;
 	struct ally_btn_sysfs_entry *button_entries;
+	struct ally_button_mapping button_mappings;
 } ally_prefs = {
 	.lock = __MUTEX_INITIALIZER(ally_prefs.lock),
 };
 
+/**
+ * find_button_by_name() - Find a button code map by its name
+ * @name: name of the button code to look up
+ *
+ * Return: the matching button code map, or NULL if not found.
+ */
+static const struct btn_code_map *find_button_by_name(const char *name)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ally_btn_codes); i++) {
+		if (!strcmp(ally_btn_codes[i].name, name))
+			return &ally_btn_codes[i];
+	}
+
+	return NULL;
+}
+
+static void ally_set_button_pair_mappings_default(struct ally_button_mapping *map)
+{
+	const struct btn_code_map *none_btn = find_button_by_name("NONE");
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(map->button_pairs); i++) {
+		map->button_pairs[i].pair_index = i + 1;
+		map->button_pairs[i].first.remap = none_btn;
+		map->button_pairs[i].first.macro = none_btn;
+		map->button_pairs[i].second.remap = none_btn;
+		map->button_pairs[i].second.macro = none_btn;
+	}
+}
+
+static void ally_set_default_gamepad_mapping(struct ally_button_mapping *map)
+{
+	ally_set_button_pair_mappings_default(map);
+
+	map->button_pairs[BTN_PAIR_AB - 1].first.remap =
+		find_button_by_name("BTN_SOUTH");
+	map->button_pairs[BTN_PAIR_AB - 1].second.remap =
+		find_button_by_name("BTN_EAST");
+
+	map->button_pairs[BTN_PAIR_XY - 1].first.remap =
+		find_button_by_name("BTN_NORTH");
+	map->button_pairs[BTN_PAIR_XY - 1].second.remap =
+		find_button_by_name("BTN_WEST");
+
+	map->button_pairs[BTN_PAIR_BUMPER_LR - 1].first.remap =
+		find_button_by_name("BTN_TL");
+	map->button_pairs[BTN_PAIR_BUMPER_LR - 1].second.remap =
+		find_button_by_name("BTN_TR");
+
+	map->button_pairs[BTN_PAIR_STICK_LR - 1].first.remap =
+		find_button_by_name("BTN_THUMBL");
+	map->button_pairs[BTN_PAIR_STICK_LR - 1].second.remap =
+		find_button_by_name("BTN_THUMBR");
+
+	map->button_pairs[BTN_PAIR_DPAD_UPDOWN - 1].first.remap =
+		find_button_by_name("ABS_HAT0Y_NEG");
+	map->button_pairs[BTN_PAIR_DPAD_UPDOWN - 1].second.remap =
+		find_button_by_name("ABS_HAT0Y_POS");
+
+	map->button_pairs[BTN_PAIR_DPAD_LEFTRIGHT - 1].first.remap =
+		find_button_by_name("ABS_HAT0X_NEG");
+	map->button_pairs[BTN_PAIR_DPAD_LEFTRIGHT - 1].second.remap =
+		find_button_by_name("ABS_HAT0X_POS");
+
+	map->button_pairs[BTN_PAIR_TRIGGER_LR - 1].first.remap =
+		find_button_by_name("ABS_Z");
+	map->button_pairs[BTN_PAIR_TRIGGER_LR - 1].second.remap =
+		find_button_by_name("ABS_RZ");
+
+	map->button_pairs[BTN_PAIR_VIEW_MENU - 1].first.remap =
+		find_button_by_name("BTN_SELECT");
+	map->button_pairs[BTN_PAIR_VIEW_MENU - 1].second.remap =
+		find_button_by_name("BTN_START");
+
+	map->button_pairs[BTN_PAIR_M1M2 - 1].first.remap =
+		find_button_by_name("FN_M2");
+	map->button_pairs[BTN_PAIR_M1M2 - 1].second.remap =
+		find_button_by_name("FN_M1");
+}
+
+static void ally_set_default_keyboard_mapping(struct ally_button_mapping *map)
+{
+	ally_set_button_pair_mappings_default(map);
+
+	/*
+	 * Desktop mode defaults: keyboard and mouse mappings.
+	 * Buttons not listed here (dpad, view, menu) remain NONE.
+	 */
+
+	/* btn_a => KEY_SPACE, btn_b => KEY_E */
+	map->button_pairs[BTN_PAIR_AB - 1].first.remap =
+		find_button_by_name("KEY_SPACE");
+	map->button_pairs[BTN_PAIR_AB - 1].second.remap =
+		find_button_by_name("KEY_E");
+
+	/* btn_x => KEY_R, btn_y => KEY_F */
+	map->button_pairs[BTN_PAIR_XY - 1].first.remap =
+		find_button_by_name("KEY_R");
+	map->button_pairs[BTN_PAIR_XY - 1].second.remap =
+		find_button_by_name("KEY_F");
+
+	/* LB => wheel up, RB => wheel down */
+	map->button_pairs[BTN_PAIR_BUMPER_LR - 1].first.remap =
+		find_button_by_name("REL_WHEEL_HI_RES_UP");
+	map->button_pairs[BTN_PAIR_BUMPER_LR - 1].second.remap =
+		find_button_by_name("REL_WHEEL_HI_RES_DOWN");
+
+	/* left stick click => left click, right stick click => left shift */
+	map->button_pairs[BTN_PAIR_STICK_LR - 1].first.remap =
+		find_button_by_name("BTN_LEFT");
+	map->button_pairs[BTN_PAIR_STICK_LR - 1].second.remap =
+		find_button_by_name("KEY_LEFTSHIFT");
+
+	/* LT => left click, RT => right click */
+	map->button_pairs[BTN_PAIR_TRIGGER_LR - 1].first.remap =
+		find_button_by_name("BTN_LEFT");
+	map->button_pairs[BTN_PAIR_TRIGGER_LR - 1].second.remap =
+		find_button_by_name("BTN_RIGHT");
+
+	/* M2 => FN_M2, M1 => FN_M1 */
+	map->button_pairs[BTN_PAIR_M1M2 - 1].first.remap =
+		find_button_by_name("FN_M2");
+	map->button_pairs[BTN_PAIR_M1M2 - 1].second.remap =
+		find_button_by_name("FN_M1");
+}
+
+/**
+ * ally_remap_code_valid() - Check if a remap target is valid for a button
+ * @btn: button to remap
+ * @gamepad_mode: gamepad mode to validate the remap against
+ * @code: remap target to check
+ * @is_macro: whether the target is assigned to the macro mapping
+ *
+ * M1 and M2 can be remapped to anything at any time.
+ * All other buttons may only be remapped to gamepad buttons (BTN_TYPE_PAD)
+ * when in gamepad mode, and to keyboard/mouse/media codes when in desktop
+ * (keyboard) mode.  BTN_TYPE_NONE (unmapped) is always allowed.
+ * Macro mappings are executed by the MCU as input sequences on the virtual
+ * keyboard and are accepted regardless of the current gamepad mode.
+ *
+ * Return: true if the remap is valid, false otherwise.
+ */
+static bool ally_remap_code_valid(enum ally_button_id btn, u8 gamepad_mode,
+				  const struct btn_code_map *code, bool is_macro)
+{
+	if (!code)
+		return false;
+
+	/* M1 and M2 can be remapped to everything */
+	if (btn == ALLY_BTN_M1 || btn == ALLY_BTN_M2)
+		return true;
+
+	/* NONE is always valid */
+	if (code->type == BTN_TYPE_NONE)
+		return true;
+
+	/* Macros are not restricted by the controller emulation mode */
+	if (is_macro)
+		return true;
+
+	if (gamepad_mode == ALLY_GAMEPAD_MODE_GAMEPAD)
+		return code->type == BTN_TYPE_PAD;
+
+	/* Desktop / keyboard mode: allow keyboard, mouse and media */
+	return code->type == BTN_TYPE_KB ||
+	       code->type == BTN_TYPE_MOUSE ||
+	       code->type == BTN_TYPE_MEDIA;
+}
+
+/**
+ * ally_encode_button_code() - Pack one button code into an MCU mapping slot
+ * @buf: command buffer to write
+ * @offset: byte offset of the slot in @buf
+ * @code: button code to encode
+ *
+ * The slot is %ASUS_ALLY_BTN_FUNCTIONS_LEN bytes. Byte 0 is the type. A pad
+ * value sits at byte 1, a keyboard value at byte 2, a media value at byte 3
+ * and a mouse value at byte 4.
+ */
+static void ally_encode_button_code(u8 *buf, unsigned int offset,
+				    const struct btn_code_map *code)
+{
+	u8 bytes[ASUS_ALLY_BTN_FUNCTIONS_LEN] = {};
+
+	buf[offset] = code->type;
+	if (!code->type)
+		return;
+
+	bytes[0] = code->type;
+	switch (code->type) {
+	case BTN_TYPE_NONE:
+		break;
+	case BTN_TYPE_PAD:
+		bytes[1] = code->value;
+		break;
+	case BTN_TYPE_KB:
+		bytes[2] = code->value;
+		break;
+	case BTN_TYPE_MEDIA:
+		bytes[3] = code->value;
+		break;
+	case BTN_TYPE_MOUSE:
+		bytes[4] = code->value;
+		break;
+	}
+
+	memcpy(&buf[offset], bytes, sizeof(bytes));
+}
+
+/**
+ * ally_set_button_mapping() - Set the button mapping for a button pair
+ * @hdev: HID device
+ * @mapping: button pair mapping to send to the device
+ *
+ * Return: count of data transferred, negative if error.
+ */
+static int ally_set_button_mapping(struct hid_device *hdev,
+				   struct button_pair_map *mapping)
+{
+	/*
+	 * The MCU mapping block is four consecutive 11-byte entries
+	 * starting at buf[5]: first remap 5-15, first macro 16-26,
+	 * second remap 27-37, second macro 38-48. Each entry is one
+	 * ally_encode_button_code() slot.
+	 */
+	size_t buf_len;
+
+	if (!mapping || !mapping->first.remap || !mapping->first.macro ||
+	    !mapping->second.remap || !mapping->second.macro)
+		return -EINVAL;
+
+	/*
+	 * The mapping block spans buf[4]..buf[48]: give ally_alloc_cmd() its
+	 * size so the fit check protects the fixed-offset writes below.
+	 */
+	u8 *buf __free(kfree) = ally_alloc_cmd(hdev, CMD_SET_MAPPING, NULL,
+					       1 + ASUS_ALLY_BTN_CODE_LEN,
+					       &buf_len);
+	if (!buf)
+		return -ENOMEM;
+
+	/*
+	 * This packet is slightly different from the other
+	 * as before the packet length there is an extra byte
+	 * which is the pair index.
+	 */
+	buf[3] = mapping->pair_index;
+	buf[4] = ASUS_ALLY_BTN_CODE_LEN;
+
+	/* First remap, first macro, second remap, second macro. */
+	ally_encode_button_code(buf, 5, mapping->first.remap);
+	ally_encode_button_code(buf, 16, mapping->first.macro);
+	ally_encode_button_code(buf, 27, mapping->second.remap);
+	ally_encode_button_code(buf, 38, mapping->second.macro);
+
+	return ally_gamepad_send_packet(hdev, buf, buf_len);
+}
+
+/**
+ * ally_apply_button_mappings() - Push the recorded mappings of the current
+ * gamepad mode to the controller
+ * @hdev: HID device
+ *
+ * An MCU reset restores the firmware default mappings: push the recorded
+ * ones again so that the hardware keeps matching what userspace
+ * configured. The caller holds ally_prefs.lock, as the sysfs stores that
+ * update a single pair do.
+ */
+static void ally_apply_button_mappings(struct hid_device *hdev)
+{
+	struct ally_button_mapping *mode_map;
+	int i, ret;
+
+	mode_map = &ally_prefs.button_mappings;
+
+	for (i = 0; i < ARRAY_SIZE(mode_map->button_pairs); i++) {
+		mode_map->button_pairs[i].pair_index = i + 1;
+
+		ret = ally_set_button_mapping(hdev,
+					      &mode_map->button_pairs[i]);
+		if (ret < 0) {
+			hid_warn(hdev,
+				 "Failed to restore button mappings: %d\n",
+				 ret);
+			return;
+		}
+	}
+}
+
+/**
+ * get_button_pair_info() - Get the pair index and position of a button
+ * @button_id: button to look up
+ * @pair_idx: output pointer for the pair index of the button
+ * @is_first: output pointer for the position of the button within the pair
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+static int get_button_pair_info(enum ally_button_id button_id,
+				enum btn_pair_index *pair_idx,
+				bool *is_first)
+{
+	switch (button_id) {
+	case ALLY_BTN_DU:
+		*pair_idx = BTN_PAIR_DPAD_UPDOWN;
+		*is_first = true;
+		break;
+	case ALLY_BTN_DD:
+		*pair_idx = BTN_PAIR_DPAD_UPDOWN;
+		*is_first = false;
+		break;
+	case ALLY_BTN_DL:
+		*pair_idx = BTN_PAIR_DPAD_LEFTRIGHT;
+		*is_first = true;
+		break;
+	case ALLY_BTN_DR:
+		*pair_idx = BTN_PAIR_DPAD_LEFTRIGHT;
+		*is_first = false;
+		break;
+	case ALLY_BTN_J0B:
+		*pair_idx = BTN_PAIR_STICK_LR;
+		*is_first = true;
+		break;
+	case ALLY_BTN_J1B:
+		*pair_idx = BTN_PAIR_STICK_LR;
+		*is_first = false;
+		break;
+	case ALLY_BTN_LB:
+		*pair_idx = BTN_PAIR_BUMPER_LR;
+		*is_first = true;
+		break;
+	case ALLY_BTN_RB:
+		*pair_idx = BTN_PAIR_BUMPER_LR;
+		*is_first = false;
+		break;
+	case ALLY_BTN_A:
+		*pair_idx = BTN_PAIR_AB;
+		*is_first = true;
+		break;
+	case ALLY_BTN_B:
+		*pair_idx = BTN_PAIR_AB;
+		*is_first = false;
+		break;
+	case ALLY_BTN_X:
+		*pair_idx = BTN_PAIR_XY;
+		*is_first = true;
+		break;
+	case ALLY_BTN_Y:
+		*pair_idx = BTN_PAIR_XY;
+		*is_first = false;
+		break;
+	case ALLY_BTN_VIEW:
+		*pair_idx = BTN_PAIR_VIEW_MENU;
+		*is_first = true;
+		break;
+	case ALLY_BTN_MENU:
+		*pair_idx = BTN_PAIR_VIEW_MENU;
+		*is_first = false;
+		break;
+	case ALLY_BTN_M1:
+		*pair_idx = BTN_PAIR_M1M2;
+		*is_first = false;
+		break;
+	case ALLY_BTN_M2:
+		*pair_idx = BTN_PAIR_M1M2;
+		*is_first = true;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static ssize_t button_remap_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct button_remap_attr *btn_attr = to_button_remap_attr(attr);
+	const struct btn_code_map *code;
+	enum ally_button_id button_id = btn_attr->button_id;
+	enum btn_pair_index pair_idx;
+	struct button_pair_map *pair;
+	struct button_map *btn_map;
+	bool is_first;
+	int ret;
+
+	ret = get_button_pair_info(button_id, &pair_idx, &is_first);
+	if (ret < 0)
+		return ret;
+
+	guard(mutex)(&ally_prefs.lock);
+
+	pair = &ally_prefs.button_mappings.button_pairs[pair_idx - 1];
+	btn_map = is_first ? &pair->first : &pair->second;
+	code = btn_attr->is_macro ? btn_map->macro : btn_map->remap;
+
+	/*
+	 * The mappings are never NULL: the defaults, the mode-switch
+	 * re-defaults and the store rollback all guarantee it. A miss
+	 * means a broken default table, so fail loudly instead of
+	 * dereferencing.
+	 */
+	if (!code)
+		return -EIO;
+
+	return sysfs_emit(buf, "%s\n", code->name);
+}
+
+static ssize_t button_remap_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct hid_device *hdev = to_hid_device(dev);
+	struct button_remap_attr *btn_attr = to_button_remap_attr(attr);
+	enum ally_button_id button_id = btn_attr->button_id;
+	struct ally_button_mapping *mode_map;
+	const struct btn_code_map *code;
+	const struct btn_code_map *old_code;
+	enum btn_pair_index pair_idx;
+	struct button_pair_map *pair;
+	struct button_map *btn_map;
+	char btn_name[32];
+	bool is_first;
+	int ret, i;
+
+	if (sscanf(buf, "%31s", btn_name) != 1)
+		return -EINVAL;
+
+	code = find_button_by_name(btn_name);
+	if (!code)
+		return -EINVAL;
+
+	ret = get_button_pair_info(button_id, &pair_idx, &is_first);
+	if (ret < 0)
+		return ret;
+
+	guard(mutex)(&ally_prefs.lock);
+
+	/*
+	 * Validate the remap target while holding the lock: the
+	 * gamepad mode can change concurrently, and the check must
+	 * be done against the very mode the mapping is written to.
+	 */
+	if (!ally_remap_code_valid(button_id, ally_prefs.gamepad_mode, code,
+				   btn_attr->is_macro))
+		return -EINVAL;
+
+	/* Access the mapping for current gamepad mode */
+	pair = &ally_prefs.button_mappings.button_pairs[pair_idx - 1];
+	btn_map = is_first ? &pair->first : &pair->second;
+
+	if (btn_attr->is_macro) {
+		old_code = btn_map->macro;
+		btn_map->macro = code;
+	} else {
+		old_code = btn_map->remap;
+		btn_map->remap = code;
+	}
+
+	/* Update pair index */
+	pair->pair_index = pair_idx;
+
+	/*
+	 * Send mapping to device with the caveat that first
+	 * generation devices require individual button pair updates.
+	 */
+	if (ally_prefs.is_ally_x) {
+		ret = ally_set_button_mapping(hdev, pair);
+		if (ret < 0)
+			goto err_restore;
+	} else {
+		mode_map = &ally_prefs.button_mappings;
+		for (i = 0; i < ARRAY_SIZE(mode_map->button_pairs); i++) {
+			mode_map->button_pairs[i].pair_index = i + 1;
+			ret = ally_set_button_mapping(hdev,
+						      &mode_map->button_pairs[i]);
+			if (ret < 0) {
+				/*
+				 * Pairs are pushed one at a time. This pair
+				 * already reached the hardware when a later
+				 * pair is the one that failed.
+				 */
+				if (i > pair_idx - 1)
+					goto err_restore_hw;
+				goto err_restore;
+			}
+		}
+	}
+	sysfs_notify(&dev->kobj, ally_button_names[btn_attr->button_id],
+		     btn_attr->is_macro ? "macro" : "remap");
+	return count;
+
+err_restore_hw:
+	if (btn_attr->is_macro)
+		btn_map->macro = old_code;
+	else
+		btn_map->remap = old_code;
+
+	/* Try to recover the mapping presented to the user. */
+	ally_set_button_mapping(hdev, pair);
+	goto err_out;
+
+err_restore:
+	if (btn_attr->is_macro)
+		btn_map->macro = old_code;
+	else
+		btn_map->remap = old_code;
+
+err_out:
+	hid_err(hdev, "Failed to set button mapping: %d\n", ret);
+	return ret;
+}
+
+/**
+ * button_remap_attr_create() - Create a button remap attribute
+ * @button_id: button the attribute is for
+ * @is_macro: whether the attribute controls the macro mapping
+ *
+ * Return: the newly created attribute, or NULL on allocation failure.
+ */
+static struct button_remap_attr *button_remap_attr_create(enum ally_button_id button_id,
+							  bool is_macro)
+{
+	struct button_remap_attr *const attr = kzalloc_obj(*attr);
+
+	if (!attr)
+		return NULL;
+
+	attr->button_id = button_id;
+	attr->is_macro = is_macro;
+	sysfs_attr_init(&attr->dev_attr.attr);
+	attr->dev_attr.attr.name = is_macro ? "macro" : "remap";
+	attr->dev_attr.attr.mode = 0644;
+	attr->dev_attr.show = button_remap_show;
+	attr->dev_attr.store = button_remap_store;
+
+	return attr;
+}
+
+/**
+ * btn_remap_available_show() - Show the list of valid remap targets for a button
+ * @dev: device the attribute belongs to
+ * @attr: attribute being read
+ * @buf: buffer to write the list into
+ *
+ * M1/M2 list everything; other buttons list only the codes valid for the
+ * active mode (gamepad buttons in gamepad mode, keyboard / mouse / media
+ * in desktop mode).
+ *
+ * Return: number of characters written.
+ */
+static ssize_t btn_remap_available_show(struct device *dev,
+					struct device_attribute *attr, char *buf)
+{
+	struct ally_btn_sysfs_entry *const entry = container_of(attr,
+		struct ally_btn_sysfs_entry, attr_remap_available);
+	enum ally_button_id btn = entry->btn;
+	u8 mode;
+	ssize_t len = 0;
+	int i;
+
+	scoped_guard(mutex, &ally_prefs.lock)
+		mode = ally_prefs.gamepad_mode;
+
+	for (i = 0; i < ARRAY_SIZE(ally_btn_codes); i++) {
+		if (!ally_remap_code_valid(btn, mode, &ally_btn_codes[i], false))
+			continue;
+		len += sysfs_emit_at(buf, len, "%s ", ally_btn_codes[i].name);
+	}
+
+	if (len > 0)
+		buf[len - 1] = '\n';
+
+	return len;
+}
+
+static void ally_mapping_defaults(void)
+{
+	guard(mutex)(&ally_prefs.lock);
+
+	if (ally_prefs.initialized)
+		return;
+
+	ally_set_default_gamepad_mapping(&ally_prefs.button_mappings);
+}
+
 /**
  * ally_check_capability() - Check if a specific capability is supported
  * @hdev: HID device to query
@@ -1532,12 +2328,35 @@ static ssize_t gamepad_mode_store(struct device *dev, struct device_attribute *a
 	/* The text index maps to the byte the MCU accepts. */
 	mode_byte = ally_gamepad_mode_value[mode];
 
-	scoped_guard(mutex, &ally_prefs.lock) {
-		ret = ally_set_gamepad_mode(hdev, mode_byte);
-		if (ret < 0)
-			return ret;
+	guard(mutex)(&ally_prefs.lock);
+
+	ret = ally_set_gamepad_mode(hdev, mode_byte);
+	if (ret < 0)
+		return ret;
 
-		ally_prefs.gamepad_mode = mode_byte;
+	ally_prefs.gamepad_mode = mode_byte;
+
+	/*
+	 * The MCU restores its own defaults for the new mode. Refresh the
+	 * cache so a later read reports what the firmware is using, then
+	 * wake anyone polling the remap, macro, and remap_available files.
+	 */
+	if (mode_byte == ALLY_GAMEPAD_MODE_GAMEPAD)
+		ally_set_default_gamepad_mapping(&ally_prefs.button_mappings);
+	else if (mode_byte == ALLY_GAMEPAD_MODE_KEYBOARD)
+		ally_set_default_keyboard_mapping(&ally_prefs.button_mappings);
+
+	if (ally_prefs.button_entries) {
+		int i;
+
+		for (i = 0; i < ALLY_BTN_MAX; i++) {
+			sysfs_notify(&dev->kobj,
+				     ally_prefs.button_entries[i].group.name, "remap");
+			sysfs_notify(&dev->kobj,
+				     ally_prefs.button_entries[i].group.name, "macro");
+			sysfs_notify(&dev->kobj,
+				     ally_prefs.button_entries[i].group.name, "remap_available");
+		}
 	}
 
 	hid_dbg(hdev, "Set gamepad mode to %s\n", ally_gamepad_mode_text[mode]);
@@ -2429,11 +3248,9 @@ static void ally_btn_turbo_init_attrs(struct ally_btn_sysfs_entry *entry)
 
 static struct ally_btn_sysfs_entry *ally_create_button_attributes(struct hid_device *hdev)
 {
+	const size_t entries_attr_index = ally_prefs.turbo_support ? 4 : 0;
 	int i, ret;
 
-	if (!ally_prefs.turbo_support)
-		return NULL;
-
 	struct ally_btn_sysfs_entry *entries __free(kfree) = kzalloc_objs(*entries, ALLY_BTN_MAX);
 	if (!entries)
 		return ERR_PTR(-ENOMEM);
@@ -2441,13 +3258,33 @@ static struct ally_btn_sysfs_entry *ally_create_button_attributes(struct hid_dev
 	for (i = 0; i < ALLY_BTN_MAX; i++) {
 		entries[i].btn = i;
 
-		if (!ally_btn_param(i)) {
-			hid_err(hdev, "Invalid button id %d for turbo attributes\n", i);
-			ret = -EINVAL;
+		if (ally_prefs.turbo_support) {
+			if (!ally_btn_param(i)) {
+				hid_err(hdev, "Invalid button id %d for turbo attributes\n", i);
+				ret = -EINVAL;
+				goto ally_btn_err_cleanup;
+			}
+
+			ally_btn_turbo_init_attrs(&entries[i]);
+		}
+
+		entries[i].remap_attr = button_remap_attr_create(i, false);
+		entries[i].macro_attr = button_remap_attr_create(i, true);
+		if (!entries[i].remap_attr || !entries[i].macro_attr) {
+			ret = -ENOMEM;
 			goto ally_btn_err_cleanup;
 		}
 
-		ally_btn_turbo_init_attrs(&entries[i]);
+		sysfs_attr_init(&entries[i].attr_remap_available.attr);
+		entries[i].attr_remap_available.attr.name = "remap_available";
+		entries[i].attr_remap_available.attr.mode = 0444;
+		entries[i].attr_remap_available.show = btn_remap_available_show;
+
+		entries[i].attrs[entries_attr_index + 0] = &entries[i].remap_attr->dev_attr.attr;
+		entries[i].attrs[entries_attr_index + 1] = &entries[i].macro_attr->dev_attr.attr;
+		entries[i].attrs[entries_attr_index + 2] = &entries[i].attr_remap_available.attr;
+		entries[i].attrs[entries_attr_index + 3] = NULL;
+
 		entries[i].group.name = ally_button_names[i];
 		entries[i].group.attrs = entries[i].attrs;
 
@@ -2465,6 +3302,11 @@ static struct ally_btn_sysfs_entry *ally_create_button_attributes(struct hid_dev
 	while (i--)
 		sysfs_remove_group(&hdev->dev.kobj, &entries[i].group);
 
+	for (i = 0; i < ALLY_BTN_MAX; i++) {
+		kfree(entries[i].remap_attr);
+		kfree(entries[i].macro_attr);
+	}
+
 	return ERR_PTR(ret);
 }
 
@@ -2477,11 +3319,19 @@ static void ally_remove_button_attributes(struct hid_device *hdev)
 	if (!entries)
 		return;
 
-	for (i = 0; i < ALLY_BTN_MAX; i++)
+	/*
+	 * Unpublish first. A mode-store notify holds the prefs lock and must
+	 * see either the live array or NULL.
+	 */
+	ally_prefs.button_entries = NULL;
+
+	for (i = 0; i < ALLY_BTN_MAX; i++) {
 		sysfs_remove_group(&hdev->dev.kobj, &entries[i].group);
+		kfree(entries[i].remap_attr);
+		kfree(entries[i].macro_attr);
+	}
 
 	kfree(entries);
-	ally_prefs.button_entries = NULL;
 }
 
 static int ally_prefs_setup(struct hid_device *hdev)
@@ -2497,6 +3347,7 @@ static int ally_prefs_setup(struct hid_device *hdev)
 	ally_joystick_defaults();
 	ally_trigger_defaults();
 	ally_curve_defaults();
+	ally_mapping_defaults();
 
 	guard(mutex)(&ally_prefs.lock);
 
@@ -2534,13 +3385,11 @@ static int ally_prefs_setup(struct hid_device *hdev)
 		}
 	}
 
-	if (ally_prefs.turbo_support) {
-		entries = ally_create_button_attributes(hdev);
-		if (IS_ERR(entries)) {
-			ret = PTR_ERR(entries);
-			hid_err(hdev, "Failed to create button attributes: %d\n", ret);
-			goto err_cal_groups;
-		}
+	entries = ally_create_button_attributes(hdev);
+	if (IS_ERR(entries)) {
+		ret = PTR_ERR(entries);
+		hid_err(hdev, "Failed to create button attributes: %d\n", ret);
+		goto err_cal_groups;
 	}
 
 	ally_prefs.button_entries = entries;
@@ -2934,6 +3783,9 @@ static int hid_asus_ally_init(struct hid_device *hdev)
 			hid_warn(hdev, "Failed to restore turbo parameters: %d\n", ret);
 	}
 
+	if (ally_prefs.initialized && ally_prefs.button_entries)
+		ally_apply_button_mappings(hdev);
+
 	return 0;
 }
 
-- 
2.47.3