STRUCT TP_FINGER(9)

🌸 struct tp_finger(9) — the kernel API manual, but make it bestie-friendly 🌸

Okay so this is a page from the Kernel API Manual, and it's all about struct tp_finger — literally the single trackpad finger structure, and it's le16-aligned (iykyk, that's little-endian 16-bit alignment, the little detail that makes everything work). Get into it. 💅

✨ SYNOPSIS ✨

struct tp_finger {
    __le16 origin;
    __le16 abs_x;
    __le16 abs_y;
    __le16 rel_x;
    __le16 rel_y;
    __le16 tool_major;
    __le16 tool_minor;
    __le16 orientation;
    __le16 touch_major;
    __le16 touch_minor;
    __le16 unused[2];
    __le16 pressure;
    __le16 multi;
    __le16 crc16;
 };

That's the whole squad, bestie. Now let's meet the members one by one — no skipping, every single one ate. 🫶

🎀 Members 🎀

• origin — this one's zero when you're switching track finger. Basically its little "new finger, who dis" signal. 😭
• abs_x — the absolute x coordinate. Where you at, horizontally? 🔥
• abs_y — the absolute y coordinate. Up-down realness. ✨
• rel_x — relative x coordinate. Like, how much did you move from last time. 🌸
• rel_y — relative y coordinate. Same vibe, vertical edition. 🦋
• tool_major — tool area, major axis. Fancy. 💅
• tool_minor — tool area, minor axis. The supporting character. 👑
• orientation — it's 16384 when it's a point, otherwise it's an 15 bit angle. I know. Just trust the math bestie. 🔢
• touch_major — touch area, major axis. Your fingertip but make it official. ✨
• touch_minor — touch area, minor axis. The other axis of your fingertip. 🍓
• unused — zeros. That's the whole description. They're just there, being zero, vibing. 💜
• pressure — the pressure on the forcetouch touchpad. Yes, it feels you. 😭
• multi — one finger: varies. more fingers: constant. That's the rule, don't @ me. 🌈
• crc16 — okay this one's important. On the last finger it's the crc over the whole message struct (i.e. message header + this struct) minus the last crc16 field. It's unknown on all other fingers — like, nobody knows. It's giving mystery. 💀

Real talk though: that crc16 situation is a whole vibe check — last finger only, and it covers everything except itself. Don't forget the message header in that count, bestie. 🧚

🌈 SEE ALSO 🌈

Kernel file ./drivers/input/keyboard/applespi.c struct keyboard_protocol(9), struct touchpad_protocol(9), struct command_protocol_tp_info(9), struct touchpad_info_protocol(9), struct command_protocol_mt_init(9), struct command_protocol_capsl(9), struct command_protocol_bl(9), struct message(9), struct spi_packet(9) — go read your friends, they're iconic too. 📚✨

Kernel source file ./drivers/input/keyboard — dated October 2026. That's the sign-off babes, mwah. 🫶💖