STRUCT COMMAND_PROTOCOL_CAPSL(9)

💅 NAME (aka what is this even)

struct command_protocol_capsl — the literal toggle-the-caps-lock-LED message, bestie. Like, the whole struct is just "hey keyboard, light up that little light" and honestly? Iconic. 🎀

Here's the tea: message.type = 0x0151, message.length = 0x0002. That's it. That's the whole vibe.

✨ SYNOPSIS ✨

struct command_protocol_capsl {
    u8 unknown;
    u8 led;
    __le16 crc16;
 };

Look at her. Three fields. No notes. 🫶

🌸 Members (the cast of characters) 🌸

• unknown — this one's 0x01 and the docs are like "length?" with a whole question mark, so we're all just guessing together fr fr. It has a value of 0x01 and honestly it's giving mystery main character energy. 🙈
• led — the actual star of the show ✨ 0 = off, 2 = on. (Yes, not 1. Two. That's the vibe check and it passed.) 🔥
• crc16 — the integrity checker 💀 this is the crc over the whole message struct — that means the message header plus this struct — minus this here crc16 field itself. Lowkey the most important member and it's just doing math in the corner. Not me being obsessed with a checksum. 😭

Don't forget: the crc covers the message header + this struct, but it does not cover the crc16 field. That's the rule. Periodt. 💅

🦋 SEE ALSO 🦋

Ok so there's a whole friend group here and you should meet all of them 🫶:

• Kernel file ./drivers/input/keyboard/applespi.c
• struct keyboard_protocol(9)
• struct tp_finger(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_bl(9)
• struct message(9)
• struct spi_packet(9)

Ok that's the whole page, bestie! Go forth and toggle that caps-lock LED responsibly 💖

Signed, sealed, delivered from ./drivers/input/keyboard in the October 2026 era of the Kernel API Manual — stan the kernel, drink water, and don't forget to check your crc16. 🌈👑