kobo-core 0.4.0

Kobo e-reader device SDK: device database, sysfs/ioctl, rendering, audio pipeline, trait surface
Documentation 
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// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Nayeem Bin Ahsan
pub const EV_SYN: u16 = 0x00;
pub const EV_KEY: u16 = 0x01;
pub const EV_ABS: u16 = 0x03;
pub const SYN_REPORT: u16 = 0x00;
pub const ABS_MT_POSITION_X: u16 = 0x35;
pub const ABS_MT_POSITION_Y: u16 = 0x36;
pub const BTN_TOUCH_CODE: u16 = 330;

pub const EVIOCGABS_X: libc::c_ulong = 0x80184572;
pub const EVIOCGABS_Y: libc::c_ulong = 0x80184576;

/// Decode (type, code, value) from a 16-byte arm evdev `input_event`. The first
/// 8 bytes are the timeval timestamp, ignored. Layout is ARM-32 specific
/// (timeval=8, type=2, code=2, value=4 = 16 bytes); a 64-bit target has a
/// 24-byte input_event and this decoder would misread it.
pub fn decode_input_event(buf: &[u8; 16]) -> (u16, u16, i32) {
    // Only meaningful on the actual target: `libc::timeval` is 16 bytes on a
    // 64-bit host (two `i64`s), so this would fire on every `cargo test` run
    // on a dev machine even though the decoder is never handed a real evdev
    // buffer there. On 32-bit ARM -- what this device and this decoder's byte
    // offsets assume -- `timeval` is two `i32`s and the check is exact.
    #[cfg(target_arch = "arm")]
    debug_assert_eq!(
        std::mem::size_of::<libc::timeval>() + 8,
        16,
        "input_event layout changed - this decoder assumes 32-bit ARM"
    );
    (
        u16::from_le_bytes([buf[8], buf[9]]),
        u16::from_le_bytes([buf[10], buf[11]]),
        i32::from_le_bytes([buf[12], buf[13], buf[14], buf[15]]),
    )
}

#[repr(C)]
#[derive(Default)]
pub struct InputAbsinfo {
    pub value: i32,
    pub minimum: i32,
    pub maximum: i32,
    pub fuzz: i32,
    pub flat: i32,
    pub resolution: i32,
}

pub fn query_abs_max(fd: libc::c_int, ioctl: libc::c_ulong) -> i32 {
    let mut info = InputAbsinfo::default();
    // SAFETY: ioctl with an EVIOCGABS-class code writes one `struct input_absinfo` into the
    // supplied &mut. `info` is a valid, initialized, exclusively-borrowed value of exactly
    // that layout (C-compatible #[repr(C)] struct of 5 i32). fd/ioctl are caller-provided
    // kernel tokens; a bad fd returns -1 (ignored) and `info` stays default.
    unsafe {
        libc::ioctl(fd, ioctl as _, &mut info);
    }
    info.maximum
}