0x40A3 · fnInversionMultiHost

fnInversionForMultiHostDevices controls whether F-row keys behave as standard function keys or as their labeled media / special-key actions by default. Unlike the single-host predecessor 0x40A2 (fnInversionWithDefaultState), this variant stores an independent inversion state for each host slot.

getGlobalFnInversion (function 0) reads the current state, the factory-default state, and the device capabilities for a given HostIndex. setGlobalFnInversion (function 1) writes the desired FnInversionState for a host slot; the device persists the value in its own non-volatile memory and returns the resulting FnInversionInfo.

• FnInversionState — Off (F-keys behave as labeled function keys), On (F-keys behave as media / special-key actions).
• FnInversionCapabilities — MANUAL_FN_LOCK flag indicates the device supports manual Fn-lock control.
• FnInversionInfo — response struct carrying host_index, state, default_state, and capabilities.

Spec: Logitech HID++ 2.0 — fnInversionForMultiHostDevices. Used by: Typed wrapper in openlogi-hidpp.

Function reference

The FnInversionMultiHostFeature wrapper (0x40a3) exposes:

Methods

All methods are async and return Result<_, Hidpp20Error>.

Types

FnInversionInfo

Function-key inversion state for a host slot.

FnInversionState

Function-key inversion state.

FnInversionCapabilities

Function-key inversion capabilities (bitflags).

HostIndex

A host slot selector (defined in hosts_info).

Wire format

Requests carry a 3-byte payload; responses are parsed from the 16-byte long payload returned by extend_payload().

get_global_fn_inversion (fn 0)

Request: [host_index, 0x00, 0x00]

• Byte 0: host_index — u8 encoding of HostIndex (0xff = current slot, 0x00–0xfe = zero-based slot index)
• Bytes 1–2: reserved, always 0x00

Response (byte → field):

set_global_fn_inversion (fn 1)

Request: [host_index, state, 0x00]

• Byte 0: host_index — u8 encoding of HostIndex
• Byte 1: state — u8 encoding of FnInversionState (0 = Off, 1 = On)
• Byte 2: reserved, always 0x00

Response (byte → field): identical layout to get_global_fn_inversion — the device echoes back the resulting FnInversionInfo for the host slot.

Usage (Rust)

use hidpp::{
    device::Device,
    feature::fn_inversion::{FnInversionMultiHostFeature, FnInversionState},
};

// mut device: Device, already created via Device::new(channel, index)
device.enumerate_features().await?;
if let Some(feat) = device.get_feature::<FnInversionMultiHostFeature>() {
    // Read the current state for the active host slot.
    let info = feat.get_global_fn_inversion(hidpp::feature::hosts_info::HostIndex::Current).await?;
    println!("state={:?}, default={:?}, caps={:?}", info.state, info.default_state, info.capabilities);

    // Enable Fn-inversion on host slot 0.
    let updated = feat
        .set_global_fn_inversion(hidpp::feature::hosts_info::HostIndex::Slot(0), FnInversionState::On)
        .await?;
    println!("new state={:?}", updated.state);
}