sdk/fidl/fuchsia.hardware.google.nanohub/nanohubdisplay.fidl

// Copyright 2025 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.hardware.google.nanohub;

using zx;

/// Represents the various modes the MCU display can be in.
type DisplayMode = flexible enum : uint8 {
    /// The display is not in a known state.
    NONE = 0;
    /// The MCU stack is driving the display initializing.
    INIT = 1;
    /// The display is off.
    OFF = 2;
    /// The display is in an idle, low-power state.
    IDLE = 3;
    /// The display is on.
    ON = 4;
    /// The display is in a high-brightness mode.
    HIGH_BRIGHTNESS = 5;
};

/// Represents the current state of the MCU display.
type DisplayState = table {
    /// The current mode of the display.
    1: mode DisplayMode;
};

/// Contains synchronization information for the MCU display.
type DisplaySyncInfo = table {
    /// The current mode of the display.
    1: display_mode DisplayMode;
    /// The current panel mode.
    2: panel_mode uint8;
    /// The normal brightness mode brightness level.
    3: normal_brightness uint16;
    /// The always-on-display brightness level.
    4: always_on_display_brightness uint16;
};

/// Selects which processor has ownership of the display.
type DisplaySelect = flexible enum : int64 {
    /// The MCU (Microcontroller Unit) has control of the display. This
    /// corresponds to a low signal on the display select GPIO pin.
    LOW = 0;
    /// The AP (Application Processor) has control of the display. This
    /// corresponds to a high signal on the display select GPIO pin.
    HIGH = 1;
};

/// Protocol for interacting with the Google-specific display hardware.
@discoverable
closed protocol DisplayDevice {
    /// Gets the current state of the display.
    strict GetDisplayState() -> (DisplayState) error zx.Status;
    /// Gets synchronization information for the display. This can include
    /// the display's mode, panel mode, and brightness levels.
    strict GetDisplayInfo() -> (DisplaySyncInfo) error zx.Status;
    /// Gets the current display owner, which is either the AP (Application
    /// Processor) or the MCU (Microcontroller Unit).
    strict GetDisplaySelect() -> (table {
        1: display_select DisplaySelect;
    }) error zx.Status;
    /// Sets the display owner to be either the AP (Application Processor) or
    /// the MCU (Microcontroller Unit).
    strict SetDisplaySelect(table {
        1: display_select DisplaySelect;
    }) -> () error zx.Status;
};

/// The service that provides access to the display device.
service DisplayService {
    /// The display device.
    mcudisplay client_end:DisplayDevice;
};