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applications: nrf_desktop: Add keys state utility
Change introduces keys state utility. The utility is used to track state of the pressed keys. Jira: NCSDK-33998 Signed-off-by: Marek Pieta <[email protected]>
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‎applications/nrf_desktop/src/util/CMakeLists.txt‎

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@@ -16,6 +16,9 @@ target_sources_ifdef(CONFIG_DESKTOP_HID_KEYMAP
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target_sources_ifdef(CONFIG_DESKTOP_HWID
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app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/hwid.c)
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target_sources_ifdef(CONFIG_DESKTOP_KEYS_STATE
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app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/keys_state.c)
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target_sources_ifdef(CONFIG_DESKTOP_ADV_PROV_UUID16_ALL
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app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/bt_le_adv_prov_uuid16.c)
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‎applications/nrf_desktop/src/util/Kconfig‎

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@@ -12,5 +12,6 @@ rsource "Kconfig.hid_eventq"
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rsource "Kconfig.hid_keymap"
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rsource "Kconfig.hid_reportq"
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rsource "Kconfig.hwid"
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rsource "Kconfig.keys_state"
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endmenu

‎applications/nrf_desktop/src/util/Kconfig.keys_state‎

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#
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# Copyright (c) 2025 Nordic Semiconductor ASA
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#
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# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
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#
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menuconfig DESKTOP_KEYS_STATE
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bool "Enable keys state utility"
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help
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The utility can be used to track the state of active keys.
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if DESKTOP_KEYS_STATE
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config DESKTOP_KEYS_STATE_KEY_CNT_MAX
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int "Maximum number of keys that can be simultaneously active"
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default 8
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range 1 255
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help
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The configuration option determines the maximum number of keys that
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can be simultaneously tracked by the keys state.
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module = DESKTOP_KEYS_STATE
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module-str = keys state
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source "subsys/logging/Kconfig.template.log_config"
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endif # DESKTOP_KEYS_STATE

‎applications/nrf_desktop/src/util/keys_state.c‎

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/*
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* Copyright (c) 2025 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
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*/
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#include "keys_state.h"
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <zephyr/sys/__assert.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(keys_state, CONFIG_DESKTOP_KEYS_STATE_LOG_LEVEL);
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#define INVALID_KEY_IDX UINT8_MAX
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static bool keys_state_is_initialized(const struct keys_state *ks)
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{
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return (ks->cnt_max > 0);
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}
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void keys_state_init(struct keys_state *ks, uint8_t key_cnt_max)
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{
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LOG_DBG("ks:%p, key_cnt_max:%" PRIu8, (void *)ks, key_cnt_max);
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__ASSERT_NO_MSG(!keys_state_is_initialized(ks));
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__ASSERT_NO_MSG((key_cnt_max > 0) && (key_cnt_max <= ARRAY_SIZE(ks->keys)));
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ks->cnt_max = key_cnt_max;
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keys_state_clear(ks);
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}
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static struct active_key *get_key(struct keys_state *ks, uint8_t idx, uint16_t key_id)
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{
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if (idx >= ks->cnt) {
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return NULL;
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}
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struct active_key *key = &ks->keys[idx];
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return ((key->id == key_id) && (key->press_cnt > 0)) ? key : NULL;
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}
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static struct active_key *alloc_key(struct keys_state *ks, uint8_t idx, uint16_t key_id)
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{
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LOG_DBG("ks:%p, key ID:0x%" PRIx16, (void *)ks, key_id);
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__ASSERT_NO_MSG(ks->cnt <= ks->cnt_max);
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if ((idx == INVALID_KEY_IDX) || (ks->cnt == ks->cnt_max)) {
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return NULL;
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}
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__ASSERT_NO_MSG(idx <= ks->cnt);
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/* Shift active keys to make space for the new key. */
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for (uint8_t i = ks->cnt; i > idx; i--) {
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ks->keys[i] = ks->keys[i - 1];
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}
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struct active_key *key = &ks->keys[idx];
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key->id = key_id;
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key->press_cnt = 0;
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ks->cnt++;
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return key;
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}
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static uint8_t get_key_idx(struct keys_state *ks, uint16_t key_id)
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{
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BUILD_ASSERT(ARRAY_SIZE(ks->keys) <= INVALID_KEY_IDX);
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uint8_t idx;
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for (idx = 0; idx < ks->cnt; idx++) {
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/* Find slot for provided key ID. Active keys are sorted ascending by key ID. */
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if (key_id <= ks->keys[idx].id) {
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break;
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}
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}
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__ASSERT_NO_MSG(idx <= ks->cnt_max);
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return (idx == ks->cnt_max) ? INVALID_KEY_IDX : idx;
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}
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static void free_key(struct keys_state *ks, uint8_t idx)
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{
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__ASSERT_NO_MSG(idx < ks->cnt);
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LOG_DBG("ks:%p, key ID:0x%" PRIx16, (void *)ks, ks->keys[idx].id);
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/* Shift active keys to maintain ascending order. */
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for (uint8_t i = idx; i < (ks->cnt - 1); i++) {
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ks->keys[i] = ks->keys[i + 1];
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}
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ks->cnt--;
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/* Free the last active key. */
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ks->keys[ks->cnt].id = 0;
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ks->keys[ks->cnt].press_cnt = 0;
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}
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int keys_state_key_update(struct keys_state *ks, uint16_t key_id, bool pressed, bool *ks_changed)
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{
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LOG_DBG("ks:%p, key ID:0x%" PRIx16 " %s",
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(void *)ks, key_id, pressed ? "press" : "release");
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__ASSERT_NO_MSG(ks_changed);
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int err = 0;
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uint8_t prev_cnt = ks->cnt;
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uint8_t key_idx = get_key_idx(ks, key_id);
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struct active_key *key = get_key(ks, key_idx, key_id);
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if (key) {
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/* Key already active. */
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} else if (pressed) {
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/* Try to allocate new active key for key press. */
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key = alloc_key(ks, key_idx, key_id);
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}
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if (key) {
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__ASSERT_NO_MSG(pressed || (key->press_cnt > 0));
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key->press_cnt += (pressed ? (1) : (-1));
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if (key->press_cnt == 0) {
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/* Key no longer active. */
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free_key(ks, key_idx);
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}
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} else {
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if (pressed) {
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/* Cannot allocate new active key. */
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err = -ENOBUFS;
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} else {
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/* Released key not active. */
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err = -ENOENT;
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}
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}
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*ks_changed = (prev_cnt != ks->cnt);
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return err;
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}
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void keys_state_clear(struct keys_state *ks)
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{
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LOG_DBG("ks:%p", (void *)ks);
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if (keys_state_is_initialized(ks)) {
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memset(ks->keys, 0, sizeof(ks->keys));
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ks->cnt = 0;
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}
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}
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size_t keys_state_keys_get(const struct keys_state *ks, uint16_t *res, size_t res_size)
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{
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LOG_DBG("ks:%p", (void *)ks);
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__ASSERT_NO_MSG(ks->cnt <= ks->cnt_max);
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__ASSERT_NO_MSG(res_size >= ks->cnt_max);
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ARG_UNUSED(res_size);
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for (uint8_t i = 0; i < ks->cnt; i++) {
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res[i] = ks->keys[i].id;
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}
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return ks->cnt;
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}

‎applications/nrf_desktop/src/util/keys_state.h‎

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/*
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* Copyright (c) 2025 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
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*/
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#ifndef _KEYS_STATE_H_
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#define _KEYS_STATE_H_
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/**
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* @file
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* @defgroup keys_state Keys state
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* @{
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* @brief Utility used to track state of active keys.
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#define KEYS_MAX_CNT CONFIG_DESKTOP_KEYS_STATE_KEY_CNT_MAX
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/** @brief Structure used to track an active key. */
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struct active_key {
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uint16_t id; /**< Key ID. */
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uint16_t press_cnt; /**< Keypress counter. */
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};
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/**@brief Keys state structure. */
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struct keys_state {
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struct active_key keys[KEYS_MAX_CNT]; /**< Active keys. */
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uint8_t cnt; /**< Current number of active keys. */
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uint8_t cnt_max; /**< Maximum number of active keys. */
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};
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/**
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* @brief Initialize a keys state object.
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*
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* A keys state object must be initialized to track active keys.
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*
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* The function asserts if maximum number of active keys exceeds the value allowed by Kconfig
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* configuration.
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*
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* @param[in] ks A keys state object.
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* @param[in] key_cnt_max Maximum number of active keys.
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*/
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void keys_state_init(struct keys_state *ks, uint8_t key_cnt_max);
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/**
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* @brief Notify keys state about a key press/release
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*
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* The utility can record multiple key presses for a given key ID. The same number of key releases
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* is needed for the utility to report release of the key.
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*
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* @param[in] ks A keys state object.
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* @param[in] key_id Key ID.
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* @param[in] pressed Information if key was pressed or released.
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* @param[out] ks_changed Information if state of the pressed keys changed.
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*
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* @retval 0 when successful.
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* @retval -ENOENT if key is released, but related key press was not recorded by the utility.
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* @retval -ENOBUFS if key is pressed and number of active keys exceeds the limit.
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*/
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int keys_state_key_update(struct keys_state *ks, uint16_t key_id, bool pressed, bool *ks_changed);
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/**
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* @brief Clear keys state
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*
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* The function drops all of the tracked active key presses.
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*
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* @param[in] ks A keys state object.
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*/
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void keys_state_clear(struct keys_state *ks);
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/**
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* @brief Get keys state
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*
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* The function fills the provided array with key IDs of all the active keys. The utility keeps key
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* IDs sorted in ascending order to ensure consistent results.
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*
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* The function asserts if size of the provided array is too small to handle the maximum number of
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* active keys.
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*
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* @param[in] ks A keys state object.
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* @param[out] res Array to be filled with key IDs of active keys.
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* @param[in] res_size Size of the provided array.
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*
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* @return Number of keys written.
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*/
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size_t keys_state_keys_get(const struct keys_state *ks, uint16_t *res, size_t res_size);
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#ifdef __cplusplus
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}
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#endif
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/**
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* @}
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*/
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#endif /*_KEYS_STATE_H_ */

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