// SPDX-License-Identifier: GPL-2.0
/*
 * Keyboard backlight LED driver for the Wilco Embedded Controller
 *
 * Copyright 2019 Google LLC
 *
 * Since the EC will never change the backlight level of its own accord,
 * we don't need to implement a brightness_get() method.
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/leds.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/slab.h>

#define WILCO_EC_COMMAND_KBBL           0x75
#define WILCO_KBBL_MODE_FLAG_PWM        BIT(1)  /* Set brightness by percent. */
#define WILCO_KBBL_DEFAULT_BRIGHTNESS   0

struct wilco_keyboard_leds {
        struct wilco_ec_device *ec;
        struct led_classdev keyboard;
};

enum wilco_kbbl_subcommand {
        WILCO_KBBL_SUBCMD_GET_FEATURES = 0x00,
        WILCO_KBBL_SUBCMD_GET_STATE    = 0x01,
        WILCO_KBBL_SUBCMD_SET_STATE    = 0x02,
};

/**
 * struct wilco_keyboard_leds_msg - Message to/from EC for keyboard LED control.
 * @command: Always WILCO_EC_COMMAND_KBBL.
 * @status: Set by EC to 0 on success, 0xFF on failure.
 * @subcmd: One of enum wilco_kbbl_subcommand.
 * @reserved3: Should be 0.
 * @mode: Bit flags for used mode, we want to use WILCO_KBBL_MODE_FLAG_PWM.
 * @reserved5to8: Should be 0.
 * @percent: Brightness in 0-100. Only meaningful in PWM mode.
 * @reserved10to15: Should be 0.
 */
struct wilco_keyboard_leds_msg {
        u8 command;
        u8 status;
        u8 subcmd;
        u8 reserved3;
        u8 mode;
        u8 reserved5to8[4];
        u8 percent;
        u8 reserved10to15[6];
} __packed;

/* Send a request, get a response, and check that the response is good. */
static int send_kbbl_msg(struct wilco_ec_device *ec,
                         struct wilco_keyboard_leds_msg *request,
                         struct wilco_keyboard_leds_msg *response)
{
        struct wilco_ec_message msg;
        int ret;

        memset(&msg, 0, sizeof(msg));
        msg.type = WILCO_EC_MSG_LEGACY;
        msg.request_data = request;
        msg.request_size = sizeof(*request);
        msg.response_data = response;
        msg.response_size = sizeof(*response);

        ret = wilco_ec_mailbox(ec, &msg);
        if (ret < 0) {
                dev_err(ec->dev,
                        "Failed sending keyboard LEDs command: %d\n", ret);
                return ret;
        }

        return 0;
}

static int set_kbbl(struct wilco_ec_device *ec, enum led_brightness brightness)
{
        struct wilco_keyboard_leds_msg request;
        struct wilco_keyboard_leds_msg response;
        int ret;

        memset(&request, 0, sizeof(request));
        request.command = WILCO_EC_COMMAND_KBBL;
        request.subcmd  = WILCO_KBBL_SUBCMD_SET_STATE;
        request.mode    = WILCO_KBBL_MODE_FLAG_PWM;
        request.percent = brightness;

        ret = send_kbbl_msg(ec, &request, &response);
        if (ret < 0)
                return ret;

        if (response.status) {
                dev_err(ec->dev,
                        "EC reported failure sending keyboard LEDs command: %d\n",
                        response.status);
                return -EIO;
        }

        return 0;
}

static int kbbl_exist(struct wilco_ec_device *ec, bool *exists)
{
        struct wilco_keyboard_leds_msg request;
        struct wilco_keyboard_leds_msg response;
        int ret;

        memset(&request, 0, sizeof(request));
        request.command = WILCO_EC_COMMAND_KBBL;
        request.subcmd  = WILCO_KBBL_SUBCMD_GET_FEATURES;

        ret = send_kbbl_msg(ec, &request, &response);
        if (ret < 0)
                return ret;

        *exists = response.status != 0xFF;

        return 0;
}

/**
 * kbbl_init() - Initialize the state of the keyboard backlight.
 * @ec: EC device to talk to.
 *
 * Gets the current brightness, ensuring that the BIOS already initialized the
 * backlight to PWM mode. If not in PWM mode, then the current brightness is
 * meaningless, so set the brightness to WILCO_KBBL_DEFAULT_BRIGHTNESS.
 *
 * Return: Final brightness of the keyboard, or negative error code on failure.
 */
static int kbbl_init(struct wilco_ec_device *ec)
{
        struct wilco_keyboard_leds_msg request;
        struct wilco_keyboard_leds_msg response;
        int ret;

        memset(&request, 0, sizeof(request));
        request.command = WILCO_EC_COMMAND_KBBL;
        request.subcmd  = WILCO_KBBL_SUBCMD_GET_STATE;

        ret = send_kbbl_msg(ec, &request, &response);
        if (ret < 0)
                return ret;

        if (response.status) {
                dev_err(ec->dev,
                        "EC reported failure sending keyboard LEDs command: %d\n",
                        response.status);
                return -EIO;
        }

        if (response.mode & WILCO_KBBL_MODE_FLAG_PWM)
                return response.percent;

        ret = set_kbbl(ec, WILCO_KBBL_DEFAULT_BRIGHTNESS);
        if (ret < 0)
                return ret;

        return WILCO_KBBL_DEFAULT_BRIGHTNESS;
}

static int wilco_keyboard_leds_set(struct led_classdev *cdev,
                                   enum led_brightness brightness)
{
        struct wilco_keyboard_leds *wkl =
                container_of(cdev, struct wilco_keyboard_leds, keyboard);
        return set_kbbl(wkl->ec, brightness);
}

int wilco_keyboard_leds_init(struct wilco_ec_device *ec)
{
        struct wilco_keyboard_leds *wkl;
        bool leds_exist;
        int ret;

        ret = kbbl_exist(ec, &leds_exist);
        if (ret < 0) {
                dev_err(ec->dev,
                        "Failed checking keyboard LEDs support: %d\n", ret);
                return ret;
        }
        if (!leds_exist)
                return 0;

        wkl = devm_kzalloc(ec->dev, sizeof(*wkl), GFP_KERNEL);
        if (!wkl)
                return -ENOMEM;

        wkl->ec = ec;
        wkl->keyboard.name = "platform::kbd_backlight";
        wkl->keyboard.max_brightness = 100;
        wkl->keyboard.flags = LED_CORE_SUSPENDRESUME;
        wkl->keyboard.brightness_set_blocking = wilco_keyboard_leds_set;
        ret = kbbl_init(ec);
        if (ret < 0)
                return ret;
        wkl->keyboard.brightness = ret;

        return devm_led_classdev_register(ec->dev, &wkl->keyboard);
}