// SPDX-License-Identifier: GPL-2.0+
/*
 * Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM).
 *
 * Copyright (C) 2022-2023 Maximilian Luz <luzmaximilian@gmail.com>
 */

#include <linux/bitops.h>
#include <linux/hwmon.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>

#include <linux/surface_aggregator/controller.h>
#include <linux/surface_aggregator/device.h>

/* -- SAM interface. -------------------------------------------------------- */

/*
 * Available sensors are indicated by a 16-bit bitfield, where a 1 marks the
 * presence of a sensor. So we have at most 16 possible sensors/channels.
 */
#define SSAM_TMP_SENSOR_MAX_COUNT       16

/*
 * All names observed so far are 6 characters long, but there's only
 * zeros after the name, so perhaps they can be longer. This number reflects
 * the maximum zero-padded space observed in the returned buffer.
 */
#define SSAM_TMP_SENSOR_NAME_LENGTH     18

struct ssam_tmp_get_name_rsp {
        __le16 unknown1;
        char unknown2;
        char name[SSAM_TMP_SENSOR_NAME_LENGTH];
} __packed;

static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);

SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
        .target_category = SSAM_SSH_TC_TMP,
        .command_id      = 0x04,
});

SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
        .target_category = SSAM_SSH_TC_TMP,
        .command_id      = 0x01,
});

SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, {
        .target_category = SSAM_SSH_TC_TMP,
        .command_id      = 0x0e,
});

static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors)
{
        __le16 sensors_le;
        int status;

        status = __ssam_tmp_get_available_sensors(sdev, &sensors_le);
        if (status)
                return status;

        *sensors = le16_to_cpu(sensors_le);
        return 0;
}

static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature)
{
        __le16 temp_le;
        int status;

        status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le);
        if (status)
                return status;

        /* Convert 1/10 °K to 1/1000 °C */
        *temperature = (le16_to_cpu(temp_le) - 2731) * 100L;
        return 0;
}

static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len)
{
        struct ssam_tmp_get_name_rsp name_rsp;
        int status;

        status =  __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp);
        if (status)
                return status;

        /*
         * This should not fail unless the name in the returned struct is not
         * null-terminated or someone changed something in the struct
         * definitions above, since our buffer and struct have the same
         * capacity by design. So if this fails, log an error message. Since
         * the more likely cause is that the returned string isn't
         * null-terminated, we might have received garbage (as opposed to just
         * an incomplete string), so also fail the function.
         */
        status = strscpy(buf, name_rsp.name, buf_len);
        if (status < 0) {
                dev_err(&sdev->dev, "received non-null-terminated sensor name string\n");
                return status;
        }

        return 0;
}

/* -- Driver.---------------------------------------------------------------- */

struct ssam_temp {
        struct ssam_device *sdev;
        s16 sensors;
        char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH];
};

static umode_t ssam_temp_hwmon_is_visible(const void *data,
                                          enum hwmon_sensor_types type,
                                          u32 attr, int channel)
{
        const struct ssam_temp *ssam_temp = data;

        if (!(ssam_temp->sensors & BIT(channel)))
                return 0;

        return 0444;
}

static int ssam_temp_hwmon_read(struct device *dev,
                                enum hwmon_sensor_types type,
                                u32 attr, int channel, long *value)
{
        const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);

        return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value);
}

static int ssam_temp_hwmon_read_string(struct device *dev,
                                       enum hwmon_sensor_types type,
                                       u32 attr, int channel, const char **str)
{
        const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);

        *str = ssam_temp->names[channel];
        return 0;
}

static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = {
        HWMON_CHANNEL_INFO(chip,
                           HWMON_C_REGISTER_TZ),
        HWMON_CHANNEL_INFO(temp,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL,
                           HWMON_T_INPUT | HWMON_T_LABEL),
        NULL
};

static const struct hwmon_ops ssam_temp_hwmon_ops = {
        .is_visible = ssam_temp_hwmon_is_visible,
        .read = ssam_temp_hwmon_read,
        .read_string = ssam_temp_hwmon_read_string,
};

static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
        .ops = &ssam_temp_hwmon_ops,
        .info = ssam_temp_hwmon_info,
};

static int ssam_temp_probe(struct ssam_device *sdev)
{
        struct ssam_temp *ssam_temp;
        struct device *hwmon_dev;
        s16 sensors;
        int channel;
        int status;

        status = ssam_tmp_get_available_sensors(sdev, &sensors);
        if (status)
                return status;

        ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL);
        if (!ssam_temp)
                return -ENOMEM;

        ssam_temp->sdev = sdev;
        ssam_temp->sensors = sensors;

        /* Retrieve the name for each available sensor. */
        for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) {
                if (!(sensors & BIT(channel)))
                        continue;

                status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel],
                                           SSAM_TMP_SENSOR_NAME_LENGTH);
                if (status)
                        return status;
        }

        hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp,
                                                         &ssam_temp_hwmon_chip_info, NULL);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct ssam_device_id ssam_temp_match[] = {
        { SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
        { },
};
MODULE_DEVICE_TABLE(ssam, ssam_temp_match);

static struct ssam_device_driver ssam_temp = {
        .probe = ssam_temp_probe,
        .match_table = ssam_temp_match,
        .driver = {
                .name = "surface_temp",
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};
module_ssam_device_driver(ssam_temp);

MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
MODULE_LICENSE("GPL");