/*-
 * Copyright (c) 2018-2019 Marc Priggemeyer <marc.priggemeyer@gmail.com>
 * Copyright (c) 2019-2020 Vladimir Kondratyev <wulf@FreeBSD.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * I2C HID transport backend.
 */

#include <sys/cdefs.h>
#include "opt_hid.h"

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/callout.h>
#include <sys/endian.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/proc.h>
#include <sys/rman.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/taskqueue.h>

#include <machine/resource.h>

#include <contrib/dev/acpica/include/acpi.h>
#include <contrib/dev/acpica/include/accommon.h>
#include <dev/acpica/acpivar.h>

#include <dev/evdev/input.h>

#include <dev/hid/hid.h>
#include <dev/hid/hidquirk.h>

#include <dev/iicbus/iic.h>
#include <dev/iicbus/iicbus.h>
#include <dev/iicbus/iiconf.h>

#include "hid_if.h"

#ifdef IICHID_DEBUG
static int iichid_debug = 0;

static SYSCTL_NODE(_hw, OID_AUTO, iichid, CTLFLAG_RW, 0, "I2C HID");
SYSCTL_INT(_hw_iichid, OID_AUTO, debug, CTLFLAG_RWTUN,
    &iichid_debug, 1, "Debug level");

#define DPRINTFN(sc, n, ...) do {                       \
        if (iichid_debug >= (n))                        \
                device_printf((sc)->dev, __VA_ARGS__);  \
} while (0)
#define DPRINTF(sc, ...)        DPRINTFN(sc, 1, __VA_ARGS__)
#else
#define DPRINTFN(...)           do {} while (0)
#define DPRINTF(...)            do {} while (0)
#endif

typedef hid_size_t      iichid_size_t;
#define IICHID_SIZE_MAX (UINT16_MAX - 2)

/* 7.2 */
enum {
        I2C_HID_CMD_DESCR       = 0x0,
        I2C_HID_CMD_RESET       = 0x1,
        I2C_HID_CMD_GET_REPORT  = 0x2,
        I2C_HID_CMD_SET_REPORT  = 0x3,
        I2C_HID_CMD_GET_IDLE    = 0x4,
        I2C_HID_CMD_SET_IDLE    = 0x5,
        I2C_HID_CMD_GET_PROTO   = 0x6,
        I2C_HID_CMD_SET_PROTO   = 0x7,
        I2C_HID_CMD_SET_POWER   = 0x8,
};

#define I2C_HID_POWER_ON                0x0
#define I2C_HID_POWER_OFF               0x1

#define IICHID_RESET_TIMEOUT            5       /* seconds */

/*
 * Since interrupt resource acquisition is not always possible (in case of GPIO
 * interrupts) iichid now supports a sampling_mode.
 * Set dev.iichid.<unit>.sampling_rate_slow to a value greater then 0
 * to activate sampling. A value of 0 is possible but will not reset the
 * callout and, thereby, disable further report requests. Do not set the
 * sampling_rate_fast value too high as it may result in periodical lags of
 * cursor motion.
 */
#define IICHID_SAMPLING_RATE_FAST       80
#define IICHID_SAMPLING_RATE_SLOW       10
#define IICHID_SAMPLING_HYSTERESIS      16      /* ~ 2x fast / slow */

/* 5.1.1 - HID Descriptor Format */
struct i2c_hid_desc {
        uint16_t wHIDDescLength;
        uint16_t bcdVersion;
        uint16_t wReportDescLength;
        uint16_t wReportDescRegister;
        uint16_t wInputRegister;
        uint16_t wMaxInputLength;
        uint16_t wOutputRegister;
        uint16_t wMaxOutputLength;
        uint16_t wCommandRegister;
        uint16_t wDataRegister;
        uint16_t wVendorID;
        uint16_t wProductID;
        uint16_t wVersionID;
        uint32_t reserved;
} __packed;

#define IICHID_REG_NONE -1
#define IICHID_REG_ACPI (UINT16_MAX + 1)
#define IICHID_REG_ELAN 0x0001

static const struct iichid_id {
        char *id;
        int reg;
} iichid_ids[] = {
        { "ELAN0000",   IICHID_REG_ELAN },
        { "PNP0C50",    IICHID_REG_ACPI },
        { "ACPI0C50",   IICHID_REG_ACPI },
        { NULL,         0 },
};

enum iichid_powerstate_how {
        IICHID_PS_NULL,
        IICHID_PS_ON,
        IICHID_PS_OFF,
};

/*
 * Locking: no internal locks are used. To serialize access to shared members,
 * external iicbus lock should be taken.  That allows to make locking greatly
 * simple at the cost of running front interrupt handlers with locked bus.
 */
struct iichid_softc {
        device_t                dev;
        struct mtx              mtx;

        bool                    probe_done;
        int                     probe_result;

        struct hid_device_info  hw;
        uint16_t                addr;   /* Shifted left by 1 */
        struct i2c_hid_desc     desc;

        hid_intr_t              *intr_handler;
        void                    *intr_ctx;
        uint8_t                 *intr_buf;
        iichid_size_t           intr_bufsize;

        int                     irq_rid;
        struct resource         *irq_res;
        void                    *irq_cookie;

#ifdef IICHID_SAMPLING
        int                     sampling_rate_slow;     /* iicbus lock */
        int                     sampling_rate_fast;
        int                     sampling_hysteresis;
        int                     missing_samples;        /* iicbus lock */
        int                     dup_samples;            /* iicbus lock */
        iichid_size_t           dup_size;               /* iicbus lock */
        bool                    callout_setup;          /* iicbus lock */
        uint8_t                 *dup_buf;
        struct taskqueue        *taskqueue;
        struct timeout_task     sampling_task;          /* iicbus lock */
#endif

        struct task             suspend_task;
        bool                    open;                   /* iicbus lock */
        bool                    suspend;                /* iicbus lock */
        bool                    power_on;               /* iicbus lock */
        bool                    reset_acked;            /* iichid mtx */
};

static device_probe_t   iichid_probe;
static device_attach_t  iichid_attach;
static device_detach_t  iichid_detach;
static device_resume_t  iichid_resume;
static device_suspend_t iichid_suspend;

static void     iichid_suspend_task(void *, int);

#ifdef IICHID_SAMPLING
static int      iichid_setup_callout(struct iichid_softc *);
static int      iichid_reset_callout(struct iichid_softc *);
static void     iichid_teardown_callout(struct iichid_softc *);
#endif

static inline int
acpi_is_iichid(ACPI_HANDLE handle)
{
        const struct iichid_id *ids;
        UINT32  sta;
        int reg;

        for (ids = iichid_ids; ids->id != NULL; ids++) {
                if (acpi_MatchHid(handle, ids->id)) {
                        reg = ids->reg;
                        break;
                }
        }
        if (ids->id == NULL)
                return (IICHID_REG_NONE);

        /*
         * If no _STA method or if it failed, then assume that
         * the device is present.
         */
        if (ACPI_FAILURE(acpi_GetInteger(handle, "_STA", &sta)) ||
            ACPI_DEVICE_PRESENT(sta))
                return (reg);

        return (IICHID_REG_NONE);
}

static ACPI_STATUS
iichid_get_config_reg(ACPI_HANDLE handle, uint16_t *config_reg)
{
        ACPI_OBJECT *result;
        ACPI_BUFFER acpi_buf;
        ACPI_STATUS status;

        /*
         * function (_DSM) to be evaluated to retrieve the address of
         * the configuration register of the HID device.
         */
        /* 3cdff6f7-4267-4555-ad05-b30a3d8938de */
        static uint8_t dsm_guid[ACPI_UUID_LENGTH] = {
                0xF7, 0xF6, 0xDF, 0x3C, 0x67, 0x42, 0x55, 0x45,
                0xAD, 0x05, 0xB3, 0x0A, 0x3D, 0x89, 0x38, 0xDE,
        };

        status = acpi_EvaluateDSMTyped(handle, dsm_guid, 1, 1, NULL, &acpi_buf,
            ACPI_TYPE_INTEGER);
        if (ACPI_FAILURE(status)) {
                printf("%s: error evaluating _DSM\n", __func__);
                return (status);
        }
        result = (ACPI_OBJECT *) acpi_buf.Pointer;
        *config_reg = result->Integer.Value & 0xFFFF;

        AcpiOsFree(result);
        return (status);
}

static int
iichid_cmd_read(struct iichid_softc* sc, void *buf, iichid_size_t maxlen,
    iichid_size_t *actual_len)
{
        int error;

        /*
         * 6.1.3 - Retrieval of Input Reports
         * DEVICE returns the length (2 Bytes) and the entire Input Report.
         */

        memset(buf, 0xaa, 2);   // In case nothing gets read
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_RD, maxlen, buf },
        };

        if (!sc->reset_acked) {
                msgs[0].len = 2;
        }

        error = iicbus_transfer(sc->dev, msgs, nitems(msgs));
        if (error != 0)
                return (error);

        DPRINTFN(sc, 5, "%*D\n", msgs[0].len, msgs[0].buf, " ");

        uint16_t actlen = le16dec(buf);

        if (actlen == 0) {
                if (!sc->reset_acked) {
                        mtx_lock(&sc->mtx);
                        sc->reset_acked = true;
                        wakeup(&sc->reset_acked);
                        mtx_unlock(&sc->mtx);
                }
        }

        if (actlen <= 2 || actlen > maxlen) {
                actlen = 0;
        }
        if (actual_len != NULL) {
                *actual_len = actlen;
        }

        return (error);
}

static int
iichid_cmd_write(struct iichid_softc *sc, const void *buf, iichid_size_t len)
{
        /* 6.2.3 - Sending Output Reports. */
        uint8_t *cmdreg = (uint8_t *)&sc->desc.wOutputRegister;
        uint16_t replen = 2 + len;
        uint8_t cmd[4] = { cmdreg[0], cmdreg[1], replen & 0xFF, replen >> 8 };
        struct iic_msg msgs[] = {
            {sc->addr, IIC_M_WR | IIC_M_NOSTOP, sizeof(cmd), cmd},
            {sc->addr, IIC_M_WR | IIC_M_NOSTART, len, __DECONST(void *, buf)},
        };

        if (le16toh(sc->desc.wMaxOutputLength) == 0)
                return (IIC_ENOTSUPP);
        if (len < 2)
                return (IIC_ENOTSUPP);

        DPRINTF(sc, "HID command I2C_HID_CMD_WRITE (len %d): "
            "%*D\n", len, len, buf, " ");

        return (iicbus_transfer(sc->dev, msgs, nitems(msgs)));
}

static int
iichid_cmd_get_hid_desc(struct iichid_softc *sc, uint16_t config_reg,
    struct i2c_hid_desc *hid_desc)
{
        /*
         * 5.2.2 - HID Descriptor Retrieval
         * register is passed from the controller.
         */
        uint16_t cmd = htole16(config_reg);
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_WR | IIC_M_NOSTOP, 2, (uint8_t *)&cmd },
            { sc->addr, IIC_M_RD, sizeof(*hid_desc), (uint8_t *)hid_desc },
        };
        int error;

        DPRINTF(sc, "HID command I2C_HID_CMD_DESCR at 0x%x\n", config_reg);

        error = iicbus_transfer(sc->dev, msgs, nitems(msgs));
        if (error != 0)
                return (error);

        DPRINTF(sc, "HID descriptor: %*D\n",
            (int)sizeof(struct i2c_hid_desc), hid_desc, " ");

        return (0);
}

static int
iichid_set_power(struct iichid_softc *sc, uint8_t param)
{
        uint8_t *cmdreg = (uint8_t *)&sc->desc.wCommandRegister;
        uint8_t cmd[] = { cmdreg[0], cmdreg[1], param, I2C_HID_CMD_SET_POWER };
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_WR, sizeof(cmd), cmd },
        };

        DPRINTF(sc, "HID command I2C_HID_CMD_SET_POWER(%d)\n", param);

        return (iicbus_transfer(sc->dev, msgs, nitems(msgs)));
}

static int
iichid_reset(struct iichid_softc *sc)
{
        uint8_t *cmdreg = (uint8_t *)&sc->desc.wCommandRegister;
        uint8_t cmd[] = { cmdreg[0], cmdreg[1], 0, I2C_HID_CMD_RESET };
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_WR, sizeof(cmd), cmd },
        };

        DPRINTF(sc, "HID command I2C_HID_CMD_RESET\n");

        return (iicbus_transfer(sc->dev, msgs, nitems(msgs)));
}

static int
iichid_cmd_get_report_desc(struct iichid_softc* sc, void *buf,
    iichid_size_t len)
{
        uint16_t cmd = sc->desc.wReportDescRegister;
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_WR | IIC_M_NOSTOP, 2, (uint8_t *)&cmd },
            { sc->addr, IIC_M_RD, len, buf },
        };
        int error;

        DPRINTF(sc, "HID command I2C_HID_REPORT_DESCR at 0x%x with size %d\n",
            le16toh(cmd), len);

        error = iicbus_transfer(sc->dev, msgs, nitems(msgs));
        if (error != 0)
                return (error);

        DPRINTF(sc, "HID report descriptor: %*D\n", len, buf, " ");

        return (0);
}

static int
iichid_cmd_get_report(struct iichid_softc* sc, void *buf, iichid_size_t maxlen,
    iichid_size_t *actual_len, uint8_t type, uint8_t id)
{
        /*
         * 7.2.2.4 - "The protocol is optimized for Report < 15.  If a
         * report ID >= 15 is necessary, then the Report ID in the Low Byte
         * must be set to 1111 and a Third Byte is appended to the protocol.
         * This Third Byte contains the entire/actual report ID."
         */
        uint8_t *dtareg = (uint8_t *)&sc->desc.wDataRegister;
        uint8_t *cmdreg = (uint8_t *)&sc->desc.wCommandRegister;
        uint8_t cmd[] = {   /*________|______id>=15_____|______id<15______*/
                                                    cmdreg[0]              ,
                                                    cmdreg[1]              ,
                            (id >= 15 ? 15 | (type << 4): id | (type << 4)),
                                              I2C_HID_CMD_GET_REPORT       ,
                            (id >= 15 ?         id      :    dtareg[0]    ),
                            (id >= 15 ?    dtareg[0]    :    dtareg[1]    ),
                            (id >= 15 ?    dtareg[1]    :       0         ),
                        };
        int cmdlen    =     (id >= 15 ?         7       :       6         );
        uint8_t actbuf[2] = { 0, 0 };
        uint16_t actlen;
        int d, error;
        struct iic_msg msgs[] = {
            { sc->addr, IIC_M_WR | IIC_M_NOSTOP, cmdlen, cmd },
            { sc->addr, IIC_M_RD | IIC_M_NOSTOP, 2, actbuf },
            { sc->addr, IIC_M_RD | IIC_M_NOSTART, maxlen, buf },
        };

        if (maxlen == 0)
                return (EINVAL);

        DPRINTF(sc, "HID command I2C_HID_CMD_GET_REPORT %d "
            "(type %d, len %d)\n", id, type, maxlen);

        /*
         * 7.2.2.2 - Response will be a 2-byte length value, the report
         * id (1 byte, if defined in Report Descriptor), and then the report.
         */
        error = iicbus_transfer(sc->dev, msgs, nitems(msgs));
        if (error != 0)
                return (error);

        actlen = actbuf[0] | actbuf[1] << 8;
        if (actlen != maxlen + 2)
                DPRINTF(sc, "response size %d != expected length %d\n",
                    actlen, maxlen + 2);

        if (actlen <= 2 || actlen == 0xFFFF)
                return (ENOMSG);

        d = id != 0 ? *(uint8_t *)buf : 0;
        if (d != id) {
                DPRINTF(sc, "response report id %d != %d\n", d, id);
                return (EBADMSG);
        }

        actlen -= 2;
        if (actlen > maxlen)
                actlen = maxlen;
        if (actual_len != NULL)
                *actual_len = actlen;

        DPRINTF(sc, "response: %*D %*D\n", 2, actbuf, " ", actlen, buf, " ");

        return (0);
}

static int
iichid_cmd_set_report(struct iichid_softc* sc, const void *buf,
    iichid_size_t len, uint8_t type, uint8_t id)
{
        /*
         * 7.2.2.4 - "The protocol is optimized for Report < 15.  If a
         * report ID >= 15 is necessary, then the Report ID in the Low Byte
         * must be set to 1111 and a Third Byte is appended to the protocol.
         * This Third Byte contains the entire/actual report ID."
         */
        uint8_t *dtareg = (uint8_t *)&sc->desc.wDataRegister;
        uint8_t *cmdreg = (uint8_t *)&sc->desc.wCommandRegister;
        uint16_t replen = 2 + len;
        uint8_t cmd[] = {   /*________|______id>=15_____|______id<15______*/
                                                    cmdreg[0]              ,
                                                    cmdreg[1]              ,
                            (id >= 15 ? 15 | (type << 4): id | (type << 4)),
                                              I2C_HID_CMD_SET_REPORT       ,
                            (id >= 15 ?         id      :    dtareg[0]    ),
                            (id >= 15 ?    dtareg[0]    :    dtareg[1]    ),
                            (id >= 15 ?    dtareg[1]    :   replen & 0xff ),
                            (id >= 15 ?   replen & 0xff :   replen >> 8   ),
                            (id >= 15 ?   replen >> 8   :       0         ),
                        };
        int cmdlen    =     (id >= 15 ?         9       :       8         );
        struct iic_msg msgs[] = {
            {sc->addr, IIC_M_WR | IIC_M_NOSTOP, cmdlen, cmd},
            {sc->addr, IIC_M_WR | IIC_M_NOSTART, len, __DECONST(void *, buf)},
        };

        DPRINTF(sc, "HID command I2C_HID_CMD_SET_REPORT %d (type %d, len %d): "
            "%*D\n", id, type, len, len, buf, " ");

        return (iicbus_transfer(sc->dev, msgs, nitems(msgs)));
}

#ifdef IICHID_SAMPLING
static void
iichid_sampling_task(void *context, int pending)
{
        struct iichid_softc *sc;
        device_t parent;
        iichid_size_t actual;
        bool bus_requested;
        int error, rate;

        sc = context;
        parent = device_get_parent(sc->dev);

        bus_requested = false;
        if (iicbus_request_bus(parent, sc->dev, IIC_WAIT) != 0)
                goto rearm;
        bus_requested = true;

        if (!sc->power_on)
                goto out;

        error = iichid_cmd_read(sc, sc->intr_buf, sc->intr_bufsize, &actual);
        if (error == 0) {
                if (actual > 0) {
                        sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, actual - 2);
                        sc->missing_samples = 0;
                        if (sc->dup_size != actual ||
                            memcmp(sc->dup_buf, sc->intr_buf, actual) != 0) {
                                sc->dup_size = actual;
                                memcpy(sc->dup_buf, sc->intr_buf, actual);
                                sc->dup_samples = 0;
                        } else
                                ++sc->dup_samples;
                } else {
                        if (++sc->missing_samples == 1)
                                sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, 0);
                        sc->dup_samples = 0;
                }
        } else
                DPRINTF(sc, "read error occurred: %d\n", error);

rearm:
        if (sc->callout_setup && sc->sampling_rate_slow > 0) {
                if (sc->missing_samples >= sc->sampling_hysteresis ||
                    sc->dup_samples >= sc->sampling_hysteresis)
                        rate = sc->sampling_rate_slow;
                else
                        rate = sc->sampling_rate_fast;
                taskqueue_enqueue_timeout_sbt(sc->taskqueue, &sc->sampling_task,
                    SBT_1S / MAX(rate, 1), 0, C_PREL(2));
        }
out:
        if (bus_requested)
                iicbus_release_bus(parent, sc->dev);
}
#endif  /* IICHID_SAMPLING */

static void
iichid_intr(void *context)
{
        struct iichid_softc *sc;
        device_t parent;
        iichid_size_t actual;
        int error;

        sc = context;
        parent = device_get_parent(sc->dev);

        /*
         * Designware(IG4) driver-specific hack.
         * Requesting of an I2C bus with IIC_DONTWAIT parameter enables polled
         * mode in the driver, making possible iicbus_transfer execution from
         * interrupt handlers and callouts.
         */
        if (iicbus_request_bus(parent, sc->dev, IIC_DONTWAIT) != 0)
                return;

        /*
         * Reading of input reports of I2C devices residing in SLEEP state is
         * not allowed and often returns a garbage.  If a HOST needs to
         * communicate with the DEVICE it MUST issue a SET POWER command
         * (to ON) before any other command. As some hardware requires reads to
         * acknowledge interrupts we fetch only length header and discard it.
         */
        THREAD_SLEEPING_OK();
        error = iichid_cmd_read(sc, sc->intr_buf, sc->intr_bufsize, &actual);
        THREAD_NO_SLEEPING();
        if (error == 0) {
                if (sc->power_on && sc->open) {
                        if (actual != 0)
                                sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2,
                                    actual - 2);
                        else
                                DPRINTF(sc, "no data received\n");
                }
        } else
                DPRINTF(sc, "read error occurred: %d\n", error);

        iicbus_release_bus(parent, sc->dev);
}

static int
iichid_set_power_state(struct iichid_softc *sc,
     enum iichid_powerstate_how how_open,
     enum iichid_powerstate_how how_suspend)
{
        device_t parent;
        int error;
        int how_request;
        bool power_on;

        /*
         * Request iicbus early as sc->suspend and sc->power_on
         * are protected by iicbus internal lock.
         */
        parent = device_get_parent(sc->dev);
        /* Allow to interrupt open()/close() handlers by SIGINT */
        how_request = how_open == IICHID_PS_NULL ? IIC_WAIT : IIC_INTRWAIT;
        error = iicbus_request_bus(parent, sc->dev, how_request);
        if (error != 0)
                return (error);

        switch (how_open) {
        case IICHID_PS_ON:
                sc->open = true;
                break;
        case IICHID_PS_OFF:
                sc->open = false;
                break;
        case IICHID_PS_NULL:
        default:
                break;
        }

        switch (how_suspend) {
        case IICHID_PS_ON:
                sc->suspend = false;
                break;
        case IICHID_PS_OFF:
                sc->suspend = true;
                break;
        case IICHID_PS_NULL:
        default:
                break;
        }

        power_on = sc->open & !sc->suspend;

        if (power_on != sc->power_on) {
                error = iichid_set_power(sc,
                    power_on ? I2C_HID_POWER_ON : I2C_HID_POWER_OFF);

                sc->power_on = power_on;
#ifdef IICHID_SAMPLING
                if (sc->sampling_rate_slow >= 0 && sc->intr_handler != NULL) {
                        if (power_on) {
                                iichid_setup_callout(sc);
                                iichid_reset_callout(sc);
                        } else
                                iichid_teardown_callout(sc);
                }
#endif
        }

        iicbus_release_bus(parent, sc->dev);

        return (error);
}

static int
iichid_setup_interrupt(struct iichid_softc *sc)
{
        sc->irq_cookie = 0;

        int error = bus_setup_intr(sc->dev, sc->irq_res,
            INTR_TYPE_TTY|INTR_MPSAFE, NULL, iichid_intr, sc, &sc->irq_cookie);
        if (error != 0)
                DPRINTF(sc, "Could not setup interrupt handler\n");
        else
                DPRINTF(sc, "successfully setup interrupt\n");

        return (error);
}

static void
iichid_teardown_interrupt(struct iichid_softc *sc)
{
        if (sc->irq_cookie)
                bus_teardown_intr(sc->dev, sc->irq_res, sc->irq_cookie);

        sc->irq_cookie = 0;
}

#ifdef IICHID_SAMPLING
static int
iichid_setup_callout(struct iichid_softc *sc)
{

        if (sc->sampling_rate_slow < 0) {
                DPRINTF(sc, "sampling_rate is below 0, can't setup callout\n");
                return (EINVAL);
        }

        sc->callout_setup = true;
        DPRINTF(sc, "successfully setup callout\n");
        return (0);
}

static int
iichid_reset_callout(struct iichid_softc *sc)
{

        if (sc->sampling_rate_slow <= 0) {
                DPRINTF(sc, "sampling_rate is below or equal to 0, "
                    "can't reset callout\n");
                return (EINVAL);
        }

        if (!sc->callout_setup)
                return (EINVAL);

        /* Start with slow sampling. */
        sc->missing_samples = sc->sampling_hysteresis;
        sc->dup_samples = 0;
        sc->dup_size = 0;
        taskqueue_enqueue_timeout(sc->taskqueue, &sc->sampling_task, 0);

        return (0);
}

static void
iichid_teardown_callout(struct iichid_softc *sc)
{

        sc->callout_setup = false;
        taskqueue_cancel_timeout(sc->taskqueue, &sc->sampling_task, NULL);
        DPRINTF(sc, "tore callout down\n");
}

static int
iichid_sysctl_sampling_rate_handler(SYSCTL_HANDLER_ARGS)
{
        struct iichid_softc *sc;
        device_t parent;
        int error, oldval, value;

        sc = arg1;

        value = sc->sampling_rate_slow;
        error = sysctl_handle_int(oidp, &value, 0, req);

        if (error != 0 || req->newptr == NULL ||
            value == sc->sampling_rate_slow)
                return (error);

        /* Can't switch to interrupt mode if it is not supported. */
        if (sc->irq_res == NULL && value < 0)
                return (EINVAL);

        parent = device_get_parent(sc->dev);
        error = iicbus_request_bus(parent, sc->dev, IIC_WAIT);
        if (error != 0)
                return (iic2errno(error));

        oldval = sc->sampling_rate_slow;
        sc->sampling_rate_slow = value;

        if (oldval < 0 && value >= 0) {
                iichid_teardown_interrupt(sc);
                if (sc->power_on)
                        iichid_setup_callout(sc);
        } else if (oldval >= 0 && value < 0) {
                if (sc->power_on)
                        iichid_teardown_callout(sc);
                iichid_setup_interrupt(sc);
        }

        if (sc->power_on && value > 0)
                iichid_reset_callout(sc);

        iicbus_release_bus(parent, sc->dev);

        DPRINTF(sc, "new sampling_rate value: %d\n", value);

        return (0);
}
#endif /* IICHID_SAMPLING */

static void
iichid_intr_setup(device_t dev, device_t child __unused, hid_intr_t intr,
    void *context, struct hid_rdesc_info *rdesc)
{
        struct iichid_softc *sc;
        device_t parent;

        if (intr == NULL)
                return;

        sc = device_get_softc(dev);
        /*
         * Start with wMaxInputLength to follow HID-over-I2C specs. Than if
         * semi-HID device like ietp(4) requested changing of input buffer
         * size with report descriptor overloading, find the longest input
         * report in the descriptor, and add two for the length field.
         */
        rdesc->rdsize = rdesc->rdsize == 0 ?
            le16toh(sc->desc.wMaxInputLength) - 2 : rdesc->isize;
        /* Write and get/set_report sizes are limited by I2C-HID protocol. */
        rdesc->grsize = rdesc->srsize = IICHID_SIZE_MAX;
        rdesc->wrsize = IICHID_SIZE_MAX;

        parent = device_get_parent(sc->dev);
        iicbus_request_bus(parent, sc->dev, IIC_WAIT);

        sc->intr_handler = intr;
        sc->intr_ctx = context;
        sc->intr_bufsize = rdesc->rdsize + 2;
        sc->intr_buf = realloc(sc->intr_buf, sc->intr_bufsize,
            M_DEVBUF, M_WAITOK | M_ZERO);
#ifdef IICHID_SAMPLING
        sc->dup_buf = realloc(sc->dup_buf, sc->intr_bufsize,
            M_DEVBUF, M_WAITOK | M_ZERO);
        taskqueue_start_threads(&sc->taskqueue, 1, PI_TTY,
            "%s taskq", device_get_nameunit(sc->dev));
#endif
        iicbus_release_bus(parent, sc->dev);
}

static void
iichid_intr_unsetup(device_t dev, device_t child __unused)
{
#ifdef IICHID_SAMPLING
        struct iichid_softc *sc;

        sc = device_get_softc(dev);
        taskqueue_drain_all(sc->taskqueue);
#endif
}

static int
iichid_intr_start(device_t dev, device_t child __unused)
{
        struct iichid_softc *sc;

        sc = device_get_softc(dev);
        DPRINTF(sc, "iichid device open\n");
        if (!sc->open)
                iichid_set_power_state(sc, IICHID_PS_ON, IICHID_PS_NULL);

        return (0);
}

static int
iichid_intr_stop(device_t dev, device_t child __unused)
{
        struct iichid_softc *sc;

        sc = device_get_softc(dev);
        DPRINTF(sc, "iichid device close\n");
        /*
         * 8.2 - The HOST determines that there are no active applications
         * that are currently using the specific HID DEVICE.  The HOST
         * is recommended to issue a HIPO command to the DEVICE to force
         * the DEVICE in to a lower power state.
         */
        iichid_set_power_state(sc, IICHID_PS_OFF, IICHID_PS_NULL);

        return (0);
}

static void
iichid_intr_poll(device_t dev, device_t child __unused)
{
        struct iichid_softc *sc;
        iichid_size_t actual;
        int error;

        sc = device_get_softc(dev);
        error = iichid_cmd_read(sc, sc->intr_buf, sc->intr_bufsize, &actual);
        if (error == 0 && actual != 0)
                sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, actual);
}

/*
 * HID interface
 */
static int
iichid_get_rdesc(device_t dev, device_t child __unused, void *buf,
    hid_size_t len)
{
        struct iichid_softc *sc;
        int error;

        sc = device_get_softc(dev);
        error = iichid_cmd_get_report_desc(sc, buf, len);
        if (error)
                DPRINTF(sc, "failed to fetch report descriptor: %d\n", error);

        return (iic2errno(error));
}

static int
iichid_read(device_t dev, device_t child __unused, void *buf,
    hid_size_t maxlen, hid_size_t *actlen)
{
        struct iichid_softc *sc;
        device_t parent;
        uint8_t *tmpbuf;
        int error;

        if (maxlen > IICHID_SIZE_MAX)
                return (EMSGSIZE);
        sc = device_get_softc(dev);
        parent = device_get_parent(sc->dev);
        error = iicbus_request_bus(parent, sc->dev, IIC_WAIT);
        if (error == 0) {
                tmpbuf = malloc(maxlen + 2, M_DEVBUF, M_WAITOK | M_ZERO);
                error = iichid_cmd_read(sc, tmpbuf, maxlen + 2, actlen);
                iicbus_release_bus(parent, sc->dev);
                if (*actlen > 0)
                        memcpy(buf, tmpbuf + 2, *actlen);
                free(tmpbuf, M_DEVBUF);
        }
        return (iic2errno(error));
}

static int
iichid_write(device_t dev, device_t child __unused, const void *buf,
    hid_size_t len)
{
        struct iichid_softc *sc;

        if (len > IICHID_SIZE_MAX)
                return (EMSGSIZE);
        sc = device_get_softc(dev);
        return (iic2errno(iichid_cmd_write(sc, buf, len)));
}

static int
iichid_get_report(device_t dev, device_t child __unused, void *buf,
    hid_size_t maxlen, hid_size_t *actlen, uint8_t type, uint8_t id)
{
        struct iichid_softc *sc;

        if (maxlen > IICHID_SIZE_MAX)
                return (EMSGSIZE);
        sc = device_get_softc(dev);
        return (iic2errno(
            iichid_cmd_get_report(sc, buf, maxlen, actlen, type, id)));
}

static int
iichid_set_report(device_t dev, device_t child __unused, const void *buf,
    hid_size_t len, uint8_t type, uint8_t id)
{
        struct iichid_softc *sc;

        if (len > IICHID_SIZE_MAX)
                return (EMSGSIZE);
        sc = device_get_softc(dev);
        return (iic2errno(iichid_cmd_set_report(sc, buf, len, type, id)));
}

static int
iichid_set_idle(device_t dev, device_t child __unused,
    uint16_t duration, uint8_t id)
{
        return (ENOTSUP);
}

static int
iichid_set_protocol(device_t dev, device_t child __unused, uint16_t protocol)
{
        return (ENOTSUP);
}

static int
iichid_ioctl(device_t dev, device_t child __unused, unsigned long cmd,
    uintptr_t data)
{
        int error;

        switch (cmd) {
        case I2CRDWR:
                error = iic2errno(iicbus_transfer(dev,
                    ((struct iic_rdwr_data *)data)->msgs,
                    ((struct iic_rdwr_data *)data)->nmsgs));
                break;
        default:
                error = EINVAL;
        }

        return (error);
}

static int
iichid_fill_device_info(struct i2c_hid_desc *desc, ACPI_HANDLE handle,
    struct hid_device_info *hw)
{
        ACPI_DEVICE_INFO *device_info;

        hw->idBus = BUS_I2C;
        hw->idVendor = le16toh(desc->wVendorID);
        hw->idProduct = le16toh(desc->wProductID);
        hw->idVersion = le16toh(desc->wVersionID);

        /* get ACPI HID. It is a base part of the device name. */
        if (ACPI_FAILURE(AcpiGetObjectInfo(handle, &device_info)))
                return (ENXIO);

        if (device_info->Valid & ACPI_VALID_HID)
                strlcpy(hw->idPnP, device_info->HardwareId.String,
                    HID_PNP_ID_SIZE);
        snprintf(hw->name, sizeof(hw->name), "%s:%02lX %04X:%04X",
            (device_info->Valid & ACPI_VALID_HID) ?
            device_info->HardwareId.String : "Unknown",
            (device_info->Valid & ACPI_VALID_UID) ?
            strtoul(device_info->UniqueId.String, NULL, 10) : 0UL,
            le16toh(desc->wVendorID), le16toh(desc->wProductID));

        AcpiOsFree(device_info);

        strlcpy(hw->serial, "", sizeof(hw->serial));
        hw->rdescsize = le16toh(desc->wReportDescLength);
        if (desc->wOutputRegister == 0 || desc->wMaxOutputLength == 0)
                hid_add_dynamic_quirk(hw, HQ_NOWRITE);

        return (0);
}

static int
iichid_probe(device_t dev)
{
        struct iichid_softc *sc;
        ACPI_HANDLE handle;
        uint16_t config_reg;
        int error, reg;

        sc = device_get_softc(dev);
        sc->dev = dev;
        if (sc->probe_done)
                goto done;

        sc->probe_done = true;
        sc->probe_result = ENXIO;

        if (acpi_disabled("iichid"))
                return (ENXIO);

        sc->addr = iicbus_get_addr(dev) << 1;
        if (sc->addr == 0)
                return (ENXIO);

        handle = acpi_get_handle(dev);
        if (handle == NULL)
                return (ENXIO);

        reg = acpi_is_iichid(handle);
        if (reg == IICHID_REG_NONE)
                return (ENXIO);

        if (reg == IICHID_REG_ACPI) {
                if (ACPI_FAILURE(iichid_get_config_reg(handle, &config_reg)))
                        return (ENXIO);
        } else
                config_reg = (uint16_t)reg;

        DPRINTF(sc, "  IICbus addr       : 0x%02X\n", sc->addr >> 1);
        DPRINTF(sc, "  HID descriptor reg: 0x%02X\n", config_reg);

        error = iichid_cmd_get_hid_desc(sc, config_reg, &sc->desc);
        if (error) {
                DPRINTF(sc, "could not retrieve HID descriptor from the "
                    "device: %d\n", error);
                return (ENXIO);
        }

        if (le16toh(sc->desc.wHIDDescLength) != 30 ||
            le16toh(sc->desc.bcdVersion) != 0x100 ||
            le16toh(sc->desc.wMaxInputLength) < 2) {
                DPRINTF(sc, "HID descriptor is broken\n");
                return (ENXIO);
        }

        /* Setup hid_device_info so we can figure out quirks for the device. */
        if (iichid_fill_device_info(&sc->desc, handle, &sc->hw) != 0) {
                DPRINTF(sc, "error evaluating AcpiGetObjectInfo\n");
                return (ENXIO);
        }

        if (hid_test_quirk(&sc->hw, HQ_HID_IGNORE))
                return (ENXIO);

        sc->probe_result = BUS_PROBE_DEFAULT;
done:
        if (sc->probe_result <= BUS_PROBE_SPECIFIC)
                device_set_descf(dev, "%s I2C HID device", sc->hw.name);
        return (sc->probe_result);
}

static int
iichid_attach(device_t dev)
{
        struct iichid_softc *sc;
        device_t child;
        int error;

        sc = device_get_softc(dev);
        error = iichid_set_power(sc, I2C_HID_POWER_ON);
        if (error) {
                device_printf(dev, "failed to power on: %d\n", error);
                return (ENXIO);
        }
        sc->power_on = true;

        mtx_init(&sc->mtx, device_get_nameunit(dev), NULL, MTX_DEF);
        sc->intr_bufsize = le16toh(sc->desc.wMaxInputLength) - 2;
        sc->intr_buf = malloc(sc->intr_bufsize, M_DEVBUF, M_WAITOK | M_ZERO);
        TASK_INIT(&sc->suspend_task, 0, iichid_suspend_task, sc);
#ifdef IICHID_SAMPLING
        sc->taskqueue = taskqueue_create_fast("iichid_tq", M_WAITOK | M_ZERO,
            taskqueue_thread_enqueue, &sc->taskqueue);
        TIMEOUT_TASK_INIT(sc->taskqueue, &sc->sampling_task, 0,
            iichid_sampling_task, sc);

        sc->sampling_rate_slow = -1;
        sc->sampling_rate_fast = IICHID_SAMPLING_RATE_FAST;
        sc->sampling_hysteresis = IICHID_SAMPLING_HYSTERESIS;
        sc->dup_buf = malloc(sc->intr_bufsize, M_DEVBUF, M_WAITOK | M_ZERO);
#endif

        sc->irq_rid = 0;
        sc->irq_res = bus_alloc_resource_any(sc->dev, SYS_RES_IRQ,
            &sc->irq_rid, RF_ACTIVE);

        if (sc->irq_res != NULL) {
                DPRINTF(sc, "allocated irq at %p and rid %d\n",
                    sc->irq_res, sc->irq_rid);
                error = iichid_setup_interrupt(sc);
        }

        if (sc->irq_res == NULL || error != 0) {
#ifdef IICHID_SAMPLING
                device_printf(sc->dev,
                    "Using sampling mode\n");
                sc->sampling_rate_slow = IICHID_SAMPLING_RATE_SLOW;
#else
                device_printf(sc->dev, "Interrupt setup failed\n");
                if (sc->irq_res != NULL)
                        bus_release_resource(dev, SYS_RES_IRQ, sc->irq_rid,
                            sc->irq_res);
                iichid_detach(dev);
                error = ENXIO;
                goto done;
#endif
        }

#ifdef IICHID_SAMPLING
        SYSCTL_ADD_PROC(device_get_sysctl_ctx(sc->dev),
                SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev)),
                OID_AUTO, "sampling_rate_slow", CTLTYPE_INT | CTLFLAG_RWTUN,
                sc, 0, iichid_sysctl_sampling_rate_handler, "I",
                "idle sampling rate in num/second");
        SYSCTL_ADD_INT(device_get_sysctl_ctx(sc->dev),
                SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev)),
                OID_AUTO, "sampling_rate_fast", CTLFLAG_RWTUN,
                &sc->sampling_rate_fast, 0,
                "active sampling rate in num/second");
        SYSCTL_ADD_INT(device_get_sysctl_ctx(sc->dev),
                SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev)),
                OID_AUTO, "sampling_hysteresis", CTLFLAG_RWTUN,
                &sc->sampling_hysteresis, 0,
                "number of missing samples before enabling of slow mode");
        hid_add_dynamic_quirk(&sc->hw, HQ_IICHID_SAMPLING);
#endif /* IICHID_SAMPLING */

        /*
         * Windows driver sleeps for 1ms between the SET_POWER and RESET
         * commands. So we too as some devices may depend on this.
         */
        pause("iichid", (hz + 999) / 1000);

        error = iichid_reset(sc);
        if (error) {
                device_printf(dev, "failed to reset hardware: %d\n", error);
                iichid_detach(dev);
                error = ENXIO;
                goto done;
        }

        /* Wait for RESET response */
#ifdef IICHID_SAMPLING
        if (sc->sampling_rate_slow >= 0) {
                pause("iichid", (hz + 999) / 1000);
                (void)iichid_cmd_read(sc, sc->intr_buf, 0, NULL);
        } else
#endif /* IICHID_SAMPLING */
        {
                mtx_lock(&sc->mtx);
                if (!sc->reset_acked && !cold) {
                        error = mtx_sleep(&sc->reset_acked,  &sc->mtx, 0,
                            "iichid_reset", hz * IICHID_RESET_TIMEOUT);
                        if (error != 0)
                                device_printf(sc->dev,
                                    "Reset timeout expired\n");
                }
                mtx_unlock(&sc->mtx);
        }

        child = device_add_child(dev, "hidbus", DEVICE_UNIT_ANY);
        if (child == NULL) {
                device_printf(sc->dev, "Could not add I2C device\n");
                iichid_detach(dev);
                error = ENOMEM;
                goto done;
        }

        device_set_ivars(child, &sc->hw);
        bus_attach_children(dev);
        error = 0;
done:
        iicbus_request_bus(device_get_parent(dev), dev, IIC_WAIT);
        if (!sc->open) {
                (void)iichid_set_power(sc, I2C_HID_POWER_OFF);
                sc->power_on = false;
        }
        iicbus_release_bus(device_get_parent(dev), dev);
        return (error);
}

static int
iichid_detach(device_t dev)
{
        struct iichid_softc *sc;
        int error;

        sc = device_get_softc(dev);
        error = bus_generic_detach(dev);
        if (error)
                return (error);
        iichid_teardown_interrupt(sc);
        if (sc->irq_res != NULL)
                bus_release_resource(dev, SYS_RES_IRQ, sc->irq_rid,
                    sc->irq_res);
#ifdef IICHID_SAMPLING
        if (sc->taskqueue != NULL)
                taskqueue_free(sc->taskqueue);
        sc->taskqueue = NULL;
        free(sc->dup_buf, M_DEVBUF);
#endif
        free(sc->intr_buf, M_DEVBUF);
        mtx_destroy(&sc->mtx);
        return (0);
}

static void
iichid_suspend_task(void *context, int pending)
{
        struct iichid_softc *sc = context;

        iichid_teardown_interrupt(sc);
}

static int
iichid_suspend(device_t dev)
{
        struct iichid_softc *sc;
        int error;

        sc = device_get_softc(dev);
        (void)bus_generic_suspend(dev);
        /*
         * 8.2 - The HOST is going into a deep power optimized state and wishes
         * to put all the devices into a low power state also.  The HOST
         * is recommended to issue a HIPO command to the DEVICE to force
         * the DEVICE in to a lower power state.
         */
        DPRINTF(sc, "Suspend called, setting device to power_state 1\n");
        error = iichid_set_power_state(sc, IICHID_PS_NULL, IICHID_PS_OFF);
        if (error != 0)
                DPRINTF(sc, "Could not set power_state, error: %d\n", error);
        else
                DPRINTF(sc, "Successfully set power_state\n");

#ifdef IICHID_SAMPLING
        if (sc->sampling_rate_slow < 0)
#endif
        {
                /*
                 * bus_teardown_intr can not be executed right here as it wants
                 * to run on certain CPU to interacts with LAPIC while suspend
                 * thread is bound to CPU0. So run it from taskqueue context.
                 */
#ifdef IICHID_SAMPLING
#define suspend_thread  sc->taskqueue
#else
#define suspend_thread  taskqueue_thread
#endif
                taskqueue_enqueue(suspend_thread, &sc->suspend_task);
                taskqueue_drain(suspend_thread, &sc->suspend_task);
        }

        return (0);
}

static int
iichid_resume(device_t dev)
{
        struct iichid_softc *sc;
        int error;

        sc = device_get_softc(dev);
#ifdef IICHID_SAMPLING
        if (sc->sampling_rate_slow < 0)
#endif
                iichid_setup_interrupt(sc);

        DPRINTF(sc, "Resume called, setting device to power_state 0\n");
        error = iichid_set_power_state(sc, IICHID_PS_NULL, IICHID_PS_ON);
        if (error != 0)
                DPRINTF(sc, "Could not set power_state, error: %d\n", error);
        else
                DPRINTF(sc, "Successfully set power_state\n");
        (void)bus_generic_resume(dev);

        return (0);
}

static device_method_t iichid_methods[] = {
        DEVMETHOD(device_probe,         iichid_probe),
        DEVMETHOD(device_attach,        iichid_attach),
        DEVMETHOD(device_detach,        iichid_detach),
        DEVMETHOD(device_suspend,       iichid_suspend),
        DEVMETHOD(device_resume,        iichid_resume),

        DEVMETHOD(hid_intr_setup,       iichid_intr_setup),
        DEVMETHOD(hid_intr_unsetup,     iichid_intr_unsetup),
        DEVMETHOD(hid_intr_start,       iichid_intr_start),
        DEVMETHOD(hid_intr_stop,        iichid_intr_stop),
        DEVMETHOD(hid_intr_poll,        iichid_intr_poll),

        /* HID interface */
        DEVMETHOD(hid_get_rdesc,        iichid_get_rdesc),
        DEVMETHOD(hid_read,             iichid_read),
        DEVMETHOD(hid_write,            iichid_write),
        DEVMETHOD(hid_get_report,       iichid_get_report),
        DEVMETHOD(hid_set_report,       iichid_set_report),
        DEVMETHOD(hid_set_idle,         iichid_set_idle),
        DEVMETHOD(hid_set_protocol,     iichid_set_protocol),
        DEVMETHOD(hid_ioctl,            iichid_ioctl),

        DEVMETHOD_END
};

static driver_t iichid_driver = {
        .name = "iichid",
        .methods = iichid_methods,
        .size = sizeof(struct iichid_softc),
};

DRIVER_MODULE(iichid, iicbus, iichid_driver, NULL, NULL);
MODULE_DEPEND(iichid, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);
MODULE_DEPEND(iichid, acpi, 1, 1, 1);
MODULE_DEPEND(iichid, hid, 1, 1, 1);
MODULE_DEPEND(iichid, hidbus, 1, 1, 1);
MODULE_VERSION(iichid, 1);
IICBUS_ACPI_PNP_INFO(iichid_ids);