/*
 *  ec.c - ACPI Embedded Controller Driver (v2.2)
 *
 *  Copyright (C) 2001-2014 Intel Corporation
 *    Author: 2014       Lv Zheng <lv.zheng@intel.com>
 *            2006, 2007 Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
 *            2006       Denis Sadykov <denis.m.sadykov@intel.com>
 *            2004       Luming Yu <luming.yu@intel.com>
 *            2001, 2002 Andy Grover <andrew.grover@intel.com>
 *            2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2008      Alexey Starikovskiy <astarikovskiy@suse.de>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or (at
 *  your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

/* Uncomment next line to get verbose printout */
/* #define DEBUG */
#define pr_fmt(fmt) "ACPI : EC: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <asm/io.h>

#include "internal.h"

#define ACPI_EC_CLASS                   "embedded_controller"
#define ACPI_EC_DEVICE_NAME             "Embedded Controller"
#define ACPI_EC_FILE_INFO               "info"

/* EC status register */
#define ACPI_EC_FLAG_OBF        0x01    /* Output buffer full */
#define ACPI_EC_FLAG_IBF        0x02    /* Input buffer full */
#define ACPI_EC_FLAG_CMD        0x08    /* Input buffer contains a command */
#define ACPI_EC_FLAG_BURST      0x10    /* burst mode */
#define ACPI_EC_FLAG_SCI        0x20    /* EC-SCI occurred */

/* EC commands */
enum ec_command {
        ACPI_EC_COMMAND_READ = 0x80,
        ACPI_EC_COMMAND_WRITE = 0x81,
        ACPI_EC_BURST_ENABLE = 0x82,
        ACPI_EC_BURST_DISABLE = 0x83,
        ACPI_EC_COMMAND_QUERY = 0x84,
};

#define ACPI_EC_DELAY           500     /* Wait 500ms max. during EC ops */
#define ACPI_EC_UDELAY_GLK      1000    /* Wait 1ms max. to get global lock */
#define ACPI_EC_MSI_UDELAY      550     /* Wait 550us for MSI EC */
#define ACPI_EC_CLEAR_MAX       100     /* Maximum number of events to query
                                         * when trying to clear the EC */

enum {
        EC_FLAGS_QUERY_PENDING,         /* Query is pending */
        EC_FLAGS_GPE_STORM,             /* GPE storm detected */
        EC_FLAGS_HANDLERS_INSTALLED,    /* Handlers for GPE and
                                         * OpReg are installed */
        EC_FLAGS_BLOCKED,               /* Transactions are blocked */
};

#define ACPI_EC_COMMAND_POLL            0x01 /* Available for command byte */
#define ACPI_EC_COMMAND_COMPLETE        0x02 /* Completed last byte */

/* ec.c is compiled in acpi namespace so this shows up as acpi.ec_delay param */
static unsigned int ec_delay __read_mostly = ACPI_EC_DELAY;
module_param(ec_delay, uint, 0644);
MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");

/*
 * If the number of false interrupts per one transaction exceeds
 * this threshold, will think there is a GPE storm happened and
 * will disable the GPE for normal transaction.
 */
static unsigned int ec_storm_threshold  __read_mostly = 8;
module_param(ec_storm_threshold, uint, 0644);
MODULE_PARM_DESC(ec_storm_threshold, "Maxim false GPE numbers not considered as GPE storm");

struct acpi_ec_query_handler {
        struct list_head node;
        acpi_ec_query_func func;
        acpi_handle handle;
        void *data;
        u8 query_bit;
};

struct transaction {
        const u8 *wdata;
        u8 *rdata;
        unsigned short irq_count;
        u8 command;
        u8 wi;
        u8 ri;
        u8 wlen;
        u8 rlen;
        u8 flags;
};

struct acpi_ec *boot_ec, *first_ec;
EXPORT_SYMBOL(first_ec);

static int EC_FLAGS_MSI; /* Out-of-spec MSI controller */
static int EC_FLAGS_VALIDATE_ECDT; /* ASUStec ECDTs need to be validated */
static int EC_FLAGS_SKIP_DSDT_SCAN; /* Not all BIOS survive early DSDT scan */
static int EC_FLAGS_CLEAR_ON_RESUME; /* Needs acpi_ec_clear() on boot/resume */
static int EC_FLAGS_QUERY_HANDSHAKE; /* Needs QR_EC issued when SCI_EVT set */

/* --------------------------------------------------------------------------
 *                           Transaction Management
 * -------------------------------------------------------------------------- */

static inline u8 acpi_ec_read_status(struct acpi_ec *ec)
{
        u8 x = inb(ec->command_addr);

        pr_debug("EC_SC(R) = 0x%2.2x "
                 "SCI_EVT=%d BURST=%d CMD=%d IBF=%d OBF=%d\n",
                 x,
                 !!(x & ACPI_EC_FLAG_SCI),
                 !!(x & ACPI_EC_FLAG_BURST),
                 !!(x & ACPI_EC_FLAG_CMD),
                 !!(x & ACPI_EC_FLAG_IBF),
                 !!(x & ACPI_EC_FLAG_OBF));
        return x;
}

static inline u8 acpi_ec_read_data(struct acpi_ec *ec)
{
        u8 x = inb(ec->data_addr);

        pr_debug("EC_DATA(R) = 0x%2.2x\n", x);
        return x;
}

static inline void acpi_ec_write_cmd(struct acpi_ec *ec, u8 command)
{
        pr_debug("EC_SC(W) = 0x%2.2x\n", command);
        outb(command, ec->command_addr);
}

static inline void acpi_ec_write_data(struct acpi_ec *ec, u8 data)
{
        pr_debug("EC_DATA(W) = 0x%2.2x\n", data);
        outb(data, ec->data_addr);
}

#ifdef DEBUG
static const char *acpi_ec_cmd_string(u8 cmd)
{
        switch (cmd) {
        case 0x80:
                return "RD_EC";
        case 0x81:
                return "WR_EC";
        case 0x82:
                return "BE_EC";
        case 0x83:
                return "BD_EC";
        case 0x84:
                return "QR_EC";
        }
        return "UNKNOWN";
}
#else
#define acpi_ec_cmd_string(cmd)         "UNDEF"
#endif

static int ec_transaction_completed(struct acpi_ec *ec)
{
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&ec->lock, flags);
        if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_COMPLETE))
                ret = 1;
        spin_unlock_irqrestore(&ec->lock, flags);
        return ret;
}

static bool advance_transaction(struct acpi_ec *ec)
{
        struct transaction *t;
        u8 status;
        bool wakeup = false;

        pr_debug("===== %s (%d) =====\n",
                 in_interrupt() ? "IRQ" : "TASK", smp_processor_id());
        status = acpi_ec_read_status(ec);
        t = ec->curr;
        if (!t)
                goto err;
        if (t->flags & ACPI_EC_COMMAND_POLL) {
                if (t->wlen > t->wi) {
                        if ((status & ACPI_EC_FLAG_IBF) == 0)
                                acpi_ec_write_data(ec, t->wdata[t->wi++]);
                        else
                                goto err;
                } else if (t->rlen > t->ri) {
                        if ((status & ACPI_EC_FLAG_OBF) == 1) {
                                t->rdata[t->ri++] = acpi_ec_read_data(ec);
                                if (t->rlen == t->ri) {
                                        t->flags |= ACPI_EC_COMMAND_COMPLETE;
                                        if (t->command == ACPI_EC_COMMAND_QUERY)
                                                pr_debug("***** Command(%s) hardware completion *****\n",
                                                         acpi_ec_cmd_string(t->command));
                                        wakeup = true;
                                }
                        } else
                                goto err;
                } else if (t->wlen == t->wi &&
                           (status & ACPI_EC_FLAG_IBF) == 0) {
                        t->flags |= ACPI_EC_COMMAND_COMPLETE;
                        wakeup = true;
                }
                return wakeup;
        } else {
                if (EC_FLAGS_QUERY_HANDSHAKE &&
                    !(status & ACPI_EC_FLAG_SCI) &&
                    (t->command == ACPI_EC_COMMAND_QUERY)) {
                        t->flags |= ACPI_EC_COMMAND_POLL;
                        t->rdata[t->ri++] = 0x00;
                        t->flags |= ACPI_EC_COMMAND_COMPLETE;
                        pr_debug("***** Command(%s) software completion *****\n",
                                 acpi_ec_cmd_string(t->command));
                        wakeup = true;
                } else if ((status & ACPI_EC_FLAG_IBF) == 0) {
                        acpi_ec_write_cmd(ec, t->command);
                        t->flags |= ACPI_EC_COMMAND_POLL;
                } else
                        goto err;
                return wakeup;
        }
err:
        /*
         * If SCI bit is set, then don't think it's a false IRQ
         * otherwise will take a not handled IRQ as a false one.
         */
        if (!(status & ACPI_EC_FLAG_SCI)) {
                if (in_interrupt() && t)
                        ++t->irq_count;
        }
        return wakeup;
}

static void start_transaction(struct acpi_ec *ec)
{
        ec->curr->irq_count = ec->curr->wi = ec->curr->ri = 0;
        ec->curr->flags = 0;
        (void)advance_transaction(ec);
}

static int acpi_ec_sync_query(struct acpi_ec *ec, u8 *data);

static int ec_check_sci_sync(struct acpi_ec *ec, u8 state)
{
        if (state & ACPI_EC_FLAG_SCI) {
                if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
                        return acpi_ec_sync_query(ec, NULL);
        }
        return 0;
}

static int ec_poll(struct acpi_ec *ec)
{
        unsigned long flags;
        int repeat = 5; /* number of command restarts */

        while (repeat--) {
                unsigned long delay = jiffies +
                        msecs_to_jiffies(ec_delay);
                do {
                        /* don't sleep with disabled interrupts */
                        if (EC_FLAGS_MSI || irqs_disabled()) {
                                udelay(ACPI_EC_MSI_UDELAY);
                                if (ec_transaction_completed(ec))
                                        return 0;
                        } else {
                                if (wait_event_timeout(ec->wait,
                                                ec_transaction_completed(ec),
                                                msecs_to_jiffies(1)))
                                        return 0;
                        }
                        spin_lock_irqsave(&ec->lock, flags);
                        (void)advance_transaction(ec);
                        spin_unlock_irqrestore(&ec->lock, flags);
                } while (time_before(jiffies, delay));
                pr_debug("controller reset, restart transaction\n");
                spin_lock_irqsave(&ec->lock, flags);
                start_transaction(ec);
                spin_unlock_irqrestore(&ec->lock, flags);
        }
        return -ETIME;
}

static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
                                        struct transaction *t)
{
        unsigned long tmp;
        int ret = 0;

        if (EC_FLAGS_MSI)
                udelay(ACPI_EC_MSI_UDELAY);
        /* start transaction */
        spin_lock_irqsave(&ec->lock, tmp);
        /* following two actions should be kept atomic */
        ec->curr = t;
        pr_debug("***** Command(%s) started *****\n",
                 acpi_ec_cmd_string(t->command));
        start_transaction(ec);
        if (ec->curr->command == ACPI_EC_COMMAND_QUERY) {
                clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
                pr_debug("***** Event stopped *****\n");
        }
        spin_unlock_irqrestore(&ec->lock, tmp);
        ret = ec_poll(ec);
        spin_lock_irqsave(&ec->lock, tmp);
        pr_debug("***** Command(%s) stopped *****\n",
                 acpi_ec_cmd_string(t->command));
        ec->curr = NULL;
        spin_unlock_irqrestore(&ec->lock, tmp);
        return ret;
}

static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
{
        int status;
        u32 glk;

        if (!ec || (!t) || (t->wlen && !t->wdata) || (t->rlen && !t->rdata))
                return -EINVAL;
        if (t->rdata)
                memset(t->rdata, 0, t->rlen);
        mutex_lock(&ec->mutex);
        if (test_bit(EC_FLAGS_BLOCKED, &ec->flags)) {
                status = -EINVAL;
                goto unlock;
        }
        if (ec->global_lock) {
                status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
                if (ACPI_FAILURE(status)) {
                        status = -ENODEV;
                        goto unlock;
                }
        }
        /* disable GPE during transaction if storm is detected */
        if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
                /* It has to be disabled, so that it doesn't trigger. */
                acpi_disable_gpe(NULL, ec->gpe);
        }

        status = acpi_ec_transaction_unlocked(ec, t);

        /* check if we received SCI during transaction */
        ec_check_sci_sync(ec, acpi_ec_read_status(ec));
        if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
                msleep(1);
                /* It is safe to enable the GPE outside of the transaction. */
                acpi_enable_gpe(NULL, ec->gpe);
        } else if (t->irq_count > ec_storm_threshold) {
                pr_info("GPE storm detected(%d GPEs), "
                        "transactions will use polling mode\n",
                        t->irq_count);
                set_bit(EC_FLAGS_GPE_STORM, &ec->flags);
        }
        if (ec->global_lock)
                acpi_release_global_lock(glk);
unlock:
        mutex_unlock(&ec->mutex);
        return status;
}

static int acpi_ec_burst_enable(struct acpi_ec *ec)
{
        u8 d;
        struct transaction t = {.command = ACPI_EC_BURST_ENABLE,
                                .wdata = NULL, .rdata = &d,
                                .wlen = 0, .rlen = 1};

        return acpi_ec_transaction(ec, &t);
}

static int acpi_ec_burst_disable(struct acpi_ec *ec)
{
        struct transaction t = {.command = ACPI_EC_BURST_DISABLE,
                                .wdata = NULL, .rdata = NULL,
                                .wlen = 0, .rlen = 0};

        return (acpi_ec_read_status(ec) & ACPI_EC_FLAG_BURST) ?
                                acpi_ec_transaction(ec, &t) : 0;
}

static int acpi_ec_read(struct acpi_ec *ec, u8 address, u8 *data)
{
        int result;
        u8 d;
        struct transaction t = {.command = ACPI_EC_COMMAND_READ,
                                .wdata = &address, .rdata = &d,
                                .wlen = 1, .rlen = 1};

        result = acpi_ec_transaction(ec, &t);
        *data = d;
        return result;
}

static int acpi_ec_write(struct acpi_ec *ec, u8 address, u8 data)
{
        u8 wdata[2] = { address, data };
        struct transaction t = {.command = ACPI_EC_COMMAND_WRITE,
                                .wdata = wdata, .rdata = NULL,
                                .wlen = 2, .rlen = 0};

        return acpi_ec_transaction(ec, &t);
}

int ec_read(u8 addr, u8 *val)
{
        int err;
        u8 temp_data;

        if (!first_ec)
                return -ENODEV;

        err = acpi_ec_read(first_ec, addr, &temp_data);

        if (!err) {
                *val = temp_data;
                return 0;
        }
        return err;
}
EXPORT_SYMBOL(ec_read);

int ec_write(u8 addr, u8 val)
{
        int err;

        if (!first_ec)
                return -ENODEV;

        err = acpi_ec_write(first_ec, addr, val);

        return err;
}
EXPORT_SYMBOL(ec_write);

int ec_transaction(u8 command,
                   const u8 *wdata, unsigned wdata_len,
                   u8 *rdata, unsigned rdata_len)
{
        struct transaction t = {.command = command,
                                .wdata = wdata, .rdata = rdata,
                                .wlen = wdata_len, .rlen = rdata_len};

        if (!first_ec)
                return -ENODEV;

        return acpi_ec_transaction(first_ec, &t);
}
EXPORT_SYMBOL(ec_transaction);

/* Get the handle to the EC device */
acpi_handle ec_get_handle(void)
{
        if (!first_ec)
                return NULL;
        return first_ec->handle;
}
EXPORT_SYMBOL(ec_get_handle);

/*
 * Process _Q events that might have accumulated in the EC.
 * Run with locked ec mutex.
 */
static void acpi_ec_clear(struct acpi_ec *ec)
{
        int i, status;
        u8 value = 0;

        for (i = 0; i < ACPI_EC_CLEAR_MAX; i++) {
                status = acpi_ec_sync_query(ec, &value);
                if (status || !value)
                        break;
        }

        if (unlikely(i == ACPI_EC_CLEAR_MAX))
                pr_warn("Warning: Maximum of %d stale EC events cleared\n", i);
        else
                pr_info("%d stale EC events cleared\n", i);
}

void acpi_ec_block_transactions(void)
{
        struct acpi_ec *ec = first_ec;

        if (!ec)
                return;

        mutex_lock(&ec->mutex);
        /* Prevent transactions from being carried out */
        set_bit(EC_FLAGS_BLOCKED, &ec->flags);
        mutex_unlock(&ec->mutex);
}

void acpi_ec_unblock_transactions(void)
{
        struct acpi_ec *ec = first_ec;

        if (!ec)
                return;

        mutex_lock(&ec->mutex);
        /* Allow transactions to be carried out again */
        clear_bit(EC_FLAGS_BLOCKED, &ec->flags);

        if (EC_FLAGS_CLEAR_ON_RESUME)
                acpi_ec_clear(ec);

        mutex_unlock(&ec->mutex);
}

void acpi_ec_unblock_transactions_early(void)
{
        /*
         * Allow transactions to happen again (this function is called from
         * atomic context during wakeup, so we don't need to acquire the mutex).
         */
        if (first_ec)
                clear_bit(EC_FLAGS_BLOCKED, &first_ec->flags);
}

static int acpi_ec_query_unlocked(struct acpi_ec *ec, u8 *data)
{
        int result;
        u8 d;
        struct transaction t = {.command = ACPI_EC_COMMAND_QUERY,
                                .wdata = NULL, .rdata = &d,
                                .wlen = 0, .rlen = 1};

        if (!ec || !data)
                return -EINVAL;
        /*
         * Query the EC to find out which _Qxx method we need to evaluate.
         * Note that successful completion of the query causes the ACPI_EC_SCI
         * bit to be cleared (and thus clearing the interrupt source).
         */
        result = acpi_ec_transaction_unlocked(ec, &t);
        if (result)
                return result;
        if (!d)
                return -ENODATA;
        *data = d;
        return 0;
}

/* --------------------------------------------------------------------------
                                Event Management
   -------------------------------------------------------------------------- */
int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit,
                              acpi_handle handle, acpi_ec_query_func func,
                              void *data)
{
        struct acpi_ec_query_handler *handler =
            kzalloc(sizeof(struct acpi_ec_query_handler), GFP_KERNEL);

        if (!handler)
                return -ENOMEM;

        handler->query_bit = query_bit;
        handler->handle = handle;
        handler->func = func;
        handler->data = data;
        mutex_lock(&ec->mutex);
        list_add(&handler->node, &ec->list);
        mutex_unlock(&ec->mutex);
        return 0;
}
EXPORT_SYMBOL_GPL(acpi_ec_add_query_handler);

void acpi_ec_remove_query_handler(struct acpi_ec *ec, u8 query_bit)
{
        struct acpi_ec_query_handler *handler, *tmp;

        mutex_lock(&ec->mutex);
        list_for_each_entry_safe(handler, tmp, &ec->list, node) {
                if (query_bit == handler->query_bit) {
                        list_del(&handler->node);
                        kfree(handler);
                }
        }
        mutex_unlock(&ec->mutex);
}
EXPORT_SYMBOL_GPL(acpi_ec_remove_query_handler);

static void acpi_ec_run(void *cxt)
{
        struct acpi_ec_query_handler *handler = cxt;

        if (!handler)
                return;
        pr_debug("##### Query(0x%02x) started #####\n", handler->query_bit);
        if (handler->func)
                handler->func(handler->data);
        else if (handler->handle)
                acpi_evaluate_object(handler->handle, NULL, NULL, NULL);
        pr_debug("##### Query(0x%02x) stopped #####\n", handler->query_bit);
        kfree(handler);
}

static int acpi_ec_sync_query(struct acpi_ec *ec, u8 *data)
{
        u8 value = 0;
        int status;
        struct acpi_ec_query_handler *handler, *copy;

        status = acpi_ec_query_unlocked(ec, &value);
        if (data)
                *data = value;
        if (status)
                return status;

        list_for_each_entry(handler, &ec->list, node) {
                if (value == handler->query_bit) {
                        /* have custom handler for this bit */
                        copy = kmalloc(sizeof(*handler), GFP_KERNEL);
                        if (!copy)
                                return -ENOMEM;
                        memcpy(copy, handler, sizeof(*copy));
                        pr_debug("##### Query(0x%02x) scheduled #####\n",
                                 handler->query_bit);
                        return acpi_os_execute((copy->func) ?
                                OSL_NOTIFY_HANDLER : OSL_GPE_HANDLER,
                                acpi_ec_run, copy);
                }
        }
        return 0;
}

static void acpi_ec_gpe_query(void *ec_cxt)
{
        struct acpi_ec *ec = ec_cxt;

        if (!ec)
                return;
        mutex_lock(&ec->mutex);
        acpi_ec_sync_query(ec, NULL);
        mutex_unlock(&ec->mutex);
}

static int ec_check_sci(struct acpi_ec *ec, u8 state)
{
        if (state & ACPI_EC_FLAG_SCI) {
                if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
                        pr_debug("***** Event started *****\n");
                        return acpi_os_execute(OSL_NOTIFY_HANDLER,
                                acpi_ec_gpe_query, ec);
                }
        }
        return 0;
}

static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
        u32 gpe_number, void *data)
{
        unsigned long flags;
        struct acpi_ec *ec = data;

        spin_lock_irqsave(&ec->lock, flags);
        if (advance_transaction(ec))
                wake_up(&ec->wait);
        spin_unlock_irqrestore(&ec->lock, flags);
        ec_check_sci(ec, acpi_ec_read_status(ec));
        return ACPI_INTERRUPT_HANDLED | ACPI_REENABLE_GPE;
}

/* --------------------------------------------------------------------------
 *                           Address Space Management
 * -------------------------------------------------------------------------- */

static acpi_status
acpi_ec_space_handler(u32 function, acpi_physical_address address,
                      u32 bits, u64 *value64,
                      void *handler_context, void *region_context)
{
        struct acpi_ec *ec = handler_context;
        int result = 0, i, bytes = bits / 8;
        u8 *value = (u8 *)value64;

        if ((address > 0xFF) || !value || !handler_context)
                return AE_BAD_PARAMETER;

        if (function != ACPI_READ && function != ACPI_WRITE)
                return AE_BAD_PARAMETER;

        if (EC_FLAGS_MSI || bits > 8)
                acpi_ec_burst_enable(ec);

        for (i = 0; i < bytes; ++i, ++address, ++value)
                result = (function == ACPI_READ) ?
                        acpi_ec_read(ec, address, value) :
                        acpi_ec_write(ec, address, *value);

        if (EC_FLAGS_MSI || bits > 8)
                acpi_ec_burst_disable(ec);

        switch (result) {
        case -EINVAL:
                return AE_BAD_PARAMETER;
        case -ENODEV:
                return AE_NOT_FOUND;
        case -ETIME:
                return AE_TIME;
        default:
                return AE_OK;
        }
}

/* --------------------------------------------------------------------------
 *                             Driver Interface
 * -------------------------------------------------------------------------- */

static acpi_status
ec_parse_io_ports(struct acpi_resource *resource, void *context);

static struct acpi_ec *make_acpi_ec(void)
{
        struct acpi_ec *ec = kzalloc(sizeof(struct acpi_ec), GFP_KERNEL);

        if (!ec)
                return NULL;
        ec->flags = 1 << EC_FLAGS_QUERY_PENDING;
        mutex_init(&ec->mutex);
        init_waitqueue_head(&ec->wait);
        INIT_LIST_HEAD(&ec->list);
        spin_lock_init(&ec->lock);
        return ec;
}

static acpi_status
acpi_ec_register_query_methods(acpi_handle handle, u32 level,
                               void *context, void **return_value)
{
        char node_name[5];
        struct acpi_buffer buffer = { sizeof(node_name), node_name };
        struct acpi_ec *ec = context;
        int value = 0;
        acpi_status status;

        status = acpi_get_name(handle, ACPI_SINGLE_NAME, &buffer);

        if (ACPI_SUCCESS(status) && sscanf(node_name, "_Q%x", &value) == 1)
                acpi_ec_add_query_handler(ec, value, handle, NULL, NULL);
        return AE_OK;
}

static acpi_status
ec_parse_device(acpi_handle handle, u32 Level, void *context, void **retval)
{
        acpi_status status;
        unsigned long long tmp = 0;
        struct acpi_ec *ec = context;

        /* clear addr values, ec_parse_io_ports depend on it */
        ec->command_addr = ec->data_addr = 0;

        status = acpi_walk_resources(handle, METHOD_NAME__CRS,
                                     ec_parse_io_ports, ec);
        if (ACPI_FAILURE(status))
                return status;

        /* Get GPE bit assignment (EC events). */
        /* TODO: Add support for _GPE returning a package */
        status = acpi_evaluate_integer(handle, "_GPE", NULL, &tmp);
        if (ACPI_FAILURE(status))
                return status;
        ec->gpe = tmp;
        /* Use the global lock for all EC transactions? */
        tmp = 0;
        acpi_evaluate_integer(handle, "_GLK", NULL, &tmp);
        ec->global_lock = tmp;
        ec->handle = handle;
        return AE_CTRL_TERMINATE;
}

static int ec_install_handlers(struct acpi_ec *ec)
{
        acpi_status status;

        if (test_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags))
                return 0;
        status = acpi_install_gpe_handler(NULL, ec->gpe,
                                  ACPI_GPE_EDGE_TRIGGERED,
                                  &acpi_ec_gpe_handler, ec);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        acpi_enable_gpe(NULL, ec->gpe);
        status = acpi_install_address_space_handler(ec->handle,
                                                    ACPI_ADR_SPACE_EC,
                                                    &acpi_ec_space_handler,
                                                    NULL, ec);
        if (ACPI_FAILURE(status)) {
                if (status == AE_NOT_FOUND) {
                        /*
                         * Maybe OS fails in evaluating the _REG object.
                         * The AE_NOT_FOUND error will be ignored and OS
                         * continue to initialize EC.
                         */
                        pr_err("Fail in evaluating the _REG object"
                                " of EC device. Broken bios is suspected.\n");
                } else {
                        acpi_disable_gpe(NULL, ec->gpe);
                        acpi_remove_gpe_handler(NULL, ec->gpe,
                                &acpi_ec_gpe_handler);
                        return -ENODEV;
                }
        }

        set_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags);
        return 0;
}

static void ec_remove_handlers(struct acpi_ec *ec)
{
        if (!test_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags))
                return;
        acpi_disable_gpe(NULL, ec->gpe);
        if (ACPI_FAILURE(acpi_remove_address_space_handler(ec->handle,
                                ACPI_ADR_SPACE_EC, &acpi_ec_space_handler)))
                pr_err("failed to remove space handler\n");
        if (ACPI_FAILURE(acpi_remove_gpe_handler(NULL, ec->gpe,
                                &acpi_ec_gpe_handler)))
                pr_err("failed to remove gpe handler\n");
        clear_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags);
}

static int acpi_ec_add(struct acpi_device *device)
{
        struct acpi_ec *ec = NULL;
        int ret;

        strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
        strcpy(acpi_device_class(device), ACPI_EC_CLASS);

        /* Check for boot EC */
        if (boot_ec &&
            (boot_ec->handle == device->handle ||
             boot_ec->handle == ACPI_ROOT_OBJECT)) {
                ec = boot_ec;
                boot_ec = NULL;
        } else {
                ec = make_acpi_ec();
                if (!ec)
                        return -ENOMEM;
        }
        if (ec_parse_device(device->handle, 0, ec, NULL) !=
                AE_CTRL_TERMINATE) {
                        kfree(ec);
                        return -EINVAL;
        }

        /* Find and register all query methods */
        acpi_walk_namespace(ACPI_TYPE_METHOD, ec->handle, 1,
                            acpi_ec_register_query_methods, NULL, ec, NULL);

        if (!first_ec)
                first_ec = ec;
        device->driver_data = ec;

        ret = !!request_region(ec->data_addr, 1, "EC data");
        WARN(!ret, "Could not request EC data io port 0x%lx", ec->data_addr);
        ret = !!request_region(ec->command_addr, 1, "EC cmd");
        WARN(!ret, "Could not request EC cmd io port 0x%lx", ec->command_addr);

        pr_info("GPE = 0x%lx, I/O: command/status = 0x%lx, data = 0x%lx\n",
                          ec->gpe, ec->command_addr, ec->data_addr);

        ret = ec_install_handlers(ec);

        /* EC is fully operational, allow queries */
        clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);

        /* Clear stale _Q events if hardware might require that */
        if (EC_FLAGS_CLEAR_ON_RESUME) {
                mutex_lock(&ec->mutex);
                acpi_ec_clear(ec);
                mutex_unlock(&ec->mutex);
        }
        return ret;
}

static int acpi_ec_remove(struct acpi_device *device)
{
        struct acpi_ec *ec;
        struct acpi_ec_query_handler *handler, *tmp;

        if (!device)
                return -EINVAL;

        ec = acpi_driver_data(device);
        ec_remove_handlers(ec);
        mutex_lock(&ec->mutex);
        list_for_each_entry_safe(handler, tmp, &ec->list, node) {
                list_del(&handler->node);
                kfree(handler);
        }
        mutex_unlock(&ec->mutex);
        release_region(ec->data_addr, 1);
        release_region(ec->command_addr, 1);
        device->driver_data = NULL;
        if (ec == first_ec)
                first_ec = NULL;
        kfree(ec);
        return 0;
}

static acpi_status
ec_parse_io_ports(struct acpi_resource *resource, void *context)
{
        struct acpi_ec *ec = context;

        if (resource->type != ACPI_RESOURCE_TYPE_IO)
                return AE_OK;

        /*
         * The first address region returned is the data port, and
         * the second address region returned is the status/command
         * port.
         */
        if (ec->data_addr == 0)
                ec->data_addr = resource->data.io.minimum;
        else if (ec->command_addr == 0)
                ec->command_addr = resource->data.io.minimum;
        else
                return AE_CTRL_TERMINATE;

        return AE_OK;
}

int __init acpi_boot_ec_enable(void)
{
        if (!boot_ec || test_bit(EC_FLAGS_HANDLERS_INSTALLED, &boot_ec->flags))
                return 0;
        if (!ec_install_handlers(boot_ec)) {
                first_ec = boot_ec;
                return 0;
        }
        return -EFAULT;
}

static const struct acpi_device_id ec_device_ids[] = {
        {"PNP0C09", 0},
        {"", 0},
};

/* Some BIOS do not survive early DSDT scan, skip it */
static int ec_skip_dsdt_scan(const struct dmi_system_id *id)
{
        EC_FLAGS_SKIP_DSDT_SCAN = 1;
        return 0;
}

/* ASUStek often supplies us with broken ECDT, validate it */
static int ec_validate_ecdt(const struct dmi_system_id *id)
{
        EC_FLAGS_VALIDATE_ECDT = 1;
        return 0;
}

/* MSI EC needs special treatment, enable it */
static int ec_flag_msi(const struct dmi_system_id *id)
{
        pr_debug("Detected MSI hardware, enabling workarounds.\n");
        EC_FLAGS_MSI = 1;
        EC_FLAGS_VALIDATE_ECDT = 1;
        return 0;
}

/*
 * Clevo M720 notebook actually works ok with IRQ mode, if we lifted
 * the GPE storm threshold back to 20
 */
static int ec_enlarge_storm_threshold(const struct dmi_system_id *id)
{
        pr_debug("Setting the EC GPE storm threshold to 20\n");
        ec_storm_threshold  = 20;
        return 0;
}

/*
 * Acer EC firmware refuses to respond QR_EC when SCI_EVT is not set, for
 * which case, we complete the QR_EC without issuing it to the firmware.
 * https://bugzilla.kernel.org/show_bug.cgi?id=86211
 */
static int ec_flag_query_handshake(const struct dmi_system_id *id)
{
        pr_debug("Detected the EC firmware requiring QR_EC issued when SCI_EVT set\n");
        EC_FLAGS_QUERY_HANDSHAKE = 1;
        return 0;
}

/*
 * On some hardware it is necessary to clear events accumulated by the EC during
 * sleep. These ECs stop reporting GPEs until they are manually polled, if too
 * many events are accumulated. (e.g. Samsung Series 5/9 notebooks)
 *
 * https://bugzilla.kernel.org/show_bug.cgi?id=44161
 *
 * Ideally, the EC should also be instructed NOT to accumulate events during
 * sleep (which Windows seems to do somehow), but the interface to control this
 * behaviour is not known at this time.
 *
 * Models known to be affected are Samsung 530Uxx/535Uxx/540Uxx/550Pxx/900Xxx,
 * however it is very likely that other Samsung models are affected.
 *
 * On systems which don't accumulate _Q events during sleep, this extra check
 * should be harmless.
 */
static int ec_clear_on_resume(const struct dmi_system_id *id)
{
        pr_debug("Detected system needing EC poll on resume.\n");
        EC_FLAGS_CLEAR_ON_RESUME = 1;
        return 0;
}

static struct dmi_system_id ec_dmi_table[] __initdata = {
        {
        ec_skip_dsdt_scan, "Compal JFL92", {
        DMI_MATCH(DMI_BIOS_VENDOR, "COMPAL"),
        DMI_MATCH(DMI_BOARD_NAME, "JFL92") }, NULL},
        {
        ec_flag_msi, "MSI hardware", {
        DMI_MATCH(DMI_BIOS_VENDOR, "Micro-Star")}, NULL},
        {
        ec_flag_msi, "MSI hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star")}, NULL},
        {
        ec_flag_msi, "MSI hardware", {
        DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-Star")}, NULL},
        {
        ec_flag_msi, "MSI hardware", {
        DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-STAR")}, NULL},
        {
        ec_flag_msi, "Quanta hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
        DMI_MATCH(DMI_PRODUCT_NAME, "TW8/SW8/DW8"),}, NULL},
        {
        ec_flag_msi, "Quanta hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
        DMI_MATCH(DMI_PRODUCT_NAME, "TW9/SW9"),}, NULL},
        {
        ec_flag_msi, "Clevo W350etq", {
        DMI_MATCH(DMI_SYS_VENDOR, "CLEVO CO."),
        DMI_MATCH(DMI_PRODUCT_NAME, "W35_37ET"),}, NULL},
        {
        ec_validate_ecdt, "ASUS hardware", {
        DMI_MATCH(DMI_BIOS_VENDOR, "ASUS") }, NULL},
        {
        ec_validate_ecdt, "ASUS hardware", {
        DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTeK Computer Inc.") }, NULL},
        {
        ec_enlarge_storm_threshold, "CLEVO hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "CLEVO Co."),
        DMI_MATCH(DMI_PRODUCT_NAME, "M720T/M730T"),}, NULL},
        {
        ec_skip_dsdt_scan, "HP Folio 13", {
        DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
        DMI_MATCH(DMI_PRODUCT_NAME, "HP Folio 13"),}, NULL},
        {
        ec_validate_ecdt, "ASUS hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "ASUSTek Computer Inc."),
        DMI_MATCH(DMI_PRODUCT_NAME, "L4R"),}, NULL},
        {
        ec_clear_on_resume, "Samsung hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD.")}, NULL},
        {
        ec_flag_query_handshake, "Acer hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "Acer"), }, NULL},
        {},
};

int __init acpi_ec_ecdt_probe(void)
{
        acpi_status status;
        struct acpi_ec *saved_ec = NULL;
        struct acpi_table_ecdt *ecdt_ptr;

        boot_ec = make_acpi_ec();
        if (!boot_ec)
                return -ENOMEM;
        /*
         * Generate a boot ec context
         */
        dmi_check_system(ec_dmi_table);
        status = acpi_get_table(ACPI_SIG_ECDT, 1,
                                (struct acpi_table_header **)&ecdt_ptr);
        if (ACPI_SUCCESS(status)) {
                pr_info("EC description table is found, configuring boot EC\n");
                boot_ec->command_addr = ecdt_ptr->control.address;
                boot_ec->data_addr = ecdt_ptr->data.address;
                boot_ec->gpe = ecdt_ptr->gpe;
                boot_ec->handle = ACPI_ROOT_OBJECT;
                acpi_get_handle(ACPI_ROOT_OBJECT, ecdt_ptr->id,
                                &boot_ec->handle);
                /* Don't trust ECDT, which comes from ASUSTek */
                if (!EC_FLAGS_VALIDATE_ECDT)
                        goto install;
                saved_ec = kmemdup(boot_ec, sizeof(struct acpi_ec), GFP_KERNEL);
                if (!saved_ec)
                        return -ENOMEM;
        /* fall through */
        }

        if (EC_FLAGS_SKIP_DSDT_SCAN) {
                kfree(saved_ec);
                return -ENODEV;
        }

        /* This workaround is needed only on some broken machines,
         * which require early EC, but fail to provide ECDT */
        pr_debug("Look up EC in DSDT\n");
        status = acpi_get_devices(ec_device_ids[0].id, ec_parse_device,
                                        boot_ec, NULL);
        /* Check that acpi_get_devices actually find something */
        if (ACPI_FAILURE(status) || !boot_ec->handle)
                goto error;
        if (saved_ec) {
                /* try to find good ECDT from ASUSTek */
                if (saved_ec->command_addr != boot_ec->command_addr ||
                    saved_ec->data_addr != boot_ec->data_addr ||
                    saved_ec->gpe != boot_ec->gpe ||
                    saved_ec->handle != boot_ec->handle)
                        pr_info("ASUSTek keeps feeding us with broken "
                        "ECDT tables, which are very hard to workaround. "
                        "Trying to use DSDT EC info instead. Please send "
                        "output of acpidump to linux-acpi@vger.kernel.org\n");
                kfree(saved_ec);
                saved_ec = NULL;
        } else {
                /* We really need to limit this workaround, the only ASUS,
                * which needs it, has fake EC._INI method, so use it as flag.
                * Keep boot_ec struct as it will be needed soon.
                */
                if (!dmi_name_in_vendors("ASUS") ||
                    !acpi_has_method(boot_ec->handle, "_INI"))
                        return -ENODEV;
        }
install:
        if (!ec_install_handlers(boot_ec)) {
                first_ec = boot_ec;
                return 0;
        }
error:
        kfree(boot_ec);
        kfree(saved_ec);
        boot_ec = NULL;
        return -ENODEV;
}

static struct acpi_driver acpi_ec_driver = {
        .name = "ec",
        .class = ACPI_EC_CLASS,
        .ids = ec_device_ids,
        .ops = {
                .add = acpi_ec_add,
                .remove = acpi_ec_remove,
                },
};

int __init acpi_ec_init(void)
{
        int result = 0;

        /* Now register the driver for the EC */
        result = acpi_bus_register_driver(&acpi_ec_driver);
        if (result < 0)
                return -ENODEV;

        return result;
}

/* EC driver currently not unloadable */
#if 0
static void __exit acpi_ec_exit(void)
{

        acpi_bus_unregister_driver(&acpi_ec_driver);
}
#endif  /* 0 */