// SPDX-License-Identifier: GPL-2.0+
/*
 * ipmi_ssif.c
 *
 * The interface to the IPMI driver for SMBus access to a SMBus
 * compliant device.  Called SSIF by the IPMI spec.
 *
 * Author: Intel Corporation
 *         Todd Davis <todd.c.davis@intel.com>
 *
 * Rewritten by Corey Minyard <minyard@acm.org> to support the
 * non-blocking I2C interface, add support for multi-part
 * transactions, add PEC support, and general clenaup.
 *
 * Copyright 2003 Intel Corporation
 * Copyright 2005 MontaVista Software
 */

/*
 * This file holds the "policy" for the interface to the SSIF state
 * machine.  It does the configuration, handles timers and interrupts,
 * and drives the real SSIF state machine.
 */

#define pr_fmt(fmt) "ipmi_ssif: " fmt
#define dev_fmt(fmt) "ipmi_ssif: " fmt

#if defined(MODVERSIONS)
#include <linux/modversions.h>
#endif

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/timer.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/i2c.h>
#include <linux/ipmi_smi.h>
#include <linux/init.h>
#include <linux/dmi.h>
#include <linux/kthread.h>
#include <linux/acpi.h>
#include <linux/ctype.h>
#include <linux/time64.h>
#include "ipmi_dmi.h"

#define DEVICE_NAME "ipmi_ssif"

#define IPMI_GET_SYSTEM_INTERFACE_CAPABILITIES_CMD      0x57

#define SSIF_IPMI_REQUEST                       2
#define SSIF_IPMI_MULTI_PART_REQUEST_START      6
#define SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE     7
#define SSIF_IPMI_MULTI_PART_REQUEST_END        8
#define SSIF_IPMI_RESPONSE                      3
#define SSIF_IPMI_MULTI_PART_RESPONSE_MIDDLE    9

/* ssif_debug is a bit-field
 *      SSIF_DEBUG_MSG -        commands and their responses
 *      SSIF_DEBUG_STATES -     message states
 *      SSIF_DEBUG_TIMING -      Measure times between events in the driver
 */
#define SSIF_DEBUG_TIMING       4
#define SSIF_DEBUG_STATE        2
#define SSIF_DEBUG_MSG          1
#define SSIF_NODEBUG            0
#define SSIF_DEFAULT_DEBUG      (SSIF_NODEBUG)

/*
 * Timer values
 */
#define SSIF_MSG_USEC           20000   /* 20ms between message tries. */
#define SSIF_MSG_PART_USEC      5000    /* 5ms for a message part */

/* How many times to we retry sending/receiving the message. */
#define SSIF_SEND_RETRIES       5
#define SSIF_RECV_RETRIES       250

#define SSIF_MSG_MSEC           (SSIF_MSG_USEC / 1000)
#define SSIF_MSG_JIFFIES        ((SSIF_MSG_USEC * 1000) / TICK_NSEC)
#define SSIF_MSG_PART_JIFFIES   ((SSIF_MSG_PART_USEC * 1000) / TICK_NSEC)

/*
 * Timeout for the watch, only used for get flag timer.
 */
#define SSIF_WATCH_MSG_TIMEOUT          msecs_to_jiffies(10)
#define SSIF_WATCH_WATCHDOG_TIMEOUT     msecs_to_jiffies(250)

enum ssif_intf_state {
        SSIF_NORMAL,
        SSIF_GETTING_FLAGS,
        SSIF_GETTING_EVENTS,
        SSIF_CLEARING_FLAGS,
        SSIF_GETTING_MESSAGES,
        /* FIXME - add watchdog stuff. */
};

#define SSIF_IDLE(ssif)  ((ssif)->ssif_state == SSIF_NORMAL \
                          && (ssif)->curr_msg == NULL)

/*
 * Indexes into stats[] in ssif_info below.
 */
enum ssif_stat_indexes {
        /* Number of total messages sent. */
        SSIF_STAT_sent_messages = 0,

        /*
         * Number of message parts sent.  Messages may be broken into
         * parts if they are long.
         */
        SSIF_STAT_sent_messages_parts,

        /*
         * Number of time a message was retried.
         */
        SSIF_STAT_send_retries,

        /*
         * Number of times the send of a message failed.
         */
        SSIF_STAT_send_errors,

        /*
         * Number of message responses received.
         */
        SSIF_STAT_received_messages,

        /*
         * Number of message fragments received.
         */
        SSIF_STAT_received_message_parts,

        /*
         * Number of times the receive of a message was retried.
         */
        SSIF_STAT_receive_retries,

        /*
         * Number of errors receiving messages.
         */
        SSIF_STAT_receive_errors,

        /*
         * Number of times a flag fetch was requested.
         */
        SSIF_STAT_flag_fetches,

        /*
         * Number of times the hardware didn't follow the state machine.
         */
        SSIF_STAT_hosed,

        /*
         * Number of received events.
         */
        SSIF_STAT_events,

        /* Number of asyncronous messages received. */
        SSIF_STAT_incoming_messages,

        /* Number of watchdog pretimeouts. */
        SSIF_STAT_watchdog_pretimeouts,

        /* Number of alers received. */
        SSIF_STAT_alerts,

        /* Always add statistics before this value, it must be last. */
        SSIF_NUM_STATS
};

struct ssif_addr_info {
        struct i2c_board_info binfo;
        char *adapter_name;
        int debug;
        int slave_addr;
        enum ipmi_addr_src addr_src;
        union ipmi_smi_info_union addr_info;
        struct device *dev;
        struct i2c_client *client;

        struct mutex clients_mutex;
        struct list_head clients;

        struct list_head link;
};

struct ssif_info;

typedef void (*ssif_i2c_done)(struct ssif_info *ssif_info, int result,
                             unsigned char *data, unsigned int len);

struct ssif_info {
        struct ipmi_smi     *intf;
        spinlock_t          lock;
        struct ipmi_smi_msg *waiting_msg;
        struct ipmi_smi_msg *curr_msg;
        enum ssif_intf_state ssif_state;
        unsigned long       ssif_debug;

        struct ipmi_smi_handlers handlers;

        enum ipmi_addr_src addr_source; /* ACPI, PCI, SMBIOS, hardcode, etc. */
        union ipmi_smi_info_union addr_info;

        /*
         * Flags from the last GET_MSG_FLAGS command, used when an ATTN
         * is set to hold the flags until we are done handling everything
         * from the flags.
         */
#define RECEIVE_MSG_AVAIL       0x01
#define EVENT_MSG_BUFFER_FULL   0x02
#define WDT_PRE_TIMEOUT_INT     0x08
        unsigned char       msg_flags;

        u8                  global_enables;
        bool                has_event_buffer;
        bool                supports_alert;

        /*
         * Used to tell what we should do with alerts.  If we are
         * waiting on a response, read the data immediately.
         */
        bool                got_alert;
        bool                waiting_alert;

        /*
         * If set to true, this will request events the next time the
         * state machine is idle.
         */
        bool                req_events;

        /*
         * If set to true, this will request flags the next time the
         * state machine is idle.
         */
        bool                req_flags;

        /*
         * Used to perform timer operations when run-to-completion
         * mode is on.  This is a countdown timer.
         */
        int                 rtc_us_timer;

        /* Used for sending/receiving data.  +1 for the length. */
        unsigned char data[IPMI_MAX_MSG_LENGTH + 1];
        unsigned int  data_len;

        /* Temp receive buffer, gets copied into data. */
        unsigned char recv[I2C_SMBUS_BLOCK_MAX];

        struct i2c_client *client;
        ssif_i2c_done done_handler;

        /* Thread interface handling */
        struct task_struct *thread;
        struct completion wake_thread;
        bool stopping;
        int i2c_read_write;
        int i2c_command;
        unsigned char *i2c_data;
        unsigned int i2c_size;

        struct timer_list retry_timer;
        int retries_left;

        long watch_timeout;             /* Timeout for flags check, 0 if off. */
        struct timer_list watch_timer;  /* Flag fetch timer. */

        /* Info from SSIF cmd */
        unsigned char max_xmit_msg_size;
        unsigned char max_recv_msg_size;
        bool cmd8_works; /* See test_multipart_messages() for details. */
        unsigned int  multi_support;
        int           supports_pec;

#define SSIF_NO_MULTI           0
#define SSIF_MULTI_2_PART       1
#define SSIF_MULTI_n_PART       2
        unsigned char *multi_data;
        unsigned int  multi_len;
        unsigned int  multi_pos;

        atomic_t stats[SSIF_NUM_STATS];
};

#define ssif_inc_stat(ssif, stat) \
        atomic_inc(&(ssif)->stats[SSIF_STAT_ ## stat])
#define ssif_get_stat(ssif, stat) \
        ((unsigned int) atomic_read(&(ssif)->stats[SSIF_STAT_ ## stat]))

static bool initialized;
static bool platform_registered;

static void return_hosed_msg(struct ssif_info *ssif_info,
                             struct ipmi_smi_msg *msg);
static void start_next_msg(struct ssif_info *ssif_info, unsigned long *flags);
static int start_send(struct ssif_info *ssif_info,
                      unsigned char   *data,
                      unsigned int    len);

static unsigned long *ipmi_ssif_lock_cond(struct ssif_info *ssif_info,
                                          unsigned long *flags)
        __acquires(&ssif_info->lock)
{
        spin_lock_irqsave(&ssif_info->lock, *flags);
        return flags;
}

static void ipmi_ssif_unlock_cond(struct ssif_info *ssif_info,
                                  unsigned long *flags)
        __releases(&ssif_info->lock)
{
        spin_unlock_irqrestore(&ssif_info->lock, *flags);
}

static void deliver_recv_msg(struct ssif_info *ssif_info,
                             struct ipmi_smi_msg *msg)
{
        if (msg->rsp_size < 0) {
                return_hosed_msg(ssif_info, msg);
                dev_err(&ssif_info->client->dev,
                        "%s: Malformed message: rsp_size = %d\n",
                       __func__, msg->rsp_size);
        } else {
                ipmi_smi_msg_received(ssif_info->intf, msg);
        }
}

static void return_hosed_msg(struct ssif_info *ssif_info,
                             struct ipmi_smi_msg *msg)
{
        ssif_inc_stat(ssif_info, hosed);

        /* Make it a response */
        msg->rsp[0] = msg->data[0] | 4;
        msg->rsp[1] = msg->data[1];
        msg->rsp[2] = 0xFF; /* Unknown error. */
        msg->rsp_size = 3;

        deliver_recv_msg(ssif_info, msg);
}

/*
 * Must be called with the message lock held.  This will release the
 * message lock.  Note that the caller will check SSIF_IDLE and start a
 * new operation, so there is no need to check for new messages to
 * start in here.
 */
static void start_clear_flags(struct ssif_info *ssif_info, unsigned long *flags)
{
        unsigned char msg[3];

        ssif_info->msg_flags &= ~WDT_PRE_TIMEOUT_INT;
        ssif_info->ssif_state = SSIF_CLEARING_FLAGS;
        ipmi_ssif_unlock_cond(ssif_info, flags);

        /* Make sure the watchdog pre-timeout flag is not set at startup. */
        msg[0] = (IPMI_NETFN_APP_REQUEST << 2);
        msg[1] = IPMI_CLEAR_MSG_FLAGS_CMD;
        msg[2] = WDT_PRE_TIMEOUT_INT;

        if (start_send(ssif_info, msg, 3) != 0) {
                /* Error, just go to normal state. */
                ssif_info->ssif_state = SSIF_NORMAL;
        }
}

static void start_flag_fetch(struct ssif_info *ssif_info, unsigned long *flags)
{
        unsigned char mb[2];

        ssif_info->req_flags = false;
        ssif_info->ssif_state = SSIF_GETTING_FLAGS;
        ipmi_ssif_unlock_cond(ssif_info, flags);

        mb[0] = (IPMI_NETFN_APP_REQUEST << 2);
        mb[1] = IPMI_GET_MSG_FLAGS_CMD;
        if (start_send(ssif_info, mb, 2) != 0)
                ssif_info->ssif_state = SSIF_NORMAL;
}

static void check_start_send(struct ssif_info *ssif_info, unsigned long *flags,
                             struct ipmi_smi_msg *msg)
{
        if (start_send(ssif_info, msg->data, msg->data_size) != 0) {
                unsigned long oflags;

                flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
                ssif_info->curr_msg = NULL;
                ssif_info->ssif_state = SSIF_NORMAL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
                ipmi_free_smi_msg(msg);
        }
}

static void start_event_fetch(struct ssif_info *ssif_info, unsigned long *flags)
{
        struct ipmi_smi_msg *msg;

        ssif_info->req_events = false;

        msg = ipmi_alloc_smi_msg();
        if (!msg) {
                ssif_info->ssif_state = SSIF_NORMAL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
                return;
        }

        ssif_info->curr_msg = msg;
        ssif_info->ssif_state = SSIF_GETTING_EVENTS;
        ipmi_ssif_unlock_cond(ssif_info, flags);

        msg->data[0] = (IPMI_NETFN_APP_REQUEST << 2);
        msg->data[1] = IPMI_READ_EVENT_MSG_BUFFER_CMD;
        msg->data_size = 2;

        check_start_send(ssif_info, flags, msg);
}

static void start_recv_msg_fetch(struct ssif_info *ssif_info,
                                 unsigned long *flags)
{
        struct ipmi_smi_msg *msg;

        msg = ipmi_alloc_smi_msg();
        if (!msg) {
                ssif_info->ssif_state = SSIF_NORMAL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
                return;
        }

        ssif_info->curr_msg = msg;
        ssif_info->ssif_state = SSIF_GETTING_MESSAGES;
        ipmi_ssif_unlock_cond(ssif_info, flags);

        msg->data[0] = (IPMI_NETFN_APP_REQUEST << 2);
        msg->data[1] = IPMI_GET_MSG_CMD;
        msg->data_size = 2;

        check_start_send(ssif_info, flags, msg);
}

/*
 * Must be called with the message lock held.  This will release the
 * message lock.  Note that the caller will check SSIF_IDLE and start a
 * new operation, so there is no need to check for new messages to
 * start in here.
 */
static void handle_flags(struct ssif_info *ssif_info, unsigned long *flags)
{
        if (ssif_info->msg_flags & WDT_PRE_TIMEOUT_INT) {
                /* Watchdog pre-timeout */
                ssif_inc_stat(ssif_info, watchdog_pretimeouts);
                start_clear_flags(ssif_info, flags);
                ipmi_smi_watchdog_pretimeout(ssif_info->intf);
        } else if (ssif_info->msg_flags & RECEIVE_MSG_AVAIL)
                /* Messages available. */
                start_recv_msg_fetch(ssif_info, flags);
        else if (ssif_info->msg_flags & EVENT_MSG_BUFFER_FULL)
                /* Events available. */
                start_event_fetch(ssif_info, flags);
        else {
                ssif_info->ssif_state = SSIF_NORMAL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
        }
}

static int ipmi_ssif_thread(void *data)
{
        struct ssif_info *ssif_info = data;

        while (!kthread_should_stop()) {
                int result;

                /* Wait for something to do */
                result = wait_for_completion_interruptible(
                                                &ssif_info->wake_thread);
                if (ssif_info->stopping)
                        break;
                if (result == -ERESTARTSYS)
                        continue;
                init_completion(&ssif_info->wake_thread);

                if (ssif_info->i2c_read_write == I2C_SMBUS_WRITE) {
                        result = i2c_smbus_write_block_data(
                                ssif_info->client, ssif_info->i2c_command,
                                ssif_info->i2c_data[0],
                                ssif_info->i2c_data + 1);
                        ssif_info->done_handler(ssif_info, result, NULL, 0);
                } else {
                        result = i2c_smbus_read_block_data(
                                ssif_info->client, ssif_info->i2c_command,
                                ssif_info->i2c_data);
                        if (result < 0)
                                ssif_info->done_handler(ssif_info, result,
                                                        NULL, 0);
                        else
                                ssif_info->done_handler(ssif_info, 0,
                                                        ssif_info->i2c_data,
                                                        result);
                }
        }

        return 0;
}

static void ssif_i2c_send(struct ssif_info *ssif_info,
                        ssif_i2c_done handler,
                        int read_write, int command,
                        unsigned char *data, unsigned int size)
{
        ssif_info->done_handler = handler;

        ssif_info->i2c_read_write = read_write;
        ssif_info->i2c_command = command;
        ssif_info->i2c_data = data;
        ssif_info->i2c_size = size;
        complete(&ssif_info->wake_thread);
}


static void msg_done_handler(struct ssif_info *ssif_info, int result,
                             unsigned char *data, unsigned int len);

static void start_get(struct ssif_info *ssif_info)
{
        ssif_info->rtc_us_timer = 0;
        ssif_info->multi_pos = 0;

        ssif_i2c_send(ssif_info, msg_done_handler, I2C_SMBUS_READ,
                  SSIF_IPMI_RESPONSE,
                  ssif_info->recv, I2C_SMBUS_BLOCK_DATA);
}

static void retry_timeout(struct timer_list *t)
{
        struct ssif_info *ssif_info = from_timer(ssif_info, t, retry_timer);
        unsigned long oflags, *flags;
        bool waiting;

        if (ssif_info->stopping)
                return;

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        waiting = ssif_info->waiting_alert;
        ssif_info->waiting_alert = false;
        ipmi_ssif_unlock_cond(ssif_info, flags);

        if (waiting)
                start_get(ssif_info);
}

static void watch_timeout(struct timer_list *t)
{
        struct ssif_info *ssif_info = from_timer(ssif_info, t, watch_timer);
        unsigned long oflags, *flags;

        if (ssif_info->stopping)
                return;

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        if (ssif_info->watch_timeout) {
                mod_timer(&ssif_info->watch_timer,
                          jiffies + ssif_info->watch_timeout);
                if (SSIF_IDLE(ssif_info)) {
                        start_flag_fetch(ssif_info, flags); /* Releases lock */
                        return;
                }
                ssif_info->req_flags = true;
        }
        ipmi_ssif_unlock_cond(ssif_info, flags);
}

static void ssif_alert(struct i2c_client *client, enum i2c_alert_protocol type,
                       unsigned int data)
{
        struct ssif_info *ssif_info = i2c_get_clientdata(client);
        unsigned long oflags, *flags;
        bool do_get = false;

        if (type != I2C_PROTOCOL_SMBUS_ALERT)
                return;

        ssif_inc_stat(ssif_info, alerts);

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        if (ssif_info->waiting_alert) {
                ssif_info->waiting_alert = false;
                del_timer(&ssif_info->retry_timer);
                do_get = true;
        } else if (ssif_info->curr_msg) {
                ssif_info->got_alert = true;
        }
        ipmi_ssif_unlock_cond(ssif_info, flags);
        if (do_get)
                start_get(ssif_info);
}

static int start_resend(struct ssif_info *ssif_info);

static void msg_done_handler(struct ssif_info *ssif_info, int result,
                             unsigned char *data, unsigned int len)
{
        struct ipmi_smi_msg *msg;
        unsigned long oflags, *flags;

        /*
         * We are single-threaded here, so no need for a lock until we
         * start messing with driver states or the queues.
         */

        if (result < 0) {
                ssif_info->retries_left--;
                if (ssif_info->retries_left > 0) {
                        ssif_inc_stat(ssif_info, receive_retries);

                        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
                        ssif_info->waiting_alert = true;
                        ssif_info->rtc_us_timer = SSIF_MSG_USEC;
                        if (!ssif_info->stopping)
                                mod_timer(&ssif_info->retry_timer,
                                          jiffies + SSIF_MSG_JIFFIES);
                        ipmi_ssif_unlock_cond(ssif_info, flags);
                        return;
                }

                ssif_inc_stat(ssif_info, receive_errors);

                if  (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                        dev_dbg(&ssif_info->client->dev,
                                "%s: Error %d\n", __func__, result);
                len = 0;
                goto continue_op;
        }

        if ((len > 1) && (ssif_info->multi_pos == 0)
                                && (data[0] == 0x00) && (data[1] == 0x01)) {
                /* Start of multi-part read.  Start the next transaction. */
                int i;

                ssif_inc_stat(ssif_info, received_message_parts);

                /* Remove the multi-part read marker. */
                len -= 2;
                data += 2;
                for (i = 0; i < len; i++)
                        ssif_info->data[i] = data[i];
                ssif_info->multi_len = len;
                ssif_info->multi_pos = 1;

                ssif_i2c_send(ssif_info, msg_done_handler, I2C_SMBUS_READ,
                         SSIF_IPMI_MULTI_PART_RESPONSE_MIDDLE,
                         ssif_info->recv, I2C_SMBUS_BLOCK_DATA);
                return;
        } else if (ssif_info->multi_pos) {
                /* Middle of multi-part read.  Start the next transaction. */
                int i;
                unsigned char blocknum;

                if (len == 0) {
                        result = -EIO;
                        if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                                dev_dbg(&ssif_info->client->dev,
                                        "Middle message with no data\n");

                        goto continue_op;
                }

                blocknum = data[0];
                len--;
                data++;

                if (blocknum != 0xff && len != 31) {
                    /* All blocks but the last must have 31 data bytes. */
                        result = -EIO;
                        if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                                dev_dbg(&ssif_info->client->dev,
                                        "Received middle message <31\n");

                        goto continue_op;
                }

                if (ssif_info->multi_len + len > IPMI_MAX_MSG_LENGTH) {
                        /* Received message too big, abort the operation. */
                        result = -E2BIG;
                        if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                                dev_dbg(&ssif_info->client->dev,
                                        "Received message too big\n");

                        goto continue_op;
                }

                for (i = 0; i < len; i++)
                        ssif_info->data[i + ssif_info->multi_len] = data[i];
                ssif_info->multi_len += len;
                if (blocknum == 0xff) {
                        /* End of read */
                        len = ssif_info->multi_len;
                        data = ssif_info->data;
                } else if (blocknum + 1 != ssif_info->multi_pos) {
                        /*
                         * Out of sequence block, just abort.  Block
                         * numbers start at zero for the second block,
                         * but multi_pos starts at one, so the +1.
                         */
                        if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                                dev_dbg(&ssif_info->client->dev,
                                        "Received message out of sequence, expected %u, got %u\n",
                                        ssif_info->multi_pos - 1, blocknum);
                        result = -EIO;
                } else {
                        ssif_inc_stat(ssif_info, received_message_parts);

                        ssif_info->multi_pos++;

                        ssif_i2c_send(ssif_info, msg_done_handler,
                                  I2C_SMBUS_READ,
                                  SSIF_IPMI_MULTI_PART_RESPONSE_MIDDLE,
                                  ssif_info->recv,
                                  I2C_SMBUS_BLOCK_DATA);
                        return;
                }
        }

 continue_op:
        if (result < 0) {
                ssif_inc_stat(ssif_info, receive_errors);
        } else {
                ssif_inc_stat(ssif_info, received_messages);
                ssif_inc_stat(ssif_info, received_message_parts);
        }

        if (ssif_info->ssif_debug & SSIF_DEBUG_STATE)
                dev_dbg(&ssif_info->client->dev,
                        "DONE 1: state = %d, result=%d\n",
                        ssif_info->ssif_state, result);

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        msg = ssif_info->curr_msg;
        if (msg) {
                if (data) {
                        if (len > IPMI_MAX_MSG_LENGTH)
                                len = IPMI_MAX_MSG_LENGTH;
                        memcpy(msg->rsp, data, len);
                } else {
                        len = 0;
                }
                msg->rsp_size = len;
                ssif_info->curr_msg = NULL;
        }

        switch (ssif_info->ssif_state) {
        case SSIF_NORMAL:
                ipmi_ssif_unlock_cond(ssif_info, flags);
                if (!msg)
                        break;

                if (result < 0)
                        return_hosed_msg(ssif_info, msg);
                else
                        deliver_recv_msg(ssif_info, msg);
                break;

        case SSIF_GETTING_FLAGS:
                /* We got the flags from the SSIF, now handle them. */
                if ((result < 0) || (len < 4) || (data[2] != 0)) {
                        /*
                         * Error fetching flags, or invalid length,
                         * just give up for now.
                         */
                        ssif_info->ssif_state = SSIF_NORMAL;
                        ipmi_ssif_unlock_cond(ssif_info, flags);
                        dev_warn(&ssif_info->client->dev,
                                 "Error getting flags: %d %d, %x\n",
                                 result, len, (len >= 3) ? data[2] : 0);
                } else if (data[0] != (IPMI_NETFN_APP_REQUEST | 1) << 2
                           || data[1] != IPMI_GET_MSG_FLAGS_CMD) {
                        /*
                         * Don't abort here, maybe it was a queued
                         * response to a previous command.
                         */
                        ipmi_ssif_unlock_cond(ssif_info, flags);
                        dev_warn(&ssif_info->client->dev,
                                 "Invalid response getting flags: %x %x\n",
                                 data[0], data[1]);
                } else {
                        ssif_inc_stat(ssif_info, flag_fetches);
                        ssif_info->msg_flags = data[3];
                        handle_flags(ssif_info, flags);
                }
                break;

        case SSIF_CLEARING_FLAGS:
                /* We cleared the flags. */
                if ((result < 0) || (len < 3) || (data[2] != 0)) {
                        /* Error clearing flags */
                        dev_warn(&ssif_info->client->dev,
                                 "Error clearing flags: %d %d, %x\n",
                                 result, len, (len >= 3) ? data[2] : 0);
                } else if (data[0] != (IPMI_NETFN_APP_REQUEST | 1) << 2
                           || data[1] != IPMI_CLEAR_MSG_FLAGS_CMD) {
                        dev_warn(&ssif_info->client->dev,
                                 "Invalid response clearing flags: %x %x\n",
                                 data[0], data[1]);
                }
                ssif_info->ssif_state = SSIF_NORMAL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
                break;

        case SSIF_GETTING_EVENTS:
                if ((result < 0) || (len < 3) || (msg->rsp[2] != 0)) {
                        /* Error getting event, probably done. */
                        msg->done(msg);

                        /* Take off the event flag. */
                        ssif_info->msg_flags &= ~EVENT_MSG_BUFFER_FULL;
                        handle_flags(ssif_info, flags);
                } else if (msg->rsp[0] != (IPMI_NETFN_APP_REQUEST | 1) << 2
                           || msg->rsp[1] != IPMI_READ_EVENT_MSG_BUFFER_CMD) {
                        dev_warn(&ssif_info->client->dev,
                                 "Invalid response getting events: %x %x\n",
                                 msg->rsp[0], msg->rsp[1]);
                        msg->done(msg);
                        /* Take off the event flag. */
                        ssif_info->msg_flags &= ~EVENT_MSG_BUFFER_FULL;
                        handle_flags(ssif_info, flags);
                } else {
                        handle_flags(ssif_info, flags);
                        ssif_inc_stat(ssif_info, events);
                        deliver_recv_msg(ssif_info, msg);
                }
                break;

        case SSIF_GETTING_MESSAGES:
                if ((result < 0) || (len < 3) || (msg->rsp[2] != 0)) {
                        /* Error getting event, probably done. */
                        msg->done(msg);

                        /* Take off the msg flag. */
                        ssif_info->msg_flags &= ~RECEIVE_MSG_AVAIL;
                        handle_flags(ssif_info, flags);
                } else if (msg->rsp[0] != (IPMI_NETFN_APP_REQUEST | 1) << 2
                           || msg->rsp[1] != IPMI_GET_MSG_CMD) {
                        dev_warn(&ssif_info->client->dev,
                                 "Invalid response clearing flags: %x %x\n",
                                 msg->rsp[0], msg->rsp[1]);
                        msg->done(msg);

                        /* Take off the msg flag. */
                        ssif_info->msg_flags &= ~RECEIVE_MSG_AVAIL;
                        handle_flags(ssif_info, flags);
                } else {
                        ssif_inc_stat(ssif_info, incoming_messages);
                        handle_flags(ssif_info, flags);
                        deliver_recv_msg(ssif_info, msg);
                }
                break;
        }

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        if (SSIF_IDLE(ssif_info) && !ssif_info->stopping) {
                if (ssif_info->req_events)
                        start_event_fetch(ssif_info, flags);
                else if (ssif_info->req_flags)
                        start_flag_fetch(ssif_info, flags);
                else
                        start_next_msg(ssif_info, flags);
        } else
                ipmi_ssif_unlock_cond(ssif_info, flags);

        if (ssif_info->ssif_debug & SSIF_DEBUG_STATE)
                dev_dbg(&ssif_info->client->dev,
                        "DONE 2: state = %d.\n", ssif_info->ssif_state);
}

static void msg_written_handler(struct ssif_info *ssif_info, int result,
                                unsigned char *data, unsigned int len)
{
        /* We are single-threaded here, so no need for a lock. */
        if (result < 0) {
                ssif_info->retries_left--;
                if (ssif_info->retries_left > 0) {
                        if (!start_resend(ssif_info)) {
                                ssif_inc_stat(ssif_info, send_retries);
                                return;
                        }
                        /* request failed, just return the error. */
                        ssif_inc_stat(ssif_info, send_errors);

                        if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                                dev_dbg(&ssif_info->client->dev,
                                        "%s: Out of retries\n", __func__);
                        msg_done_handler(ssif_info, -EIO, NULL, 0);
                        return;
                }

                ssif_inc_stat(ssif_info, send_errors);

                /*
                 * Got an error on transmit, let the done routine
                 * handle it.
                 */
                if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
                        dev_dbg(&ssif_info->client->dev,
                                "%s: Error  %d\n", __func__, result);

                msg_done_handler(ssif_info, result, NULL, 0);
                return;
        }

        if (ssif_info->multi_data) {
                /*
                 * In the middle of a multi-data write.  See the comment
                 * in the SSIF_MULTI_n_PART case in the probe function
                 * for details on the intricacies of this.
                 */
                int left, to_write;
                unsigned char *data_to_send;
                unsigned char cmd;

                ssif_inc_stat(ssif_info, sent_messages_parts);

                left = ssif_info->multi_len - ssif_info->multi_pos;
                to_write = left;
                if (to_write > 32)
                        to_write = 32;
                /* Length byte. */
                ssif_info->multi_data[ssif_info->multi_pos] = to_write;
                data_to_send = ssif_info->multi_data + ssif_info->multi_pos;
                ssif_info->multi_pos += to_write;
                cmd = SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE;
                if (ssif_info->cmd8_works) {
                        if (left == to_write) {
                                cmd = SSIF_IPMI_MULTI_PART_REQUEST_END;
                                ssif_info->multi_data = NULL;
                        }
                } else if (to_write < 32) {
                        ssif_info->multi_data = NULL;
                }

                ssif_i2c_send(ssif_info, msg_written_handler,
                          I2C_SMBUS_WRITE, cmd,
                          data_to_send, I2C_SMBUS_BLOCK_DATA);
        } else {
                /* Ready to request the result. */
                unsigned long oflags, *flags;

                ssif_inc_stat(ssif_info, sent_messages);
                ssif_inc_stat(ssif_info, sent_messages_parts);

                flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
                if (ssif_info->got_alert) {
                        /* The result is already ready, just start it. */
                        ssif_info->got_alert = false;
                        ipmi_ssif_unlock_cond(ssif_info, flags);
                        start_get(ssif_info);
                } else {
                        /* Wait a jiffie then request the next message */
                        ssif_info->waiting_alert = true;
                        ssif_info->retries_left = SSIF_RECV_RETRIES;
                        ssif_info->rtc_us_timer = SSIF_MSG_PART_USEC;
                        if (!ssif_info->stopping)
                                mod_timer(&ssif_info->retry_timer,
                                          jiffies + SSIF_MSG_PART_JIFFIES);
                        ipmi_ssif_unlock_cond(ssif_info, flags);
                }
        }
}

static int start_resend(struct ssif_info *ssif_info)
{
        int command;

        ssif_info->got_alert = false;

        if (ssif_info->data_len > 32) {
                command = SSIF_IPMI_MULTI_PART_REQUEST_START;
                ssif_info->multi_data = ssif_info->data;
                ssif_info->multi_len = ssif_info->data_len;
                /*
                 * Subtle thing, this is 32, not 33, because we will
                 * overwrite the thing at position 32 (which was just
                 * transmitted) with the new length.
                 */
                ssif_info->multi_pos = 32;
                ssif_info->data[0] = 32;
        } else {
                ssif_info->multi_data = NULL;
                command = SSIF_IPMI_REQUEST;
                ssif_info->data[0] = ssif_info->data_len;
        }

        ssif_i2c_send(ssif_info, msg_written_handler, I2C_SMBUS_WRITE,
                   command, ssif_info->data, I2C_SMBUS_BLOCK_DATA);

        return 0;
}

static int start_send(struct ssif_info *ssif_info,
                      unsigned char   *data,
                      unsigned int    len)
{
        if (len > IPMI_MAX_MSG_LENGTH)
                return -E2BIG;
        if (len > ssif_info->max_xmit_msg_size)
                return -E2BIG;

        ssif_info->retries_left = SSIF_SEND_RETRIES;
        memcpy(ssif_info->data + 1, data, len);
        ssif_info->data_len = len;
        return start_resend(ssif_info);
}

/* Must be called with the message lock held. */
static void start_next_msg(struct ssif_info *ssif_info, unsigned long *flags)
{
        struct ipmi_smi_msg *msg;
        unsigned long oflags;

 restart:
        if (!SSIF_IDLE(ssif_info)) {
                ipmi_ssif_unlock_cond(ssif_info, flags);
                return;
        }

        if (!ssif_info->waiting_msg) {
                ssif_info->curr_msg = NULL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
        } else {
                int rv;

                ssif_info->curr_msg = ssif_info->waiting_msg;
                ssif_info->waiting_msg = NULL;
                ipmi_ssif_unlock_cond(ssif_info, flags);
                rv = start_send(ssif_info,
                                ssif_info->curr_msg->data,
                                ssif_info->curr_msg->data_size);
                if (rv) {
                        msg = ssif_info->curr_msg;
                        ssif_info->curr_msg = NULL;
                        return_hosed_msg(ssif_info, msg);
                        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
                        goto restart;
                }
        }
}

static void sender(void                *send_info,
                   struct ipmi_smi_msg *msg)
{
        struct ssif_info *ssif_info = (struct ssif_info *) send_info;
        unsigned long oflags, *flags;

        BUG_ON(ssif_info->waiting_msg);
        ssif_info->waiting_msg = msg;

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        start_next_msg(ssif_info, flags);

        if (ssif_info->ssif_debug & SSIF_DEBUG_TIMING) {
                struct timespec64 t;

                ktime_get_real_ts64(&t);
                dev_dbg(&ssif_info->client->dev,
                        "**Enqueue %02x %02x: %lld.%6.6ld\n",
                        msg->data[0], msg->data[1],
                        (long long)t.tv_sec, (long)t.tv_nsec / NSEC_PER_USEC);
        }
}

static int get_smi_info(void *send_info, struct ipmi_smi_info *data)
{
        struct ssif_info *ssif_info = send_info;

        data->addr_src = ssif_info->addr_source;
        data->dev = &ssif_info->client->dev;
        data->addr_info = ssif_info->addr_info;
        get_device(data->dev);

        return 0;
}

/*
 * Upper layer wants us to request events.
 */
static void request_events(void *send_info)
{
        struct ssif_info *ssif_info = (struct ssif_info *) send_info;
        unsigned long oflags, *flags;

        if (!ssif_info->has_event_buffer)
                return;

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        ssif_info->req_events = true;
        ipmi_ssif_unlock_cond(ssif_info, flags);
}

/*
 * Upper layer is changing the flag saying whether we need to request
 * flags periodically or not.
 */
static void ssif_set_need_watch(void *send_info, unsigned int watch_mask)
{
        struct ssif_info *ssif_info = (struct ssif_info *) send_info;
        unsigned long oflags, *flags;
        long timeout = 0;

        if (watch_mask & IPMI_WATCH_MASK_CHECK_MESSAGES)
                timeout = SSIF_WATCH_MSG_TIMEOUT;
        else if (watch_mask)
                timeout = SSIF_WATCH_WATCHDOG_TIMEOUT;

        flags = ipmi_ssif_lock_cond(ssif_info, &oflags);
        if (timeout != ssif_info->watch_timeout) {
                ssif_info->watch_timeout = timeout;
                if (ssif_info->watch_timeout)
                        mod_timer(&ssif_info->watch_timer,
                                  jiffies + ssif_info->watch_timeout);
        }
        ipmi_ssif_unlock_cond(ssif_info, flags);
}

static int ssif_start_processing(void            *send_info,
                                 struct ipmi_smi *intf)
{
        struct ssif_info *ssif_info = send_info;

        ssif_info->intf = intf;

        return 0;
}

#define MAX_SSIF_BMCS 4

static unsigned short addr[MAX_SSIF_BMCS];
static int num_addrs;
module_param_array(addr, ushort, &num_addrs, 0);
MODULE_PARM_DESC(addr, "The addresses to scan for IPMI BMCs on the SSIFs.");

static char *adapter_name[MAX_SSIF_BMCS];
static int num_adapter_names;
module_param_array(adapter_name, charp, &num_adapter_names, 0);
MODULE_PARM_DESC(adapter_name, "The string name of the I2C device that has the BMC.  By default all devices are scanned.");

static int slave_addrs[MAX_SSIF_BMCS];
static int num_slave_addrs;
module_param_array(slave_addrs, int, &num_slave_addrs, 0);
MODULE_PARM_DESC(slave_addrs,
                 "The default IPMB slave address for the controller.");

static bool alerts_broken;
module_param(alerts_broken, bool, 0);
MODULE_PARM_DESC(alerts_broken, "Don't enable alerts for the controller.");

/*
 * Bit 0 enables message debugging, bit 1 enables state debugging, and
 * bit 2 enables timing debugging.  This is an array indexed by
 * interface number"
 */
static int dbg[MAX_SSIF_BMCS];
static int num_dbg;
module_param_array(dbg, int, &num_dbg, 0);
MODULE_PARM_DESC(dbg, "Turn on debugging.");

static bool ssif_dbg_probe;
module_param_named(dbg_probe, ssif_dbg_probe, bool, 0);
MODULE_PARM_DESC(dbg_probe, "Enable debugging of probing of adapters.");

static bool ssif_tryacpi = true;
module_param_named(tryacpi, ssif_tryacpi, bool, 0);
MODULE_PARM_DESC(tryacpi, "Setting this to zero will disable the default scan of the interfaces identified via ACPI");

static bool ssif_trydmi = true;
module_param_named(trydmi, ssif_trydmi, bool, 0);
MODULE_PARM_DESC(trydmi, "Setting this to zero will disable the default scan of the interfaces identified via DMI (SMBIOS)");

static DEFINE_MUTEX(ssif_infos_mutex);
static LIST_HEAD(ssif_infos);

#define IPMI_SSIF_ATTR(name) \
static ssize_t ipmi_##name##_show(struct device *dev,                   \
                                  struct device_attribute *attr,        \
                                  char *buf)                            \
{                                                                       \
        struct ssif_info *ssif_info = dev_get_drvdata(dev);             \
                                                                        \
        return sysfs_emit(buf, "%u\n", ssif_get_stat(ssif_info, name));\
}                                                                       \
static DEVICE_ATTR(name, S_IRUGO, ipmi_##name##_show, NULL)

static ssize_t ipmi_type_show(struct device *dev,
                              struct device_attribute *attr,
                              char *buf)
{
        return sysfs_emit(buf, "ssif\n");
}
static DEVICE_ATTR(type, S_IRUGO, ipmi_type_show, NULL);

IPMI_SSIF_ATTR(sent_messages);
IPMI_SSIF_ATTR(sent_messages_parts);
IPMI_SSIF_ATTR(send_retries);
IPMI_SSIF_ATTR(send_errors);
IPMI_SSIF_ATTR(received_messages);
IPMI_SSIF_ATTR(received_message_parts);
IPMI_SSIF_ATTR(receive_retries);
IPMI_SSIF_ATTR(receive_errors);
IPMI_SSIF_ATTR(flag_fetches);
IPMI_SSIF_ATTR(hosed);
IPMI_SSIF_ATTR(events);
IPMI_SSIF_ATTR(watchdog_pretimeouts);
IPMI_SSIF_ATTR(alerts);

static struct attribute *ipmi_ssif_dev_attrs[] = {
        &dev_attr_type.attr,
        &dev_attr_sent_messages.attr,
        &dev_attr_sent_messages_parts.attr,
        &dev_attr_send_retries.attr,
        &dev_attr_send_errors.attr,
        &dev_attr_received_messages.attr,
        &dev_attr_received_message_parts.attr,
        &dev_attr_receive_retries.attr,
        &dev_attr_receive_errors.attr,
        &dev_attr_flag_fetches.attr,
        &dev_attr_hosed.attr,
        &dev_attr_events.attr,
        &dev_attr_watchdog_pretimeouts.attr,
        &dev_attr_alerts.attr,
        NULL
};

static const struct attribute_group ipmi_ssif_dev_attr_group = {
        .attrs          = ipmi_ssif_dev_attrs,
};

static void shutdown_ssif(void *send_info)
{
        struct ssif_info *ssif_info = send_info;

        device_remove_group(&ssif_info->client->dev, &ipmi_ssif_dev_attr_group);
        dev_set_drvdata(&ssif_info->client->dev, NULL);

        /* make sure the driver is not looking for flags any more. */
        while (ssif_info->ssif_state != SSIF_NORMAL)
                schedule_timeout(1);

        ssif_info->stopping = true;
        del_timer_sync(&ssif_info->watch_timer);
        del_timer_sync(&ssif_info->retry_timer);
        if (ssif_info->thread) {
                complete(&ssif_info->wake_thread);
                kthread_stop(ssif_info->thread);
        }
}

static int ssif_remove(struct i2c_client *client)
{
        struct ssif_info *ssif_info = i2c_get_clientdata(client);
        struct ssif_addr_info *addr_info;

        if (!ssif_info)
                return 0;

        /*
         * After this point, we won't deliver anything asychronously
         * to the message handler.  We can unregister ourself.
         */
        ipmi_unregister_smi(ssif_info->intf);

        list_for_each_entry(addr_info, &ssif_infos, link) {
                if (addr_info->client == client) {
                        addr_info->client = NULL;
                        break;
                }
        }

        kfree(ssif_info);

        return 0;
}

static int read_response(struct i2c_client *client, unsigned char *resp)
{
        int ret = -ENODEV, retry_cnt = SSIF_RECV_RETRIES;

        while (retry_cnt > 0) {
                ret = i2c_smbus_read_block_data(client, SSIF_IPMI_RESPONSE,
                                                resp);
                if (ret > 0)
                        break;
                msleep(SSIF_MSG_MSEC);
                retry_cnt--;
                if (retry_cnt <= 0)
                        break;
        }

        return ret;
}

static int do_cmd(struct i2c_client *client, int len, unsigned char *msg,
                  int *resp_len, unsigned char *resp)
{
        int retry_cnt;
        int ret;

        retry_cnt = SSIF_SEND_RETRIES;
 retry1:
        ret = i2c_smbus_write_block_data(client, SSIF_IPMI_REQUEST, len, msg);
        if (ret) {
                retry_cnt--;
                if (retry_cnt > 0)
                        goto retry1;
                return -ENODEV;
        }

        ret = read_response(client, resp);
        if (ret > 0) {
                /* Validate that the response is correct. */
                if (ret < 3 ||
                    (resp[0] != (msg[0] | (1 << 2))) ||
                    (resp[1] != msg[1]))
                        ret = -EINVAL;
                else if (ret > IPMI_MAX_MSG_LENGTH) {
                        ret = -E2BIG;
                } else {
                        *resp_len = ret;
                        ret = 0;
                }
        }

        return ret;
}

static int ssif_detect(struct i2c_client *client, struct i2c_board_info *info)
{
        unsigned char *resp;
        unsigned char msg[3];
        int           rv;
        int           len;

        resp = kmalloc(IPMI_MAX_MSG_LENGTH, GFP_KERNEL);
        if (!resp)
                return -ENOMEM;

        /* Do a Get Device ID command, since it is required. */
        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_GET_DEVICE_ID_CMD;
        rv = do_cmd(client, 2, msg, &len, resp);
        if (rv)
                rv = -ENODEV;
        else
                strscpy(info->type, DEVICE_NAME, I2C_NAME_SIZE);
        kfree(resp);
        return rv;
}

static int strcmp_nospace(char *s1, char *s2)
{
        while (*s1 && *s2) {
                while (isspace(*s1))
                        s1++;
                while (isspace(*s2))
                        s2++;
                if (*s1 > *s2)
                        return 1;
                if (*s1 < *s2)
                        return -1;
                s1++;
                s2++;
        }
        return 0;
}

static struct ssif_addr_info *ssif_info_find(unsigned short addr,
                                             char *adapter_name,
                                             bool match_null_name)
{
        struct ssif_addr_info *info, *found = NULL;

restart:
        list_for_each_entry(info, &ssif_infos, link) {
                if (info->binfo.addr == addr) {
                        if (info->addr_src == SI_SMBIOS)
                                info->adapter_name = kstrdup(adapter_name,
                                                             GFP_KERNEL);

                        if (info->adapter_name || adapter_name) {
                                if (!info->adapter_name != !adapter_name) {
                                        /* One is NULL and one is not */
                                        continue;
                                }
                                if (adapter_name &&
                                    strcmp_nospace(info->adapter_name,
                                                   adapter_name))
                                        /* Names do not match */
                                        continue;
                        }
                        found = info;
                        break;
                }
        }

        if (!found && match_null_name) {
                /* Try to get an exact match first, then try with a NULL name */
                adapter_name = NULL;
                match_null_name = false;
                goto restart;
        }

        return found;
}

static bool check_acpi(struct ssif_info *ssif_info, struct device *dev)
{
#ifdef CONFIG_ACPI
        acpi_handle acpi_handle;

        acpi_handle = ACPI_HANDLE(dev);
        if (acpi_handle) {
                ssif_info->addr_source = SI_ACPI;
                ssif_info->addr_info.acpi_info.acpi_handle = acpi_handle;
                request_module("acpi_ipmi");
                return true;
        }
#endif
        return false;
}

static int find_slave_address(struct i2c_client *client, int slave_addr)
{
#ifdef CONFIG_IPMI_DMI_DECODE
        if (!slave_addr)
                slave_addr = ipmi_dmi_get_slave_addr(
                        SI_TYPE_INVALID,
                        i2c_adapter_id(client->adapter),
                        client->addr);
#endif

        return slave_addr;
}

static int start_multipart_test(struct i2c_client *client,
                                unsigned char *msg, bool do_middle)
{
        int retry_cnt = SSIF_SEND_RETRIES, ret;

retry_write:
        ret = i2c_smbus_write_block_data(client,
                                         SSIF_IPMI_MULTI_PART_REQUEST_START,
                                         32, msg);
        if (ret) {
                retry_cnt--;
                if (retry_cnt > 0)
                        goto retry_write;
                dev_err(&client->dev, "Could not write multi-part start, though the BMC said it could handle it.  Just limit sends to one part.\n");
                return ret;
        }

        if (!do_middle)
                return 0;

        ret = i2c_smbus_write_block_data(client,
                                         SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE,
                                         32, msg + 32);
        if (ret) {
                dev_err(&client->dev, "Could not write multi-part middle, though the BMC said it could handle it.  Just limit sends to one part.\n");
                return ret;
        }

        return 0;
}

static void test_multipart_messages(struct i2c_client *client,
                                    struct ssif_info *ssif_info,
                                    unsigned char *resp)
{
        unsigned char msg[65];
        int ret;
        bool do_middle;

        if (ssif_info->max_xmit_msg_size <= 32)
                return;

        do_middle = ssif_info->max_xmit_msg_size > 63;

        memset(msg, 0, sizeof(msg));
        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_GET_DEVICE_ID_CMD;

        /*
         * The specification is all messed up dealing with sending
         * multi-part messages.  Per what the specification says, it
         * is impossible to send a message that is a multiple of 32
         * bytes, except for 32 itself.  It talks about a "start"
         * transaction (cmd=6) that must be 32 bytes, "middle"
         * transaction (cmd=7) that must be 32 bytes, and an "end"
         * transaction.  The "end" transaction is shown as cmd=7 in
         * the text, but if that's the case there is no way to
         * differentiate between a middle and end part except the
         * length being less than 32.  But there is a table at the far
         * end of the section (that I had never noticed until someone
         * pointed it out to me) that mentions it as cmd=8.
         *
         * After some thought, I think the example is wrong and the
         * end transaction should be cmd=8.  But some systems don't
         * implement cmd=8, they use a zero-length end transaction,
         * even though that violates the SMBus specification.
         *
         * So, to work around this, this code tests if cmd=8 works.
         * If it does, then we use that.  If not, it tests zero-
         * byte end transactions.  If that works, good.  If not,
         * we only allow 63-byte transactions max.
         */

        ret = start_multipart_test(client, msg, do_middle);
        if (ret)
                goto out_no_multi_part;

        ret = i2c_smbus_write_block_data(client,
                                         SSIF_IPMI_MULTI_PART_REQUEST_END,
                                         1, msg + 64);

        if (!ret)
                ret = read_response(client, resp);

        if (ret > 0) {
                /* End transactions work, we are good. */
                ssif_info->cmd8_works = true;
                return;
        }

        ret = start_multipart_test(client, msg, do_middle);
        if (ret) {
                dev_err(&client->dev, "Second multipart test failed.\n");
                goto out_no_multi_part;
        }

        ret = i2c_smbus_write_block_data(client,
                                         SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE,
                                         0, msg + 64);
        if (!ret)
                ret = read_response(client, resp);
        if (ret > 0)
                /* Zero-size end parts work, use those. */
                return;

        /* Limit to 63 bytes and use a short middle command to mark the end. */
        if (ssif_info->max_xmit_msg_size > 63)
                ssif_info->max_xmit_msg_size = 63;
        return;

out_no_multi_part:
        ssif_info->max_xmit_msg_size = 32;
        return;
}

/*
 * Global enables we care about.
 */
#define GLOBAL_ENABLES_MASK (IPMI_BMC_EVT_MSG_BUFF | IPMI_BMC_RCV_MSG_INTR | \
                             IPMI_BMC_EVT_MSG_INTR)

static void ssif_remove_dup(struct i2c_client *client)
{
        struct ssif_info *ssif_info = i2c_get_clientdata(client);

        ipmi_unregister_smi(ssif_info->intf);
        kfree(ssif_info);
}

static int ssif_add_infos(struct i2c_client *client)
{
        struct ssif_addr_info *info;

        info = kzalloc(sizeof(*info), GFP_KERNEL);
        if (!info)
                return -ENOMEM;
        info->addr_src = SI_ACPI;
        info->client = client;
        info->adapter_name = kstrdup(client->adapter->name, GFP_KERNEL);
        info->binfo.addr = client->addr;
        list_add_tail(&info->link, &ssif_infos);
        return 0;
}

/*
 * Prefer ACPI over SMBIOS, if both are available.
 * So if we get an ACPI interface and have already registered a SMBIOS
 * interface at the same address, remove the SMBIOS and add the ACPI one.
 */
static int ssif_check_and_remove(struct i2c_client *client,
                              struct ssif_info *ssif_info)
{
        struct ssif_addr_info *info;

        list_for_each_entry(info, &ssif_infos, link) {
                if (!info->client)
                        return 0;
                if (!strcmp(info->adapter_name, client->adapter->name) &&
                    info->binfo.addr == client->addr) {
                        if (info->addr_src == SI_ACPI)
                                return -EEXIST;

                        if (ssif_info->addr_source == SI_ACPI &&
                            info->addr_src == SI_SMBIOS) {
                                dev_info(&client->dev,
                                         "Removing %s-specified SSIF interface in favor of ACPI\n",
                                         ipmi_addr_src_to_str(info->addr_src));
                                ssif_remove_dup(info->client);
                                return 0;
                        }
                }
        }
        return 0;
}

static int ssif_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
        unsigned char     msg[3];
        unsigned char     *resp;
        struct ssif_info   *ssif_info;
        int               rv = 0;
        int               len = 0;
        int               i;
        u8                slave_addr = 0;
        struct ssif_addr_info *addr_info = NULL;

        mutex_lock(&ssif_infos_mutex);
        resp = kmalloc(IPMI_MAX_MSG_LENGTH, GFP_KERNEL);
        if (!resp) {
                mutex_unlock(&ssif_infos_mutex);
                return -ENOMEM;
        }

        ssif_info = kzalloc(sizeof(*ssif_info), GFP_KERNEL);
        if (!ssif_info) {
                kfree(resp);
                mutex_unlock(&ssif_infos_mutex);
                return -ENOMEM;
        }

        if (!check_acpi(ssif_info, &client->dev)) {
                addr_info = ssif_info_find(client->addr, client->adapter->name,
                                           true);
                if (!addr_info) {
                        /* Must have come in through sysfs. */
                        ssif_info->addr_source = SI_HOTMOD;
                } else {
                        ssif_info->addr_source = addr_info->addr_src;
                        ssif_info->ssif_debug = addr_info->debug;
                        ssif_info->addr_info = addr_info->addr_info;
                        addr_info->client = client;
                        slave_addr = addr_info->slave_addr;
                }
        }

        ssif_info->client = client;
        i2c_set_clientdata(client, ssif_info);

        rv = ssif_check_and_remove(client, ssif_info);
        /* If rv is 0 and addr source is not SI_ACPI, continue probing */
        if (!rv && ssif_info->addr_source == SI_ACPI) {
                rv = ssif_add_infos(client);
                if (rv) {
                        dev_err(&client->dev, "Out of memory!, exiting ..\n");
                        goto out;
                }
        } else if (rv) {
                dev_err(&client->dev, "Not probing, Interface already present\n");
                goto out;
        }

        slave_addr = find_slave_address(client, slave_addr);

        dev_info(&client->dev,
                 "Trying %s-specified SSIF interface at i2c address 0x%x, adapter %s, slave address 0x%x\n",
                ipmi_addr_src_to_str(ssif_info->addr_source),
                client->addr, client->adapter->name, slave_addr);

        /* Now check for system interface capabilities */
        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_GET_SYSTEM_INTERFACE_CAPABILITIES_CMD;
        msg[2] = 0; /* SSIF */
        rv = do_cmd(client, 3, msg, &len, resp);
        if (!rv && (len >= 3) && (resp[2] == 0)) {
                if (len < 7) {
                        if (ssif_dbg_probe)
                                dev_dbg(&ssif_info->client->dev,
                                        "SSIF info too short: %d\n", len);
                        goto no_support;
                }

                /* Got a good SSIF response, handle it. */
                ssif_info->max_xmit_msg_size = resp[5];
                ssif_info->max_recv_msg_size = resp[6];
                ssif_info->multi_support = (resp[4] >> 6) & 0x3;
                ssif_info->supports_pec = (resp[4] >> 3) & 0x1;

                /* Sanitize the data */
                switch (ssif_info->multi_support) {
                case SSIF_NO_MULTI:
                        if (ssif_info->max_xmit_msg_size > 32)
                                ssif_info->max_xmit_msg_size = 32;
                        if (ssif_info->max_recv_msg_size > 32)
                                ssif_info->max_recv_msg_size = 32;
                        break;

                case SSIF_MULTI_2_PART:
                        if (ssif_info->max_xmit_msg_size > 63)
                                ssif_info->max_xmit_msg_size = 63;
                        if (ssif_info->max_recv_msg_size > 62)
                                ssif_info->max_recv_msg_size = 62;
                        break;

                case SSIF_MULTI_n_PART:
                        /* We take whatever size given, but do some testing. */
                        break;

                default:
                        /* Data is not sane, just give up. */
                        goto no_support;
                }
        } else {
 no_support:
                /* Assume no multi-part or PEC support */
                dev_info(&ssif_info->client->dev,
                         "Error fetching SSIF: %d %d %2.2x, your system probably doesn't support this command so using defaults\n",
                        rv, len, resp[2]);

                ssif_info->max_xmit_msg_size = 32;
                ssif_info->max_recv_msg_size = 32;
                ssif_info->multi_support = SSIF_NO_MULTI;
                ssif_info->supports_pec = 0;
        }

        test_multipart_messages(client, ssif_info, resp);

        /* Make sure the NMI timeout is cleared. */
        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_CLEAR_MSG_FLAGS_CMD;
        msg[2] = WDT_PRE_TIMEOUT_INT;
        rv = do_cmd(client, 3, msg, &len, resp);
        if (rv || (len < 3) || (resp[2] != 0))
                dev_warn(&ssif_info->client->dev,
                         "Unable to clear message flags: %d %d %2.2x\n",
                         rv, len, resp[2]);

        /* Attempt to enable the event buffer. */
        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_GET_BMC_GLOBAL_ENABLES_CMD;
        rv = do_cmd(client, 2, msg, &len, resp);
        if (rv || (len < 4) || (resp[2] != 0)) {
                dev_warn(&ssif_info->client->dev,
                         "Error getting global enables: %d %d %2.2x\n",
                         rv, len, resp[2]);
                rv = 0; /* Not fatal */
                goto found;
        }

        ssif_info->global_enables = resp[3];

        if (resp[3] & IPMI_BMC_EVT_MSG_BUFF) {
                ssif_info->has_event_buffer = true;
                /* buffer is already enabled, nothing to do. */
                goto found;
        }

        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_SET_BMC_GLOBAL_ENABLES_CMD;
        msg[2] = ssif_info->global_enables | IPMI_BMC_EVT_MSG_BUFF;
        rv = do_cmd(client, 3, msg, &len, resp);
        if (rv || (len < 2)) {
                dev_warn(&ssif_info->client->dev,
                         "Error setting global enables: %d %d %2.2x\n",
                         rv, len, resp[2]);
                rv = 0; /* Not fatal */
                goto found;
        }

        if (resp[2] == 0) {
                /* A successful return means the event buffer is supported. */
                ssif_info->has_event_buffer = true;
                ssif_info->global_enables |= IPMI_BMC_EVT_MSG_BUFF;
        }

        /* Some systems don't behave well if you enable alerts. */
        if (alerts_broken)
                goto found;

        msg[0] = IPMI_NETFN_APP_REQUEST << 2;
        msg[1] = IPMI_SET_BMC_GLOBAL_ENABLES_CMD;
        msg[2] = ssif_info->global_enables | IPMI_BMC_RCV_MSG_INTR;
        rv = do_cmd(client, 3, msg, &len, resp);
        if (rv || (len < 2)) {
                dev_warn(&ssif_info->client->dev,
                         "Error setting global enables: %d %d %2.2x\n",
                         rv, len, resp[2]);
                rv = 0; /* Not fatal */
                goto found;
        }

        if (resp[2] == 0) {
                /* A successful return means the alert is supported. */
                ssif_info->supports_alert = true;
                ssif_info->global_enables |= IPMI_BMC_RCV_MSG_INTR;
        }

 found:
        if (ssif_dbg_probe) {
                dev_dbg(&ssif_info->client->dev,
                       "%s: i2c_probe found device at i2c address %x\n",
                       __func__, client->addr);
        }

        spin_lock_init(&ssif_info->lock);
        ssif_info->ssif_state = SSIF_NORMAL;
        timer_setup(&ssif_info->retry_timer, retry_timeout, 0);
        timer_setup(&ssif_info->watch_timer, watch_timeout, 0);

        for (i = 0; i < SSIF_NUM_STATS; i++)
                atomic_set(&ssif_info->stats[i], 0);

        if (ssif_info->supports_pec)
                ssif_info->client->flags |= I2C_CLIENT_PEC;

        ssif_info->handlers.owner = THIS_MODULE;
        ssif_info->handlers.start_processing = ssif_start_processing;
        ssif_info->handlers.shutdown = shutdown_ssif;
        ssif_info->handlers.get_smi_info = get_smi_info;
        ssif_info->handlers.sender = sender;
        ssif_info->handlers.request_events = request_events;
        ssif_info->handlers.set_need_watch = ssif_set_need_watch;

        {
                unsigned int thread_num;

                thread_num = ((i2c_adapter_id(ssif_info->client->adapter)
                               << 8) |
                              ssif_info->client->addr);
                init_completion(&ssif_info->wake_thread);
                ssif_info->thread = kthread_run(ipmi_ssif_thread, ssif_info,
                                               "kssif%4.4x", thread_num);
                if (IS_ERR(ssif_info->thread)) {
                        rv = PTR_ERR(ssif_info->thread);
                        dev_notice(&ssif_info->client->dev,
                                   "Could not start kernel thread: error %d\n",
                                   rv);
                        goto out;
                }
        }

        dev_set_drvdata(&ssif_info->client->dev, ssif_info);
        rv = device_add_group(&ssif_info->client->dev,
                              &ipmi_ssif_dev_attr_group);
        if (rv) {
                dev_err(&ssif_info->client->dev,
                        "Unable to add device attributes: error %d\n",
                        rv);
                goto out;
        }

        rv = ipmi_register_smi(&ssif_info->handlers,
                               ssif_info,
                               &ssif_info->client->dev,
                               slave_addr);
        if (rv) {
                dev_err(&ssif_info->client->dev,
                        "Unable to register device: error %d\n", rv);
                goto out_remove_attr;
        }

 out:
        if (rv) {
                if (addr_info)
                        addr_info->client = NULL;

                dev_err(&ssif_info->client->dev,
                        "Unable to start IPMI SSIF: %d\n", rv);
                i2c_set_clientdata(client, NULL);
                kfree(ssif_info);
        }
        kfree(resp);
        mutex_unlock(&ssif_infos_mutex);
        return rv;

out_remove_attr:
        device_remove_group(&ssif_info->client->dev, &ipmi_ssif_dev_attr_group);
        dev_set_drvdata(&ssif_info->client->dev, NULL);
        goto out;
}

static int new_ssif_client(int addr, char *adapter_name,
                           int debug, int slave_addr,
                           enum ipmi_addr_src addr_src,
                           struct device *dev)
{
        struct ssif_addr_info *addr_info;
        int rv = 0;

        mutex_lock(&ssif_infos_mutex);
        if (ssif_info_find(addr, adapter_name, false)) {
                rv = -EEXIST;
                goto out_unlock;
        }

        addr_info = kzalloc(sizeof(*addr_info), GFP_KERNEL);
        if (!addr_info) {
                rv = -ENOMEM;
                goto out_unlock;
        }

        if (adapter_name) {
                addr_info->adapter_name = kstrdup(adapter_name, GFP_KERNEL);
                if (!addr_info->adapter_name) {
                        kfree(addr_info);
                        rv = -ENOMEM;
                        goto out_unlock;
                }
        }

        strncpy(addr_info->binfo.type, DEVICE_NAME,
                sizeof(addr_info->binfo.type));
        addr_info->binfo.addr = addr;
        addr_info->binfo.platform_data = addr_info;
        addr_info->debug = debug;
        addr_info->slave_addr = slave_addr;
        addr_info->addr_src = addr_src;
        addr_info->dev = dev;

        if (dev)
                dev_set_drvdata(dev, addr_info);

        list_add_tail(&addr_info->link, &ssif_infos);

        /* Address list will get it */

out_unlock:
        mutex_unlock(&ssif_infos_mutex);
        return rv;
}

static void free_ssif_clients(void)
{
        struct ssif_addr_info *info, *tmp;

        mutex_lock(&ssif_infos_mutex);
        list_for_each_entry_safe(info, tmp, &ssif_infos, link) {
                list_del(&info->link);
                kfree(info->adapter_name);
                kfree(info);
        }
        mutex_unlock(&ssif_infos_mutex);
}

static unsigned short *ssif_address_list(void)
{
        struct ssif_addr_info *info;
        unsigned int count = 0, i = 0;
        unsigned short *address_list;

        list_for_each_entry(info, &ssif_infos, link)
                count++;

        address_list = kcalloc(count + 1, sizeof(*address_list),
                               GFP_KERNEL);
        if (!address_list)
                return NULL;

        list_for_each_entry(info, &ssif_infos, link) {
                unsigned short addr = info->binfo.addr;
                int j;

                for (j = 0; j < i; j++) {
                        if (address_list[j] == addr)
                                /* Found a dup. */
                                break;
                }
                if (j == i) /* Didn't find it in the list. */
                        address_list[i++] = addr;
        }
        address_list[i] = I2C_CLIENT_END;

        return address_list;
}

#ifdef CONFIG_ACPI
static const struct acpi_device_id ssif_acpi_match[] = {
        { "IPI0001", 0 },
        { },
};
MODULE_DEVICE_TABLE(acpi, ssif_acpi_match);
#endif

#ifdef CONFIG_DMI
static int dmi_ipmi_probe(struct platform_device *pdev)

{
        u8 slave_addr = 0;
        u16 i2c_addr;
        int rv;

        if (!ssif_trydmi)
                return -ENODEV;

        rv = device_property_read_u16(&pdev->dev, "i2c-addr", &i2c_addr);
        if (rv) {
                dev_warn(&pdev->dev, "No i2c-addr property\n");
                return -ENODEV;
        }

        rv = device_property_read_u8(&pdev->dev, "slave-addr", &slave_addr);
        if (rv)
                slave_addr = 0x20;

        return new_ssif_client(i2c_addr, NULL, 0,
                               slave_addr, SI_SMBIOS, &pdev->dev);
}
#else
static int dmi_ipmi_probe(struct platform_device *pdev)
{
        return -ENODEV;
}
#endif

static const struct i2c_device_id ssif_id[] = {
        { DEVICE_NAME, 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ssif_id);

static struct i2c_driver ssif_i2c_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver         = {
                .name                   = DEVICE_NAME
        },
        .probe          = ssif_probe,
        .remove         = ssif_remove,
        .alert          = ssif_alert,
        .id_table       = ssif_id,
        .detect         = ssif_detect
};

static int ssif_platform_probe(struct platform_device *dev)
{
        return dmi_ipmi_probe(dev);
}

static int ssif_platform_remove(struct platform_device *dev)
{
        struct ssif_addr_info *addr_info = dev_get_drvdata(&dev->dev);

        if (!addr_info)
                return 0;

        mutex_lock(&ssif_infos_mutex);
        list_del(&addr_info->link);
        kfree(addr_info);
        mutex_unlock(&ssif_infos_mutex);
        return 0;
}

static const struct platform_device_id ssif_plat_ids[] = {
    { "dmi-ipmi-ssif", 0 },
    { }
};

static struct platform_driver ipmi_driver = {
        .driver = {
                .name = DEVICE_NAME,
        },
        .probe          = ssif_platform_probe,
        .remove         = ssif_platform_remove,
        .id_table       = ssif_plat_ids
};

static int init_ipmi_ssif(void)
{
        int i;
        int rv;

        if (initialized)
                return 0;

        pr_info("IPMI SSIF Interface driver\n");

        /* build list for i2c from addr list */
        for (i = 0; i < num_addrs; i++) {
                rv = new_ssif_client(addr[i], adapter_name[i],
                                     dbg[i], slave_addrs[i],
                                     SI_HARDCODED, NULL);
                if (rv)
                        pr_err("Couldn't add hardcoded device at addr 0x%x\n",
                               addr[i]);
        }

        if (ssif_tryacpi)
                ssif_i2c_driver.driver.acpi_match_table =
                        ACPI_PTR(ssif_acpi_match);

        if (ssif_trydmi) {
                rv = platform_driver_register(&ipmi_driver);
                if (rv)
                        pr_err("Unable to register driver: %d\n", rv);
                else
                        platform_registered = true;
        }

        ssif_i2c_driver.address_list = ssif_address_list();

        rv = i2c_add_driver(&ssif_i2c_driver);
        if (!rv)
                initialized = true;

        return rv;
}
module_init(init_ipmi_ssif);

static void cleanup_ipmi_ssif(void)
{
        if (!initialized)
                return;

        initialized = false;

        i2c_del_driver(&ssif_i2c_driver);

        kfree(ssif_i2c_driver.address_list);

        if (ssif_trydmi && platform_registered)
                platform_driver_unregister(&ipmi_driver);

        free_ssif_clients();
}
module_exit(cleanup_ipmi_ssif);

MODULE_ALIAS("platform:dmi-ipmi-ssif");
MODULE_AUTHOR("Todd C Davis <todd.c.davis@intel.com>, Corey Minyard <minyard@acm.org>");
MODULE_DESCRIPTION("IPMI driver for management controllers on a SMBus");
MODULE_LICENSE("GPL");