// SPDX-License-Identifier: GPL-2.0-only
/*
 * Function Control Protocol (IEC 61883-1) helper functions
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 */

#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include "fcp.h"
#include "lib.h"
#include "amdtp-stream.h"

#define CTS_AVC 0x00

#define ERROR_RETRIES   3
#define ERROR_DELAY_MS  5
#define FCP_TIMEOUT_MS  125

int avc_general_set_sig_fmt(struct fw_unit *unit, unsigned int rate,
                            enum avc_general_plug_dir dir,
                            unsigned short pid)
{
        unsigned int sfc;
        u8 *buf;
        bool flag;
        int err;

        flag = false;
        for (sfc = 0; sfc < CIP_SFC_COUNT; sfc++) {
                if (amdtp_rate_table[sfc] == rate) {
                        flag = true;
                        break;
                }
        }
        if (!flag)
                return -EINVAL;

        buf = kzalloc(8, GFP_KERNEL);
        if (buf == NULL)
                return -ENOMEM;

        buf[0] = 0x00;          /* AV/C CONTROL */
        buf[1] = 0xff;          /* UNIT */
        if (dir == AVC_GENERAL_PLUG_DIR_IN)
                buf[2] = 0x19;  /* INPUT PLUG SIGNAL FORMAT */
        else
                buf[2] = 0x18;  /* OUTPUT PLUG SIGNAL FORMAT */
        buf[3] = 0xff & pid;    /* plug id */
        buf[4] = 0x90;          /* EOH_1, Form_1, FMT. AM824 */
        buf[5] = 0x07 & sfc;    /* FDF-hi. AM824, frequency */
        buf[6] = 0xff;          /* FDF-mid. AM824, SYT hi (not used)*/
        buf[7] = 0xff;          /* FDF-low. AM824, SYT lo (not used) */

        /* do transaction and check buf[1-5] are the same against command */
        err = fcp_avc_transaction(unit, buf, 8, buf, 8,
                                  BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5));
        if (err < 0)
                ;
        else if (err < 8)
                err = -EIO;
        else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
                err = -ENOSYS;
        else if (buf[0] == 0x0a) /* REJECTED */
                err = -EINVAL;
        if (err < 0)
                goto end;

        err = 0;
end:
        kfree(buf);
        return err;
}
EXPORT_SYMBOL(avc_general_set_sig_fmt);

int avc_general_get_sig_fmt(struct fw_unit *unit, unsigned int *rate,
                            enum avc_general_plug_dir dir,
                            unsigned short pid)
{
        unsigned int sfc;
        u8 *buf;
        int err;

        buf = kzalloc(8, GFP_KERNEL);
        if (buf == NULL)
                return -ENOMEM;

        buf[0] = 0x01;          /* AV/C STATUS */
        buf[1] = 0xff;          /* Unit */
        if (dir == AVC_GENERAL_PLUG_DIR_IN)
                buf[2] = 0x19;  /* INPUT PLUG SIGNAL FORMAT */
        else
                buf[2] = 0x18;  /* OUTPUT PLUG SIGNAL FORMAT */
        buf[3] = 0xff & pid;    /* plug id */
        buf[4] = 0x90;          /* EOH_1, Form_1, FMT. AM824 */
        buf[5] = 0xff;          /* FDF-hi. AM824, frequency */
        buf[6] = 0xff;          /* FDF-mid. AM824, SYT hi (not used) */
        buf[7] = 0xff;          /* FDF-low. AM824, SYT lo (not used) */

        /* do transaction and check buf[1-4] are the same against command */
        err = fcp_avc_transaction(unit, buf, 8, buf, 8,
                                  BIT(1) | BIT(2) | BIT(3) | BIT(4));
        if (err < 0)
                ;
        else if (err < 8)
                err = -EIO;
        else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
                err = -ENOSYS;
        else if (buf[0] == 0x0a) /* REJECTED */
                err = -EINVAL;
        else if (buf[0] == 0x0b) /* IN TRANSITION */
                err = -EAGAIN;
        if (err < 0)
                goto end;

        /* check sfc field and pick up rate */
        sfc = 0x07 & buf[5];
        if (sfc >= CIP_SFC_COUNT) {
                err = -EAGAIN;  /* also in transition */
                goto end;
        }

        *rate = amdtp_rate_table[sfc];
        err = 0;
end:
        kfree(buf);
        return err;
}
EXPORT_SYMBOL(avc_general_get_sig_fmt);

int avc_general_get_plug_info(struct fw_unit *unit, unsigned int subunit_type,
                              unsigned int subunit_id, unsigned int subfunction,
                              u8 info[AVC_PLUG_INFO_BUF_BYTES])
{
        u8 *buf;
        int err;

        /* extended subunit in spec.4.2 is not supported */
        if ((subunit_type == 0x1E) || (subunit_id == 5))
                return -EINVAL;

        buf = kzalloc(8, GFP_KERNEL);
        if (buf == NULL)
                return -ENOMEM;

        buf[0] = 0x01;  /* AV/C STATUS */
        /* UNIT or Subunit, Functionblock */
        buf[1] = ((subunit_type & 0x1f) << 3) | (subunit_id & 0x7);
        buf[2] = 0x02;  /* PLUG INFO */
        buf[3] = 0xff & subfunction;

        err = fcp_avc_transaction(unit, buf, 8, buf, 8, BIT(1) | BIT(2));
        if (err < 0)
                ;
        else if (err < 8)
                err = -EIO;
        else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
                err = -ENOSYS;
        else if (buf[0] == 0x0a) /* REJECTED */
                err = -EINVAL;
        else if (buf[0] == 0x0b) /* IN TRANSITION */
                err = -EAGAIN;
        if (err < 0)
                goto end;

        info[0] = buf[4];
        info[1] = buf[5];
        info[2] = buf[6];
        info[3] = buf[7];

        err = 0;
end:
        kfree(buf);
        return err;
}
EXPORT_SYMBOL(avc_general_get_plug_info);

static DEFINE_SPINLOCK(transactions_lock);
static LIST_HEAD(transactions);

enum fcp_state {
        STATE_PENDING,
        STATE_BUS_RESET,
        STATE_COMPLETE,
        STATE_DEFERRED,
};

struct fcp_transaction {
        struct list_head list;
        struct fw_unit *unit;
        void *response_buffer;
        unsigned int response_size;
        unsigned int response_match_bytes;
        enum fcp_state state;
        wait_queue_head_t wait;
        bool deferrable;
};

/**
 * fcp_avc_transaction - send an AV/C command and wait for its response
 * @unit: a unit on the target device
 * @command: a buffer containing the command frame; must be DMA-able
 * @command_size: the size of @command
 * @response: a buffer for the response frame
 * @response_size: the maximum size of @response
 * @response_match_bytes: a bitmap specifying the bytes used to detect the
 *                        correct response frame
 *
 * This function sends a FCP command frame to the target and waits for the
 * corresponding response frame to be returned.
 *
 * Because it is possible for multiple FCP transactions to be active at the
 * same time, the correct response frame is detected by the value of certain
 * bytes.  These bytes must be set in @response before calling this function,
 * and the corresponding bits must be set in @response_match_bytes.
 *
 * @command and @response can point to the same buffer.
 *
 * Returns the actual size of the response frame, or a negative error code.
 */
int fcp_avc_transaction(struct fw_unit *unit,
                        const void *command, unsigned int command_size,
                        void *response, unsigned int response_size,
                        unsigned int response_match_bytes)
{
        struct fcp_transaction t;
        int tcode, ret, tries = 0;

        t.unit = unit;
        t.response_buffer = response;
        t.response_size = response_size;
        t.response_match_bytes = response_match_bytes;
        t.state = STATE_PENDING;
        init_waitqueue_head(&t.wait);
        t.deferrable = (*(const u8 *)command == 0x00 || *(const u8 *)command == 0x03);

        scoped_guard(spinlock_irq, &transactions_lock) {
                list_add_tail(&t.list, &transactions);
        }

        for (;;) {
                tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
                                          : TCODE_WRITE_BLOCK_REQUEST;
                ret = snd_fw_transaction(t.unit, tcode,
                                         CSR_REGISTER_BASE + CSR_FCP_COMMAND,
                                         (void *)command, command_size, 0);
                if (ret < 0)
                        break;
deferred:
                wait_event_timeout(t.wait, t.state != STATE_PENDING,
                                   msecs_to_jiffies(FCP_TIMEOUT_MS));

                if (t.state == STATE_DEFERRED) {
                        /*
                         * 'AV/C General Specification' define no time limit
                         * on command completion once an INTERIM response has
                         * been sent. but we promise to finish this function
                         * for a caller. Here we use FCP_TIMEOUT_MS for next
                         * interval. This is not in the specification.
                         */
                        t.state = STATE_PENDING;
                        goto deferred;
                } else if (t.state == STATE_COMPLETE) {
                        ret = t.response_size;
                        break;
                } else if (t.state == STATE_BUS_RESET) {
                        msleep(ERROR_DELAY_MS);
                } else if (++tries >= ERROR_RETRIES) {
                        dev_err(&t.unit->device, "FCP command timed out\n");
                        ret = -EIO;
                        break;
                }
        }

        scoped_guard(spinlock_irq, &transactions_lock) {
                list_del(&t.list);
        }

        return ret;
}
EXPORT_SYMBOL(fcp_avc_transaction);

/**
 * fcp_bus_reset - inform the target handler about a bus reset
 * @unit: the unit that might be used by fcp_avc_transaction()
 *
 * This function must be called from the driver's .update handler to inform
 * the FCP transaction handler that a bus reset has happened.  Any pending FCP
 * transactions are retried.
 */
void fcp_bus_reset(struct fw_unit *unit)
{
        struct fcp_transaction *t;

        guard(spinlock_irq)(&transactions_lock);
        list_for_each_entry(t, &transactions, list) {
                if (t->unit == unit &&
                    (t->state == STATE_PENDING ||
                     t->state == STATE_DEFERRED)) {
                        t->state = STATE_BUS_RESET;
                        wake_up(&t->wait);
                }
        }
}
EXPORT_SYMBOL(fcp_bus_reset);

/* checks whether the response matches the masked bytes in response_buffer */
static bool is_matching_response(struct fcp_transaction *transaction,
                                 const void *response, size_t length)
{
        const u8 *p1, *p2;
        unsigned int mask, i;

        p1 = response;
        p2 = transaction->response_buffer;
        mask = transaction->response_match_bytes;

        for (i = 0; ; ++i) {
                if ((mask & 1) && p1[i] != p2[i])
                        return false;
                mask >>= 1;
                if (!mask)
                        return true;
                if (--length == 0)
                        return false;
        }
}

static void fcp_response(struct fw_card *card, struct fw_request *request,
                         int tcode, int destination, int source,
                         int generation, unsigned long long offset,
                         void *data, size_t length, void *callback_data)
{
        struct fcp_transaction *t;

        if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
                return;

        guard(spinlock_irqsave)(&transactions_lock);
        list_for_each_entry(t, &transactions, list) {
                struct fw_device *device = fw_parent_device(t->unit);
                if (device->card != card ||
                    device->generation != generation)
                        continue;
                smp_rmb(); /* node_id vs. generation */
                if (device->node_id != source)
                        continue;

                if (t->state == STATE_PENDING &&
                    is_matching_response(t, data, length)) {
                        if (t->deferrable && *(const u8 *)data == 0x0f) {
                                t->state = STATE_DEFERRED;
                        } else {
                                t->state = STATE_COMPLETE;
                                t->response_size = min_t(unsigned int, length,
                                                         t->response_size);
                                memcpy(t->response_buffer, data,
                                       t->response_size);
                        }
                        wake_up(&t->wait);
                }
        }
}

static struct fw_address_handler response_register_handler = {
        .length = 0x200,
        .address_callback = fcp_response,
};

static int __init fcp_module_init(void)
{
        static const struct fw_address_region response_register_region = {
                .start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
                .end = CSR_REGISTER_BASE + CSR_FCP_END,
        };

        fw_core_add_address_handler(&response_register_handler,
                                    &response_register_region);

        return 0;
}

static void __exit fcp_module_exit(void)
{
        WARN_ON(!list_empty(&transactions));
        fw_core_remove_address_handler(&response_register_handler);
}

module_init(fcp_module_init);
module_exit(fcp_module_exit);