// SPDX-License-Identifier: GPL-2.0-only
/*
 * tascam-hwdep.c - a part of driver for TASCAM FireWire series
 *
 * Copyright (c) 2015 Takashi Sakamoto
 */

/*
 * This codes give three functionality.
 *
 * 1.get firewire node information
 * 2.get notification about starting/stopping stream
 * 3.lock/unlock stream
 */

#include "tascam.h"

static long tscm_hwdep_read_locked(struct snd_tscm *tscm, char __user *buf,
                                   long count, loff_t *offset)
        __releases(&tscm->lock)
{
        struct snd_firewire_event_lock_status event = {
                .type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
        };

        event.status = (tscm->dev_lock_count > 0);
        tscm->dev_lock_changed = false;
        count = min_t(long, count, sizeof(event));

        spin_unlock_irq(&tscm->lock);

        if (copy_to_user(buf, &event, count))
                return -EFAULT;

        return count;
}

static long tscm_hwdep_read_queue(struct snd_tscm *tscm, char __user *buf,
                                  long remained, loff_t *offset)
        __releases(&tscm->lock)
{
        char __user *pos = buf;
        unsigned int type = SNDRV_FIREWIRE_EVENT_TASCAM_CONTROL;
        struct snd_firewire_tascam_change *entries = tscm->queue;
        long count;

        // At least, one control event can be copied.
        if (remained < sizeof(type) + sizeof(*entries)) {
                spin_unlock_irq(&tscm->lock);
                return -EINVAL;
        }

        // Copy the type field later.
        count = sizeof(type);
        remained -= sizeof(type);
        pos += sizeof(type);

        while (true) {
                unsigned int head_pos;
                unsigned int tail_pos;
                unsigned int length;

                if (tscm->pull_pos == tscm->push_pos)
                        break;
                else if (tscm->pull_pos < tscm->push_pos)
                        tail_pos = tscm->push_pos;
                else
                        tail_pos = SND_TSCM_QUEUE_COUNT;
                head_pos = tscm->pull_pos;

                length = (tail_pos - head_pos) * sizeof(*entries);
                if (remained < length)
                        length = rounddown(remained, sizeof(*entries));
                if (length == 0)
                        break;

                spin_unlock_irq(&tscm->lock);
                if (copy_to_user(pos, &entries[head_pos], length))
                        return -EFAULT;

                spin_lock_irq(&tscm->lock);

                tscm->pull_pos = tail_pos % SND_TSCM_QUEUE_COUNT;

                count += length;
                remained -= length;
                pos += length;
        }

        spin_unlock_irq(&tscm->lock);

        if (copy_to_user(buf, &type, sizeof(type)))
                return -EFAULT;

        return count;
}

static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
                       loff_t *offset)
{
        struct snd_tscm *tscm = hwdep->private_data;
        DEFINE_WAIT(wait);

        spin_lock_irq(&tscm->lock);

        while (!tscm->dev_lock_changed && tscm->push_pos == tscm->pull_pos) {
                prepare_to_wait(&tscm->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
                spin_unlock_irq(&tscm->lock);
                schedule();
                finish_wait(&tscm->hwdep_wait, &wait);
                if (signal_pending(current))
                        return -ERESTARTSYS;
                spin_lock_irq(&tscm->lock);
        }

        // NOTE: The acquired lock should be released in callee side.
        if (tscm->dev_lock_changed) {
                count = tscm_hwdep_read_locked(tscm, buf, count, offset);
        } else if (tscm->push_pos != tscm->pull_pos) {
                count = tscm_hwdep_read_queue(tscm, buf, count, offset);
        } else {
                spin_unlock_irq(&tscm->lock);
                count = 0;
        }

        return count;
}

static __poll_t hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
                               poll_table *wait)
{
        struct snd_tscm *tscm = hwdep->private_data;

        poll_wait(file, &tscm->hwdep_wait, wait);

        guard(spinlock_irq)(&tscm->lock);
        if (tscm->dev_lock_changed || tscm->push_pos != tscm->pull_pos)
                return EPOLLIN | EPOLLRDNORM;
        else
                return 0;
}

static int hwdep_get_info(struct snd_tscm *tscm, void __user *arg)
{
        struct fw_device *dev = fw_parent_device(tscm->unit);
        struct snd_firewire_get_info info;

        memset(&info, 0, sizeof(info));
        info.type = SNDRV_FIREWIRE_TYPE_TASCAM;
        info.card = dev->card->index;
        *(__be32 *)&info.guid[0] = cpu_to_be32(dev->config_rom[3]);
        *(__be32 *)&info.guid[4] = cpu_to_be32(dev->config_rom[4]);
        strscpy(info.device_name, dev_name(&dev->device),
                sizeof(info.device_name));

        if (copy_to_user(arg, &info, sizeof(info)))
                return -EFAULT;

        return 0;
}

static int hwdep_lock(struct snd_tscm *tscm)
{
        guard(spinlock_irq)(&tscm->lock);

        if (tscm->dev_lock_count == 0) {
                tscm->dev_lock_count = -1;
                return 0;
        } else {
                return -EBUSY;
        }
}

static int hwdep_unlock(struct snd_tscm *tscm)
{
        guard(spinlock_irq)(&tscm->lock);

        if (tscm->dev_lock_count == -1) {
                tscm->dev_lock_count = 0;
                return 0;
        } else {
                return -EBADFD;
        }
}

static int tscm_hwdep_state(struct snd_tscm *tscm, void __user *arg)
{
        if (copy_to_user(arg, tscm->state, sizeof(tscm->state)))
                return -EFAULT;

        return 0;
}

static int hwdep_release(struct snd_hwdep *hwdep, struct file *file)
{
        struct snd_tscm *tscm = hwdep->private_data;

        guard(spinlock_irq)(&tscm->lock);
        if (tscm->dev_lock_count == -1)
                tscm->dev_lock_count = 0;

        return 0;
}

static int hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
            unsigned int cmd, unsigned long arg)
{
        struct snd_tscm *tscm = hwdep->private_data;

        switch (cmd) {
        case SNDRV_FIREWIRE_IOCTL_GET_INFO:
                return hwdep_get_info(tscm, (void __user *)arg);
        case SNDRV_FIREWIRE_IOCTL_LOCK:
                return hwdep_lock(tscm);
        case SNDRV_FIREWIRE_IOCTL_UNLOCK:
                return hwdep_unlock(tscm);
        case SNDRV_FIREWIRE_IOCTL_TASCAM_STATE:
                return tscm_hwdep_state(tscm, (void __user *)arg);
        default:
                return -ENOIOCTLCMD;
        }
}

#ifdef CONFIG_COMPAT
static int hwdep_compat_ioctl(struct snd_hwdep *hwdep, struct file *file,
                              unsigned int cmd, unsigned long arg)
{
        return hwdep_ioctl(hwdep, file, cmd,
                           (unsigned long)compat_ptr(arg));
}
#else
#define hwdep_compat_ioctl NULL
#endif

int snd_tscm_create_hwdep_device(struct snd_tscm *tscm)
{
        static const struct snd_hwdep_ops ops = {
                .read           = hwdep_read,
                .release        = hwdep_release,
                .poll           = hwdep_poll,
                .ioctl          = hwdep_ioctl,
                .ioctl_compat   = hwdep_compat_ioctl,
        };
        struct snd_hwdep *hwdep;
        int err;

        err = snd_hwdep_new(tscm->card, "Tascam", 0, &hwdep);
        if (err < 0)
                return err;

        strscpy(hwdep->name, "Tascam");
        hwdep->iface = SNDRV_HWDEP_IFACE_FW_TASCAM;
        hwdep->ops = ops;
        hwdep->private_data = tscm;
        hwdep->exclusive = true;

        tscm->hwdep = hwdep;

        return err;
}