/*
 * fireworks_hwdep.c - a part of driver for Fireworks based devices
 *
 * Copyright (c) 2013-2014 Takashi Sakamoto
 *
 * Licensed under the terms of the GNU General Public License, version 2.
 */

/*
 * This codes have five functionalities.
 *
 * 1.get information about firewire node
 * 2.get notification about starting/stopping stream
 * 3.lock/unlock streaming
 * 4.transmit command of EFW transaction
 * 5.receive response of EFW transaction
 *
 */

#include "fireworks.h"

static long
hwdep_read_resp_buf(struct snd_efw *efw, char __user *buf, long remained,
                    loff_t *offset)
{
        unsigned int length, till_end, type;
        struct snd_efw_transaction *t;
        u8 *pull_ptr;
        long count = 0;

        if (remained < sizeof(type) + sizeof(struct snd_efw_transaction))
                return -ENOSPC;

        /* data type is SNDRV_FIREWIRE_EVENT_EFW_RESPONSE */
        type = SNDRV_FIREWIRE_EVENT_EFW_RESPONSE;
        if (copy_to_user(buf, &type, sizeof(type)))
                return -EFAULT;
        remained -= sizeof(type);
        buf += sizeof(type);

        /* write into buffer as many responses as possible */
        spin_lock_irq(&efw->lock);

        /*
         * When another task reaches here during this task's access to user
         * space, it picks up current position in buffer and can read the same
         * series of responses.
         */
        pull_ptr = efw->pull_ptr;

        while (efw->push_ptr != pull_ptr) {
                t = (struct snd_efw_transaction *)(pull_ptr);
                length = be32_to_cpu(t->length) * sizeof(__be32);

                /* confirm enough space for this response */
                if (remained < length)
                        break;

                /* copy from ring buffer to user buffer */
                while (length > 0) {
                        till_end = snd_efw_resp_buf_size -
                                (unsigned int)(pull_ptr - efw->resp_buf);
                        till_end = min_t(unsigned int, length, till_end);

                        spin_unlock_irq(&efw->lock);

                        if (copy_to_user(buf, pull_ptr, till_end))
                                return -EFAULT;

                        spin_lock_irq(&efw->lock);

                        pull_ptr += till_end;
                        if (pull_ptr >= efw->resp_buf + snd_efw_resp_buf_size)
                                pull_ptr -= snd_efw_resp_buf_size;

                        length -= till_end;
                        buf += till_end;
                        count += till_end;
                        remained -= till_end;
                }
        }

        /*
         * All of tasks can read from the buffer nearly simultaneously, but the
         * last position for each task is different depending on the length of
         * given buffer. Here, for simplicity, a position of buffer is set by
         * the latest task. It's better for a listening application to allow one
         * thread to read from the buffer. Unless, each task can read different
         * sequence of responses depending on variation of buffer length.
         */
        efw->pull_ptr = pull_ptr;

        spin_unlock_irq(&efw->lock);

        return count;
}

static long
hwdep_read_locked(struct snd_efw *efw, char __user *buf, long count,
                  loff_t *offset)
{
        union snd_firewire_event event = {
                .lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
        };

        spin_lock_irq(&efw->lock);

        event.lock_status.status = (efw->dev_lock_count > 0);
        efw->dev_lock_changed = false;

        spin_unlock_irq(&efw->lock);

        count = min_t(long, count, sizeof(event.lock_status));

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

        return count;
}

static long
hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
           loff_t *offset)
{
        struct snd_efw *efw = hwdep->private_data;
        DEFINE_WAIT(wait);
        bool dev_lock_changed;
        bool queued;

        spin_lock_irq(&efw->lock);

        dev_lock_changed = efw->dev_lock_changed;
        queued = efw->push_ptr != efw->pull_ptr;

        while (!dev_lock_changed && !queued) {
                prepare_to_wait(&efw->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
                spin_unlock_irq(&efw->lock);
                schedule();
                finish_wait(&efw->hwdep_wait, &wait);
                if (signal_pending(current))
                        return -ERESTARTSYS;
                spin_lock_irq(&efw->lock);
                dev_lock_changed = efw->dev_lock_changed;
                queued = efw->push_ptr != efw->pull_ptr;
        }

        spin_unlock_irq(&efw->lock);

        if (dev_lock_changed)
                count = hwdep_read_locked(efw, buf, count, offset);
        else if (queued)
                count = hwdep_read_resp_buf(efw, buf, count, offset);

        return count;
}

static long
hwdep_write(struct snd_hwdep *hwdep, const char __user *data, long count,
            loff_t *offset)
{
        struct snd_efw *efw = hwdep->private_data;
        u32 seqnum;
        u8 *buf;

        if (count < sizeof(struct snd_efw_transaction) ||
            SND_EFW_RESPONSE_MAXIMUM_BYTES < count)
                return -EINVAL;

        buf = memdup_user(data, count);
        if (IS_ERR(buf))
                return PTR_ERR(buf);

        /* check seqnum is not for kernel-land */
        seqnum = be32_to_cpu(((struct snd_efw_transaction *)buf)->seqnum);
        if (seqnum > SND_EFW_TRANSACTION_USER_SEQNUM_MAX) {
                count = -EINVAL;
                goto end;
        }

        if (snd_efw_transaction_cmd(efw->unit, buf, count) < 0)
                count = -EIO;
end:
        kfree(buf);
        return count;
}

static __poll_t
hwdep_poll(struct snd_hwdep *hwdep, struct file *file, poll_table *wait)
{
        struct snd_efw *efw = hwdep->private_data;
        __poll_t events;

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

        spin_lock_irq(&efw->lock);
        if (efw->dev_lock_changed || efw->pull_ptr != efw->push_ptr)
                events = EPOLLIN | EPOLLRDNORM;
        else
                events = 0;
        spin_unlock_irq(&efw->lock);

        return events | EPOLLOUT;
}

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

        memset(&info, 0, sizeof(info));
        info.type = SNDRV_FIREWIRE_TYPE_FIREWORKS;
        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]);
        strlcpy(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_efw *efw)
{
        int err;

        spin_lock_irq(&efw->lock);

        if (efw->dev_lock_count == 0) {
                efw->dev_lock_count = -1;
                err = 0;
        } else {
                err = -EBUSY;
        }

        spin_unlock_irq(&efw->lock);

        return err;
}

static int
hwdep_unlock(struct snd_efw *efw)
{
        int err;

        spin_lock_irq(&efw->lock);

        if (efw->dev_lock_count == -1) {
                efw->dev_lock_count = 0;
                err = 0;
        } else {
                err = -EBADFD;
        }

        spin_unlock_irq(&efw->lock);

        return err;
}

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

        spin_lock_irq(&efw->lock);
        if (efw->dev_lock_count == -1)
                efw->dev_lock_count = 0;
        spin_unlock_irq(&efw->lock);

        return 0;
}

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

        switch (cmd) {
        case SNDRV_FIREWIRE_IOCTL_GET_INFO:
                return hwdep_get_info(efw, (void __user *)arg);
        case SNDRV_FIREWIRE_IOCTL_LOCK:
                return hwdep_lock(efw);
        case SNDRV_FIREWIRE_IOCTL_UNLOCK:
                return hwdep_unlock(efw);
        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_efw_create_hwdep_device(struct snd_efw *efw)
{
        static const struct snd_hwdep_ops ops = {
                .read           = hwdep_read,
                .write          = hwdep_write,
                .release        = hwdep_release,
                .poll           = hwdep_poll,
                .ioctl          = hwdep_ioctl,
                .ioctl_compat   = hwdep_compat_ioctl,
        };
        struct snd_hwdep *hwdep;
        int err;

        err = snd_hwdep_new(efw->card, "Fireworks", 0, &hwdep);
        if (err < 0)
                goto end;
        strcpy(hwdep->name, "Fireworks");
        hwdep->iface = SNDRV_HWDEP_IFACE_FW_FIREWORKS;
        hwdep->ops = ops;
        hwdep->private_data = efw;
        hwdep->exclusive = true;
end:
        return err;
}