tascam-hwdep.c

// 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_t events;

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

	spin_lock_irq(&tscm->lock);
	if (tscm->dev_lock_changed || tscm->push_pos != tscm->pull_pos)
		events = EPOLLIN | EPOLLRDNORM;
	else
		events = 0;
	spin_unlock_irq(&tscm->lock);

	return events;
}

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)
{
	int err;

	spin_lock_irq(&tscm->lock);

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

	spin_unlock_irq(&tscm->lock);

	return err;
}

static int hwdep_unlock(struct snd_tscm *tscm)
{
	int err;

	spin_lock_irq(&tscm->lock);

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

	spin_unlock_irq(&tscm->lock);

	return err;
}

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;

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

	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;
}