sound/firewire/fireface/ff-hwdep.c

Source file repositories/reference/linux-study-clean/sound/firewire/fireface/ff-hwdep.c

File Facts

System
Linux kernel
Corpus path
sound/firewire/fireface/ff-hwdep.c
Extension
.c
Size
4336 bytes
Lines
191
Domain
Driver Families
Bucket
sound/firewire
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * ff-hwdep.c - a part of driver for RME Fireface series
 *
 * Copyright (c) 2015-2017 Takashi Sakamoto
 */

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

#include "ff.h"

static bool has_msg(struct snd_ff *ff)
{
	if (ff->spec->protocol->has_msg)
		return ff->spec->protocol->has_msg(ff);
	else
		return 0;
}

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

	spin_lock_irq(&ff->lock);

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

	if (ff->dev_lock_changed && count >= sizeof(struct snd_firewire_event_lock_status)) {
		struct snd_firewire_event_lock_status ev = {
			.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
			.status = (ff->dev_lock_count > 0),
		};

		ff->dev_lock_changed = false;

		spin_unlock_irq(&ff->lock);

		if (copy_to_user(buf, &ev, sizeof(ev)))
			return -EFAULT;
		count = sizeof(ev);
	} else if (has_msg(ff)) {
		// NOTE: Acquired spin lock should be released before accessing to user space in the
		// callback since the access can cause page fault.
		count = ff->spec->protocol->copy_msg_to_user(ff, buf, count);
		spin_unlock_irq(&ff->lock);
	} else {
		spin_unlock_irq(&ff->lock);

		count = 0;
	}

	return count;
}

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

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

	guard(spinlock_irq)(&ff->lock);
	if (ff->dev_lock_changed || has_msg(ff))
		return EPOLLIN | EPOLLRDNORM;
	else
		return 0;
}

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

	memset(&info, 0, sizeof(info));

Annotation

Implementation Notes