path: root/drivers/dma/dmaengine.c

/*
 * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * The full GNU General Public License is included in this distribution in the
 * file called COPYING.
 */

/*
 * This code implements the DMA subsystem. It provides a HW-neutral interface
 * for other kernel code to use asynchronous memory copy capabilities,
 * if present, and allows different HW DMA drivers to register as providing
 * this capability.
 *
 * Due to the fact we are accelerating what is already a relatively fast
 * operation, the code goes to great lengths to avoid additional overhead,
 * such as locking.
 *
 * LOCKING:
 *
 * The subsystem keeps a global list of dma_device structs it is protected by a
 * mutex, dma_list_mutex.
 *
 * A subsystem can get access to a channel by calling dmaengine_get() followed
 * by dma_find_channel(), or if it has need for an exclusive channel it can call
 * dma_request_channel().  Once a channel is allocated a reference is taken
 * against its corresponding driver to disable removal.
 *
 * Each device has a channels list, which runs unlocked but is never modified
 * once the device is registered, it's just setup by the driver.
 *
 * See Documentation/dmaengine.txt for more details
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/device.h>
#include <linux/dmaengine.h>
#include <linux/hardirq.h>
#include <linux/spinlock.h>
#include <linux/percpu.h>
#include <linux/rcupdate.h>
#include <linux/mutex.h>
#include <linux/jiffies.h>
#include <linux/rculist.h>
#include <linux/idr.h>

static DEFINE_MUTEX(dma_list_mutex);
static LIST_HEAD(dma_device_list);
static long dmaengine_ref_count;
static struct idr dma_idr;

/* --- sysfs implementation --- */

/**
 * dev_to_dma_chan - convert a device pointer to the its sysfs container object
 * @dev - device node
 *
 * Must be called under dma_list_mutex
 */
static struct dma_chan *dev_to_dma_chan(struct device *dev)
{
	struct dma_chan_dev *chan_dev;

	chan_dev = container_of(dev, typeof(*chan_dev), device);
	return chan_dev->chan;
}

static ssize_t show_memcpy_count(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dma_chan *chan;
	unsigned long count = 0;
	int i;
	int err;

	mutex_lock(&dma_list_mutex);
	chan = dev_to_dma_chan(dev);
	if (chan) {
		for_each_possible_cpu(i)
			count += per_cpu_ptr(chan->local, i)->memcpy_count;
		err = sprintf(buf, "%lu\n", count);
	} else
		err = -ENODEV;
	mutex_unlock(&dma_list_mutex);

	return err;
}

static ssize_t show_bytes_transferred(struct device *dev, struct device_attribute *attr,
				      char *buf)
{
	struct dma_chan *chan;
	unsigned long count = 0;
	int i;
	int err;

	mutex_lock(&dma_list_mutex);
	chan = dev_to_dma_chan(dev);
	if (chan) {
		for_each_possible_cpu(i)
			count += per_cpu_ptr(chan->local, i)->bytes_transferred;
		err = sprintf(buf, "%lu\n", count);
	} else
		err = -ENODEV;
	mutex_unlock(&dma_list_mutex);

	return err;
}

static ssize_t show_in_use(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dma_chan *chan;
	int err;

	mutex_lock(&dma_list_mutex);
	chan = dev_to_dma_chan(dev);
	if (chan)
		err = sprintf(buf, "%d\n", chan->client_count);
	else
		err = -ENODEV;
	mutex_unlock(&dma_list_mutex);

	return err;
}

static struct device_attribute dma_attrs[] = {
	__ATTR(memcpy_count, S_IRUGO, show_memcpy_count, NULL),
	__ATTR(bytes_transferred, S_IRUGO, show_bytes_transferred, NULL),
	__ATTR(in_use, S_IRUGO, show_in_use, NULL),
	__ATTR_NULL
};

static void chan_dev_release(struct device *dev)
{
	struct dma_chan_dev *chan_dev;

	chan_dev = container_of(dev, typeof(*chan_dev), device);
	if (atomic_dec_and_test(chan_dev->idr_ref)) {
		mutex_lock(&dma_list_mutex);
		idr_remove(&dma_idr, chan_dev->dev_id);
		mutex_unlock(&dma_list_mutex);
		kfree(chan_dev->idr_ref);
	}
	kfree(chan_dev);
}

static struct class dma_devclass =