linux/drivers/dma/virt-dma.h

/*
 * Virtual DMA channel support for DMAengine
 *
 * Copyright (C) 2012 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#ifndef VIRT_DMA_H
#define VIRT_DMA_H

#include <linux/dmaengine.h>
#include <linux/interrupt.h>

#include "dmaengine.h"

struct virt_dma_desc {
	struct dma_async_tx_descriptor tx;
	/* protected by vc.lock */
	struct list_head node;
};

struct virt_dma_chan {
	struct dma_chan	chan;
	struct tasklet_struct task;
	void (*desc_free)(struct virt_dma_desc *);

	spinlock_t lock;

	/* protected by vc.lock */
	struct list_head desc_submitted;
	struct list_head desc_issued;
	struct list_head desc_completed;

	struct virt_dma_desc *cyclic;
};

static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
{
	return container_of(chan, struct virt_dma_chan, chan);
}

void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head);
void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);

/**
 * vchan_tx_prep - prepare a descriptor
 * @vc: virtual channel allocating this descriptor
 * @vd: virtual descriptor to prepare
 * @tx_flags: flags argument passed in to prepare function
 */
static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan *vc,
	struct virt_dma_desc *vd, unsigned long tx_flags)
{
	extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);

	dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
	vd->tx.flags = tx_flags;
	vd->tx.tx_submit = vchan_tx_submit;

	return &vd->tx;
}

/**
 * vchan_issue_pending - move submitted descriptors to issued list
 * @vc: virtual channel to update
 *
 * vc.lock must be held by caller
 */
static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
{
	list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
	return !list_empty(&vc->desc_issued);
}

/**
 * vchan_cookie_complete - report completion of a descriptor
 * @vd: virtual descriptor to update
 *
 * vc.lock must be held by caller
 */
static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
{
	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
	dma_cookie_t cookie;

	cookie = vd->tx.cookie;
	dma_cookie_complete(&vd->tx);
	dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
		 vd, cookie);
	list_add_tail(&vd->node, &vc->desc_completed);

	tasklet_schedule(&vc->task);
}

/**
 * vchan_cyclic_callback - report the completion of a period
 * @vd: virtual descriptor
 */
static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
{
	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);

	vc->cyclic = vd;
	tasklet_schedule(&vc->task);
}

/**
 * vchan_next_desc - peek at the next descriptor to be processed
 * @vc: virtual channel to obtain descriptor from
 *
 * vc.lock must be held by caller
 */
static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
{
	if (list_empty(&vc->desc_issued))
		return NULL;

	return list_first_entry(&vc->desc_issued, struct virt_dma_desc, node);
}

/**
 * vchan_get_all_descriptors - obtain all submitted and issued descriptors
 * @vc: virtual channel to get descriptors from
 * @head: list of descriptors found
 *
 * vc.lock must be held by caller
 *
 * Removes all submitted and issued descriptors from internal lists, and
 * provides a list of all descriptors found
 */
static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
	struct list_head *head)
{
	list_splice_tail_init(&vc->desc_submitted, head);
	list_splice_tail_init(&vc->desc_issued, head);
	list_splice_tail_init(&vc->desc_completed, head);
}

static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
{
	unsigned long flags;
	LIST_HEAD(head);

	spin_lock_irqsave(&vc->lock, flags);
	vchan_get_all_descriptors(vc, &head);
	spin_unlock_irqrestore(&vc->lock, flags);

	vchan_dma_desc_free_list(vc, &head);
}

/**
 * vchan_synchronize() - synchronize callback execution to the current context
 * @vc: virtual channel to synchronize
 *
 * Makes sure that all scheduled or active callbacks have finished running. For
 * proper operation the caller has to ensure that no new callbacks are scheduled
 * after the invocation of this function started.
 */
static inline void vchan_synchronize(struct virt_dma_chan *vc)
{
	tasklet_kill(&vc->task);
}

#endif