alistair23-linux/drivers/dma/dmaengine.h

/*
 * The contents of this file are private to DMA engine drivers, and is not
 * part of the API to be used by DMA engine users.
 */
#ifndef DMAENGINE_H
#define DMAENGINE_H

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

/**
 * dma_cookie_assign - assign a DMA engine cookie to the descriptor
 * @tx: descriptor needing cookie
 *
 * Assign a unique non-zero per-channel cookie to the descriptor.
 * Note: caller is expected to hold a lock to prevent concurrency.
 */
static inline dma_cookie_t dma_cookie_assign(struct dma_async_tx_descriptor *tx)
{
	struct dma_chan *chan = tx->chan;
	dma_cookie_t cookie;

	cookie = chan->cookie + 1;
	if (cookie < DMA_MIN_COOKIE)
		cookie = DMA_MIN_COOKIE;
	tx->cookie = chan->cookie = cookie;

	return cookie;
}

/**
 * dma_cookie_complete - complete a descriptor
 * @tx: descriptor to complete
 *
 * Mark this descriptor complete by updating the channels completed
 * cookie marker.  Zero the descriptors cookie to prevent accidental
 * repeated completions.
 *
 * Note: caller is expected to hold a lock to prevent concurrency.
 */
static inline void dma_cookie_complete(struct dma_async_tx_descriptor *tx)
{
	BUG_ON(tx->cookie < DMA_MIN_COOKIE);
	tx->chan->completed_cookie = tx->cookie;
	tx->cookie = 0;
}

#endif