drivers/dma/virt-dma.c

Source file repositories/reference/linux-study-clean/drivers/dma/virt-dma.c

File Facts

System
Linux kernel
Corpus path
drivers/dma/virt-dma.c
Extension
.c
Size
3587 bytes
Lines
144
Domain
Driver Families
Bucket
drivers/dma
Inferred role
Driver Families: exported/initcall integration point
Status
integration 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
/*
 * Virtual DMA channel support for DMAengine
 *
 * Copyright (C) 2012 Russell King
 */
#include <linux/device.h>
#include <linux/dmaengine.h>
#include <linux/module.h>
#include <linux/spinlock.h>

#include "virt-dma.h"

static struct virt_dma_desc *to_virt_desc(struct dma_async_tx_descriptor *tx)
{
	return container_of(tx, struct virt_dma_desc, tx);
}

dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
{
	struct virt_dma_chan *vc = to_virt_chan(tx->chan);
	struct virt_dma_desc *vd = to_virt_desc(tx);
	unsigned long flags;
	dma_cookie_t cookie;

	spin_lock_irqsave(&vc->lock, flags);
	cookie = dma_cookie_assign(tx);

	list_move_tail(&vd->node, &vc->desc_submitted);
	spin_unlock_irqrestore(&vc->lock, flags);

	dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: submitted\n",
		vc, vd, cookie);

	return cookie;
}
EXPORT_SYMBOL_GPL(vchan_tx_submit);

/**
 * vchan_tx_desc_free - free a reusable descriptor
 * @tx: the transfer
 *
 * This function frees a previously allocated reusable descriptor. The only
 * other way is to clear the DMA_CTRL_REUSE flag and submit one last time the
 * transfer.
 *
 * Returns 0 upon success
 */
int vchan_tx_desc_free(struct dma_async_tx_descriptor *tx)
{
	struct virt_dma_chan *vc = to_virt_chan(tx->chan);
	struct virt_dma_desc *vd = to_virt_desc(tx);
	unsigned long flags;

	spin_lock_irqsave(&vc->lock, flags);
	list_del(&vd->node);
	spin_unlock_irqrestore(&vc->lock, flags);

	dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: freeing\n",
		vc, vd, vd->tx.cookie);
	vc->desc_free(vd);
	return 0;
}
EXPORT_SYMBOL_GPL(vchan_tx_desc_free);

struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
	dma_cookie_t cookie)
{
	struct virt_dma_desc *vd;

	list_for_each_entry(vd, &vc->desc_issued, node)
		if (vd->tx.cookie == cookie)
			return vd;

	return NULL;
}
EXPORT_SYMBOL_GPL(vchan_find_desc);

/*
 * This tasklet handles the completion of a DMA descriptor by
 * calling its callback and freeing it.
 */
static void vchan_complete(struct tasklet_struct *t)
{
	struct virt_dma_chan *vc = from_tasklet(vc, t, task);
	struct virt_dma_desc *vd, *_vd;
	struct dmaengine_desc_callback cb;
	LIST_HEAD(head);

	spin_lock_irq(&vc->lock);

Annotation

Implementation Notes