Date:	Thu, 12 Dec 2013 15:53:05 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [RFC] dma-buf: Implement test module

On Thu, Dec 12, 2013 at 03:36:29PM +0100, Thierry Reding wrote:
> This is a simple test module that can be used to allocate, export and
> delete DMA-BUF objects. It can be used to test DMA-BUF sharing in
> systems that lack a real second driver.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/base/Kconfig        |   4 +
>  drivers/base/Makefile       |   1 +
>  drivers/base/dma-buf-test.c | 308 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 313 insertions(+)
>  create mode 100644 drivers/base/dma-buf-test.c
> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index e373671652b0..bed2abb9491b 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -200,6 +200,10 @@ config DMA_SHARED_BUFFER
>  	  APIs extension; the file's descriptor can then be passed on to other
>  	  driver.
>  
> +config DMA_BUF_TEST
> +	tristate "DMA-BUF test module"
> +	depends on DMA_SHARED_BUFFER
> +
>  config DMA_CMA
>  	bool "DMA Contiguous Memory Allocator"
>  	depends on HAVE_DMA_CONTIGUOUS && CMA
> diff --git a/drivers/base/Makefile b/drivers/base/Makefile
> index 94e8a80e87f8..cad983b6626f 100644
> --- a/drivers/base/Makefile
> +++ b/drivers/base/Makefile
> @@ -25,3 +25,4 @@ obj-$(CONFIG_PINCTRL) += pinctrl.o
>  
>  ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
>  
> +obj-$(CONFIG_DMA_BUF_TEST) += dma-buf-test.o
> diff --git a/drivers/base/dma-buf-test.c b/drivers/base/dma-buf-test.c
> new file mode 100644
> index 000000000000..f5498b74a09b
> --- /dev/null
> +++ b/drivers/base/dma-buf-test.c
> @@ -0,0 +1,308 @@
> +#include <linux/dma-buf.h>
> +#include <linux/err.h>
> +#include <linux/fs.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +struct dmabuf_create {
> +	__u32 flags;
> +	__u32 size;
> +};
> +
> +#define DMABUF_IOCTL_BASE	'D'
> +#define DMABUF_IOCTL_CREATE	_IOWR(DMABUF_IOCTL_BASE, 0, struct dmabuf_create)
> +#define DMABUF_IOCTL_DELETE	_IOWR(DMABUF_IOCTL_BASE, 1, int)
> +#define DMABUF_IOCTL_EXPORT	_IOWR(DMABUF_IOCTL_BASE, 2, int)

Shouldn't we put this into an uapi header somewhere? Also I think the
ioctl interface is a bit convoluted - I'd just make one single interface
which directly returns a new dma-buf fd. Removing it can be handled with
close, no other ioctls required imo. The explicit export step is kinda
only for subsystems that already have an existing buffer handle space, but
we don't have this here.

Otherwise very much wanted.
-Daniel

> +
> +struct dmabuf_file {
> +	struct dma_buf *buf;
> +	dma_addr_t phys;
> +	size_t size;
> +	void *virt;
> +};
> +
> +static int dmabuf_attach(struct dma_buf *buf, struct device *dev,
> +			 struct dma_buf_attachment *attach)
> +{
> +	return 0;
> +}
> +
> +static void dmabuf_detach(struct dma_buf *buf,
> +			  struct dma_buf_attachment *attach)
> +{
> +}
> +
> +static struct sg_table *dmabuf_map_dma_buf(struct dma_buf_attachment *attach,
> +					   enum dma_data_direction dir)
> +{
> +	struct dmabuf_file *priv = attach->dmabuf->priv;
> +	struct sg_table *sgt;
> +
> +	sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
> +	if (!sgt)
> +		return NULL;
> +
> +	if (sg_alloc_table(sgt, 1, GFP_KERNEL)) {
> +		kfree(sgt);
> +		return NULL;
> +	}
> +
> +	sg_dma_address(sgt->sgl) = priv->phys;
> +	sg_dma_len(sgt->sgl) = priv->size;
> +
> +	return sgt;
> +}
> +
> +static void dmabuf_unmap_dma_buf(struct dma_buf_attachment *attach,
> +				 struct sg_table *sgt,
> +				 enum dma_data_direction dir)
> +{
> +	sg_free_table(sgt);
> +	kfree(sgt);
> +}
> +
> +static void dmabuf_release(struct dma_buf *buf)
> +{
> +}
> +
> +static int dmabuf_begin_cpu_access(struct dma_buf *buf, size_t size,
> +				   size_t length,
> +				   enum dma_data_direction direction)
> +{
> +	return 0;
> +}
> +
> +static void dmabuf_end_cpu_access(struct dma_buf *buf, size_t size,
> +				  size_t length,
> +				  enum dma_data_direction direction)
> +{
> +}
> +
> +static void *dmabuf_kmap_atomic(struct dma_buf *buf, unsigned long page)
> +{
> +	return NULL;
> +}
> +
> +static void dmabuf_kunmap_atomic(struct dma_buf *buf, unsigned long page,
> +				 void *vaddr)
> +{
> +}
> +
> +static void *dmabuf_kmap(struct dma_buf *buf, unsigned long page)
> +{
> +	return NULL;
> +}
> +
> +static void dmabuf_kunmap(struct dma_buf *buf, unsigned long page, void *vaddr)
> +{
> +}
> +
> +static void dmabuf_vm_open(struct vm_area_struct *vma)
> +{
> +}
> +
> +static void dmabuf_vm_close(struct vm_area_struct *vma)
> +{
> +}
> +
> +static int dmabuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> +	return 0;
> +}
> +
> +static const struct vm_operations_struct dmabuf_vm_ops = {
> +	.open = dmabuf_vm_open,
> +	.close = dmabuf_vm_close,
> +	.fault = dmabuf_vm_fault,
> +};
> +
> +static int dmabuf_mmap(struct dma_buf *buf, struct vm_area_struct *vma)
> +{
> +	pgprot_t prot = vm_get_page_prot(vma->vm_flags);
> +	struct dmabuf_file *priv = buf->priv;
> +
> +	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
> +	vma->vm_ops = &dmabuf_vm_ops;
> +	vma->vm_private_data = priv;
> +	vma->vm_page_prot = pgprot_writecombine(prot);
> +
> +	return remap_pfn_range(vma, vma->vm_start, priv->phys >> PAGE_SHIFT,
> +			       vma->vm_end - vma->vm_start, vma->vm_page_prot);
> +}
> +
> +static void *dmabuf_vmap(struct dma_buf *buf)
> +{
> +	return NULL;
> +}
> +
> +static void dmabuf_vunmap(struct dma_buf *buf, void *vaddr)
> +{
> +}
> +
> +static const struct dma_buf_ops dmabuf_ops = {
> +	.attach = dmabuf_attach,
> +	.detach = dmabuf_detach,
> +	.map_dma_buf = dmabuf_map_dma_buf,
> +	.unmap_dma_buf = dmabuf_unmap_dma_buf,
> +	.release = dmabuf_release,
> +	.begin_cpu_access = dmabuf_begin_cpu_access,
> +	.end_cpu_access = dmabuf_end_cpu_access,
> +	.kmap_atomic = dmabuf_kmap_atomic,
> +	.kunmap_atomic = dmabuf_kunmap_atomic,
> +	.kmap = dmabuf_kmap,
> +	.kunmap = dmabuf_kunmap,
> +	.mmap = dmabuf_mmap,
> +	.vmap = dmabuf_vmap,
> +	.vunmap = dmabuf_vunmap,
> +};
> +
> +static int dmabuf_file_open(struct inode *inode, struct file *file)
> +{
> +	struct dmabuf_file *priv;
> +	int ret = 0;
> +
> +	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	file->private_data = priv;
> +
> +	return ret;
> +}
> +
> +static int dmabuf_file_release(struct inode *inode, struct file *file)
> +{
> +	struct dmabuf_file *priv = file->private_data;
> +	int ret = 0;
> +
> +	if (priv->virt)
> +		dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys);
> +
> +	if (priv->buf)
> +		dma_buf_put(priv->buf);
> +
> +	kfree(priv);
> +
> +	return ret;
> +}
> +
> +static int dmabuf_ioctl_create(struct dmabuf_file *priv, const void __user *data)
> +{
> +	struct dmabuf_create args;
> +	int ret = 0;
> +
> +	if (priv->buf || priv->virt)
> +		return -EBUSY;
> +
> +	if (copy_from_user(&args, data, sizeof(args)))
> +		return -EFAULT;
> +
> +	priv->virt = dma_alloc_writecombine(NULL, args.size, &priv->phys,
> +					    GFP_KERNEL | __GFP_NOWARN);
> +	if (!priv->virt)
> +		return -ENOMEM;
> +
> +	priv->buf = dma_buf_export(priv, &dmabuf_ops, args.size, args.flags);
> +	if (!priv->buf) {
> +		ret = -ENOMEM;
> +		goto free;
> +	}
> +
> +	if (IS_ERR(priv->buf)) {
> +		ret = PTR_ERR(priv->buf);
> +		goto free;
> +	}
> +
> +	priv->size = args.size;
> +
> +	return 0;
> +
> +free:
> +	dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys);
> +	priv->virt = NULL;
> +	return ret;
> +}
> +
> +static int dmabuf_ioctl_delete(struct dmabuf_file *priv, unsigned long flags)
> +{
> +	dma_free_writecombine(NULL, priv->size, priv->virt, priv->phys);
> +	priv->virt = NULL;
> +	priv->phys = 0;
> +	priv->size = 0;
> +
> +	dma_buf_put(priv->buf);
> +	priv->buf = NULL;
> +
> +	return 0;
> +}
> +
> +static int dmabuf_ioctl_export(struct dmabuf_file *priv, unsigned long flags)
> +{
> +	int err;
> +
> +	get_dma_buf(priv->buf);
> +
> +	err = dma_buf_fd(priv->buf, flags);
> +	if (err < 0)
> +		dma_buf_put(priv->buf);
> +
> +	return err;
> +}
> +
> +static long dmabuf_file_ioctl(struct file *file, unsigned int cmd,
> +			      unsigned long arg)
> +{
> +	struct dmabuf_file *priv = file->private_data;
> +	long ret = 0;
> +
> +	switch (cmd) {
> +	case DMABUF_IOCTL_CREATE:
> +		ret = dmabuf_ioctl_create(priv, (const void __user *)arg);
> +		break;
> +
> +	case DMABUF_IOCTL_DELETE:
> +		ret = dmabuf_ioctl_delete(priv, arg);
> +		break;
> +
> +	case DMABUF_IOCTL_EXPORT:
> +		ret = dmabuf_ioctl_export(priv, arg);
> +		break;
> +
> +	default:
> +		ret = -ENOTTY;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct file_operations dmabuf_fops = {
> +	.owner = THIS_MODULE,
> +	.open = dmabuf_file_open,
> +	.release = dmabuf_file_release,
> +	.unlocked_ioctl = dmabuf_file_ioctl,
> +};
> +
> +static struct miscdevice dmabuf_device = {
> +	.minor = 128,
> +	.name = "dmabuf",
> +	.fops = &dmabuf_fops,
> +};
> +
> +static int __init dmabuf_init(void)
> +{
> +	return misc_register(&dmabuf_device);
> +}
> +module_init(dmabuf_init);
> +
> +static void __exit dmabuf_exit(void)
> +{
> +	misc_deregister(&dmabuf_device);
> +}
> +module_exit(dmabuf_exit);
> +
> +MODULE_AUTHOR("Thierry Reding <treding@...dia.com>");
> +MODULE_DESCRIPTION("DMA-BUF test driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.8.4.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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