Subject: Re: [RFC][PATCH] dma-buf: Introduce dma-buf test module
To: Sumit Semwal <sumit.semwal@linaro.org>, linaro-mm-sig@lists.linaro.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-media@vger.kernel.org
References: <1489521859-20701-1-git-send-email-labbott@redhat.com>
 <20170314201303.2o6bhyn5yudjx4m6@phenom.ffwll.local>
From: Laura Abbott <labbott@redhat.com>
Message-ID: <93fc4722-bffc-e96b-0191-bd3bf875aaf8@redhat.com>
Date: Tue, 14 Mar 2017 13:30:30 -0700
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On 03/14/2017 01:13 PM, Daniel Vetter wrote:
> On Tue, Mar 14, 2017 at 01:04:19PM -0700, Laura Abbott wrote:
>>
>> dma-buf is designed to share buffers. Sharing means that there needs to
>> be another subsystem to accept those buffers. Introduce a simple test
>> module to act as a dummy system to accept dma_bufs from elsewhere. The
>> goal is to provide a very simple interface to validate exported buffers
>> do something reasonable. This is based on ion_test.c that existed for
>> the Ion framework.
>>
>> Signed-off-by: Laura Abbott <labbott@redhat.com>
>> ---
>> This is basically a drop in of what was available as
>> drivers/staging/android/ion/ion_test.c. Given it has no Ion specific
>> parts it might be useful as a more general test module. RFC mostly
>> to see if this is generally useful or not.
> 
> We already have a test dma-buf driver, which also handles reservation
> objects and can create fences to provoke signalling races an all kinds of
> other fun. It's drivers/gpu/drm/vgem.
> 
> If there's anything missing in there, patches very much welcome.
> -Daniel
> 

Thanks for that pointer. It certainly looks more complete vs. allocating
a platform_device. I'll look and see if there's anything that needs
extension. Plus this means I can probably delete more code from Ion (woo)

Thanks,
Laura

>> ---
>>  drivers/dma-buf/Kconfig           |   9 ++
>>  drivers/dma-buf/Makefile          |   1 +
>>  drivers/dma-buf/dma-buf-test.c    | 309 ++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/dma_buf_test.h |  67 +++++++++
>>  4 files changed, 386 insertions(+)
>>  create mode 100644 drivers/dma-buf/dma-buf-test.c
>>  create mode 100644 include/uapi/linux/dma_buf_test.h
>>
>> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
>> index ed3b785..8b3fdb1 100644
>> --- a/drivers/dma-buf/Kconfig
>> +++ b/drivers/dma-buf/Kconfig
>> @@ -30,4 +30,13 @@ config SW_SYNC
>>  	  WARNING: improper use of this can result in deadlocking kernel
>>  	  drivers from userspace. Intended for test and debug only.
>>  
>> +config DMA_BUF_TEST
>> +	bool "Test module for dma-buf"
>> +	default n
>> +	---help---
>> +	  A test module to validate dma_buf APIs. This should not be
>> +	  enabled for general use.
>> +
>> +	  Say N here unless you know you want this.
>> +
>>  endmenu
>> diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
>> index c33bf88..5029608 100644
>> --- a/drivers/dma-buf/Makefile
>> +++ b/drivers/dma-buf/Makefile
>> @@ -1,3 +1,4 @@
>>  obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o
>>  obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
>>  obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o
>> +obj-$(CONFIG_DMA_BUF_TEST)	+= dma-buf-test.o
>> diff --git a/drivers/dma-buf/dma-buf-test.c b/drivers/dma-buf/dma-buf-test.c
>> new file mode 100644
>> index 0000000..3af131c
>> --- /dev/null
>> +++ b/drivers/dma-buf/dma-buf-test.c
>> @@ -0,0 +1,309 @@
>> +/*
>> + * Copyright (C) 2013 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License versdma_buf 2, as published by the Free Software Foundatdma_buf, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * 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.
>> + *
>> + */
>> +
>> +#define pr_fmt(fmt) "dma-buf-test: " fmt
>> +
>> +#include <linux/dma-buf.h>
>> +#include <linux/dma-direction.h>
>> +#include <linux/fs.h>
>> +#include <linux/miscdevice.h>
>> +#include <linux/mm.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/sched.h>
>> +#include <linux/slab.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/vmalloc.h>
>> +
>> +#include <uapi/linux/dma_buf_test.h>
>> +
>> +struct dma_buf_test_device {
>> +	struct miscdevice misc;
>> +};
>> +
>> +struct dma_buf_test_data {
>> +	struct dma_buf *dma_buf;
>> +	struct device *dev;
>> +};
>> +
>> +static int dma_buf_handle_test_dma(struct device *dev, struct dma_buf *dma_buf,
>> +			       void __user *ptr, size_t offset, size_t size,
>> +			       bool write)
>> +{
>> +	int ret = 0;
>> +	struct dma_buf_attachment *attach;
>> +	struct sg_table *table;
>> +	pgprot_t pgprot = pgprot_writecombine(PAGE_KERNEL);
>> +	enum dma_data_direction dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
>> +	struct sg_page_iter sg_iter;
>> +	unsigned long offset_page;
>> +
>> +	attach = dma_buf_attach(dma_buf, dev);
>> +	if (IS_ERR(attach))
>> +		return PTR_ERR(attach);
>> +
>> +	table = dma_buf_map_attachment(attach, dir);
>> +	if (IS_ERR(table))
>> +		return PTR_ERR(table);
>> +
>> +	offset_page = offset >> PAGE_SHIFT;
>> +	offset %= PAGE_SIZE;
>> +
>> +	for_each_sg_page(table->sgl, &sg_iter, table->nents, offset_page) {
>> +		struct page *page = sg_page_iter_page(&sg_iter);
>> +		void *vaddr = vmap(&page, 1, VM_MAP, pgprot);
>> +		size_t to_copy = PAGE_SIZE - offset;
>> +
>> +		to_copy = min(to_copy, size);
>> +		if (!vaddr) {
>> +			ret = -ENOMEM;
>> +			goto err;
>> +		}
>> +
>> +		if (write)
>> +			ret = copy_from_user(vaddr + offset, ptr, to_copy);
>> +		else
>> +			ret = copy_to_user(ptr, vaddr + offset, to_copy);
>> +
>> +		vunmap(vaddr);
>> +		if (ret) {
>> +			ret = -EFAULT;
>> +			goto err;
>> +		}
>> +		size -= to_copy;
>> +		if (!size)
>> +			break;
>> +		ptr += to_copy;
>> +		offset = 0;
>> +	}
>> +
>> +err:
>> +	dma_buf_unmap_attachment(attach, table, dir);
>> +	dma_buf_detach(dma_buf, attach);
>> +	return ret;
>> +}
>> +
>> +static int dma_buf_handle_test_kernel(struct dma_buf *dma_buf, void __user *ptr,
>> +				  size_t offset, size_t size, bool write)
>> +{
>> +	int ret;
>> +	unsigned long page_offset = offset >> PAGE_SHIFT;
>> +	size_t copy_offset = offset % PAGE_SIZE;
>> +	size_t copy_size = size;
>> +	enum dma_data_direction dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
>> +
>> +	if (offset > dma_buf->size || size > dma_buf->size - offset)
>> +		return -EINVAL;
>> +
>> +	ret = dma_buf_begin_cpu_access(dma_buf, dir);
>> +	if (ret)
>> +		return ret;
>> +
>> +	while (copy_size > 0) {
>> +		size_t to_copy;
>> +		void *vaddr = dma_buf_kmap(dma_buf, page_offset);
>> +
>> +		if (!vaddr)
>> +			goto err;
>> +
>> +		to_copy = min_t(size_t, PAGE_SIZE - copy_offset, copy_size);
>> +
>> +		if (write)
>> +			ret = copy_from_user(vaddr + copy_offset, ptr, to_copy);
>> +		else
>> +			ret = copy_to_user(ptr, vaddr + copy_offset, to_copy);
>> +
>> +		dma_buf_kunmap(dma_buf, page_offset, vaddr);
>> +		if (ret) {
>> +			ret = -EFAULT;
>> +			goto err;
>> +		}
>> +
>> +		copy_size -= to_copy;
>> +		ptr += to_copy;
>> +		page_offset++;
>> +		copy_offset = 0;
>> +	}
>> +err:
>> +	dma_buf_end_cpu_access(dma_buf, dir);
>> +	return ret;
>> +}
>> +
>> +static long dma_buf_test_ioctl(struct file *filp, unsigned int cmd,
>> +			   unsigned long arg)
>> +{
>> +	struct dma_buf_test_data *test_data = filp->private_data;
>> +	int ret = 0;
>> +
>> +	union {
>> +		struct dma_buf_test_rw_data test_rw;
>> +	} data;
>> +
>> +	if (_IOC_SIZE(cmd) > sizeof(data))
>> +		return -EINVAL;
>> +
>> +	if (_IOC_DIR(cmd) & _IOC_WRITE)
>> +		if (copy_from_user(&data, (void __user *)arg, _IOC_SIZE(cmd)))
>> +			return -EFAULT;
>> +
>> +	switch (cmd) {
>> +	case DMA_BUF_IOC_TEST_SET_FD:
>> +	{
>> +		struct dma_buf *dma_buf = NULL;
>> +		int fd = arg;
>> +
>> +		if (fd >= 0) {
>> +			dma_buf = dma_buf_get((int)arg);
>> +			if (IS_ERR(dma_buf))
>> +				return PTR_ERR(dma_buf);
>> +		}
>> +		if (test_data->dma_buf)
>> +			dma_buf_put(test_data->dma_buf);
>> +		test_data->dma_buf = dma_buf;
>> +		break;
>> +	}
>> +	case DMA_BUF_IOC_TEST_DMA_MAPPING:
>> +	{
>> +		ret = dma_buf_handle_test_dma(test_data->dev,
>> +					  test_data->dma_buf,
>> +					  u64_to_user_ptr(data.test_rw.ptr),
>> +					  data.test_rw.offset,
>> +					  data.test_rw.size,
>> +					  data.test_rw.write);
>> +		break;
>> +	}
>> +	case DMA_BUF_IOC_TEST_KERNEL_MAPPING:
>> +	{
>> +		ret = dma_buf_handle_test_kernel(test_data->dma_buf,
>> +					     u64_to_user_ptr(data.test_rw.ptr),
>> +					     data.test_rw.offset,
>> +					     data.test_rw.size,
>> +					     data.test_rw.write);
>> +		break;
>> +	}
>> +	default:
>> +		return -ENOTTY;
>> +	}
>> +
>> +	if (_IOC_DIR(cmd) & _IOC_READ) {
>> +		if (copy_to_user((void __user *)arg, &data, sizeof(data)))
>> +			return -EFAULT;
>> +	}
>> +	return ret;
>> +}
>> +
>> +static int dma_buf_test_open(struct inode *inode, struct file *file)
>> +{
>> +	struct dma_buf_test_data *data;
>> +	struct miscdevice *miscdev = file->private_data;
>> +
>> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
>> +	if (!data)
>> +		return -ENOMEM;
>> +
>> +	data->dev = miscdev->parent;
>> +
>> +	file->private_data = data;
>> +
>> +	return 0;
>> +}
>> +
>> +static int dma_buf_test_release(struct inode *inode, struct file *file)
>> +{
>> +	struct dma_buf_test_data *data = file->private_data;
>> +
>> +	kfree(data);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct file_operations dma_buf_test_fops = {
>> +	.owner = THIS_MODULE,
>> +	.unlocked_ioctl = dma_buf_test_ioctl,
>> +	.compat_ioctl = dma_buf_test_ioctl,
>> +	.open = dma_buf_test_open,
>> +	.release = dma_buf_test_release,
>> +};
>> +
>> +static int __init dma_buf_test_probe(struct platform_device *pdev)
>> +{
>> +	int ret;
>> +	struct dma_buf_test_device *testdev;
>> +
>> +	testdev = devm_kzalloc(&pdev->dev, sizeof(struct dma_buf_test_device),
>> +			       GFP_KERNEL);
>> +	if (!testdev)
>> +		return -ENOMEM;
>> +
>> +	testdev->misc.minor = MISC_DYNAMIC_MINOR;
>> +	testdev->misc.name = "dma_buf-test";
>> +	testdev->misc.fops = &dma_buf_test_fops;
>> +	testdev->misc.parent = &pdev->dev;
>> +	/*
>> +	 * We need to force 'something' for a DMA mask. This isn't an actual
>> +	 * device and won't be doing actual DMA so pick 'something' that
>> +	 * probably won't blow up. Probably.
>> +	 */
>> +	dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
>> +	ret = misc_register(&testdev->misc);
>> +	if (ret) {
>> +		pr_err("failed to register misc device.\n");
>> +		return ret;
>> +	}
>> +
>> +	platform_set_drvdata(pdev, testdev);
>> +
>> +	return 0;
>> +}
>> +
>> +static int dma_buf_test_remove(struct platform_device *pdev)
>> +{
>> +	struct dma_buf_test_device *testdev;
>> +
>> +	testdev = platform_get_drvdata(pdev);
>> +	if (!testdev)
>> +		return -ENODATA;
>> +
>> +	misc_deregister(&testdev->misc);
>> +	return 0;
>> +}
>> +
>> +static struct platform_device *dma_buf_test_pdev;
>> +static struct platform_driver dma_buf_test_platform_driver = {
>> +	.remove = dma_buf_test_remove,
>> +	.driver = {
>> +		.name = "dma_buf-test",
>> +	},
>> +};
>> +
>> +static int __init dma_buf_test_init(void)
>> +{
>> +	dma_buf_test_pdev = platform_device_register_simple("dma-buf-test",
>> +							-1, NULL, 0);
>> +	if (IS_ERR(dma_buf_test_pdev))
>> +		return PTR_ERR(dma_buf_test_pdev);
>> +
>> +	return platform_driver_probe(&dma_buf_test_platform_driver,
>> +				     dma_buf_test_probe);
>> +}
>> +
>> +static void __exit dma_buf_test_exit(void)
>> +{
>> +	platform_driver_unregister(&dma_buf_test_platform_driver);
>> +	platform_device_unregister(dma_buf_test_pdev);
>> +}
>> +
>> +module_init(dma_buf_test_init);
>> +module_exit(dma_buf_test_exit);
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/uapi/linux/dma_buf_test.h b/include/uapi/linux/dma_buf_test.h
>> new file mode 100644
>> index 0000000..af2d521
>> --- /dev/null
>> +++ b/include/uapi/linux/dma_buf_test.h
>> @@ -0,0 +1,67 @@
>> +/*
>> + * Copyright (C) 2011 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License versdma_buf 2, as published by the Free Software Foundatdma_buf, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * 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.
>> + *
>> + */
>> +
>> +#ifndef _UAPI_LINUX_DMA_BUF_TEST_H
>> +#define _UAPI_LINUX_DMA_BUF_TEST_H
>> +
>> +#include <linux/ioctl.h>
>> +#include <linux/types.h>
>> +
>> +/**
>> + * struct dma_buf_test_rw_data - metadata passed to the kernel to read handle
>> + * @ptr:	a pointer to an area at least as large as size
>> + * @offset:	offset into the dma_buf buffer to start reading
>> + * @size:	size to read or write
>> + * @write:	1 to write, 0 to read
>> + */
>> +struct dma_buf_test_rw_data {
>> +	__u64 ptr;
>> +	__u64 offset;
>> +	__u64 size;
>> +	int write;
>> +	int __padding;
>> +};
>> +
>> +#define DMA_BUF_IOC_MAGIC		'I'
>> +
>> +/**
>> + * DOC: DMA_BUF_IOC_TEST_SET_DMA_BUF - attach a dma buf to the test driver
>> + *
>> + * Attaches a dma buf fd to the test driver.  Passing a second fd or -1 will
>> + * release the first fd.
>> + */
>> +#define DMA_BUF_IOC_TEST_SET_FD \
>> +			_IO(DMA_BUF_IOC_MAGIC, 0xf0)
>> +
>> +/**
>> + * DOC: DMA_BUF_IOC_TEST_DMA_MAPPING - read or write memory from a handle as DMA
>> + *
>> + * Reads or writes the memory from a handle using an uncached mapping.  Can be
>> + * used by unit tests to emulate a DMA engine as close as possible.  Only
>> + * expected to be used for debugging and testing, may not always be available.
>> + */
>> +#define DMA_BUF_IOC_TEST_DMA_MAPPING \
>> +			_IOW(DMA_BUF_IOC_MAGIC, 0xf1, struct dma_buf_test_rw_data)
>> +
>> +/**
>> + * DOC: DMA_BUF_IOC_TEST_KERNEL_MAPPING - read or write memory from a handle
>> + *
>> + * Reads or writes the memory from a handle using a kernel mapping.  Can be
>> + * used by unit tests to test heap map_kernel functdma_bufs.  Only expected to be
>> + * used for debugging and testing, may not always be available.
>> + */
>> +#define DMA_BUF_IOC_TEST_KERNEL_MAPPING \
>> +			_IOW(DMA_BUF_IOC_MAGIC, 0xf2, struct dma_buf_test_rw_data)
>> +
>> +#endif /* _UAPI_LINUX_DMA_BUF_TEST_H */
>> -- 
>> 2.7.4
>>
>> _______________________________________________
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