[RFC][PATCH] dma-buf: Introduce dma-buf test module

[Laura Abbott]

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@xxxxxxxxxx>
---
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.
---
 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