[PATCH RFC 1/1] uio: Add dma-buf import ioctls

[Hyun Kwon]

Add the dmabuf map / unmap interfaces. This allows the user driver
to be able to import the external dmabuf and use it from user space.

Signed-off-by: Hyun Kwon <hyun.kwon@xxxxxxxxxx>
---
 drivers/uio/Makefile         |   2 +-
 drivers/uio/uio.c            |  43 +++++++++
 drivers/uio/uio_dmabuf.c     | 210 +++++++++++++++++++++++++++++++++++++++++++
 drivers/uio/uio_dmabuf.h     |  26 ++++++
 include/uapi/linux/uio/uio.h |  33 +++++++
 5 files changed, 313 insertions(+), 1 deletion(-)
 create mode 100644 drivers/uio/uio_dmabuf.c
 create mode 100644 drivers/uio/uio_dmabuf.h
 create mode 100644 include/uapi/linux/uio/uio.h

diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
index c285dd2..5da16c7 100644
--- a/drivers/uio/Makefile
+++ b/drivers/uio/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_UIO)	+= uio.o
+obj-$(CONFIG_UIO)	+= uio.o uio_dmabuf.o
 obj-$(CONFIG_UIO_CIF)	+= uio_cif.o
 obj-$(CONFIG_UIO_PDRV_GENIRQ)	+= uio_pdrv_genirq.o
 obj-$(CONFIG_UIO_DMEM_GENIRQ)	+= uio_dmem_genirq.o
diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 1313422..6841f98 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -24,6 +24,12 @@
 #include <linux/kobject.h>
 #include <linux/cdev.h>
 #include <linux/uio_driver.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+
+#include <uapi/linux/uio/uio.h>
+
+#include "uio_dmabuf.h"
 
 #define UIO_MAX_DEVICES		(1U << MINORBITS)
 
@@ -454,6 +460,8 @@ static irqreturn_t uio_interrupt(int irq, void *dev_id)
 struct uio_listener {
 	struct uio_device *dev;
 	s32 event_count;
+	struct list_head dbufs;
+	struct mutex dbufs_lock; /* protect @dbufs */
 };
 
 static int uio_open(struct inode *inode, struct file *filep)
@@ -500,6 +508,9 @@ static int uio_open(struct inode *inode, struct file *filep)
 	if (ret)
 		goto err_infoopen;
 
+	INIT_LIST_HEAD(&listener->dbufs);
+	mutex_init(&listener->dbufs_lock);
+
 	return 0;
 
 err_infoopen:
@@ -529,6 +540,10 @@ static int uio_release(struct inode *inode, struct file *filep)
 	struct uio_listener *listener = filep->private_data;
 	struct uio_device *idev = listener->dev;
 
+	ret = uio_dmabuf_cleanup(idev, &listener->dbufs, &listener->dbufs_lock);
+	if (ret)
+		dev_err(&idev->dev, "failed to clean up the dma bufs\n");
+
 	mutex_lock(&idev->info_lock);
 	if (idev->info && idev->info->release)
 		ret = idev->info->release(idev->info, inode);
@@ -652,6 +667,33 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
 	return retval ? retval : sizeof(s32);
 }
 
+static long uio_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+	struct uio_listener *listener = filep->private_data;
+	struct uio_device *idev = listener->dev;
+	long ret;
+
+	if (!idev->info)
+		return -EIO;
+
+	switch (cmd) {
+	case UIO_IOC_MAP_DMABUF:
+		ret = uio_dmabuf_map(idev, &listener->dbufs,
+				     &listener->dbufs_lock, (void __user *)arg);
+		break;
+	case UIO_IOC_UNMAP_DMABUF:
+		ret = uio_dmabuf_unmap(idev, &listener->dbufs,
+				       &listener->dbufs_lock,
+				       (void __user *)arg);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
 static int uio_find_mem_index(struct vm_area_struct *vma)
 {
 	struct uio_device *idev = vma->vm_private_data;
@@ -821,6 +863,7 @@ static const struct file_operations uio_fops = {
 	.write		= uio_write,
 	.mmap		= uio_mmap,
 	.poll		= uio_poll,
+	.unlocked_ioctl	= uio_ioctl,
 	.fasync		= uio_fasync,
 	.llseek		= noop_llseek,
 };
diff --git a/drivers/uio/uio_dmabuf.c b/drivers/uio/uio_dmabuf.c
new file mode 100644
index 0000000..b18f146
--- /dev/null
+++ b/drivers/uio/uio_dmabuf.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Xilinx, Inc.
+ *
+ * Author: Hyun Woo Kwon <hyun.kwon@xxxxxxxxxx>
+ *
+ * DMA buf support for UIO device
+ *
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <linux/uio_driver.h>
+#include <linux/slab.h>
+
+#include <uapi/linux/uio/uio.h>
+
+#include "uio_dmabuf.h"
+
+struct uio_dmabuf_mem {
+	int dbuf_fd;
+	struct dma_buf *dbuf;
+	struct dma_buf_attachment *dbuf_attach;
+	struct sg_table *sgt;
+	enum dma_data_direction dir;
+	struct list_head list;
+};
+
+long uio_dmabuf_map(struct uio_device *dev, struct list_head *dbufs,
+		    struct mutex *dbufs_lock, void __user *user_args)
+{
+	struct uio_dmabuf_args args;
+	struct uio_dmabuf_mem *dbuf_mem;
+	struct dma_buf *dbuf;
+	struct dma_buf_attachment *dbuf_attach;
+	enum dma_data_direction dir;
+	struct sg_table *sgt;
+	long ret;
+
+	if (copy_from_user(&args, user_args, sizeof(args))) {
+		ret = -EFAULT;
+		dev_err(dev->dev.parent, "failed to copy from user\n");
+		goto err;
+	}
+
+	dbuf = dma_buf_get(args.dbuf_fd);
+	if (IS_ERR(dbuf)) {
+		dev_err(dev->dev.parent, "failed to get dmabuf\n");
+		return PTR_ERR(dbuf);
+	}
+
+	dbuf_attach = dma_buf_attach(dbuf, dev->dev.parent);
+	if (IS_ERR(dbuf_attach)) {
+		dev_err(dev->dev.parent, "failed to attach dmabuf\n");
+		ret = PTR_ERR(dbuf_attach);
+		goto err_put;
+	}
+
+	switch (args.dir) {
+	case UIO_DMABUF_DIR_BIDIR:
+		dir = DMA_BIDIRECTIONAL;
+		break;
+	case UIO_DMABUF_DIR_TO_DEV:
+		dir = DMA_TO_DEVICE;
+		break;
+	case UIO_DMABUF_DIR_FROM_DEV:
+		dir = DMA_FROM_DEVICE;
+		break;
+	default:
+		/* Not needed with check. Just here for any future change  */
+		dev_err(dev->dev.parent, "invalid direction\n");
+		ret = -EINVAL;
+		goto err_detach;
+	}
+
+	sgt = dma_buf_map_attachment(dbuf_attach, dir);
+	if (IS_ERR(sgt)) {
+		dev_err(dev->dev.parent, "failed to get dmabuf scatterlist\n");
+		ret = PTR_ERR(sgt);
+		goto err_detach;
+	}
+
+	/* Accept only contiguous one */
+	if (sgt->nents != 1) {
+		dma_addr_t next_addr = sg_dma_address(sgt->sgl);
+		struct scatterlist *s;
+		unsigned int i;
+
+		for_each_sg(sgt->sgl, s, sgt->nents, i) {
+			if (!sg_dma_len(s))
+				continue;
+
+			if (sg_dma_address(s) != next_addr) {
+				dev_err(dev->dev.parent,
+					"dmabuf not contiguous\n");
+				ret = -EINVAL;
+				goto err_unmap;
+			}
+
+			next_addr = sg_dma_address(s) + sg_dma_len(s);
+		}
+	}
+
+	dbuf_mem = kzalloc(sizeof(*dbuf_mem), GFP_KERNEL);
+	if (!dbuf_mem) {
+		ret = -ENOMEM;
+		goto err_unmap;
+	}
+
+	dbuf_mem->dbuf_fd = args.dbuf_fd;
+	dbuf_mem->dbuf = dbuf;
+	dbuf_mem->dbuf_attach = dbuf_attach;
+	dbuf_mem->sgt = sgt;
+	dbuf_mem->dir = dir;
+	args.dma_addr = sg_dma_address(sgt->sgl);
+	args.size = dbuf->size;
+
+	if (copy_to_user(user_args, &args, sizeof(args))) {
+		ret = -EFAULT;
+		dev_err(dev->dev.parent, "failed to copy to user\n");
+		goto err_free;
+	}
+
+	mutex_lock(dbufs_lock);
+	list_add(&dbuf_mem->list, dbufs);
+	mutex_unlock(dbufs_lock);
+
+	return 0;
+
+err_free:
+	kfree(dbuf_mem);
+err_unmap:
+	dma_buf_unmap_attachment(dbuf_attach, sgt, dir);
+err_detach:
+	dma_buf_detach(dbuf, dbuf_attach);
+err_put:
+	dma_buf_put(dbuf);
+err:
+	return ret;
+}
+
+long uio_dmabuf_unmap(struct uio_device *dev, struct list_head *dbufs,
+		      struct mutex *dbufs_lock, void __user *user_args)
+
+{
+	struct uio_dmabuf_args args;
+	struct uio_dmabuf_mem *dbuf_mem;
+	long ret;
+
+	if (copy_from_user(&args, user_args, sizeof(args))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	mutex_lock(dbufs_lock);
+	list_for_each_entry(dbuf_mem, dbufs, list) {
+		if (dbuf_mem->dbuf_fd == args.dbuf_fd)
+			break;
+	}
+
+	if (dbuf_mem->dbuf_fd != args.dbuf_fd) {
+		dev_err(dev->dev.parent, "failed to find the dmabuf (%d)\n",
+			args.dbuf_fd);
+		ret = -EINVAL;
+		goto err_unlock;
+	}
+	list_del(&dbuf_mem->list);
+	mutex_unlock(dbufs_lock);
+
+	dma_buf_unmap_attachment(dbuf_mem->dbuf_attach, dbuf_mem->sgt,
+				 dbuf_mem->dir);
+	dma_buf_detach(dbuf_mem->dbuf, dbuf_mem->dbuf_attach);
+	dma_buf_put(dbuf_mem->dbuf);
+	kfree(dbuf_mem);
+
+	memset(&args, 0x0, sizeof(args));
+
+	if (copy_to_user(user_args, &args, sizeof(args))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	return 0;
+
+err_unlock:
+	mutex_unlock(dbufs_lock);
+err:
+	return ret;
+}
+
+int uio_dmabuf_cleanup(struct uio_device *dev, struct list_head *dbufs,
+		       struct mutex *dbufs_lock)
+{
+	struct uio_dmabuf_mem *dbuf_mem, *next;
+
+	mutex_lock(dbufs_lock);
+	list_for_each_entry_safe(dbuf_mem, next, dbufs, list) {
+		list_del(&dbuf_mem->list);
+		dma_buf_unmap_attachment(dbuf_mem->dbuf_attach, dbuf_mem->sgt,
+					 dbuf_mem->dir);
+		dma_buf_detach(dbuf_mem->dbuf, dbuf_mem->dbuf_attach);
+		dma_buf_put(dbuf_mem->dbuf);
+		kfree(dbuf_mem);
+	}
+	mutex_unlock(dbufs_lock);
+
+	return 0;
+}
diff --git a/drivers/uio/uio_dmabuf.h b/drivers/uio/uio_dmabuf.h
new file mode 100644
index 0000000..3020030
--- /dev/null
+++ b/drivers/uio/uio_dmabuf.h
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Xilinx, Inc.
+ *
+ * Author: Hyun Woo Kwon <hyun.kwon@xxxxxxxxxx>
+ *
+ * DMA buf support for UIO device
+ *
+ */
+
+#ifndef _UIO_DMABUF_H_
+#define _UIO_DMABUF_H_
+
+struct uio_device;
+struct list_head;
+struct mutex;
+
+long uio_dmabuf_map(struct uio_device *dev, struct list_head *dbufs,
+		    struct mutex *dbufs_lock, void __user *user_args);
+long uio_dmabuf_unmap(struct uio_device *dev, struct list_head *dbufs,
+		      struct mutex *dbufs_lock, void __user *user_args);
+
+int uio_dmabuf_cleanup(struct uio_device *dev, struct list_head *dbufs,
+		       struct mutex *dbufs_lock);
+
+#endif
diff --git a/include/uapi/linux/uio/uio.h b/include/uapi/linux/uio/uio.h
new file mode 100644
index 0000000..298bfd7
--- /dev/null
+++ b/include/uapi/linux/uio/uio.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * The header for UIO driver
+ *
+ * Copyright (C) 2019 Xilinx, Inc.
+ *
+ * Author: Hyun Woo Kwon <hyun.kwon@xxxxxxxxxx>
+ */
+
+#ifndef _UAPI_UIO_UIO_H_
+#define _UAPI_UIO_UIO_H_
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+#define UIO_DMABUF_DIR_BIDIR	1
+#define UIO_DMABUF_DIR_TO_DEV	2
+#define UIO_DMABUF_DIR_FROM_DEV	3
+#define UIO_DMABUF_DIR_NONE	4
+
+struct uio_dmabuf_args {
+	__s32	dbuf_fd;
+	__u64	dma_addr;
+	__u64	size;
+	__u32	dir;
+};
+
+#define UIO_IOC_BASE		'U'
+
+#define	UIO_IOC_MAP_DMABUF	_IOWR(UIO_IOC_BASE, 0x1, struct uio_dmabuf_args)
+#define	UIO_IOC_UNMAP_DMABUF	_IOWR(UIO_IOC_BASE, 0x2, struct uio_dmabuf_args)
+
+#endif
-- 
2.7.4