drm/gem: rename GEM CMA helpers to GEM DMA helpers

Rename "GEM CMA" helpers to "GEM DMA" helpers - considering the
hierarchy of APIs (mm/cma -> dma -> gem dma) calling them "GEM
DMA" seems to be more applicable.

Besides that, commit e57924d4ae80 ("drm/doc: Task to rename CMA helpers")
requests to rename the CMA helpers and implies that people seem to be
confused about the naming.

In order to do this renaming the following script was used:

```
	#!/bin/bash

	DIRS="drivers/gpu include/drm Documentation/gpu"

	REGEX_SYM_UPPER="[0-9A-Z_\-]"
	REGEX_SYM_LOWER="[0-9a-z_\-]"

	REGEX_GREP_UPPER="(${REGEX_SYM_UPPER}*)(GEM)_CMA_(${REGEX_SYM_UPPER}*)"
	REGEX_GREP_LOWER="(${REGEX_SYM_LOWER}*)(gem)_cma_(${REGEX_SYM_LOWER}*)"

	REGEX_SED_UPPER="s/${REGEX_GREP_UPPER}/\1\2_DMA_\3/g"
	REGEX_SED_LOWER="s/${REGEX_GREP_LOWER}/\1\2_dma_\3/g"

	# Find all upper case 'CMA' symbols and replace them with 'DMA'.
	for ff in $(grep -REHl "${REGEX_GREP_UPPER}" $DIRS)
	do
	       sed -i -E "$REGEX_SED_UPPER" $ff
	done

	# Find all lower case 'cma' symbols and replace them with 'dma'.
	for ff in $(grep -REHl "${REGEX_GREP_LOWER}" $DIRS)
	do
	       sed -i -E "$REGEX_SED_LOWER" $ff
	done

	# Replace all occurrences of 'CMA' / 'cma' in comments and
	# documentation files with 'DMA' / 'dma'.
	for ff in $(grep -RiHl " cma " $DIRS)
	do
		sed -i -E "s/ cma / dma /g" $ff
		sed -i -E "s/ CMA / DMA /g" $ff
	done

	# Rename all 'cma_obj's to 'dma_obj'.
	for ff in $(grep -RiHl "cma_obj" $DIRS)
	do
		sed -i -E "s/cma_obj/dma_obj/g" $ff
	done
```

Only a few more manual modifications were needed, e.g. reverting the
following modifications in some DRM Kconfig files

    -       select CMA if HAVE_DMA_CONTIGUOUS
    +       select DMA if HAVE_DMA_CONTIGUOUS

as well as manually picking the occurrences of 'CMA'/'cma' in comments and
documentation which relate to "GEM CMA", but not "FB CMA".

Also drivers/gpu/drm/Makefile was fixed up manually after renaming
drm_gem_cma_helper.c to drm_gem_dma_helper.c.

This patch is compile-time tested building a x86_64 kernel with
`make allyesconfig && make drivers/gpu/drm`.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> #drivers/gpu/drm/arm
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220802000405.949236-4-dakr@redhat.com

1 files changed, 602 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_gem_dma_helper.c b/drivers/gpu/drm/drm_gem_dma_helper.c
new file mode 100644
index 000000000000..f1780c01c928
--- /dev/null
+++ b/drivers/gpu/drm/drm_gem_dma_helper.c
@@ -0,0 +1,602 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * drm gem DMA helper functions
+ *
+ * Copyright (C) 2012 Sascha Hauer, Pengutronix
+ *
+ * Based on Samsung Exynos code
+ *
+ * Copyright (c) 2011 Samsung Electronics Co., Ltd.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/dma-mapping.h>
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+
+#include <drm/drm.h>
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_gem_dma_helper.h>
+#include <drm/drm_vma_manager.h>
+
+/**
+ * DOC: dma helpers
+ *
+ * The DRM GEM/DMA helpers are a means to provide buffer objects that are
+ * presented to the device as a contiguous chunk of memory. This is useful
+ * for devices that do not support scatter-gather DMA (either directly or
+ * by using an intimately attached IOMMU).
+ *
+ * For devices that access the memory bus through an (external) IOMMU then
+ * the buffer objects are allocated using a traditional page-based
+ * allocator and may be scattered through physical memory. However they
+ * are contiguous in the IOVA space so appear contiguous to devices using
+ * them.
+ *
+ * For other devices then the helpers rely on CMA to provide buffer
+ * objects that are physically contiguous in memory.
+ *
+ * For GEM callback helpers in struct &drm_gem_object functions, see likewise
+ * named functions with an _object_ infix (e.g., drm_gem_dma_object_vmap() wraps
+ * drm_gem_dma_vmap()). These helpers perform the necessary type conversion.
+ */
+
+static const struct drm_gem_object_funcs drm_gem_dma_default_funcs = {
+	.free = drm_gem_dma_object_free,
+	.print_info = drm_gem_dma_object_print_info,
+	.get_sg_table = drm_gem_dma_object_get_sg_table,
+	.vmap = drm_gem_dma_object_vmap,
+	.mmap = drm_gem_dma_object_mmap,
+	.vm_ops = &drm_gem_dma_vm_ops,
+};
+
+/**
+ * __drm_gem_dma_create - Create a GEM DMA object without allocating memory
+ * @drm: DRM device
+ * @size: size of the object to allocate
+ * @private: true if used for internal purposes
+ *
+ * This function creates and initializes a GEM DMA object of the given size,
+ * but doesn't allocate any memory to back the object.
+ *
+ * Returns:
+ * A struct drm_gem_dma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
+ */
+static struct drm_gem_dma_object *
+__drm_gem_dma_create(struct drm_device *drm, size_t size, bool private)
+{
+	struct drm_gem_dma_object *dma_obj;
+	struct drm_gem_object *gem_obj;
+	int ret = 0;
+
+	if (drm->driver->gem_create_object) {
+		gem_obj = drm->driver->gem_create_object(drm, size);
+		if (IS_ERR(gem_obj))
+			return ERR_CAST(gem_obj);
+		dma_obj = to_drm_gem_dma_obj(gem_obj);
+	} else {
+		dma_obj = kzalloc(sizeof(*dma_obj), GFP_KERNEL);
+		if (!dma_obj)
+			return ERR_PTR(-ENOMEM);
+		gem_obj = &dma_obj->base;
+	}
+
+	if (!gem_obj->funcs)
+		gem_obj->funcs = &drm_gem_dma_default_funcs;
+
+	if (private) {
+		drm_gem_private_object_init(drm, gem_obj, size);
+
+		/* Always use writecombine for dma-buf mappings */
+		dma_obj->map_noncoherent = false;
+	} else {
+		ret = drm_gem_object_init(drm, gem_obj, size);
+	}
+	if (ret)
+		goto error;
+
+	ret = drm_gem_create_mmap_offset(gem_obj);
+	if (ret) {
+		drm_gem_object_release(gem_obj);
+		goto error;
+	}
+
+	return dma_obj;
+
+error:
+	kfree(dma_obj);
+	return ERR_PTR(ret);
+}
+
+/**
+ * drm_gem_dma_create - allocate an object with the given size
+ * @drm: DRM device
+ * @size: size of the object to allocate
+ *
+ * This function creates a DMA GEM object and allocates memory as backing store.
+ * The allocated memory will occupy a contiguous chunk of bus address space.
+ *
+ * For devices that are directly connected to the memory bus then the allocated
+ * memory will be physically contiguous. For devices that access through an
+ * IOMMU, then the allocated memory is not expected to be physically contiguous
+ * because having contiguous IOVAs is sufficient to meet a devices DMA
+ * requirements.
+ *
+ * Returns:
+ * A struct drm_gem_dma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_dma_object *drm_gem_dma_create(struct drm_device *drm,
+					      size_t size)
+{
+	struct drm_gem_dma_object *dma_obj;
+	int ret;
+
+	size = round_up(size, PAGE_SIZE);
+
+	dma_obj = __drm_gem_dma_create(drm, size, false);
+	if (IS_ERR(dma_obj))
+		return dma_obj;
+
+	if (dma_obj->map_noncoherent) {
+		dma_obj->vaddr = dma_alloc_noncoherent(drm->dev, size,
+						       &dma_obj->paddr,
+						       DMA_TO_DEVICE,
+						       GFP_KERNEL | __GFP_NOWARN);
+	} else {
+		dma_obj->vaddr = dma_alloc_wc(drm->dev, size, &dma_obj->paddr,
+					      GFP_KERNEL | __GFP_NOWARN);
+	}
+	if (!dma_obj->vaddr) {
+		drm_dbg(drm, "failed to allocate buffer with size %zu\n",
+			 size);
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	return dma_obj;
+
+error:
+	drm_gem_object_put(&dma_obj->base);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_create);
+
+/**
+ * drm_gem_dma_create_with_handle - allocate an object with the given size and
+ *     return a GEM handle to it
+ * @file_priv: DRM file-private structure to register the handle for
+ * @drm: DRM device
+ * @size: size of the object to allocate
+ * @handle: return location for the GEM handle
+ *
+ * This function creates a DMA GEM object, allocating a chunk of memory as
+ * backing store. The GEM object is then added to the list of object associated
+ * with the given file and a handle to it is returned.
+ *
+ * The allocated memory will occupy a contiguous chunk of bus address space.
+ * See drm_gem_dma_create() for more details.
+ *
+ * Returns:
+ * A struct drm_gem_dma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
+ */
+static struct drm_gem_dma_object *
+drm_gem_dma_create_with_handle(struct drm_file *file_priv,
+			       struct drm_device *drm, size_t size,
+			       uint32_t *handle)
+{
+	struct drm_gem_dma_object *dma_obj;
+	struct drm_gem_object *gem_obj;
+	int ret;
+
+	dma_obj = drm_gem_dma_create(drm, size);
+	if (IS_ERR(dma_obj))
+		return dma_obj;
+
+	gem_obj = &dma_obj->base;
+
+	/*
+	 * allocate a id of idr table where the obj is registered
+	 * and handle has the id what user can see.
+	 */
+	ret = drm_gem_handle_create(file_priv, gem_obj, handle);
+	/* drop reference from allocate - handle holds it now. */
+	drm_gem_object_put(gem_obj);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return dma_obj;
+}
+
+/**
+ * drm_gem_dma_free - free resources associated with a DMA GEM object
+ * @dma_obj: DMA GEM object to free
+ *
+ * This function frees the backing memory of the DMA GEM object, cleans up the
+ * GEM object state and frees the memory used to store the object itself.
+ * If the buffer is imported and the virtual address is set, it is released.
+ */
+void drm_gem_dma_free(struct drm_gem_dma_object *dma_obj)
+{
+	struct drm_gem_object *gem_obj = &dma_obj->base;
+	struct iosys_map map = IOSYS_MAP_INIT_VADDR(dma_obj->vaddr);
+
+	if (gem_obj->import_attach) {
+		if (dma_obj->vaddr)
+			dma_buf_vunmap(gem_obj->import_attach->dmabuf, &map);
+		drm_prime_gem_destroy(gem_obj, dma_obj->sgt);
+	} else if (dma_obj->vaddr) {
+		if (dma_obj->map_noncoherent)
+			dma_free_noncoherent(gem_obj->dev->dev, dma_obj->base.size,
+					     dma_obj->vaddr, dma_obj->paddr,
+					     DMA_TO_DEVICE);
+		else
+			dma_free_wc(gem_obj->dev->dev, dma_obj->base.size,
+				    dma_obj->vaddr, dma_obj->paddr);
+	}
+
+	drm_gem_object_release(gem_obj);
+
+	kfree(dma_obj);
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_free);
+
+/**
+ * drm_gem_dma_dumb_create_internal - create a dumb buffer object
+ * @file_priv: DRM file-private structure to create the dumb buffer for
+ * @drm: DRM device
+ * @args: IOCTL data
+ *
+ * This aligns the pitch and size arguments to the minimum required. This is
+ * an internal helper that can be wrapped by a driver to account for hardware
+ * with more specific alignment requirements. It should not be used directly
+ * as their &drm_driver.dumb_create callback.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_dma_dumb_create_internal(struct drm_file *file_priv,
+				     struct drm_device *drm,
+				     struct drm_mode_create_dumb *args)
+{
+	unsigned int min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
+	struct drm_gem_dma_object *dma_obj;
+
+	if (args->pitch < min_pitch)
+		args->pitch = min_pitch;
+
+	if (args->size < args->pitch * args->height)
+		args->size = args->pitch * args->height;
+
+	dma_obj = drm_gem_dma_create_with_handle(file_priv, drm, args->size,
+						 &args->handle);
+	return PTR_ERR_OR_ZERO(dma_obj);
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_dumb_create_internal);
+
+/**
+ * drm_gem_dma_dumb_create - create a dumb buffer object
+ * @file_priv: DRM file-private structure to create the dumb buffer for
+ * @drm: DRM device
+ * @args: IOCTL data
+ *
+ * This function computes the pitch of the dumb buffer and rounds it up to an
+ * integer number of bytes per pixel. Drivers for hardware that doesn't have
+ * any additional restrictions on the pitch can directly use this function as
+ * their &drm_driver.dumb_create callback.
+ *
+ * For hardware with additional restrictions, drivers can adjust the fields
+ * set up by userspace and pass the IOCTL data along to the
+ * drm_gem_dma_dumb_create_internal() function.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_dma_dumb_create(struct drm_file *file_priv,
+			    struct drm_device *drm,
+			    struct drm_mode_create_dumb *args)
+{
+	struct drm_gem_dma_object *dma_obj;
+
+	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
+	args->size = args->pitch * args->height;
+
+	dma_obj = drm_gem_dma_create_with_handle(file_priv, drm, args->size,
+						 &args->handle);
+	return PTR_ERR_OR_ZERO(dma_obj);
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_dumb_create);
+
+const struct vm_operations_struct drm_gem_dma_vm_ops = {
+	.open = drm_gem_vm_open,
+	.close = drm_gem_vm_close,
+};
+EXPORT_SYMBOL_GPL(drm_gem_dma_vm_ops);
+
+#ifndef CONFIG_MMU
+/**
+ * drm_gem_dma_get_unmapped_area - propose address for mapping in noMMU cases
+ * @filp: file object
+ * @addr: memory address
+ * @len: buffer size
+ * @pgoff: page offset
+ * @flags: memory flags
+ *
+ * This function is used in noMMU platforms to propose address mapping
+ * for a given buffer.
+ * It's intended to be used as a direct handler for the struct
+ * &file_operations.get_unmapped_area operation.
+ *
+ * Returns:
+ * mapping address on success or a negative error code on failure.
+ */
+unsigned long drm_gem_dma_get_unmapped_area(struct file *filp,
+					    unsigned long addr,
+					    unsigned long len,
+					    unsigned long pgoff,
+					    unsigned long flags)
+{
+	struct drm_gem_dma_object *dma_obj;
+	struct drm_gem_object *obj = NULL;
+	struct drm_file *priv = filp->private_data;
+	struct drm_device *dev = priv->minor->dev;
+	struct drm_vma_offset_node *node;
+
+	if (drm_dev_is_unplugged(dev))
+		return -ENODEV;
+
+	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
+	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
+						  pgoff,
+						  len >> PAGE_SHIFT);
+	if (likely(node)) {
+		obj = container_of(node, struct drm_gem_object, vma_node);
+		/*
+		 * When the object is being freed, after it hits 0-refcnt it
+		 * proceeds to tear down the object. In the process it will
+		 * attempt to remove the VMA offset and so acquire this
+		 * mgr->vm_lock.  Therefore if we find an object with a 0-refcnt
+		 * that matches our range, we know it is in the process of being
+		 * destroyed and will be freed as soon as we release the lock -
+		 * so we have to check for the 0-refcnted object and treat it as
+		 * invalid.
+		 */
+		if (!kref_get_unless_zero(&obj->refcount))
+			obj = NULL;
+	}
+
+	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
+
+	if (!obj)
+		return -EINVAL;
+
+	if (!drm_vma_node_is_allowed(node, priv)) {
+		drm_gem_object_put(obj);
+		return -EACCES;
+	}
+
+	dma_obj = to_drm_gem_dma_obj(obj);
+
+	drm_gem_object_put(obj);
+
+	return dma_obj->vaddr ? (unsigned long)dma_obj->vaddr : -EINVAL;
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_get_unmapped_area);
+#endif
+
+/**
+ * drm_gem_dma_print_info() - Print &drm_gem_dma_object info for debugfs
+ * @dma_obj: DMA GEM object
+ * @p: DRM printer
+ * @indent: Tab indentation level
+ *
+ * This function prints paddr and vaddr for use in e.g. debugfs output.
+ */
+void drm_gem_dma_print_info(const struct drm_gem_dma_object *dma_obj,
+			    struct drm_printer *p, unsigned int indent)
+{
+	drm_printf_indent(p, indent, "paddr=%pad\n", &dma_obj->paddr);
+	drm_printf_indent(p, indent, "vaddr=%p\n", dma_obj->vaddr);
+}
+EXPORT_SYMBOL(drm_gem_dma_print_info);
+
+/**
+ * drm_gem_dma_get_sg_table - provide a scatter/gather table of pinned
+ *     pages for a DMA GEM object
+ * @dma_obj: DMA GEM object
+ *
+ * This function exports a scatter/gather table by calling the standard
+ * DMA mapping API.
+ *
+ * Returns:
+ * A pointer to the scatter/gather table of pinned pages or NULL on failure.
+ */
+struct sg_table *drm_gem_dma_get_sg_table(struct drm_gem_dma_object *dma_obj)
+{
+	struct drm_gem_object *obj = &dma_obj->base;
+	struct sg_table *sgt;
+	int ret;
+
+	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt)
+		return ERR_PTR(-ENOMEM);
+
+	ret = dma_get_sgtable(obj->dev->dev, sgt, dma_obj->vaddr,
+			      dma_obj->paddr, obj->size);
+	if (ret < 0)
+		goto out;
+
+	return sgt;
+
+out:
+	kfree(sgt);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_get_sg_table);
+
+/**
+ * drm_gem_dma_prime_import_sg_table - produce a DMA GEM object from another
+ *     driver's scatter/gather table of pinned pages
+ * @dev: device to import into
+ * @attach: DMA-BUF attachment
+ * @sgt: scatter/gather table of pinned pages
+ *
+ * This function imports a scatter/gather table exported via DMA-BUF by
+ * another driver. Imported buffers must be physically contiguous in memory
+ * (i.e. the scatter/gather table must contain a single entry). Drivers that
+ * use the DMA helpers should set this as their
+ * &drm_driver.gem_prime_import_sg_table callback.
+ *
+ * Returns:
+ * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_object *
+drm_gem_dma_prime_import_sg_table(struct drm_device *dev,
+				  struct dma_buf_attachment *attach,
+				  struct sg_table *sgt)
+{
+	struct drm_gem_dma_object *dma_obj;
+
+	/* check if the entries in the sg_table are contiguous */
+	if (drm_prime_get_contiguous_size(sgt) < attach->dmabuf->size)
+		return ERR_PTR(-EINVAL);
+
+	/* Create a DMA GEM buffer. */
+	dma_obj = __drm_gem_dma_create(dev, attach->dmabuf->size, true);
+	if (IS_ERR(dma_obj))
+		return ERR_CAST(dma_obj);
+
+	dma_obj->paddr = sg_dma_address(sgt->sgl);
+	dma_obj->sgt = sgt;
+
+	DRM_DEBUG_PRIME("dma_addr = %pad, size = %zu\n", &dma_obj->paddr, attach->dmabuf->size);
+
+	return &dma_obj->base;
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_prime_import_sg_table);
+
+/**
+ * drm_gem_dma_vmap - map a DMA GEM object into the kernel's virtual
+ *     address space
+ * @dma_obj: DMA GEM object
+ * @map: Returns the kernel virtual address of the DMA GEM object's backing
+ *       store.
+ *
+ * This function maps a buffer into the kernel's virtual address space.
+ * Since the DMA buffers are already mapped into the kernel virtual address
+ * space this simply returns the cached virtual address.
+ *
+ * Returns:
+ * 0 on success, or a negative error code otherwise.
+ */
+int drm_gem_dma_vmap(struct drm_gem_dma_object *dma_obj,
+		     struct iosys_map *map)
+{
+	iosys_map_set_vaddr(map, dma_obj->vaddr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_vmap);
+
+/**
+ * drm_gem_dma_mmap - memory-map an exported DMA GEM object
+ * @dma_obj: DMA GEM object
+ * @vma: VMA for the area to be mapped
+ *
+ * This function maps a buffer into a userspace process's address space.
+ * In addition to the usual GEM VMA setup it immediately faults in the entire
+ * object instead of using on-demand faulting.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_dma_mmap(struct drm_gem_dma_object *dma_obj, struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = &dma_obj->base;
+	int ret;
+
+	/*
+	 * Clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
+	 * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
+	 * the whole buffer.
+	 */
+	vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
+	vma->vm_flags &= ~VM_PFNMAP;
+	vma->vm_flags |= VM_DONTEXPAND;
+
+	if (dma_obj->map_noncoherent) {
+		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+
+		ret = dma_mmap_pages(dma_obj->base.dev->dev,
+				     vma, vma->vm_end - vma->vm_start,
+				     virt_to_page(dma_obj->vaddr));
+	} else {
+		ret = dma_mmap_wc(dma_obj->base.dev->dev, vma, dma_obj->vaddr,
+				  dma_obj->paddr, vma->vm_end - vma->vm_start);
+	}
+	if (ret)
+		drm_gem_vm_close(vma);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drm_gem_dma_mmap);
+
+/**
+ * drm_gem_dma_prime_import_sg_table_vmap - PRIME import another driver's
+ *	scatter/gather table and get the virtual address of the buffer
+ * @dev: DRM device
+ * @attach: DMA-BUF attachment
+ * @sgt: Scatter/gather table of pinned pages
+ *
+ * This function imports a scatter/gather table using
+ * drm_gem_dma_prime_import_sg_table() and uses dma_buf_vmap() to get the kernel
+ * virtual address. This ensures that a DMA GEM object always has its virtual
+ * address set. This address is released when the object is freed.
+ *
+ * This function can be used as the &drm_driver.gem_prime_import_sg_table
+ * callback. The &DRM_GEM_DMA_DRIVER_OPS_VMAP macro provides a shortcut to set
+ * the necessary DRM driver operations.
+ *
+ * Returns:
+ * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_object *
+drm_gem_dma_prime_import_sg_table_vmap(struct drm_device *dev,
+				       struct dma_buf_attachment *attach,
+				       struct sg_table *sgt)
+{
+	struct drm_gem_dma_object *dma_obj;
+	struct drm_gem_object *obj;
+	struct iosys_map map;
+	int ret;
+
+	ret = dma_buf_vmap(attach->dmabuf, &map);
+	if (ret) {
+		DRM_ERROR("Failed to vmap PRIME buffer\n");
+		return ERR_PTR(ret);
+	}
+
+	obj = drm_gem_dma_prime_import_sg_table(dev, attach, sgt);
+	if (IS_ERR(obj)) {
+		dma_buf_vunmap(attach->dmabuf, &map);
+		return obj;
+	}
+
+	dma_obj = to_drm_gem_dma_obj(obj);
+	dma_obj->vaddr = map.vaddr;
+
+	return obj;
+}
+EXPORT_SYMBOL(drm_gem_dma_prime_import_sg_table_vmap);
+
+MODULE_DESCRIPTION("DRM DMA memory-management helpers");
+MODULE_IMPORT_NS(DMA_BUF);
+MODULE_LICENSE("GPL");