OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​drm_gem_shmem_helper.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright 2018 Noralf Trønnes
  */
 
 #include <linux/dma-buf.h>
 #include <linux/export.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/module.h>
 
 #ifdef CONFIG_X86
 #include <asm/set_memory.h>
 #endif
 
 #include <drm/drm.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_prime.h>
 #include <drm/drm_print.h>
 
 MODULE_IMPORT_NS(DMA_BUF);
 
 /**
  * DOC: overview
  *
  * This library provides helpers for GEM objects backed by shmem buffers
  * allocated using anonymous pageable memory.
  *
  * Functions that operate on the GEM object receive struct &drm_gem_shmem_object.
  * For GEM callback helpers in struct &drm_gem_object functions, see likewise
  * named functions with an _object_ infix (e.g., drm_gem_shmem_object_vmap() wraps
  * drm_gem_shmem_vmap()). These helpers perform the necessary type conversion.
  */
 
 static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
     .free = drm_gem_shmem_object_free,
     .print_info = drm_gem_shmem_object_print_info,
     .pin = drm_gem_shmem_object_pin,
     .unpin = drm_gem_shmem_object_unpin,
     .get_sg_table = drm_gem_shmem_object_get_sg_table,
     .vmap = drm_gem_shmem_object_vmap,
     .vunmap = drm_gem_shmem_object_vunmap,
     .mmap = drm_gem_shmem_object_mmap,
     .vm_ops = &drm_gem_shmem_vm_ops,
 };
 
 static struct drm_gem_shmem_object *
 __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
 {
     struct drm_gem_shmem_object *shmem;
     struct drm_gem_object *obj;
     int ret = 0;
 
     size = PAGE_ALIGN(size);
 
     if (dev->driver->gem_create_object) {
         obj = dev->driver->gem_create_object(dev, size);
         if (IS_ERR(obj))
             return ERR_CAST(obj);
         shmem = to_drm_gem_shmem_obj(obj);
     } else {
         shmem = kzalloc(sizeof(*shmem), GFP_KERNEL);
         if (!shmem)
             return ERR_PTR(-ENOMEM);
         obj = &shmem->base;
     }
 
     if (!obj->funcs)
         obj->funcs = &drm_gem_shmem_funcs;
 
     if (private) {
         drm_gem_private_object_init(dev, obj, size);
         shmem->map_wc = false; /* dma-buf mappings use always writecombine */
     } else {
         ret = drm_gem_object_init(dev, obj, size);
     }
     if (ret)
         goto err_free;
 
     ret = drm_gem_create_mmap_offset(obj);
     if (ret)
         goto err_release;
 
     mutex_init(&shmem->pages_lock);
     mutex_init(&shmem->vmap_lock);
     INIT_LIST_HEAD(&shmem->madv_list);
 
     if (!private) {
         /*
          * Our buffers are kept pinned, so allocating them
          * from the MOVABLE zone is a really bad idea, and
          * conflicts with CMA. See comments above new_inode()
          * why this is required _and_ expected if you're
          * going to pin these pages.
          */
         mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
                      __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
     }
 
     return shmem;
 
 err_release:
     drm_gem_object_release(obj);
 err_free:
     kfree(obj);
 
     return ERR_PTR(ret);
 }
 /**
  * drm_gem_shmem_create - Allocate an object with the given size
  * @dev: DRM device
  * @size: Size of the object to allocate
  *
  * This function creates a shmem GEM object.
  *
  * Returns:
  * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
  * error code on failure.
  */
 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
 {
     return __drm_gem_shmem_create(dev, size, false);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
 
 /**
  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
  * @shmem: shmem GEM object to free
  *
  * This function cleans up the GEM object state and frees the memory used to
  * store the object itself.
  */
 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
 
     WARN_ON(shmem->vmap_use_count);
 
     if (obj->import_attach) {
         drm_prime_gem_destroy(obj, shmem->sgt);
     } else {
         if (shmem->sgt) {
             dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
                       DMA_BIDIRECTIONAL, 0);
             sg_free_table(shmem->sgt);
             kfree(shmem->sgt);
         }
         if (shmem->pages)
             drm_gem_shmem_put_pages(shmem);
     }
 
     WARN_ON(shmem->pages_use_count);
 
     drm_gem_object_release(obj);
     mutex_destroy(&shmem->pages_lock);
     mutex_destroy(&shmem->vmap_lock);
     kfree(shmem);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
 
 static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
     struct page **pages;
 
     if (shmem->pages_use_count++ > 0)
         return 0;
 
     pages = drm_gem_get_pages(obj);
     if (IS_ERR(pages)) {
         DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
         shmem->pages_use_count = 0;
         return PTR_ERR(pages);
     }
 
     /*
      * TODO: Allocating WC pages which are correctly flushed is only
      * supported on x86. Ideal solution would be a GFP_WC flag, which also
      * ttm_pool.c could use.
      */
 #ifdef CONFIG_X86
     if (shmem->map_wc)
         set_pages_array_wc(pages, obj->size >> PAGE_SHIFT);
 #endif
 
     shmem->pages = pages;
 
     return 0;
 }
 
 /*
  * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function makes sure that backing pages exists for the shmem GEM object
  * and increases the use count.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
 {
     int ret;
 
     WARN_ON(shmem->base.import_attach);
 
     ret = mutex_lock_interruptible(&shmem->pages_lock);
     if (ret)
         return ret;
     ret = drm_gem_shmem_get_pages_locked(shmem);
     mutex_unlock(&shmem->pages_lock);
 
     return ret;
 }
 EXPORT_SYMBOL(drm_gem_shmem_get_pages);
 
 static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
 
     if (WARN_ON_ONCE(!shmem->pages_use_count))
         return;
 
     if (--shmem->pages_use_count > 0)
         return;
 
 #ifdef CONFIG_X86
     if (shmem->map_wc)
         set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
 #endif
 
     drm_gem_put_pages(obj, shmem->pages,
               shmem->pages_mark_dirty_on_put,
               shmem->pages_mark_accessed_on_put);
     shmem->pages = NULL;
 }
 
 /*
  * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function decreases the use count and puts the backing pages when use drops to zero.
  */
 void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
 {
     mutex_lock(&shmem->pages_lock);
     drm_gem_shmem_put_pages_locked(shmem);
     mutex_unlock(&shmem->pages_lock);
 }
 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
 
 /**
  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function makes sure the backing pages are pinned in memory while the
  * buffer is exported.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
 {
     WARN_ON(shmem->base.import_attach);
 
     return drm_gem_shmem_get_pages(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_pin);
 
 /**
  * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function removes the requirement that the backing pages are pinned in
  * memory.
  */
 void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
 {
     WARN_ON(shmem->base.import_attach);
 
     drm_gem_shmem_put_pages(shmem);
 }
 EXPORT_SYMBOL(drm_gem_shmem_unpin);
 
 static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
                      struct iosys_map *map)
 {
     struct drm_gem_object *obj = &shmem->base;
     int ret = 0;
 
     if (shmem->vmap_use_count++ > 0) {
         iosys_map_set_vaddr(map, shmem->vaddr);
         return 0;
     }
 
     if (obj->import_attach) {
         ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
         if (!ret) {
             if (WARN_ON(map->is_iomem)) {
                 dma_buf_vunmap(obj->import_attach->dmabuf, map);
                 ret = -EIO;
                 goto err_put_pages;
             }
             shmem->vaddr = map->vaddr;
         }
     } else {
         pgprot_t prot = PAGE_KERNEL;
 
         ret = drm_gem_shmem_get_pages(shmem);
         if (ret)
             goto err_zero_use;
 
         if (shmem->map_wc)
             prot = pgprot_writecombine(prot);
         shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
                     VM_MAP, prot);
         if (!shmem->vaddr)
             ret = -ENOMEM;
         else
             iosys_map_set_vaddr(map, shmem->vaddr);
     }
 
     if (ret) {
         DRM_DEBUG_KMS("Failed to vmap pages, error %d\n", ret);
         goto err_put_pages;
     }
 
     return 0;
 
 err_put_pages:
     if (!obj->import_attach)
         drm_gem_shmem_put_pages(shmem);
 err_zero_use:
     shmem->vmap_use_count = 0;
 
     return ret;
 }
 
 /*
  * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
  * @shmem: shmem GEM object
  * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
  *       store.
  *
  * This function makes sure that a contiguous kernel virtual address mapping
  * exists for the buffer backing the shmem GEM object. It hides the differences
  * between dma-buf imported and natively allocated objects.
  *
  * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap().
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
                struct iosys_map *map)
 {
     int ret;
 
     ret = mutex_lock_interruptible(&shmem->vmap_lock);
     if (ret)
         return ret;
     ret = drm_gem_shmem_vmap_locked(shmem, map);
     mutex_unlock(&shmem->vmap_lock);
 
     return ret;
 }
 EXPORT_SYMBOL(drm_gem_shmem_vmap);
 
 static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
                     struct iosys_map *map)
 {
     struct drm_gem_object *obj = &shmem->base;
 
     if (WARN_ON_ONCE(!shmem->vmap_use_count))
         return;
 
     if (--shmem->vmap_use_count > 0)
         return;
 
     if (obj->import_attach) {
         dma_buf_vunmap(obj->import_attach->dmabuf, map);
     } else {
         vunmap(shmem->vaddr);
         drm_gem_shmem_put_pages(shmem);
     }
 
     shmem->vaddr = NULL;
 }
 
 /*
  * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
  * @shmem: shmem GEM object
  * @map: Kernel virtual address where the SHMEM GEM object was mapped
  *
  * This function cleans up a kernel virtual address mapping acquired by
  * drm_gem_shmem_vmap(). The mapping is only removed when the use count drops to
  * zero.
  *
  * This function hides the differences between dma-buf imported and natively
  * allocated objects.
  */
 void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
               struct iosys_map *map)
 {
     mutex_lock(&shmem->vmap_lock);
     drm_gem_shmem_vunmap_locked(shmem, map);
     mutex_unlock(&shmem->vmap_lock);
 }
 EXPORT_SYMBOL(drm_gem_shmem_vunmap);
 
 static struct drm_gem_shmem_object *
 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
                  struct drm_device *dev, size_t size,
                  uint32_t *handle)
 {
     struct drm_gem_shmem_object *shmem;
     int ret;
 
     shmem = drm_gem_shmem_create(dev, size);
     if (IS_ERR(shmem))
         return shmem;
 
     /*
      * Allocate an 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, &shmem->base, handle);
     /* drop reference from allocate - handle holds it now. */
     drm_gem_object_put(&shmem->base);
     if (ret)
         return ERR_PTR(ret);
 
     return shmem;
 }
 
 /* Update madvise status, returns true if not purged, else
  * false or -errno.
  */
 int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
 {
     mutex_lock(&shmem->pages_lock);
 
     if (shmem->madv >= 0)
         shmem->madv = madv;
 
     madv = shmem->madv;
 
     mutex_unlock(&shmem->pages_lock);
 
     return (madv >= 0);
 }
 EXPORT_SYMBOL(drm_gem_shmem_madvise);
 
 void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
     struct drm_device *dev = obj->dev;
 
     WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
 
     dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
     sg_free_table(shmem->sgt);
     kfree(shmem->sgt);
     shmem->sgt = NULL;
 
     drm_gem_shmem_put_pages_locked(shmem);
 
     shmem->madv = -1;
 
     drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
     drm_gem_free_mmap_offset(obj);
 
     /* Our goal here is to return as much of the memory as
      * is possible back to the system as we are called from OOM.
      * To do this we must instruct the shmfs to drop all of its
      * backing pages, *now*.
      */
     shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
 
     invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
 }
 EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
 
 bool drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
 {
     if (!mutex_trylock(&shmem->pages_lock))
         return false;
     drm_gem_shmem_purge_locked(shmem);
     mutex_unlock(&shmem->pages_lock);
 
     return true;
 }
 EXPORT_SYMBOL(drm_gem_shmem_purge);
 
 /**
  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
  * @file: DRM file structure to create the dumb buffer for
  * @dev: 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 before calling into this function.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
                   struct drm_mode_create_dumb *args)
 {
     u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
     struct drm_gem_shmem_object *shmem;
 
     if (!args->pitch || !args->size) {
         args->pitch = min_pitch;
         args->size = PAGE_ALIGN(args->pitch * args->height);
     } else {
         /* ensure sane minimum values */
         if (args->pitch < min_pitch)
             args->pitch = min_pitch;
         if (args->size < args->pitch * args->height)
             args->size = PAGE_ALIGN(args->pitch * args->height);
     }
 
     shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
 
     return PTR_ERR_OR_ZERO(shmem);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
 
 static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 {
     struct vm_area_struct *vma = vmf->vma;
     struct drm_gem_object *obj = vma->vm_private_data;
     struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
     loff_t num_pages = obj->size >> PAGE_SHIFT;
     vm_fault_t ret;
     struct page *page;
     pgoff_t page_offset;
 
     /* We don't use vmf->pgoff since that has the fake offset */
     page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
 
     mutex_lock(&shmem->pages_lock);
 
     if (page_offset >= num_pages ||
         WARN_ON_ONCE(!shmem->pages) ||
         shmem->madv < 0) {
         ret = VM_FAULT_SIGBUS;
     } else {
         page = shmem->pages[page_offset];
 
         ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
     }
 
     mutex_unlock(&shmem->pages_lock);
 
     return ret;
 }
 
 static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 {
     struct drm_gem_object *obj = vma->vm_private_data;
     struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
     int ret;
 
     WARN_ON(shmem->base.import_attach);
 
     ret = drm_gem_shmem_get_pages(shmem);
     WARN_ON_ONCE(ret != 0);
 
     drm_gem_vm_open(vma);
 }
 
 static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
 {
     struct drm_gem_object *obj = vma->vm_private_data;
     struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 
     drm_gem_shmem_put_pages(shmem);
     drm_gem_vm_close(vma);
 }
 
 const struct vm_operations_struct drm_gem_shmem_vm_ops = {
     .fault = drm_gem_shmem_fault,
     .open = drm_gem_shmem_vm_open,
     .close = drm_gem_shmem_vm_close,
 };
 EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
 
 /**
  * drm_gem_shmem_mmap - Memory-map a shmem GEM object
  * @shmem: shmem GEM object
  * @vma: VMA for the area to be mapped
  *
  * This function implements an augmented version of the GEM DRM file mmap
  * operation for shmem objects.
  *
  * Returns:
  * 0 on success or a negative error code on failure.
  */
 int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma)
 {
     struct drm_gem_object *obj = &shmem->base;
     int ret;
 
     if (obj->import_attach) {
         /* Drop the reference drm_gem_mmap_obj() acquired.*/
         drm_gem_object_put(obj);
         vma->vm_private_data = NULL;
 
         return dma_buf_mmap(obj->dma_buf, vma, 0);
     }
 
     ret = drm_gem_shmem_get_pages(shmem);
     if (ret) {
         drm_gem_vm_close(vma);
         return ret;
     }
 
     vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
     vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
     if (shmem->map_wc)
         vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
 
 /**
  * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
  * @shmem: shmem GEM object
  * @p: DRM printer
  * @indent: Tab indentation level
  */
 void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
                   struct drm_printer *p, unsigned int indent)
 {
     drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
     drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
     drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
 }
 EXPORT_SYMBOL(drm_gem_shmem_print_info);
 
 /**
  * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
  *                              pages for a shmem GEM object
  * @shmem: shmem GEM object
  *
  * This function exports a scatter/gather table suitable for PRIME usage by
  * calling the standard DMA mapping API.
  *
  * Drivers who need to acquire an scatter/gather table for objects need to call
  * drm_gem_shmem_get_pages_sgt() instead.
  *
  * Returns:
  * A pointer to the scatter/gather table of pinned pages or NULL on failure.
  */
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
 
     WARN_ON(shmem->base.import_attach);
 
     return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SHIFT);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
 
 /**
  * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
  *               scatter/gather table for a shmem GEM object.
  * @shmem: shmem GEM object
  *
  * This function returns a scatter/gather table suitable for driver usage. If
  * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
  * table created.
  *
  * This is the main function for drivers to get at backing storage, and it hides
  * and difference between dma-buf imported and natively allocated objects.
  * drm_gem_shmem_get_sg_table() should not be directly called by drivers.
  *
  * Returns:
  * A pointer to the scatter/gather table of pinned pages or errno on failure.
  */
 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
 {
     struct drm_gem_object *obj = &shmem->base;
     int ret;
     struct sg_table *sgt;
 
     if (shmem->sgt)
         return shmem->sgt;
 
     WARN_ON(obj->import_attach);
 
     ret = drm_gem_shmem_get_pages(shmem);
     if (ret)
         return ERR_PTR(ret);
 
     sgt = drm_gem_shmem_get_sg_table(shmem);
     if (IS_ERR(sgt)) {
         ret = PTR_ERR(sgt);
         goto err_put_pages;
     }
     /* Map the pages for use by the h/w. */
     ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
     if (ret)
         goto err_free_sgt;
 
     shmem->sgt = sgt;
 
     return sgt;
 
 err_free_sgt:
     sg_free_table(sgt);
     kfree(sgt);
 err_put_pages:
     drm_gem_shmem_put_pages(shmem);
     return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);
 
 /**
  * drm_gem_shmem_prime_import_sg_table - Produce a shmem 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. Drivers that use the shmem 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_shmem_prime_import_sg_table(struct drm_device *dev,
                     struct dma_buf_attachment *attach,
                     struct sg_table *sgt)
 {
     size_t size = PAGE_ALIGN(attach->dmabuf->size);
     struct drm_gem_shmem_object *shmem;
 
     shmem = __drm_gem_shmem_create(dev, size, true);
     if (IS_ERR(shmem))
         return ERR_CAST(shmem);
 
     shmem->sgt = sgt;
 
     DRM_DEBUG_PRIME("size = %zu\n", size);
 
     return &shmem->base;
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
 
 MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
 MODULE_IMPORT_NS(DMA_BUF);
 MODULE_LICENSE("GPL v2");

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