OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​drm_prime.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

 /*
  * Copyright © 2012 Red Hat
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  *
  * Authors:
  *      Dave Airlie <airlied@redhat.com>
  *      Rob Clark <rob.clark@linaro.org>
  *
  */
 
 #include <linux/export.h>
 #include <linux/dma-buf.h>
 #include <linux/rbtree.h>
 #include <linux/module.h>
 
 #include <drm/drm.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_prime.h>
 
 #include "drm_internal.h"
 
 MODULE_IMPORT_NS(DMA_BUF);
 
 /**
  * DOC: overview and lifetime rules
  *
  * Similar to GEM global names, PRIME file descriptors are also used to share
  * buffer objects across processes. They offer additional security: as file
  * descriptors must be explicitly sent over UNIX domain sockets to be shared
  * between applications, they can't be guessed like the globally unique GEM
  * names.
  *
  * Drivers that support the PRIME API implement the
  * &drm_driver.prime_handle_to_fd and &drm_driver.prime_fd_to_handle operations.
  * GEM based drivers must use drm_gem_prime_handle_to_fd() and
  * drm_gem_prime_fd_to_handle() to implement these. For GEM based drivers the
  * actual driver interfaces is provided through the &drm_gem_object_funcs.export
  * and &drm_driver.gem_prime_import hooks.
  *
  * &dma_buf_ops implementations for GEM drivers are all individually exported
  * for drivers which need to overwrite or reimplement some of them.
  *
  * Reference Counting for GEM Drivers
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * On the export the &dma_buf holds a reference to the exported buffer object,
  * usually a &drm_gem_object. It takes this reference in the PRIME_HANDLE_TO_FD
  * IOCTL, when it first calls &drm_gem_object_funcs.export
  * and stores the exporting GEM object in the &dma_buf.priv field. This
  * reference needs to be released when the final reference to the &dma_buf
  * itself is dropped and its &dma_buf_ops.release function is called.  For
  * GEM-based drivers, the &dma_buf should be exported using
  * drm_gem_dmabuf_export() and then released by drm_gem_dmabuf_release().
  *
  * Thus the chain of references always flows in one direction, avoiding loops:
  * importing GEM object -> dma-buf -> exported GEM bo. A further complication
  * are the lookup caches for import and export. These are required to guarantee
  * that any given object will always have only one unique userspace handle. This
  * is required to allow userspace to detect duplicated imports, since some GEM
  * drivers do fail command submissions if a given buffer object is listed more
  * than once. These import and export caches in &drm_prime_file_private only
  * retain a weak reference, which is cleaned up when the corresponding object is
  * released.
  *
  * Self-importing: If userspace is using PRIME as a replacement for flink then
  * it will get a fd->handle request for a GEM object that it created.  Drivers
  * should detect this situation and return back the underlying object from the
  * dma-buf private. For GEM based drivers this is handled in
  * drm_gem_prime_import() already.
  */
 
 struct drm_prime_member {
     struct dma_buf *dma_buf;
     uint32_t handle;
 
     struct rb_node dmabuf_rb;
     struct rb_node handle_rb;
 };
 
 static int drm_prime_add_buf_handle(struct drm_prime_file_private *prime_fpriv,
                     struct dma_buf *dma_buf, uint32_t handle)
 {
     struct drm_prime_member *member;
     struct rb_node **p, *rb;
 
     member = kmalloc(sizeof(*member), GFP_KERNEL);
     if (!member)
         return -ENOMEM;
 
     get_dma_buf(dma_buf);
     member->dma_buf = dma_buf;
     member->handle = handle;
 
     rb = NULL;
     p = &prime_fpriv->dmabufs.rb_node;
     while (*p) {
         struct drm_prime_member *pos;
 
         rb = *p;
         pos = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
         if (dma_buf > pos->dma_buf)
             p = &rb->rb_right;
         else
             p = &rb->rb_left;
     }
     rb_link_node(&member->dmabuf_rb, rb, p);
     rb_insert_color(&member->dmabuf_rb, &prime_fpriv->dmabufs);
 
     rb = NULL;
     p = &prime_fpriv->handles.rb_node;
     while (*p) {
         struct drm_prime_member *pos;
 
         rb = *p;
         pos = rb_entry(rb, struct drm_prime_member, handle_rb);
         if (handle > pos->handle)
             p = &rb->rb_right;
         else
             p = &rb->rb_left;
     }
     rb_link_node(&member->handle_rb, rb, p);
     rb_insert_color(&member->handle_rb, &prime_fpriv->handles);
 
     return 0;
 }
 
 static struct dma_buf *drm_prime_lookup_buf_by_handle(struct drm_prime_file_private *prime_fpriv,
                               uint32_t handle)
 {
     struct rb_node *rb;
 
     rb = prime_fpriv->handles.rb_node;
     while (rb) {
         struct drm_prime_member *member;
 
         member = rb_entry(rb, struct drm_prime_member, handle_rb);
         if (member->handle == handle)
             return member->dma_buf;
         else if (member->handle < handle)
             rb = rb->rb_right;
         else
             rb = rb->rb_left;
     }
 
     return NULL;
 }
 
 static int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fpriv,
                        struct dma_buf *dma_buf,
                        uint32_t *handle)
 {
     struct rb_node *rb;
 
     rb = prime_fpriv->dmabufs.rb_node;
     while (rb) {
         struct drm_prime_member *member;
 
         member = rb_entry(rb, struct drm_prime_member, dmabuf_rb);
         if (member->dma_buf == dma_buf) {
             *handle = member->handle;
             return 0;
         } else if (member->dma_buf < dma_buf) {
             rb = rb->rb_right;
         } else {
             rb = rb->rb_left;
         }
     }
 
     return -ENOENT;
 }
 
 void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv,
                  uint32_t handle)
 {
     struct rb_node *rb;
 
     mutex_lock(&prime_fpriv->lock);
 
     rb = prime_fpriv->handles.rb_node;
     while (rb) {
         struct drm_prime_member *member;
 
         member = rb_entry(rb, struct drm_prime_member, handle_rb);
         if (member->handle == handle) {
             rb_erase(&member->handle_rb, &prime_fpriv->handles);
             rb_erase(&member->dmabuf_rb, &prime_fpriv->dmabufs);
 
             dma_buf_put(member->dma_buf);
             kfree(member);
             break;
         } else if (member->handle < handle) {
             rb = rb->rb_right;
         } else {
             rb = rb->rb_left;
         }
     }
 
     mutex_unlock(&prime_fpriv->lock);
 }
 
 void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
 {
     mutex_init(&prime_fpriv->lock);
     prime_fpriv->dmabufs = RB_ROOT;
     prime_fpriv->handles = RB_ROOT;
 }
 
 void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
 {
     /* by now drm_gem_release should've made sure the list is empty */
     WARN_ON(!RB_EMPTY_ROOT(&prime_fpriv->dmabufs));
 }
 
 /**
  * drm_gem_dmabuf_export - &dma_buf export implementation for GEM
  * @dev: parent device for the exported dmabuf
  * @exp_info: the export information used by dma_buf_export()
  *
  * This wraps dma_buf_export() for use by generic GEM drivers that are using
  * drm_gem_dmabuf_release(). In addition to calling dma_buf_export(), we take
  * a reference to the &drm_device and the exported &drm_gem_object (stored in
  * &dma_buf_export_info.priv) which is released by drm_gem_dmabuf_release().
  *
  * Returns the new dmabuf.
  */
 struct dma_buf *drm_gem_dmabuf_export(struct drm_device *dev,
                       struct dma_buf_export_info *exp_info)
 {
     struct drm_gem_object *obj = exp_info->priv;
     struct dma_buf *dma_buf;
 
     dma_buf = dma_buf_export(exp_info);
     if (IS_ERR(dma_buf))
         return dma_buf;
 
     drm_dev_get(dev);
     drm_gem_object_get(obj);
     dma_buf->file->f_mapping = obj->dev->anon_inode->i_mapping;
 
     return dma_buf;
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_export);
 
 /**
  * drm_gem_dmabuf_release - &dma_buf release implementation for GEM
  * @dma_buf: buffer to be released
  *
  * Generic release function for dma_bufs exported as PRIME buffers. GEM drivers
  * must use this in their &dma_buf_ops structure as the release callback.
  * drm_gem_dmabuf_release() should be used in conjunction with
  * drm_gem_dmabuf_export().
  */
 void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
 {
     struct drm_gem_object *obj = dma_buf->priv;
     struct drm_device *dev = obj->dev;
 
     /* drop the reference on the export fd holds */
     drm_gem_object_put(obj);
 
     drm_dev_put(dev);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_release);
 
 /**
  * drm_gem_prime_fd_to_handle - PRIME import function for GEM drivers
  * @dev: dev to export the buffer from
  * @file_priv: drm file-private structure
  * @prime_fd: fd id of the dma-buf which should be imported
  * @handle: pointer to storage for the handle of the imported buffer object
  *
  * This is the PRIME import function which must be used mandatorily by GEM
  * drivers to ensure correct lifetime management of the underlying GEM object.
  * The actual importing of GEM object from the dma-buf is done through the
  * &drm_driver.gem_prime_import driver callback.
  *
  * Returns 0 on success or a negative error code on failure.
  */
 int drm_gem_prime_fd_to_handle(struct drm_device *dev,
                    struct drm_file *file_priv, int prime_fd,
                    uint32_t *handle)
 {
     struct dma_buf *dma_buf;
     struct drm_gem_object *obj;
     int ret;
 
     dma_buf = dma_buf_get(prime_fd);
     if (IS_ERR(dma_buf))
         return PTR_ERR(dma_buf);
 
     mutex_lock(&file_priv->prime.lock);
 
     ret = drm_prime_lookup_buf_handle(&file_priv->prime,
             dma_buf, handle);
     if (ret == 0)
         goto out_put;
 
     /* never seen this one, need to import */
     mutex_lock(&dev->object_name_lock);
     if (dev->driver->gem_prime_import)
         obj = dev->driver->gem_prime_import(dev, dma_buf);
     else
         obj = drm_gem_prime_import(dev, dma_buf);
     if (IS_ERR(obj)) {
         ret = PTR_ERR(obj);
         goto out_unlock;
     }
 
     if (obj->dma_buf) {
         WARN_ON(obj->dma_buf != dma_buf);
     } else {
         obj->dma_buf = dma_buf;
         get_dma_buf(dma_buf);
     }
 
     /* _handle_create_tail unconditionally unlocks dev->object_name_lock. */
     ret = drm_gem_handle_create_tail(file_priv, obj, handle);
     drm_gem_object_put(obj);
     if (ret)
         goto out_put;
 
     ret = drm_prime_add_buf_handle(&file_priv->prime,
             dma_buf, *handle);
     mutex_unlock(&file_priv->prime.lock);
     if (ret)
         goto fail;
 
     dma_buf_put(dma_buf);
 
     return 0;
 
 fail:
     /* hmm, if driver attached, we are relying on the free-object path
      * to detach.. which seems ok..
      */
     drm_gem_handle_delete(file_priv, *handle);
     dma_buf_put(dma_buf);
     return ret;
 
 out_unlock:
     mutex_unlock(&dev->object_name_lock);
 out_put:
     mutex_unlock(&file_priv->prime.lock);
     dma_buf_put(dma_buf);
     return ret;
 }
 EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);
 
 int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
                  struct drm_file *file_priv)
 {
     struct drm_prime_handle *args = data;
 
     if (!dev->driver->prime_fd_to_handle)
         return -ENOSYS;
 
     return dev->driver->prime_fd_to_handle(dev, file_priv,
             args->fd, &args->handle);
 }
 
 static struct dma_buf *export_and_register_object(struct drm_device *dev,
                           struct drm_gem_object *obj,
                           uint32_t flags)
 {
     struct dma_buf *dmabuf;
 
     /* prevent races with concurrent gem_close. */
     if (obj->handle_count == 0) {
         dmabuf = ERR_PTR(-ENOENT);
         return dmabuf;
     }
 
     if (obj->funcs && obj->funcs->export)
         dmabuf = obj->funcs->export(obj, flags);
     else
         dmabuf = drm_gem_prime_export(obj, flags);
     if (IS_ERR(dmabuf)) {
         /* normally the created dma-buf takes ownership of the ref,
          * but if that fails then drop the ref
          */
         return dmabuf;
     }
 
     /*
      * Note that callers do not need to clean up the export cache
      * since the check for obj->handle_count guarantees that someone
      * will clean it up.
      */
     obj->dma_buf = dmabuf;
     get_dma_buf(obj->dma_buf);
 
     return dmabuf;
 }
 
 /**
  * drm_gem_prime_handle_to_fd - PRIME export function for GEM drivers
  * @dev: dev to export the buffer from
  * @file_priv: drm file-private structure
  * @handle: buffer handle to export
  * @flags: flags like DRM_CLOEXEC
  * @prime_fd: pointer to storage for the fd id of the create dma-buf
  *
  * This is the PRIME export function which must be used mandatorily by GEM
  * drivers to ensure correct lifetime management of the underlying GEM object.
  * The actual exporting from GEM object to a dma-buf is done through the
  * &drm_gem_object_funcs.export callback.
  */
 int drm_gem_prime_handle_to_fd(struct drm_device *dev,
                    struct drm_file *file_priv, uint32_t handle,
                    uint32_t flags,
                    int *prime_fd)
 {
     struct drm_gem_object *obj;
     int ret = 0;
     struct dma_buf *dmabuf;
 
     mutex_lock(&file_priv->prime.lock);
     obj = drm_gem_object_lookup(file_priv, handle);
     if (!obj)  {
         ret = -ENOENT;
         goto out_unlock;
     }
 
     dmabuf = drm_prime_lookup_buf_by_handle(&file_priv->prime, handle);
     if (dmabuf) {
         get_dma_buf(dmabuf);
         goto out_have_handle;
     }
 
     mutex_lock(&dev->object_name_lock);
     /* re-export the original imported object */
     if (obj->import_attach) {
         dmabuf = obj->import_attach->dmabuf;
         get_dma_buf(dmabuf);
         goto out_have_obj;
     }
 
     if (obj->dma_buf) {
         get_dma_buf(obj->dma_buf);
         dmabuf = obj->dma_buf;
         goto out_have_obj;
     }
 
     dmabuf = export_and_register_object(dev, obj, flags);
     if (IS_ERR(dmabuf)) {
         /* normally the created dma-buf takes ownership of the ref,
          * but if that fails then drop the ref
          */
         ret = PTR_ERR(dmabuf);
         mutex_unlock(&dev->object_name_lock);
         goto out;
     }
 
 out_have_obj:
     /*
      * If we've exported this buffer then cheat and add it to the import list
      * so we get the correct handle back. We must do this under the
      * protection of dev->object_name_lock to ensure that a racing gem close
      * ioctl doesn't miss to remove this buffer handle from the cache.
      */
     ret = drm_prime_add_buf_handle(&file_priv->prime,
                        dmabuf, handle);
     mutex_unlock(&dev->object_name_lock);
     if (ret)
         goto fail_put_dmabuf;
 
 out_have_handle:
     ret = dma_buf_fd(dmabuf, flags);
     /*
      * We must _not_ remove the buffer from the handle cache since the newly
      * created dma buf is already linked in the global obj->dma_buf pointer,
      * and that is invariant as long as a userspace gem handle exists.
      * Closing the handle will clean out the cache anyway, so we don't leak.
      */
     if (ret < 0) {
         goto fail_put_dmabuf;
     } else {
         *prime_fd = ret;
         ret = 0;
     }
 
     goto out;
 
 fail_put_dmabuf:
     dma_buf_put(dmabuf);
 out:
     drm_gem_object_put(obj);
 out_unlock:
     mutex_unlock(&file_priv->prime.lock);
 
     return ret;
 }
 EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);
 
 int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
                  struct drm_file *file_priv)
 {
     struct drm_prime_handle *args = data;
 
     if (!dev->driver->prime_handle_to_fd)
         return -ENOSYS;
 
     /* check flags are valid */
     if (args->flags & ~(DRM_CLOEXEC | DRM_RDWR))
         return -EINVAL;
 
     return dev->driver->prime_handle_to_fd(dev, file_priv,
             args->handle, args->flags, &args->fd);
 }
 
 /**
  * DOC: PRIME Helpers
  *
  * Drivers can implement &drm_gem_object_funcs.export and
  * &drm_driver.gem_prime_import in terms of simpler APIs by using the helper
  * functions drm_gem_prime_export() and drm_gem_prime_import(). These functions
  * implement dma-buf support in terms of some lower-level helpers, which are
  * again exported for drivers to use individually:
  *
  * Exporting buffers
  * ~~~~~~~~~~~~~~~~~
  *
  * Optional pinning of buffers is handled at dma-buf attach and detach time in
  * drm_gem_map_attach() and drm_gem_map_detach(). Backing storage itself is
  * handled by drm_gem_map_dma_buf() and drm_gem_unmap_dma_buf(), which relies on
  * &drm_gem_object_funcs.get_sg_table.
  *
  * For kernel-internal access there's drm_gem_dmabuf_vmap() and
  * drm_gem_dmabuf_vunmap(). Userspace mmap support is provided by
  * drm_gem_dmabuf_mmap().
  *
  * Note that these export helpers can only be used if the underlying backing
  * storage is fully coherent and either permanently pinned, or it is safe to pin
  * it indefinitely.
  *
  * FIXME: The underlying helper functions are named rather inconsistently.
  *
  * Importing buffers
  * ~~~~~~~~~~~~~~~~~
  *
  * Importing dma-bufs using drm_gem_prime_import() relies on
  * &drm_driver.gem_prime_import_sg_table.
  *
  * Note that similarly to the export helpers this permanently pins the
  * underlying backing storage. Which is ok for scanout, but is not the best
  * option for sharing lots of buffers for rendering.
  */
 
 /**
  * drm_gem_map_attach - dma_buf attach implementation for GEM
  * @dma_buf: buffer to attach device to
  * @attach: buffer attachment data
  *
  * Calls &drm_gem_object_funcs.pin for device specific handling. This can be
  * used as the &dma_buf_ops.attach callback. Must be used together with
  * drm_gem_map_detach().
  *
  * Returns 0 on success, negative error code on failure.
  */
 int drm_gem_map_attach(struct dma_buf *dma_buf,
                struct dma_buf_attachment *attach)
 {
     struct drm_gem_object *obj = dma_buf->priv;
 
     return drm_gem_pin(obj);
 }
 EXPORT_SYMBOL(drm_gem_map_attach);
 
 /**
  * drm_gem_map_detach - dma_buf detach implementation for GEM
  * @dma_buf: buffer to detach from
  * @attach: attachment to be detached
  *
  * Calls &drm_gem_object_funcs.pin for device specific handling.  Cleans up
  * &dma_buf_attachment from drm_gem_map_attach(). This can be used as the
  * &dma_buf_ops.detach callback.
  */
 void drm_gem_map_detach(struct dma_buf *dma_buf,
             struct dma_buf_attachment *attach)
 {
     struct drm_gem_object *obj = dma_buf->priv;
 
     drm_gem_unpin(obj);
 }
 EXPORT_SYMBOL(drm_gem_map_detach);
 
 /**
  * drm_gem_map_dma_buf - map_dma_buf implementation for GEM
  * @attach: attachment whose scatterlist is to be returned
  * @dir: direction of DMA transfer
  *
  * Calls &drm_gem_object_funcs.get_sg_table and then maps the scatterlist. This
  * can be used as the &dma_buf_ops.map_dma_buf callback. Should be used together
  * with drm_gem_unmap_dma_buf().
  *
  * Returns:sg_table containing the scatterlist to be returned; returns ERR_PTR
  * on error. May return -EINTR if it is interrupted by a signal.
  */
 struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
                      enum dma_data_direction dir)
 {
     struct drm_gem_object *obj = attach->dmabuf->priv;
     struct sg_table *sgt;
     int ret;
 
     if (WARN_ON(dir == DMA_NONE))
         return ERR_PTR(-EINVAL);
 
     if (WARN_ON(!obj->funcs->get_sg_table))
         return ERR_PTR(-ENOSYS);
 
     sgt = obj->funcs->get_sg_table(obj);
     if (IS_ERR(sgt))
         return sgt;
 
     ret = dma_map_sgtable(attach->dev, sgt, dir,
                   DMA_ATTR_SKIP_CPU_SYNC);
     if (ret) {
         sg_free_table(sgt);
         kfree(sgt);
         sgt = ERR_PTR(ret);
     }
 
     return sgt;
 }
 EXPORT_SYMBOL(drm_gem_map_dma_buf);
 
 /**
  * drm_gem_unmap_dma_buf - unmap_dma_buf implementation for GEM
  * @attach: attachment to unmap buffer from
  * @sgt: scatterlist info of the buffer to unmap
  * @dir: direction of DMA transfer
  *
  * This can be used as the &dma_buf_ops.unmap_dma_buf callback.
  */
 void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
                struct sg_table *sgt,
                enum dma_data_direction dir)
 {
     if (!sgt)
         return;
 
     dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);
     sg_free_table(sgt);
     kfree(sgt);
 }
 EXPORT_SYMBOL(drm_gem_unmap_dma_buf);
 
 /**
  * drm_gem_dmabuf_vmap - dma_buf vmap implementation for GEM
  * @dma_buf: buffer to be mapped
  * @map: the virtual address of the buffer
  *
  * Sets up a kernel virtual mapping. This can be used as the &dma_buf_ops.vmap
  * callback. Calls into &drm_gem_object_funcs.vmap for device specific handling.
  * The kernel virtual address is returned in map.
  *
  * Returns 0 on success or a negative errno code otherwise.
  */
 int drm_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct iosys_map *map)
 {
     struct drm_gem_object *obj = dma_buf->priv;
 
     return drm_gem_vmap(obj, map);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
 
 /**
  * drm_gem_dmabuf_vunmap - dma_buf vunmap implementation for GEM
  * @dma_buf: buffer to be unmapped
  * @map: the virtual address of the buffer
  *
  * Releases a kernel virtual mapping. This can be used as the
  * &dma_buf_ops.vunmap callback. Calls into &drm_gem_object_funcs.vunmap for device specific handling.
  */
 void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map)
 {
     struct drm_gem_object *obj = dma_buf->priv;
 
     drm_gem_vunmap(obj, map);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);
 
 /**
  * drm_gem_prime_mmap - PRIME mmap function for GEM drivers
  * @obj: GEM object
  * @vma: Virtual address range
  *
  * This function sets up a userspace mapping for PRIME exported buffers using
  * the same codepath that is used for regular GEM buffer mapping on the DRM fd.
  * The fake GEM offset is added to vma->vm_pgoff and &drm_driver->fops->mmap is
  * called to set up the mapping.
  *
  * Drivers can use this as their &drm_driver.gem_prime_mmap callback.
  */
 int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 {
     struct drm_file *priv;
     struct file *fil;
     int ret;
 
     /* Add the fake offset */
     vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
 
     if (obj->funcs && obj->funcs->mmap) {
         vma->vm_ops = obj->funcs->vm_ops;
 
         drm_gem_object_get(obj);
         ret = obj->funcs->mmap(obj, vma);
         if (ret) {
             drm_gem_object_put(obj);
             return ret;
         }
         vma->vm_private_data = obj;
         return 0;
     }
 
     priv = kzalloc(sizeof(*priv), GFP_KERNEL);
     fil = kzalloc(sizeof(*fil), GFP_KERNEL);
     if (!priv || !fil) {
         ret = -ENOMEM;
         goto out;
     }
 
     /* Used by drm_gem_mmap() to lookup the GEM object */
     priv->minor = obj->dev->primary;
     fil->private_data = priv;
 
     ret = drm_vma_node_allow(&obj->vma_node, priv);
     if (ret)
         goto out;
 
     ret = obj->dev->driver->fops->mmap(fil, vma);
 
     drm_vma_node_revoke(&obj->vma_node, priv);
 out:
     kfree(priv);
     kfree(fil);
 
     return ret;
 }
 EXPORT_SYMBOL(drm_gem_prime_mmap);
 
 /**
  * drm_gem_dmabuf_mmap - dma_buf mmap implementation for GEM
  * @dma_buf: buffer to be mapped
  * @vma: virtual address range
  *
  * Provides memory mapping for the buffer. This can be used as the
  * &dma_buf_ops.mmap callback. It just forwards to &drm_driver.gem_prime_mmap,
  * which should be set to drm_gem_prime_mmap().
  *
  * FIXME: There's really no point to this wrapper, drivers which need anything
  * else but drm_gem_prime_mmap can roll their own &dma_buf_ops.mmap callback.
  *
  * Returns 0 on success or a negative error code on failure.
  */
 int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
 {
     struct drm_gem_object *obj = dma_buf->priv;
     struct drm_device *dev = obj->dev;
 
     if (!dev->driver->gem_prime_mmap)
         return -ENOSYS;
 
     return dev->driver->gem_prime_mmap(obj, vma);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_mmap);
 
 static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
     .cache_sgt_mapping = true,
     .attach = drm_gem_map_attach,
     .detach = drm_gem_map_detach,
     .map_dma_buf = drm_gem_map_dma_buf,
     .unmap_dma_buf = drm_gem_unmap_dma_buf,
     .release = drm_gem_dmabuf_release,
     .mmap = drm_gem_dmabuf_mmap,
     .vmap = drm_gem_dmabuf_vmap,
     .vunmap = drm_gem_dmabuf_vunmap,
 };
 
 /**
  * drm_prime_pages_to_sg - converts a page array into an sg list
  * @dev: DRM device
  * @pages: pointer to the array of page pointers to convert
  * @nr_pages: length of the page vector
  *
  * This helper creates an sg table object from a set of pages
  * the driver is responsible for mapping the pages into the
  * importers address space for use with dma_buf itself.
  *
  * This is useful for implementing &drm_gem_object_funcs.get_sg_table.
  */
 struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev,
                        struct page **pages, unsigned int nr_pages)
 {
     struct sg_table *sg;
     size_t max_segment = 0;
     int err;
 
     sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
     if (!sg)
         return ERR_PTR(-ENOMEM);
 
     if (dev)
         max_segment = dma_max_mapping_size(dev->dev);
     if (max_segment == 0)
         max_segment = UINT_MAX;
     err = sg_alloc_table_from_pages_segment(sg, pages, nr_pages, 0,
                         nr_pages << PAGE_SHIFT,
                         max_segment, GFP_KERNEL);
     if (err) {
         kfree(sg);
         sg = ERR_PTR(err);
     }
     return sg;
 }
 EXPORT_SYMBOL(drm_prime_pages_to_sg);
 
 /**
  * drm_prime_get_contiguous_size - returns the contiguous size of the buffer
  * @sgt: sg_table describing the buffer to check
  *
  * This helper calculates the contiguous size in the DMA address space
  * of the buffer described by the provided sg_table.
  *
  * This is useful for implementing
  * &drm_gem_object_funcs.gem_prime_import_sg_table.
  */
 unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt)
 {
     dma_addr_t expected = sg_dma_address(sgt->sgl);
     struct scatterlist *sg;
     unsigned long size = 0;
     int i;
 
     for_each_sgtable_dma_sg(sgt, sg, i) {
         unsigned int len = sg_dma_len(sg);
 
         if (!len)
             break;
         if (sg_dma_address(sg) != expected)
             break;
         expected += len;
         size += len;
     }
     return size;
 }
 EXPORT_SYMBOL(drm_prime_get_contiguous_size);
 
 /**
  * drm_gem_prime_export - helper library implementation of the export callback
  * @obj: GEM object to export
  * @flags: flags like DRM_CLOEXEC and DRM_RDWR
  *
  * This is the implementation of the &drm_gem_object_funcs.export functions for GEM drivers
  * using the PRIME helpers. It is used as the default in
  * drm_gem_prime_handle_to_fd().
  */
 struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
                      int flags)
 {
     struct drm_device *dev = obj->dev;
     struct dma_buf_export_info exp_info = {
         .exp_name = KBUILD_MODNAME, /* white lie for debug */
         .owner = dev->driver->fops->owner,
         .ops = &drm_gem_prime_dmabuf_ops,
         .size = obj->size,
         .flags = flags,
         .priv = obj,
         .resv = obj->resv,
     };
 
     return drm_gem_dmabuf_export(dev, &exp_info);
 }
 EXPORT_SYMBOL(drm_gem_prime_export);
 
 /**
  * drm_gem_prime_import_dev - core implementation of the import callback
  * @dev: drm_device to import into
  * @dma_buf: dma-buf object to import
  * @attach_dev: struct device to dma_buf attach
  *
  * This is the core of drm_gem_prime_import(). It's designed to be called by
  * drivers who want to use a different device structure than &drm_device.dev for
  * attaching via dma_buf. This function calls
  * &drm_driver.gem_prime_import_sg_table internally.
  *
  * Drivers must arrange to call drm_prime_gem_destroy() from their
  * &drm_gem_object_funcs.free hook when using this function.
  */
 struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
                         struct dma_buf *dma_buf,
                         struct device *attach_dev)
 {
     struct dma_buf_attachment *attach;
     struct sg_table *sgt;
     struct drm_gem_object *obj;
     int ret;
 
     if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
         obj = dma_buf->priv;
         if (obj->dev == dev) {
             /*
              * Importing dmabuf exported from out own gem increases
              * refcount on gem itself instead of f_count of dmabuf.
              */
             drm_gem_object_get(obj);
             return obj;
         }
     }
 
     if (!dev->driver->gem_prime_import_sg_table)
         return ERR_PTR(-EINVAL);
 
     attach = dma_buf_attach(dma_buf, attach_dev);
     if (IS_ERR(attach))
         return ERR_CAST(attach);
 
     get_dma_buf(dma_buf);
 
     sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
     if (IS_ERR(sgt)) {
         ret = PTR_ERR(sgt);
         goto fail_detach;
     }
 
     obj = dev->driver->gem_prime_import_sg_table(dev, attach, sgt);
     if (IS_ERR(obj)) {
         ret = PTR_ERR(obj);
         goto fail_unmap;
     }
 
     obj->import_attach = attach;
     obj->resv = dma_buf->resv;
 
     return obj;
 
 fail_unmap:
     dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
 fail_detach:
     dma_buf_detach(dma_buf, attach);
     dma_buf_put(dma_buf);
 
     return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(drm_gem_prime_import_dev);
 
 /**
  * drm_gem_prime_import - helper library implementation of the import callback
  * @dev: drm_device to import into
  * @dma_buf: dma-buf object to import
  *
  * This is the implementation of the gem_prime_import functions for GEM drivers
  * using the PRIME helpers. Drivers can use this as their
  * &drm_driver.gem_prime_import implementation. It is used as the default
  * implementation in drm_gem_prime_fd_to_handle().
  *
  * Drivers must arrange to call drm_prime_gem_destroy() from their
  * &drm_gem_object_funcs.free hook when using this function.
  */
 struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
                         struct dma_buf *dma_buf)
 {
     return drm_gem_prime_import_dev(dev, dma_buf, dev->dev);
 }
 EXPORT_SYMBOL(drm_gem_prime_import);
 
 /**
  * drm_prime_sg_to_page_array - convert an sg table into a page array
  * @sgt: scatter-gather table to convert
  * @pages: array of page pointers to store the pages in
  * @max_entries: size of the passed-in array
  *
  * Exports an sg table into an array of pages.
  *
  * This function is deprecated and strongly discouraged to be used.
  * The page array is only useful for page faults and those can corrupt fields
  * in the struct page if they are not handled by the exporting driver.
  */
 int __deprecated drm_prime_sg_to_page_array(struct sg_table *sgt,
                         struct page **pages,
                         int max_entries)
 {
     struct sg_page_iter page_iter;
     struct page **p = pages;
 
     for_each_sgtable_page(sgt, &page_iter, 0) {
         if (WARN_ON(p - pages >= max_entries))
             return -1;
         *p++ = sg_page_iter_page(&page_iter);
     }
     return 0;
 }
 EXPORT_SYMBOL(drm_prime_sg_to_page_array);
 
 /**
  * drm_prime_sg_to_dma_addr_array - convert an sg table into a dma addr array
  * @sgt: scatter-gather table to convert
  * @addrs: array to store the dma bus address of each page
  * @max_entries: size of both the passed-in arrays
  *
  * Exports an sg table into an array of addresses.
  *
  * Drivers should use this in their &drm_driver.gem_prime_import_sg_table
  * implementation.
  */
 int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs,
                    int max_entries)
 {
     struct sg_dma_page_iter dma_iter;
     dma_addr_t *a = addrs;
 
     for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
         if (WARN_ON(a - addrs >= max_entries))
             return -1;
         *a++ = sg_page_iter_dma_address(&dma_iter);
     }
     return 0;
 }
 EXPORT_SYMBOL(drm_prime_sg_to_dma_addr_array);
 
 /**
  * drm_prime_gem_destroy - helper to clean up a PRIME-imported GEM object
  * @obj: GEM object which was created from a dma-buf
  * @sg: the sg-table which was pinned at import time
  *
  * This is the cleanup functions which GEM drivers need to call when they use
  * drm_gem_prime_import() or drm_gem_prime_import_dev() to import dma-bufs.
  */
 void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
 {
     struct dma_buf_attachment *attach;
     struct dma_buf *dma_buf;
 
     attach = obj->import_attach;
     if (sg)
         dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
     dma_buf = attach->dmabuf;
     dma_buf_detach(attach->dmabuf, attach);
     /* remove the reference */
     dma_buf_put(dma_buf);
 }
 EXPORT_SYMBOL(drm_prime_gem_destroy);

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