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 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Header file for dma buffer sharing framework.
  *
  * Copyright(C) 2011 Linaro Limited. All rights reserved.
  * Author: Sumit Semwal <sumit.semwal@ti.com>
  *
  * Many thanks to linaro-mm-sig list, and specially
  * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
  * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
  * refining of this idea.
  */
 #ifndef __DMA_BUF_H__
 #define __DMA_BUF_H__
 
 #include <linux/iosys-map.h>
 #include <linux/file.h>
 #include <linux/err.h>
 #include <linux/scatterlist.h>
 #include <linux/list.h>
 #include <linux/dma-mapping.h>
 #include <linux/fs.h>
 #include <linux/dma-fence.h>
 #include <linux/wait.h>
 
 struct device;
 struct dma_buf;
 struct dma_buf_attachment;
 
 /**
  * struct dma_buf_ops - operations possible on struct dma_buf
  * @vmap: [optional] creates a virtual mapping for the buffer into kernel
  *    address space. Same restrictions as for vmap and friends apply.
  * @vunmap: [optional] unmaps a vmap from the buffer
  */
 struct dma_buf_ops {
     /**
       * @cache_sgt_mapping:
       *
       * If true the framework will cache the first mapping made for each
       * attachment. This avoids creating mappings for attachments multiple
       * times.
       */
     bool cache_sgt_mapping;
 
     /**
      * @attach:
      *
      * This is called from dma_buf_attach() to make sure that a given
      * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
      * which support buffer objects in special locations like VRAM or
      * device-specific carveout areas should check whether the buffer could
      * be move to system memory (or directly accessed by the provided
      * device), and otherwise need to fail the attach operation.
      *
      * The exporter should also in general check whether the current
      * allocation fulfills the DMA constraints of the new device. If this
      * is not the case, and the allocation cannot be moved, it should also
      * fail the attach operation.
      *
      * Any exporter-private housekeeping data can be stored in the
      * &dma_buf_attachment.priv pointer.
      *
      * This callback is optional.
      *
      * Returns:
      *
      * 0 on success, negative error code on failure. It might return -EBUSY
      * to signal that backing storage is already allocated and incompatible
      * with the requirements of requesting device.
      */
     int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
 
     /**
      * @detach:
      *
      * This is called by dma_buf_detach() to release a &dma_buf_attachment.
      * Provided so that exporters can clean up any housekeeping for an
      * &dma_buf_attachment.
      *
      * This callback is optional.
      */
     void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
 
     /**
      * @pin:
      *
      * This is called by dma_buf_pin() and lets the exporter know that the
      * DMA-buf can't be moved any more. Ideally, the exporter should
      * pin the buffer so that it is generally accessible by all
      * devices.
      *
      * This is called with the &dmabuf.resv object locked and is mutual
      * exclusive with @cache_sgt_mapping.
      *
      * This is called automatically for non-dynamic importers from
      * dma_buf_attach().
      *
      * Note that similar to non-dynamic exporters in their @map_dma_buf
      * callback the driver must guarantee that the memory is available for
      * use and cleared of any old data by the time this function returns.
      * Drivers which pipeline their buffer moves internally must wait for
      * all moves and clears to complete.
      *
      * Returns:
      *
      * 0 on success, negative error code on failure.
      */
     int (*pin)(struct dma_buf_attachment *attach);
 
     /**
      * @unpin:
      *
      * This is called by dma_buf_unpin() and lets the exporter know that the
      * DMA-buf can be moved again.
      *
      * This is called with the dmabuf->resv object locked and is mutual
      * exclusive with @cache_sgt_mapping.
      *
      * This callback is optional.
      */
     void (*unpin)(struct dma_buf_attachment *attach);
 
     /**
      * @map_dma_buf:
      *
      * This is called by dma_buf_map_attachment() and is used to map a
      * shared &dma_buf into device address space, and it is mandatory. It
      * can only be called if @attach has been called successfully.
      *
      * This call may sleep, e.g. when the backing storage first needs to be
      * allocated, or moved to a location suitable for all currently attached
      * devices.
      *
      * Note that any specific buffer attributes required for this function
      * should get added to device_dma_parameters accessible via
      * &device.dma_params from the &dma_buf_attachment. The @attach callback
      * should also check these constraints.
      *
      * If this is being called for the first time, the exporter can now
      * choose to scan through the list of attachments for this buffer,
      * collate the requirements of the attached devices, and choose an
      * appropriate backing storage for the buffer.
      *
      * Based on enum dma_data_direction, it might be possible to have
      * multiple users accessing at the same time (for reading, maybe), or
      * any other kind of sharing that the exporter might wish to make
      * available to buffer-users.
      *
      * This is always called with the dmabuf->resv object locked when
      * the dynamic_mapping flag is true.
      *
      * Note that for non-dynamic exporters the driver must guarantee that
      * that the memory is available for use and cleared of any old data by
      * the time this function returns.  Drivers which pipeline their buffer
      * moves internally must wait for all moves and clears to complete.
      * Dynamic exporters do not need to follow this rule: For non-dynamic
      * importers the buffer is already pinned through @pin, which has the
      * same requirements. Dynamic importers otoh are required to obey the
      * dma_resv fences.
      *
      * Returns:
      *
      * A &sg_table scatter list of the backing storage of the DMA buffer,
      * already mapped into the device address space of the &device attached
      * with the provided &dma_buf_attachment. The addresses and lengths in
      * the scatter list are PAGE_SIZE aligned.
      *
      * On failure, returns a negative error value wrapped into a pointer.
      * May also return -EINTR when a signal was received while being
      * blocked.
      *
      * Note that exporters should not try to cache the scatter list, or
      * return the same one for multiple calls. Caching is done either by the
      * DMA-BUF code (for non-dynamic importers) or the importer. Ownership
      * of the scatter list is transferred to the caller, and returned by
      * @unmap_dma_buf.
      */
     struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
                      enum dma_data_direction);
     /**
      * @unmap_dma_buf:
      *
      * This is called by dma_buf_unmap_attachment() and should unmap and
      * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
      * For static dma_buf handling this might also unpin the backing
      * storage if this is the last mapping of the DMA buffer.
      */
     void (*unmap_dma_buf)(struct dma_buf_attachment *,
                   struct sg_table *,
                   enum dma_data_direction);
 
     /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
      * if the call would block.
      */
 
     /**
      * @release:
      *
      * Called after the last dma_buf_put to release the &dma_buf, and
      * mandatory.
      */
     void (*release)(struct dma_buf *);
 
     /**
      * @begin_cpu_access:
      *
      * This is called from dma_buf_begin_cpu_access() and allows the
      * exporter to ensure that the memory is actually coherent for cpu
      * access. The exporter also needs to ensure that cpu access is coherent
      * for the access direction. The direction can be used by the exporter
      * to optimize the cache flushing, i.e. access with a different
      * direction (read instead of write) might return stale or even bogus
      * data (e.g. when the exporter needs to copy the data to temporary
      * storage).
      *
      * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL
      * command for userspace mappings established through @mmap, and also
      * for kernel mappings established with @vmap.
      *
      * This callback is optional.
      *
      * Returns:
      *
      * 0 on success or a negative error code on failure. This can for
      * example fail when the backing storage can't be allocated. Can also
      * return -ERESTARTSYS or -EINTR when the call has been interrupted and
      * needs to be restarted.
      */
     int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
 
     /**
      * @end_cpu_access:
      *
      * This is called from dma_buf_end_cpu_access() when the importer is
      * done accessing the CPU. The exporter can use this to flush caches and
      * undo anything else done in @begin_cpu_access.
      *
      * This callback is optional.
      *
      * Returns:
      *
      * 0 on success or a negative error code on failure. Can return
      * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
      * to be restarted.
      */
     int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
 
     /**
      * @mmap:
      *
      * This callback is used by the dma_buf_mmap() function
      *
      * Note that the mapping needs to be incoherent, userspace is expected
      * to bracket CPU access using the DMA_BUF_IOCTL_SYNC interface.
      *
      * Because dma-buf buffers have invariant size over their lifetime, the
      * dma-buf core checks whether a vma is too large and rejects such
      * mappings. The exporter hence does not need to duplicate this check.
      * Drivers do not need to check this themselves.
      *
      * If an exporter needs to manually flush caches and hence needs to fake
      * coherency for mmap support, it needs to be able to zap all the ptes
      * pointing at the backing storage. Now linux mm needs a struct
      * address_space associated with the struct file stored in vma->vm_file
      * to do that with the function unmap_mapping_range. But the dma_buf
      * framework only backs every dma_buf fd with the anon_file struct file,
      * i.e. all dma_bufs share the same file.
      *
      * Hence exporters need to setup their own file (and address_space)
      * association by setting vma->vm_file and adjusting vma->vm_pgoff in
      * the dma_buf mmap callback. In the specific case of a gem driver the
      * exporter could use the shmem file already provided by gem (and set
      * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
      * corresponding range of the struct address_space associated with their
      * own file.
      *
      * This callback is optional.
      *
      * Returns:
      *
      * 0 on success or a negative error code on failure.
      */
     int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
 
     int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
     void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
 };
 
 /**
  * struct dma_buf - shared buffer object
  *
  * This represents a shared buffer, created by calling dma_buf_export(). The
  * userspace representation is a normal file descriptor, which can be created by
  * calling dma_buf_fd().
  *
  * Shared dma buffers are reference counted using dma_buf_put() and
  * get_dma_buf().
  *
  * Device DMA access is handled by the separate &struct dma_buf_attachment.
  */
 struct dma_buf {
     /**
      * @size:
      *
      * Size of the buffer; invariant over the lifetime of the buffer.
      */
     size_t size;
 
     /**
      * @file:
      *
      * File pointer used for sharing buffers across, and for refcounting.
      * See dma_buf_get() and dma_buf_put().
      */
     struct file *file;
 
     /**
      * @attachments:
      *
      * List of dma_buf_attachment that denotes all devices attached,
      * protected by &dma_resv lock @resv.
      */
     struct list_head attachments;
 
     /** @ops: dma_buf_ops associated with this buffer object. */
     const struct dma_buf_ops *ops;
 
     /**
      * @lock:
      *
      * Used internally to serialize list manipulation, attach/detach and
      * vmap/unmap. Note that in many cases this is superseeded by
      * dma_resv_lock() on @resv.
      */
     struct mutex lock;
 
     /**
      * @vmapping_counter:
      *
      * Used internally to refcnt the vmaps returned by dma_buf_vmap().
      * Protected by @lock.
      */
     unsigned vmapping_counter;
 
     /**
      * @vmap_ptr:
      * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
      */
     struct iosys_map vmap_ptr;
 
     /**
      * @exp_name:
      *
      * Name of the exporter; useful for debugging. See the
      * DMA_BUF_SET_NAME IOCTL.
      */
     const char *exp_name;
 
     /**
      * @name:
      *
      * Userspace-provided name; useful for accounting and debugging,
      * protected by dma_resv_lock() on @resv and @name_lock for read access.
      */
     const char *name;
 
     /** @name_lock: Spinlock to protect name acces for read access. */
     spinlock_t name_lock;
 
     /**
      * @owner:
      *
      * Pointer to exporter module; used for refcounting when exporter is a
      * kernel module.
      */
     struct module *owner;
 
     /** @list_node: node for dma_buf accounting and debugging. */
     struct list_head list_node;
 
     /** @priv: exporter specific private data for this buffer object. */
     void *priv;
 
     /**
      * @resv:
      *
      * Reservation object linked to this dma-buf.
      *
      * IMPLICIT SYNCHRONIZATION RULES:
      *
      * Drivers which support implicit synchronization of buffer access as
      * e.g. exposed in `Implicit Fence Poll Support`_ must follow the
      * below rules.
      *
      * - Drivers must add a read fence through dma_resv_add_fence() with the
      *   DMA_RESV_USAGE_READ flag for anything the userspace API considers a
      *   read access. This highly depends upon the API and window system.
      *
      * - Similarly drivers must add a write fence through
      *   dma_resv_add_fence() with the DMA_RESV_USAGE_WRITE flag for
      *   anything the userspace API considers write access.
      *
      * - Drivers may just always add a write fence, since that only
      *   causes unecessarily synchronization, but no correctness issues.
      *
      * - Some drivers only expose a synchronous userspace API with no
      *   pipelining across drivers. These do not set any fences for their
      *   access. An example here is v4l.
      *
      * - Driver should use dma_resv_usage_rw() when retrieving fences as
      *   dependency for implicit synchronization.
      *
      * DYNAMIC IMPORTER RULES:
      *
      * Dynamic importers, see dma_buf_attachment_is_dynamic(), have
      * additional constraints on how they set up fences:
      *
      * - Dynamic importers must obey the write fences and wait for them to
      *   signal before allowing access to the buffer's underlying storage
      *   through the device.
      *
      * - Dynamic importers should set fences for any access that they can't
      *   disable immediately from their &dma_buf_attach_ops.move_notify
      *   callback.
      *
      * IMPORTANT:
      *
      * All drivers and memory management related functions must obey the
      * struct dma_resv rules, specifically the rules for updating and
      * obeying fences. See enum dma_resv_usage for further descriptions.
      */
     struct dma_resv *resv;
 
     /** @poll: for userspace poll support */
     wait_queue_head_t poll;
 
     /** @cb_in: for userspace poll support */
     /** @cb_out: for userspace poll support */
     struct dma_buf_poll_cb_t {
         struct dma_fence_cb cb;
         wait_queue_head_t *poll;
 
         __poll_t active;
     } cb_in, cb_out;
 #ifdef CONFIG_DMABUF_SYSFS_STATS
     /**
      * @sysfs_entry:
      *
      * For exposing information about this buffer in sysfs. See also
      * `DMA-BUF statistics`_ for the uapi this enables.
      */
     struct dma_buf_sysfs_entry {
         struct kobject kobj;
         struct dma_buf *dmabuf;
     } *sysfs_entry;
 #endif
 };
 
 /**
  * struct dma_buf_attach_ops - importer operations for an attachment
  *
  * Attachment operations implemented by the importer.
  */
 struct dma_buf_attach_ops {
     /**
      * @allow_peer2peer:
      *
      * If this is set to true the importer must be able to handle peer
      * resources without struct pages.
      */
     bool allow_peer2peer;
 
     /**
      * @move_notify: [optional] notification that the DMA-buf is moving
      *
      * If this callback is provided the framework can avoid pinning the
      * backing store while mappings exists.
      *
      * This callback is called with the lock of the reservation object
      * associated with the dma_buf held and the mapping function must be
      * called with this lock held as well. This makes sure that no mapping
      * is created concurrently with an ongoing move operation.
      *
      * Mappings stay valid and are not directly affected by this callback.
      * But the DMA-buf can now be in a different physical location, so all
      * mappings should be destroyed and re-created as soon as possible.
      *
      * New mappings can be created after this callback returns, and will
      * point to the new location of the DMA-buf.
      */
     void (*move_notify)(struct dma_buf_attachment *attach);
 };
 
 /**
  * struct dma_buf_attachment - holds device-buffer attachment data
  * @dmabuf: buffer for this attachment.
  * @dev: device attached to the buffer.
  * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
  * @sgt: cached mapping.
  * @dir: direction of cached mapping.
  * @peer2peer: true if the importer can handle peer resources without pages.
  * @priv: exporter specific attachment data.
  * @importer_ops: importer operations for this attachment, if provided
  * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
  * @importer_priv: importer specific attachment data.
  *
  * This structure holds the attachment information between the dma_buf buffer
  * and its user device(s). The list contains one attachment struct per device
  * attached to the buffer.
  *
  * An attachment is created by calling dma_buf_attach(), and released again by
  * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
  * transfer is created by dma_buf_map_attachment() and freed again by calling
  * dma_buf_unmap_attachment().
  */
 struct dma_buf_attachment {
     struct dma_buf *dmabuf;
     struct device *dev;
     struct list_head node;
     struct sg_table *sgt;
     enum dma_data_direction dir;
     bool peer2peer;
     const struct dma_buf_attach_ops *importer_ops;
     void *importer_priv;
     void *priv;
 };
 
 /**
  * struct dma_buf_export_info - holds information needed to export a dma_buf
  * @exp_name:   name of the exporter - useful for debugging.
  * @owner:  pointer to exporter module - used for refcounting kernel module
  * @ops:    Attach allocator-defined dma buf ops to the new buffer
  * @size:   Size of the buffer - invariant over the lifetime of the buffer
  * @flags:  mode flags for the file
  * @resv:   reservation-object, NULL to allocate default one
  * @priv:   Attach private data of allocator to this buffer
  *
  * This structure holds the information required to export the buffer. Used
  * with dma_buf_export() only.
  */
 struct dma_buf_export_info {
     const char *exp_name;
     struct module *owner;
     const struct dma_buf_ops *ops;
     size_t size;
     int flags;
     struct dma_resv *resv;
     void *priv;
 };
 
 /**
  * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
  * @name: export-info name
  *
  * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
  * zeroes it out and pre-populates exp_name in it.
  */
 #define DEFINE_DMA_BUF_EXPORT_INFO(name)    \
     struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
                      .owner = THIS_MODULE }
 
 /**
  * get_dma_buf - convenience wrapper for get_file.
  * @dmabuf: [in]    pointer to dma_buf
  *
  * Increments the reference count on the dma-buf, needed in case of drivers
  * that either need to create additional references to the dmabuf on the
  * kernel side.  For example, an exporter that needs to keep a dmabuf ptr
  * so that subsequent exports don't create a new dmabuf.
  */
 static inline void get_dma_buf(struct dma_buf *dmabuf)
 {
     get_file(dmabuf->file);
 }
 
 /**
  * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
  * @dmabuf: the DMA-buf to check
  *
  * Returns true if a DMA-buf exporter wants to be called with the dma_resv
  * locked for the map/unmap callbacks, false if it doesn't wants to be called
  * with the lock held.
  */
 static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
 {
     return !!dmabuf->ops->pin;
 }
 
 /**
  * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
  * mappings
  * @attach: the DMA-buf attachment to check
  *
  * Returns true if a DMA-buf importer wants to call the map/unmap functions with
  * the dma_resv lock held.
  */
 static inline bool
 dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
 {
     return !!attach->importer_ops;
 }
 
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
                       struct device *dev);
 struct dma_buf_attachment *
 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
                const struct dma_buf_attach_ops *importer_ops,
                void *importer_priv);
 void dma_buf_detach(struct dma_buf *dmabuf,
             struct dma_buf_attachment *attach);
 int dma_buf_pin(struct dma_buf_attachment *attach);
 void dma_buf_unpin(struct dma_buf_attachment *attach);
 
 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
 
 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 struct dma_buf *dma_buf_get(int fd);
 void dma_buf_put(struct dma_buf *dmabuf);
 
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
                     enum dma_data_direction);
 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
                 enum dma_data_direction);
 void dma_buf_move_notify(struct dma_buf *dma_buf);
 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
                  enum dma_data_direction dir);
 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
                enum dma_data_direction dir);
 
 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
          unsigned long);
 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
 #endif /* __DMA_BUF_H__ */

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