| /* 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/dma-buf-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 dma_buf_map *map); |
| void (*vunmap)(struct dma_buf *dmabuf, struct dma_buf_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 dma_buf_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 shared fence through dma_resv_add_shared_fence() |
| * for anything the userspace API considers a read access. This highly |
| * depends upon the API and window system. |
| * |
| * - Similarly drivers must set the exclusive fence through |
| * dma_resv_add_excl_fence() for anything the userspace API considers |
| * write access. |
| * |
| * - Drivers may just always set the exclusive 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. |
| * |
| * 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 exclusive fence and wait for it 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 must obey the struct dma_resv rules, specifically the |
| * rules for updating fences, see &dma_resv.fence_excl and |
| * &dma_resv.fence. If these dependency rules are broken access tracking |
| * can be lost resulting in use after free issues. |
| */ |
| struct dma_resv *resv; |
| |
| /** @poll: for userspace poll support */ |
| wait_queue_head_t poll; |
| |
| /** @cb_excl: for userspace poll support */ |
| /** @cb_shared: 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 dma_buf_map *map); |
| void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map); |
| #endif /* __DMA_BUF_H__ */ |