/* 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> #include <linux/pci-p2pdma.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 { /** * @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; /** * @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. Must not be NULL */ const char *exp_name; /** * @name: * * Userspace-provided name. Default value is NULL. If not NULL, * length cannot be longer than DMA_BUF_NAME_LEN, including NIL * char. Useful for accounting and debugging. Read/Write accesses * are protected by @name_lock * * See the IOCTLs DMA_BUF_SET_NAME or DMA_BUF_SET_NAME_A/B */ const char *name; /** @name_lock: Spinlock to protect name access 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 unnecessary 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; }; /** * 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. * @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; 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; } 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); struct sg_table * dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach, enum dma_data_direction direction); void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach, struct sg_table *sg_table, enum dma_data_direction direction); 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); int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map); void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map); struct dma_buf *dma_buf_iter_begin(void); struct dma_buf *dma_buf_iter_next(struct dma_buf *dmbuf); #endif /* __DMA_BUF_H__ */
