diff options
Diffstat (limited to 'include/linux/dma-buf.h')
| -rw-r--r-- | include/linux/dma-buf.h | 641 |
1 files changed, 641 insertions, 0 deletions
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h new file mode 100644 index 000000000..9c31f1f43 --- /dev/null +++ b/include/linux/dma-buf.h @@ -0,0 +1,641 @@ +/* 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); +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); +#endif /* __DMA_BUF_H__ */ |