diff options
Diffstat (limited to 'include/linux/dma-buf.h')
| -rw-r--r-- | include/linux/dma-buf.h | 334 |
1 files changed, 261 insertions, 73 deletions
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index abf5459a5b9d..71731796c8c3 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -13,6 +13,7 @@ #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> @@ -43,18 +44,6 @@ struct dma_buf_ops { bool cache_sgt_mapping; /** - * @dynamic_mapping: - * - * If true the framework makes sure that the map/unmap_dma_buf - * callbacks are always called with the dma_resv object locked. - * - * If false the framework makes sure that the map/unmap_dma_buf - * callbacks are always called without the dma_resv object locked. - * Mutual exclusive with @cache_sgt_mapping. - */ - bool dynamic_mapping; - - /** * @attach: * * This is called from dma_buf_attach() to make sure that a given @@ -65,7 +54,7 @@ struct dma_buf_ops { * device), and otherwise need to fail the attach operation. * * The exporter should also in general check whether the current - * allocation fullfills the DMA constraints of the new device. If this + * 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. * @@ -94,13 +83,50 @@ struct dma_buf_ops { 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 - * essentially pins the DMA buffer into place, and it cannot be moved - * any more + * 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 @@ -124,15 +150,31 @@ struct dma_buf_ops { * 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 or the backing storage of the DMA buffer, + * 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. + * 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); @@ -141,9 +183,8 @@ struct dma_buf_ops { * * 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. - * It should also unpin the backing storage if this is the last mapping - * of the DMA buffer, it the exporter supports backing storage - * migration. + * 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 *, @@ -165,24 +206,19 @@ struct dma_buf_ops { * @begin_cpu_access: * * This is called from dma_buf_begin_cpu_access() and allows the - * exporter to ensure that the memory is actually available for cpu - * access - the exporter might need to allocate or swap-in and pin the - * backing storage. 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 + * 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). * - * This callback is optional. + * 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. * - * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command - * from userspace (where storage shouldn't be pinned to avoid handing - * de-factor mlock rights to userspace) and for the kernel-internal - * users of the various kmap interfaces, where the backing storage must - * be pinned to guarantee that the atomic kmap calls can succeed. Since - * there's no in-kernel users of the kmap interfaces yet this isn't a - * real problem. + * This callback is optional. * * Returns: * @@ -198,9 +234,7 @@ struct dma_buf_ops { * * 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 - * unpin any resources pinned in @begin_cpu_access. - * The result of any dma_buf kmap calls after end_cpu_access is - * undefined. + * undo anything else done in @begin_cpu_access. * * This callback is optional. * @@ -218,7 +252,7 @@ struct dma_buf_ops { * This callback is used by the dma_buf_mmap() function * * Note that the mapping needs to be incoherent, userspace is expected - * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface. + * 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 @@ -249,32 +283,12 @@ struct dma_buf_ops { */ int (*mmap)(struct dma_buf *, struct vm_area_struct *vma); - void *(*vmap)(struct dma_buf *); - void (*vunmap)(struct dma_buf *, void *vaddr); + 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 - * @size: size of the buffer - * @file: file pointer used for sharing buffers across, and for refcounting. - * @attachments: list of dma_buf_attachment that denotes all devices attached, - * protected by dma_resv lock. - * @ops: dma_buf_ops associated with this buffer object. - * @lock: used internally to serialize list manipulation, attach/detach and - * vmap/unmap - * @vmapping_counter: used internally to refcnt the vmaps - * @vmap_ptr: the current vmap ptr if vmapping_counter > 0 - * @exp_name: name of the exporter; useful for debugging. - * @name: userspace-provided name; useful for accounting and debugging, - * protected by @resv. - * @owner: pointer to exporter module; used for refcounting when exporter is a - * kernel module. - * @list_node: node for dma_buf accounting and debugging. - * @priv: exporter specific private data for this buffer object. - * @resv: reservation object linked to this dma-buf - * @poll: for userspace poll support - * @cb_excl: for userspace poll support - * @cb_shared: for userspace poll support * * This represents a shared buffer, created by calling dma_buf_export(). The * userspace representation is a normal file descriptor, which can be created by @@ -286,29 +300,196 @@ struct dma_buf_ops { * 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; - void *vmap_ptr; + + /** + * @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 support */ + /** @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_excl, cb_shared; + } 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); }; /** @@ -318,9 +499,11 @@ struct dma_buf { * @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. - * @dynamic_mapping: true if dma_buf_map/unmap_attachment() is called with the - * dma_resv lock held. + * @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 @@ -337,7 +520,9 @@ struct dma_buf_attachment { struct list_head node; struct sg_table *sgt; enum dma_data_direction dir; - bool dynamic_mapping; + bool peer2peer; + const struct dma_buf_attach_ops *importer_ops; + void *importer_priv; void *priv; }; @@ -346,7 +531,7 @@ struct dma_buf_attachment { * @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 + * @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 @@ -399,12 +584,12 @@ static inline void get_dma_buf(struct dma_buf *dmabuf) */ static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf) { - return dmabuf->ops->dynamic_mapping; + return !!dmabuf->ops->pin; } /** * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic - * mappinsg + * mappings * @attach: the DMA-buf attachment to check * * Returns true if a DMA-buf importer wants to call the map/unmap functions with @@ -413,16 +598,19 @@ static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf) static inline bool dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach) { - return attach->dynamic_mapping; + 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, - bool dynamic_mapping); + 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); @@ -442,6 +630,6 @@ int dma_buf_end_cpu_access(struct dma_buf *dma_buf, int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *, unsigned long); -void *dma_buf_vmap(struct dma_buf *); -void dma_buf_vunmap(struct dma_buf *, void *vaddr); +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__ */ |