diff options
Diffstat (limited to 'include/linux/dma-buf.h')
| -rw-r--r-- | include/linux/dma-buf.h | 273 |
1 files changed, 189 insertions, 84 deletions
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 957b398d30e5..d58e329ac0e7 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> @@ -34,15 +35,6 @@ struct dma_buf_attachment; */ 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 @@ -53,7 +45,7 @@ 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. * @@ -84,14 +76,22 @@ struct dma_buf_ops { /** * @pin: * - * This is called by dma_buf_pin and lets the exporter know that the - * DMA-buf can't be moved any more. + * 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 + * This is called with the &dmabuf.resv object locked and is mutual * exclusive with @cache_sgt_mapping. * - * This callback is optional and should only be used in limited use - * cases like scanout and not for temporary pin operations. + * 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: * @@ -102,7 +102,7 @@ struct dma_buf_ops { /** * @unpin: * - * This is called by dma_buf_unpin and lets the exporter know that the + * 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 @@ -141,15 +141,31 @@ 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); @@ -158,7 +174,7 @@ 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. - * For static dma_buf handling this might also unpins the backing + * 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 *, @@ -181,24 +197,19 @@ 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: * @@ -214,9 +225,7 @@ 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. * @@ -234,7 +243,7 @@ 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 @@ -265,33 +274,12 @@ 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. - * @name_lock: spinlock to protect name access - * @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 @@ -303,30 +291,155 @@ 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; - 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. 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 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 }; /** @@ -369,8 +482,6 @@ struct dma_buf_attach_ops { * @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 @@ -390,8 +501,6 @@ 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; @@ -403,7 +512,7 @@ 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 @@ -459,20 +568,6 @@ 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 - * mappinsg - * @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 * @@ -499,9 +594,19 @@ 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); -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); +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__ */ |