include/linux/dma-buf.h

   1 /*
   2  * Header file for dma buffer sharing framework.
   3  *
   4  * Copyright(C) 2011 Linaro Limited. All rights reserved.
   5  * Author: Sumit Semwal <sumit.semwal@ti.com>
   6  *
   7  * Many thanks to linaro-mm-sig list, and specially
   8  * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
   9  * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
  10  * refining of this idea.
  11  *
  12  * This program is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU General Public License version 2 as published by
  14  * the Free Software Foundation.
  15  *
  16  * This program is distributed in the hope that it will be useful, but WITHOUT
  17  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  19  * more details.
  20  *
  21  * You should have received a copy of the GNU General Public License along with
  22  * this program.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24 #ifndef __DMA_BUF_H__
  25 #define __DMA_BUF_H__
  26
  27 #include <linux/file.h>
  28 #include <linux/err.h>
  29 #include <linux/scatterlist.h>
  30 #include <linux/list.h>
  31 #include <linux/dma-mapping.h>
  32 #include <linux/fs.h>
  33 #include <linux/dma-fence.h>
  34 #include <linux/wait.h>
  35
  36 struct device;
  37 struct dma_buf;
  38 struct dma_buf_attachment;
  39
  40 /**
  41  * struct dma_buf_ops - operations possible on struct dma_buf
  42  * @map_atomic: maps a page from the buffer into kernel address
  43  *              space, users may not block until the subsequent unmap call.
  44  *              This callback must not sleep.
  45  * @unmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
  46  *                This Callback must not sleep.
  47  * @map: maps a page from the buffer into kernel address space.
  48  * @unmap: [optional] unmaps a page from the buffer.
  49  * @vmap: [optional] creates a virtual mapping for the buffer into kernel
  50  *        address space. Same restrictions as for vmap and friends apply.
  51  * @vunmap: [optional] unmaps a vmap from the buffer
  52  */
  53 struct dma_buf_ops {
  54         /**
  55          * @attach:
  56          *
  57          * This is called from dma_buf_attach() to make sure that a given
  58          * &device can access the provided &dma_buf. Exporters which support
  59          * buffer objects in special locations like VRAM or device-specific
  60          * carveout areas should check whether the buffer could be move to
  61          * system memory (or directly accessed by the provided device), and
  62          * otherwise need to fail the attach operation.
  63          *
  64          * The exporter should also in general check whether the current
  65          * allocation fullfills the DMA constraints of the new device. If this
  66          * is not the case, and the allocation cannot be moved, it should also
  67          * fail the attach operation.
  68          *
  69          * Any exporter-private housekeeping data can be stored in the
  70          * &dma_buf_attachment.priv pointer.
  71          *
  72          * This callback is optional.
  73          *
  74          * Returns:
  75          *
  76          * 0 on success, negative error code on failure. It might return -EBUSY
  77          * to signal that backing storage is already allocated and incompatible
  78          * with the requirements of requesting device.
  79          */
  80         int (*attach)(struct dma_buf *, struct device *,
  81                       struct dma_buf_attachment *);
  82
  83         /**
  84          * @detach:
  85          *
  86          * This is called by dma_buf_detach() to release a &dma_buf_attachment.
  87          * Provided so that exporters can clean up any housekeeping for an
  88          * &dma_buf_attachment.
  89          *
  90          * This callback is optional.
  91          */
  92         void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
  93
  94         /**
  95          * @map_dma_buf:
  96          *
  97          * This is called by dma_buf_map_attachment() and is used to map a
  98          * shared &dma_buf into device address space, and it is mandatory. It
  99          * can only be called if @attach has been called successfully. This
 100          * essentially pins the DMA buffer into place, and it cannot be moved
 101          * any more
 102          *
 103          * This call may sleep, e.g. when the backing storage first needs to be
 104          * allocated, or moved to a location suitable for all currently attached
 105          * devices.
 106          *
 107          * Note that any specific buffer attributes required for this function
 108          * should get added to device_dma_parameters accessible via
 109          * &device.dma_params from the &dma_buf_attachment. The @attach callback
 110          * should also check these constraints.
 111          *
 112          * If this is being called for the first time, the exporter can now
 113          * choose to scan through the list of attachments for this buffer,
 114          * collate the requirements of the attached devices, and choose an
 115          * appropriate backing storage for the buffer.
 116          *
 117          * Based on enum dma_data_direction, it might be possible to have
 118          * multiple users accessing at the same time (for reading, maybe), or
 119          * any other kind of sharing that the exporter might wish to make
 120          * available to buffer-users.
 121          *
 122          * Returns:
 123          *
 124          * A &sg_table scatter list of or the backing storage of the DMA buffer,
 125          * already mapped into the device address space of the &device attached
 126          * with the provided &dma_buf_attachment.
 127          *
 128          * On failure, returns a negative error value wrapped into a pointer.
 129          * May also return -EINTR when a signal was received while being
 130          * blocked.
 131          */
 132         struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
 133                                          enum dma_data_direction);
 134         /**
 135          * @unmap_dma_buf:
 136          *
 137          * This is called by dma_buf_unmap_attachment() and should unmap and
 138          * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
 139          * It should also unpin the backing storage if this is the last mapping
 140          * of the DMA buffer, it the exporter supports backing storage
 141          * migration.
 142          */
 143         void (*unmap_dma_buf)(struct dma_buf_attachment *,
 144                               struct sg_table *,
 145                               enum dma_data_direction);
 146
 147         /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
 148          * if the call would block.
 149          */
 150
 151         /**
 152          * @release:
 153          *
 154          * Called after the last dma_buf_put to release the &dma_buf, and
 155          * mandatory.
 156          */
 157         void (*release)(struct dma_buf *);
 158
 159         /**
 160          * @begin_cpu_access:
 161          *
 162          * This is called from dma_buf_begin_cpu_access() and allows the
 163          * exporter to ensure that the memory is actually available for cpu
 164          * access - the exporter might need to allocate or swap-in and pin the
 165          * backing storage. The exporter also needs to ensure that cpu access is
 166          * coherent for the access direction. The direction can be used by the
 167          * exporter to optimize the cache flushing, i.e. access with a different
 168          * direction (read instead of write) might return stale or even bogus
 169          * data (e.g. when the exporter needs to copy the data to temporary
 170          * storage).
 171          *
 172          * This callback is optional.
 173          *
 174          * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
 175          * from userspace (where storage shouldn't be pinned to avoid handing
 176          * de-factor mlock rights to userspace) and for the kernel-internal
 177          * users of the various kmap interfaces, where the backing storage must
 178          * be pinned to guarantee that the atomic kmap calls can succeed. Since
 179          * there's no in-kernel users of the kmap interfaces yet this isn't a
 180          * real problem.
 181          *
 182          * Returns:
 183          *
 184          * 0 on success or a negative error code on failure. This can for
 185          * example fail when the backing storage can't be allocated. Can also
 186          * return -ERESTARTSYS or -EINTR when the call has been interrupted and
 187          * needs to be restarted.
 188          */
 189         int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
 190
 191         /**
 192          * @end_cpu_access:
 193          *
 194          * This is called from dma_buf_end_cpu_access() when the importer is
 195          * done accessing the CPU. The exporter can use this to flush caches and
 196          * unpin any resources pinned in @begin_cpu_access.
 197          * The result of any dma_buf kmap calls after end_cpu_access is
 198          * undefined.
 199          *
 200          * This callback is optional.
 201          *
 202          * Returns:
 203          *
 204          * 0 on success or a negative error code on failure. Can return
 205          * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
 206          * to be restarted.
 207          */
 208         int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
 209         void *(*map_atomic)(struct dma_buf *, unsigned long);
 210         void (*unmap_atomic)(struct dma_buf *, unsigned long, void *);
 211         void *(*map)(struct dma_buf *, unsigned long);
 212         void (*unmap)(struct dma_buf *, unsigned long, void *);
 213
 214         /**
 215          * @mmap:
 216          *
 217          * This callback is used by the dma_buf_mmap() function
 218          *
 219          * Note that the mapping needs to be incoherent, userspace is expected
 220          * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
 221          *
 222          * Because dma-buf buffers have invariant size over their lifetime, the
 223          * dma-buf core checks whether a vma is too large and rejects such
 224          * mappings. The exporter hence does not need to duplicate this check.
 225          * Drivers do not need to check this themselves.
 226          *
 227          * If an exporter needs to manually flush caches and hence needs to fake
 228          * coherency for mmap support, it needs to be able to zap all the ptes
 229          * pointing at the backing storage. Now linux mm needs a struct
 230          * address_space associated with the struct file stored in vma->vm_file
 231          * to do that with the function unmap_mapping_range. But the dma_buf
 232          * framework only backs every dma_buf fd with the anon_file struct file,
 233          * i.e. all dma_bufs share the same file.
 234          *
 235          * Hence exporters need to setup their own file (and address_space)
 236          * association by setting vma->vm_file and adjusting vma->vm_pgoff in
 237          * the dma_buf mmap callback. In the specific case of a gem driver the
 238          * exporter could use the shmem file already provided by gem (and set
 239          * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
 240          * corresponding range of the struct address_space associated with their
 241          * own file.
 242          *
 243          * This callback is optional.
 244          *
 245          * Returns:
 246          *
 247          * 0 on success or a negative error code on failure.
 248          */
 249         int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
 250
 251         void *(*vmap)(struct dma_buf *);
 252         void (*vunmap)(struct dma_buf *, void *vaddr);
 253 };
 254
 255 /**
 256  * struct dma_buf - shared buffer object
 257  * @size: size of the buffer
 258  * @file: file pointer used for sharing buffers across, and for refcounting.
 259  * @attachments: list of dma_buf_attachment that denotes all devices attached.
 260  * @ops: dma_buf_ops associated with this buffer object.
 261  * @lock: used internally to serialize list manipulation, attach/detach and vmap/unmap
 262  * @vmapping_counter: used internally to refcnt the vmaps
 263  * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
 264  * @exp_name: name of the exporter; useful for debugging.
 265  * @owner: pointer to exporter module; used for refcounting when exporter is a
 266  *         kernel module.
 267  * @list_node: node for dma_buf accounting and debugging.
 268  * @priv: exporter specific private data for this buffer object.
 269  * @resv: reservation object linked to this dma-buf
 270  * @poll: for userspace poll support
 271  * @cb_excl: for userspace poll support
 272  * @cb_shared: for userspace poll support
 273  *
 274  * This represents a shared buffer, created by calling dma_buf_export(). The
 275  * userspace representation is a normal file descriptor, which can be created by
 276  * calling dma_buf_fd().
 277  *
 278  * Shared dma buffers are reference counted using dma_buf_put() and
 279  * get_dma_buf().
 280  *
 281  * Device DMA access is handled by the separate &struct dma_buf_attachment.
 282  */
 283 struct dma_buf {
 284         size_t size;
 285         struct file *file;
 286         struct list_head attachments;
 287         const struct dma_buf_ops *ops;
 288         struct mutex lock;
 289         unsigned vmapping_counter;
 290         void *vmap_ptr;
 291         const char *exp_name;
 292         struct module *owner;
 293         struct list_head list_node;
 294         void *priv;
 295         struct reservation_object *resv;
 296
 297         /* poll support */
 298         wait_queue_head_t poll;
 299
 300         struct dma_buf_poll_cb_t {
 301                 struct dma_fence_cb cb;
 302                 wait_queue_head_t *poll;
 303
 304                 unsigned long active;
 305         } cb_excl, cb_shared;
 306 };
 307
 308 /**
 309  * struct dma_buf_attachment - holds device-buffer attachment data
 310  * @dmabuf: buffer for this attachment.
 311  * @dev: device attached to the buffer.
 312  * @node: list of dma_buf_attachment.
 313  * @priv: exporter specific attachment data.
 314  *
 315  * This structure holds the attachment information between the dma_buf buffer
 316  * and its user device(s). The list contains one attachment struct per device
 317  * attached to the buffer.
 318  *
 319  * An attachment is created by calling dma_buf_attach(), and released again by
 320  * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
 321  * transfer is created by dma_buf_map_attachment() and freed again by calling
 322  * dma_buf_unmap_attachment().
 323  */
 324 struct dma_buf_attachment {
 325         struct dma_buf *dmabuf;
 326         struct device *dev;
 327         struct list_head node;
 328         void *priv;
 329 };
 330
 331 /**
 332  * struct dma_buf_export_info - holds information needed to export a dma_buf
 333  * @exp_name:   name of the exporter - useful for debugging.
 334  * @owner:      pointer to exporter module - used for refcounting kernel module
 335  * @ops:        Attach allocator-defined dma buf ops to the new buffer
 336  * @size:       Size of the buffer
 337  * @flags:      mode flags for the file
 338  * @resv:       reservation-object, NULL to allocate default one
 339  * @priv:       Attach private data of allocator to this buffer
 340  *
 341  * This structure holds the information required to export the buffer. Used
 342  * with dma_buf_export() only.
 343  */
 344 struct dma_buf_export_info {
 345         const char *exp_name;
 346         struct module *owner;
 347         const struct dma_buf_ops *ops;
 348         size_t size;
 349         int flags;
 350         struct reservation_object *resv;
 351         void *priv;
 352 };
 353
 354 /**
 355  * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
 356  * @name: export-info name
 357  *
 358  * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
 359  * zeroes it out and pre-populates exp_name in it.
 360  */
 361 #define DEFINE_DMA_BUF_EXPORT_INFO(name)        \
 362         struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
 363                                          .owner = THIS_MODULE }
 364
 365 /**
 366  * get_dma_buf - convenience wrapper for get_file.
 367  * @dmabuf:     [in]    pointer to dma_buf
 368  *
 369  * Increments the reference count on the dma-buf, needed in case of drivers
 370  * that either need to create additional references to the dmabuf on the
 371  * kernel side.  For example, an exporter that needs to keep a dmabuf ptr
 372  * so that subsequent exports don't create a new dmabuf.
 373  */
 374 static inline void get_dma_buf(struct dma_buf *dmabuf)
 375 {
 376         get_file(dmabuf->file);
 377 }
 378
 379 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 380                                                         struct device *dev);
 381 void dma_buf_detach(struct dma_buf *dmabuf,
 382                                 struct dma_buf_attachment *dmabuf_attach);
 383
 384 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
 385
 386 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 387 struct dma_buf *dma_buf_get(int fd);
 388 void dma_buf_put(struct dma_buf *dmabuf);
 389
 390 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
 391                                         enum dma_data_direction);
 392 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
 393                                 enum dma_data_direction);
 394 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
 395                              enum dma_data_direction dir);
 396 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
 397                            enum dma_data_direction dir);
 398 void *dma_buf_kmap_atomic(struct dma_buf *, unsigned long);
 399 void dma_buf_kunmap_atomic(struct dma_buf *, unsigned long, void *);
 400 void *dma_buf_kmap(struct dma_buf *, unsigned long);
 401 void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);
 402
 403 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
 404                  unsigned long);
 405 void *dma_buf_vmap(struct dma_buf *);
 406 void dma_buf_vunmap(struct dma_buf *, void *vaddr);
 407 #endif /* __DMA_BUF_H__ */