cregit-Linux how code gets into the kernel

Release 4.12 include/linux/dma-buf.h

Directory: include/linux
 * Header file for dma buffer sharing framework.
 * Copyright(C) 2011 Linaro Limited. All rights reserved.
 * Author: Sumit Semwal <>
 * Many thanks to linaro-mm-sig list, and specially
 * Arnd Bergmann <>, Rob Clark <> and
 * Daniel Vetter <> for their support in creation and
 * refining of this idea.
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <>.
#ifndef __DMA_BUF_H__

#define __DMA_BUF_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
 * @map_atomic: maps a page from the buffer into kernel address
 *              space, users may not block until the subsequent unmap call.
 *              This callback must not sleep.
 * @unmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
 *                This Callback must not sleep.
 * @map: maps a page from the buffer into kernel address space.
 * @unmap: [optional] unmaps a page from the buffer.
 * @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
         * &device 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 fullfills 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 device *,
		      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 *);

         * @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
         * 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.
         * Returns:
         * A &sg_table scatter list of or the backing storage of the DMA buffer,
         * already mapped into the device address space of the &device attached
         * with the provided &dma_buf_attachment.
         * On failure, returns a negative error value wrapped into a pointer.
         * May also return -EINTR when a signal was received while being
         * blocked.
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.
         * It should also unpin the backing storage if this is the last mapping
         * of the DMA buffer, it the exporter supports backing storage
         * migration.
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 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
         * 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.
         * 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.
         * 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
         * unpin any resources pinned in @begin_cpu_access.
         * The result of any dma_buf kmap calls after end_cpu_access is
         * undefined.
         * 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);
void *(*map_atomic)(struct dma_buf *, unsigned long);
void (*unmap_atomic)(struct dma_buf *, unsigned long, void *);
void *(*map)(struct dma_buf *, unsigned long);
void (*unmap)(struct dma_buf *, unsigned long, void *);

         * @mmap:
         * 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.
         * 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);

void *(*vmap)(struct dma_buf *);
void (*vunmap)(struct dma_buf *, void *vaddr);

 * 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.
 * @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.
 * @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
 * 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_t size;
struct file *file;
struct list_head attachments;
const struct dma_buf_ops *ops;
struct mutex lock;
unsigned vmapping_counter;
void *vmap_ptr;
const char *exp_name;
struct module *owner;
struct list_head list_node;
void *priv;
struct reservation_object *resv;

	/* poll support */
wait_queue_head_t poll;

struct dma_buf_poll_cb_t {
struct dma_fence_cb cb;
wait_queue_head_t *poll;

unsigned long active;

} cb_excl, cb_shared;

 * 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.
 * @priv: exporter 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;
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
 * @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 reservation_object *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.

	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); }


Rob Clark19100.00%1100.00%

struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev); void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *dmabuf_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); 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); void *dma_buf_kmap_atomic(struct dma_buf *, unsigned long); void dma_buf_kunmap_atomic(struct dma_buf *, unsigned long, void *); void *dma_buf_kmap(struct dma_buf *, unsigned long); void dma_buf_kunmap(struct dma_buf *, unsigned long, void *); 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); #endif /* __DMA_BUF_H__ */

Overall Contributors

Sumit Semwal32449.24%625.00%
Daniel Vetter21132.07%729.17%
Dave Airlie517.75%28.33%
Maarten Lankhorst345.17%28.33%
Rob Clark253.80%28.33%
Logan Gunthorpe50.76%14.17%
Chris Wilson40.61%28.33%
Paul Gortmaker30.46%14.17%
Laurent Pinchart10.15%14.17%
Directory: include/linux
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