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![Daniel Vetter](/assets/img/avatar_default.png)
Big differences to other contenders in the field (like ion) is that this also supports highmem, so we have to split up the cpu access from the kernel side into a prepare and a kmap step. Prepare is allowed to fail and should do everything required so that the kmap calls can succeed (like swapin/backing storage allocation, flushing, ...). More in-depth explanations will follow in the follow-up documentation patch. Changes in v2: - Clear up begin_cpu_access confusion noticed by Sumit Semwal. - Don't automatically fallback from the _atomic variants to the non-atomic variants. The _atomic callbacks are not allowed to sleep, so we want exporters to make this decision explicit. The function signatures are explicit, so simpler exporters can still use the same function for both. - Make the unmap functions optional. Simpler exporters with permanent mappings don't need to do anything at unmap time. Changes in v3: - Adjust the WARN_ON checks for the new ->ops functions as suggested by Rob Clark and Sumit Semwal. - Rebased on top of latest dma-buf-next git. Changes in v4: - Fixup a missing - in a return -EINVAL; statement. Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Rob Clark <rob@ti.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
252 lines
8.1 KiB
C
252 lines
8.1 KiB
C
/*
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* Header file for dma buffer sharing framework.
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*
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* Copyright(C) 2011 Linaro Limited. All rights reserved.
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* Author: Sumit Semwal <sumit.semwal@ti.com>
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*
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* Many thanks to linaro-mm-sig list, and specially
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* Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
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* Daniel Vetter <daniel@ffwll.ch> for their support in creation and
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* refining of this idea.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __DMA_BUF_H__
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#define __DMA_BUF_H__
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#include <linux/file.h>
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#include <linux/err.h>
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#include <linux/device.h>
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#include <linux/scatterlist.h>
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#include <linux/list.h>
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#include <linux/dma-mapping.h>
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#include <linux/fs.h>
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struct dma_buf;
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struct dma_buf_attachment;
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/**
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* struct dma_buf_ops - operations possible on struct dma_buf
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* @attach: [optional] allows different devices to 'attach' themselves to the
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* given buffer. It might return -EBUSY to signal that backing storage
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* is already allocated and incompatible with the requirements
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* of requesting device.
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* @detach: [optional] detach a given device from this buffer.
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* @map_dma_buf: returns list of scatter pages allocated, increases usecount
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* of the buffer. Requires atleast one attach to be called
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* before. Returned sg list should already be mapped into
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* _device_ address space. This call may sleep. May also return
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* -EINTR. Should return -EINVAL if attach hasn't been called yet.
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* @unmap_dma_buf: decreases usecount of buffer, might deallocate scatter
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* pages.
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* @release: release this buffer; to be called after the last dma_buf_put.
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* @begin_cpu_access: [optional] called before cpu access to invalidate cpu
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* caches and allocate backing storage (if not yet done)
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* respectively pin the objet into memory.
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* @end_cpu_access: [optional] called after cpu access to flush cashes.
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* @kmap_atomic: maps a page from the buffer into kernel address
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* space, users may not block until the subsequent unmap call.
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* This callback must not sleep.
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* @kunmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
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* This Callback must not sleep.
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* @kmap: maps a page from the buffer into kernel address space.
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* @kunmap: [optional] unmaps a page from the buffer.
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*/
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struct dma_buf_ops {
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int (*attach)(struct dma_buf *, struct device *,
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struct dma_buf_attachment *);
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void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
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/* For {map,unmap}_dma_buf below, any specific buffer attributes
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* required should get added to device_dma_parameters accessible
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* via dev->dma_params.
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*/
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struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
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enum dma_data_direction);
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void (*unmap_dma_buf)(struct dma_buf_attachment *,
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struct sg_table *,
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enum dma_data_direction);
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/* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
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* if the call would block.
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*/
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/* after final dma_buf_put() */
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void (*release)(struct dma_buf *);
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int (*begin_cpu_access)(struct dma_buf *, size_t, size_t,
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enum dma_data_direction);
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void (*end_cpu_access)(struct dma_buf *, size_t, size_t,
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enum dma_data_direction);
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void *(*kmap_atomic)(struct dma_buf *, unsigned long);
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void (*kunmap_atomic)(struct dma_buf *, unsigned long, void *);
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void *(*kmap)(struct dma_buf *, unsigned long);
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void (*kunmap)(struct dma_buf *, unsigned long, void *);
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};
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/**
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* struct dma_buf - shared buffer object
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* @size: size of the buffer
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* @file: file pointer used for sharing buffers across, and for refcounting.
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* @attachments: list of dma_buf_attachment that denotes all devices attached.
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* @ops: dma_buf_ops associated with this buffer object.
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* @priv: exporter specific private data for this buffer object.
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*/
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struct dma_buf {
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size_t size;
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struct file *file;
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struct list_head attachments;
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const struct dma_buf_ops *ops;
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/* mutex to serialize list manipulation and attach/detach */
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struct mutex lock;
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void *priv;
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};
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/**
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* struct dma_buf_attachment - holds device-buffer attachment data
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* @dmabuf: buffer for this attachment.
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* @dev: device attached to the buffer.
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* @node: list of dma_buf_attachment.
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* @priv: exporter specific attachment data.
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*
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* This structure holds the attachment information between the dma_buf buffer
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* and its user device(s). The list contains one attachment struct per device
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* attached to the buffer.
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*/
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struct dma_buf_attachment {
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struct dma_buf *dmabuf;
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struct device *dev;
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struct list_head node;
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void *priv;
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};
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/**
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* get_dma_buf - convenience wrapper for get_file.
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* @dmabuf: [in] pointer to dma_buf
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*
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* Increments the reference count on the dma-buf, needed in case of drivers
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* that either need to create additional references to the dmabuf on the
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* kernel side. For example, an exporter that needs to keep a dmabuf ptr
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* so that subsequent exports don't create a new dmabuf.
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*/
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static inline void get_dma_buf(struct dma_buf *dmabuf)
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{
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get_file(dmabuf->file);
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}
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#ifdef CONFIG_DMA_SHARED_BUFFER
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struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
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struct device *dev);
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void dma_buf_detach(struct dma_buf *dmabuf,
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struct dma_buf_attachment *dmabuf_attach);
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struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
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size_t size, int flags);
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int dma_buf_fd(struct dma_buf *dmabuf, int flags);
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struct dma_buf *dma_buf_get(int fd);
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void dma_buf_put(struct dma_buf *dmabuf);
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struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
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enum dma_data_direction);
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void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
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enum dma_data_direction);
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int dma_buf_begin_cpu_access(struct dma_buf *dma_buf, size_t start, size_t len,
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enum dma_data_direction dir);
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void dma_buf_end_cpu_access(struct dma_buf *dma_buf, size_t start, size_t len,
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enum dma_data_direction dir);
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void *dma_buf_kmap_atomic(struct dma_buf *, unsigned long);
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void dma_buf_kunmap_atomic(struct dma_buf *, unsigned long, void *);
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void *dma_buf_kmap(struct dma_buf *, unsigned long);
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void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);
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#else
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static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
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struct device *dev)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void dma_buf_detach(struct dma_buf *dmabuf,
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struct dma_buf_attachment *dmabuf_attach)
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{
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return;
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}
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static inline struct dma_buf *dma_buf_export(void *priv,
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const struct dma_buf_ops *ops,
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size_t size, int flags)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline int dma_buf_fd(struct dma_buf *dmabuf)
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{
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return -ENODEV;
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}
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static inline struct dma_buf *dma_buf_get(int fd)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void dma_buf_put(struct dma_buf *dmabuf)
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{
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return;
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}
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static inline struct sg_table *dma_buf_map_attachment(
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struct dma_buf_attachment *attach, enum dma_data_direction write)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
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struct sg_table *sg, enum dma_data_direction dir)
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{
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return;
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}
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static inline int dma_buf_begin_cpu_access(struct dma_buf *,
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size_t, size_t,
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enum dma_data_direction)
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{
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return -ENODEV;
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}
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static inline void dma_buf_end_cpu_access(struct dma_buf *,
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size_t, size_t,
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enum dma_data_direction)
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{
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}
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static inline void *dma_buf_kmap_atomic(struct dma_buf *, unsigned long)
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{
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return NULL;
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}
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static inline void dma_buf_kunmap_atomic(struct dma_buf *, unsigned long,
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void *)
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{
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}
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static inline void *dma_buf_kmap(struct dma_buf *, unsigned long)
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{
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return NULL;
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}
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static inline void dma_buf_kunmap(struct dma_buf *, unsigned long,
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void *)
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{
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}
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#endif /* CONFIG_DMA_SHARED_BUFFER */
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#endif /* __DMA_BUF_H__ */
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