424 lines
14 KiB
C
424 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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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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#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/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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#include <linux/dma-fence.h>
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#include <linux/wait.h>
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struct device;
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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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* @vmap: [optional] creates a virtual mapping for the buffer into kernel
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* address space. Same restrictions as for vmap and friends apply.
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* @vunmap: [optional] unmaps a vmap from the buffer
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*/
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struct dma_buf_ops {
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/**
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* @cache_sgt_mapping:
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*
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* If true the framework will cache the first mapping made for each
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* attachment. This avoids creating mappings for attachments multiple
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* times.
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*/
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bool cache_sgt_mapping;
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/**
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* @attach:
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*
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* This is called from dma_buf_attach() to make sure that a given
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* &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
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* which support buffer objects in special locations like VRAM or
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* device-specific carveout areas should check whether the buffer could
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* be move to system memory (or directly accessed by the provided
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* device), and otherwise need to fail the attach operation.
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*
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* The exporter should also in general check whether the current
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* allocation fullfills the DMA constraints of the new device. If this
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* is not the case, and the allocation cannot be moved, it should also
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* fail the attach operation.
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*
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* Any exporter-private housekeeping data can be stored in the
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* &dma_buf_attachment.priv pointer.
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*
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* This callback is optional.
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*
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* Returns:
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*
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* 0 on success, negative error code on failure. It might return -EBUSY
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* to signal that backing storage is already allocated and incompatible
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* with the requirements of requesting device.
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*/
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int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
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/**
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* @detach:
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*
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* This is called by dma_buf_detach() to release a &dma_buf_attachment.
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* Provided so that exporters can clean up any housekeeping for an
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* &dma_buf_attachment.
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*
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* This callback is optional.
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*/
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void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
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/**
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* @map_dma_buf:
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*
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* This is called by dma_buf_map_attachment() and is used to map a
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* shared &dma_buf into device address space, and it is mandatory. It
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* can only be called if @attach has been called successfully. This
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* essentially pins the DMA buffer into place, and it cannot be moved
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* any more
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*
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* This call may sleep, e.g. when the backing storage first needs to be
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* allocated, or moved to a location suitable for all currently attached
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* devices.
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*
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* Note that any specific buffer attributes required for this function
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* should get added to device_dma_parameters accessible via
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* &device.dma_params from the &dma_buf_attachment. The @attach callback
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* should also check these constraints.
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*
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* If this is being called for the first time, the exporter can now
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* choose to scan through the list of attachments for this buffer,
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* collate the requirements of the attached devices, and choose an
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* appropriate backing storage for the buffer.
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*
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* Based on enum dma_data_direction, it might be possible to have
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* multiple users accessing at the same time (for reading, maybe), or
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* any other kind of sharing that the exporter might wish to make
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* available to buffer-users.
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*
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* Returns:
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*
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* A &sg_table scatter list of or the backing storage of the DMA buffer,
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* already mapped into the device address space of the &device attached
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* with the provided &dma_buf_attachment.
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*
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* On failure, returns a negative error value wrapped into a pointer.
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* May also return -EINTR when a signal was received while being
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* blocked.
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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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/**
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* @unmap_dma_buf:
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*
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* This is called by dma_buf_unmap_attachment() and should unmap and
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* release the &sg_table allocated in @map_dma_buf, and it is mandatory.
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* It should also unpin the backing storage if this is the last mapping
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* of the DMA buffer, it the exporter supports backing storage
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* migration.
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*/
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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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/**
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* @release:
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*
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* Called after the last dma_buf_put to release the &dma_buf, and
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* mandatory.
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*/
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void (*release)(struct dma_buf *);
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/**
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* @begin_cpu_access:
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*
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* This is called from dma_buf_begin_cpu_access() and allows the
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* exporter to ensure that the memory is actually available for cpu
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* access - the exporter might need to allocate or swap-in and pin the
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* backing storage. The exporter also needs to ensure that cpu access is
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* coherent for the access direction. The direction can be used by the
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* exporter to optimize the cache flushing, i.e. access with a different
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* direction (read instead of write) might return stale or even bogus
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* data (e.g. when the exporter needs to copy the data to temporary
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* storage).
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*
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* This callback is optional.
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*
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* FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
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* from userspace (where storage shouldn't be pinned to avoid handing
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* de-factor mlock rights to userspace) and for the kernel-internal
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* users of the various kmap interfaces, where the backing storage must
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* be pinned to guarantee that the atomic kmap calls can succeed. Since
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* there's no in-kernel users of the kmap interfaces yet this isn't a
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* real problem.
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*
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* Returns:
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*
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* 0 on success or a negative error code on failure. This can for
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* example fail when the backing storage can't be allocated. Can also
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* return -ERESTARTSYS or -EINTR when the call has been interrupted and
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* needs to be restarted.
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*/
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int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
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/**
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* @end_cpu_access:
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*
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* This is called from dma_buf_end_cpu_access() when the importer is
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* done accessing the CPU. The exporter can use this to flush caches and
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* unpin any resources pinned in @begin_cpu_access.
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* The result of any dma_buf kmap calls after end_cpu_access is
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* undefined.
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*
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* This callback is optional.
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*
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* Returns:
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*
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* 0 on success or a negative error code on failure. Can return
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* -ERESTARTSYS or -EINTR when the call has been interrupted and needs
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* to be restarted.
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*/
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int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
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/**
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* @mmap:
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*
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* This callback is used by the dma_buf_mmap() function
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*
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* Note that the mapping needs to be incoherent, userspace is expected
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* to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
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*
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* Because dma-buf buffers have invariant size over their lifetime, the
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* dma-buf core checks whether a vma is too large and rejects such
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* mappings. The exporter hence does not need to duplicate this check.
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* Drivers do not need to check this themselves.
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*
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* If an exporter needs to manually flush caches and hence needs to fake
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* coherency for mmap support, it needs to be able to zap all the ptes
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* pointing at the backing storage. Now linux mm needs a struct
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* address_space associated with the struct file stored in vma->vm_file
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* to do that with the function unmap_mapping_range. But the dma_buf
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* framework only backs every dma_buf fd with the anon_file struct file,
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* i.e. all dma_bufs share the same file.
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*
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* Hence exporters need to setup their own file (and address_space)
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* association by setting vma->vm_file and adjusting vma->vm_pgoff in
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* the dma_buf mmap callback. In the specific case of a gem driver the
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* exporter could use the shmem file already provided by gem (and set
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* vm_pgoff = 0). Exporters can then zap ptes by unmapping the
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* corresponding range of the struct address_space associated with their
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* own file.
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*
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* This callback is optional.
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*
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* Returns:
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*
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* 0 on success or a negative error code on failure.
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*/
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int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
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/**
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* @map:
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*
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* Maps a page from the buffer into kernel address space. The page is
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* specified by offset into the buffer in PAGE_SIZE units.
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*
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* This callback is optional.
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*
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* Returns:
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*
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* Virtual address pointer where requested page can be accessed. NULL
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* on error or when this function is unimplemented by the exporter.
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*/
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void *(*map)(struct dma_buf *, unsigned long);
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/**
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* @unmap:
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*
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* Unmaps a page from the buffer. Page offset and address pointer should
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* be the same as the one passed to and returned by matching call to map.
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*
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* This callback is optional.
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*/
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void (*unmap)(struct dma_buf *, unsigned long, void *);
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void *(*vmap)(struct dma_buf *);
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void (*vunmap)(struct dma_buf *, void *vaddr);
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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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* @lock: used internally to serialize list manipulation, attach/detach and
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* vmap/unmap, and accesses to name
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* @vmapping_counter: used internally to refcnt the vmaps
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* @vmap_ptr: the current vmap ptr if vmapping_counter > 0
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* @exp_name: name of the exporter; useful for debugging.
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* @name: userspace-provided name; useful for accounting and debugging.
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* @owner: pointer to exporter module; used for refcounting when exporter is a
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* kernel module.
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* @list_node: node for dma_buf accounting and debugging.
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* @priv: exporter specific private data for this buffer object.
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* @resv: reservation object linked to this dma-buf
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* @poll: for userspace poll support
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* @cb_excl: for userspace poll support
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* @cb_shared: for userspace poll support
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*
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* This represents a shared buffer, created by calling dma_buf_export(). The
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* userspace representation is a normal file descriptor, which can be created by
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* calling dma_buf_fd().
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*
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* Shared dma buffers are reference counted using dma_buf_put() and
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* get_dma_buf().
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*
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* Device DMA access is handled by the separate &struct dma_buf_attachment.
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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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struct mutex lock;
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unsigned vmapping_counter;
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void *vmap_ptr;
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const char *exp_name;
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const char *name;
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struct module *owner;
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struct list_head list_node;
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void *priv;
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struct reservation_object *resv;
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/* poll support */
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wait_queue_head_t poll;
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struct dma_buf_poll_cb_t {
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struct dma_fence_cb cb;
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wait_queue_head_t *poll;
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__poll_t active;
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} cb_excl, cb_shared;
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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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* @sgt: cached mapping.
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* @dir: direction of cached mapping.
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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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* An attachment is created by calling dma_buf_attach(), and released again by
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* calling dma_buf_detach(). The DMA mapping itself needed to initiate a
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* transfer is created by dma_buf_map_attachment() and freed again by calling
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* dma_buf_unmap_attachment().
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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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struct sg_table *sgt;
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enum dma_data_direction dir;
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void *priv;
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};
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/**
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* struct dma_buf_export_info - holds information needed to export a dma_buf
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* @exp_name: name of the exporter - useful for debugging.
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* @owner: pointer to exporter module - used for refcounting kernel module
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* @ops: Attach allocator-defined dma buf ops to the new buffer
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* @size: Size of the buffer
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* @flags: mode flags for the file
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* @resv: reservation-object, NULL to allocate default one
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* @priv: Attach private data of allocator to this buffer
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*
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* This structure holds the information required to export the buffer. Used
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* with dma_buf_export() only.
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*/
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struct dma_buf_export_info {
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const char *exp_name;
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struct module *owner;
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const struct dma_buf_ops *ops;
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size_t size;
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int flags;
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struct reservation_object *resv;
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void *priv;
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};
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/**
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* DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
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* @name: export-info name
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*
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* DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
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* zeroes it out and pre-populates exp_name in it.
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*/
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#define DEFINE_DMA_BUF_EXPORT_INFO(name) \
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struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
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.owner = THIS_MODULE }
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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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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(const struct dma_buf_export_info *exp_info);
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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,
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enum dma_data_direction dir);
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int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
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enum dma_data_direction dir);
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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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int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
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unsigned long);
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void *dma_buf_vmap(struct dma_buf *);
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void dma_buf_vunmap(struct dma_buf *, void *vaddr);
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#endif /* __DMA_BUF_H__ */
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