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![Daniel Vetter](/assets/img/avatar_default.png)
It's unused. 10 years ago, back when 32bit was still fairly common and trying to not exhaust vmalloc space sounded like a worthwhile goal, adding these to dma_buf made sense. Reality is that they simply never caught on, and nowadays everyone who needs plenty of buffers will run in 64bit mode anyway. Also update the docs in this area to adjust them to reality. The actual hooks in dma_buf_ops will be removed once all the implementations are gone. Acked-by: Sumit Semwal <sumit.semwal@linaro.org> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Link: https://patchwork.freedesktop.org/patch/msgid/20191118103536.17675-10-daniel.vetter@ffwll.ch
472 lines
16 KiB
C
472 lines
16 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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* @dynamic_mapping:
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*
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* If true the framework makes sure that the map/unmap_dma_buf
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* callbacks are always called with the dma_resv object locked.
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*
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* If false the framework makes sure that the map/unmap_dma_buf
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* callbacks are always called without the dma_resv object locked.
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* Mutual exclusive with @cache_sgt_mapping.
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*/
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bool dynamic_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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* This is always called with the dmabuf->resv object locked when
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* the dynamic_mapping flag is true.
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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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* protected by dma_resv lock.
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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
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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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* protected by @resv.
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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 dma_resv *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, protected by dma_resv lock of the dmabuf.
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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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* @dynamic_mapping: true if dma_buf_map/unmap_attachment() is called with the
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* dma_resv lock held.
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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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bool dynamic_mapping;
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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 dma_resv *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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/**
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* dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
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* @dmabuf: the DMA-buf to check
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*
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* Returns true if a DMA-buf exporter wants to be called with the dma_resv
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* locked for the map/unmap callbacks, false if it doesn't wants to be called
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* with the lock held.
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*/
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static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
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{
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return dmabuf->ops->dynamic_mapping;
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}
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/**
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* dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
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* mappinsg
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* @attach: the DMA-buf attachment to check
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*
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* Returns true if a DMA-buf importer wants to call the map/unmap functions with
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* the dma_resv lock held.
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*/
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static inline bool
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dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
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{
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return attach->dynamic_mapping;
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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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struct dma_buf_attachment *
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dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
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bool dynamic_mapping);
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void dma_buf_detach(struct dma_buf *dmabuf,
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struct dma_buf_attachment *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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void dma_buf_move_notify(struct dma_buf *dma_buf);
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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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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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