2011/12/26 Sumit Semwal <sumit.semwal@xxxxxx>: > This is the first step in defining a dma buffer sharing mechanism. > > A new buffer object dma_buf is added, with operations and API to allow easy > sharing of this buffer object across devices. > > The framework allows: > - creation of a buffer object, its association with a file pointer, and > associated allocator-defined operations on that buffer. This operation is > called the 'export' operation. > - different devices to 'attach' themselves to this exported buffer object, to > facilitate backing storage negotiation, using dma_buf_attach() API. > - the exported buffer object to be shared with the other entity by asking for > its 'file-descriptor (fd)', and sharing the fd across. > - a received fd to get the buffer object back, where it can be accessed using > the associated exporter-defined operations. > - the exporter and user to share the scatterlist associated with this buffer > object using map_dma_buf and unmap_dma_buf operations. > > Atleast one 'attach()' call is required to be made prior to calling the > map_dma_buf() operation. > > Couple of building blocks in map_dma_buf() are added to ease introduction > of sync'ing across exporter and users, and late allocation by the exporter. > > For this first version, this framework will work with certain conditions: > - *ONLY* exporter will be allowed to mmap to userspace (outside of this > framework - mmap is not a buffer object operation), > - currently, *ONLY* users that do not need CPU access to the buffer are > allowed. > > More details are there in the documentation patch. > > This is based on design suggestions from many people at the mini-summits[1], > most notably from Arnd Bergmann <arnd@xxxxxxxx>, Rob Clark <rob@xxxxxx> and > Daniel Vetter <daniel@xxxxxxxx>. > > The implementation is inspired from proof-of-concept patch-set from > Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>, who demonstrated buffer sharing > between two v4l2 devices. [2] > > [1]: https://wiki.linaro.org/OfficeofCTO/MemoryManagement > [2]: http://lwn.net/Articles/454389 > > Signed-off-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx> > Signed-off-by: Sumit Semwal <sumit.semwal@xxxxxx> > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > Reviewed-by: Dave Airlie <airlied@xxxxxxxxxx> > Reviewed-and-Tested-by: Rob Clark <rob.clark@xxxxxxxxxx> > --- > drivers/base/Kconfig | 10 ++ > drivers/base/Makefile | 1 + > drivers/base/dma-buf.c | 291 +++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/dma-buf.h | 176 ++++++++++++++++++++++++++++ > 4 files changed, 478 insertions(+), 0 deletions(-) > create mode 100644 drivers/base/dma-buf.c > create mode 100644 include/linux/dma-buf.h > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > index 21cf46f..8a0e87f 100644 > --- a/drivers/base/Kconfig > +++ b/drivers/base/Kconfig > @@ -174,4 +174,14 @@ config SYS_HYPERVISOR > > source "drivers/base/regmap/Kconfig" > > +config DMA_SHARED_BUFFER > + bool "Buffer framework to be shared between drivers" > + default n > + select ANON_INODES > + help > + This option enables the framework for buffer-sharing between > + multiple drivers. A buffer is associated with a file using driver > + APIs extension; the file's descriptor can then be passed on to other > + driver. > + > endmenu > diff --git a/drivers/base/Makefile b/drivers/base/Makefile > index 99a375a..d0df046 100644 > --- a/drivers/base/Makefile > +++ b/drivers/base/Makefile > @@ -8,6 +8,7 @@ obj-$(CONFIG_DEVTMPFS) += devtmpfs.o > obj-y += power/ > obj-$(CONFIG_HAS_DMA) += dma-mapping.o > obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o > +obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o > obj-$(CONFIG_ISA) += isa.o > obj-$(CONFIG_FW_LOADER) += firmware_class.o > obj-$(CONFIG_NUMA) += node.o > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c > new file mode 100644 > index 0000000..e38ad24 > --- /dev/null > +++ b/drivers/base/dma-buf.c > @@ -0,0 +1,291 @@ > +/* > + * Framework for buffer objects that can be shared across devices/subsystems. > + * > + * Copyright(C) 2011 Linaro Limited. All rights reserved. > + * Author: Sumit Semwal <sumit.semwal@xxxxxx> > + * > + * Many thanks to linaro-mm-sig list, and specially > + * Arnd Bergmann <arnd@xxxxxxxx>, Rob Clark <rob@xxxxxx> and > + * Daniel Vetter <daniel@xxxxxxxx> for their support in creation and > + * refining of this idea. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2 as published by > + * the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, but WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + * > + * You should have received a copy of the GNU General Public License along with > + * this program. If not, see <http://www.gnu.org/licenses/>. > + */ > + > +#include <linux/fs.h> > +#include <linux/slab.h> > +#include <linux/dma-buf.h> > +#include <linux/anon_inodes.h> > +#include <linux/export.h> > + > +static inline int is_dma_buf_file(struct file *); > + > +static int dma_buf_release(struct inode *inode, struct file *file) > +{ > + struct dma_buf *dmabuf; > + > + if (!is_dma_buf_file(file)) > + return -EINVAL; > + > + dmabuf = file->private_data; > + > + dmabuf->ops->release(dmabuf); > + kfree(dmabuf); > + return 0; > +} > + > +static const struct file_operations dma_buf_fops = { > + .release = dma_buf_release, > +}; > + > +/* > + * is_dma_buf_file - Check if struct file* is associated with dma_buf > + */ > +static inline int is_dma_buf_file(struct file *file) > +{ > + return file->f_op == &dma_buf_fops; > +} > + > +/** > + * dma_buf_export - Creates a new dma_buf, and associates an anon file > + * with this buffer, so it can be exported. > + * Also connect the allocator specific data and ops to the buffer. > + * > + * @priv: [in] Attach private data of allocator to this buffer > + * @ops: [in] Attach allocator-defined dma buf ops to the new buffer. > + * @size: [in] Size of the buffer > + * @flags: [in] mode flags for the file. > + * > + * Returns, on success, a newly created dma_buf object, which wraps the > + * supplied private data and operations for dma_buf_ops. On either missing > + * ops, or error in allocating struct dma_buf, will return negative error. > + * > + */ > +struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops, > + size_t size, int flags) > +{ > + struct dma_buf *dmabuf; > + struct file *file; > + > + if (WARN_ON(!priv || !ops > + || !ops->map_dma_buf > + || !ops->unmap_dma_buf > + || !ops->release)) { > + return ERR_PTR(-EINVAL); > + } > + > + dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL); > + if (dmabuf == NULL) > + return ERR_PTR(-ENOMEM); > + > + dmabuf->priv = priv; > + dmabuf->ops = ops; > + dmabuf->size = size; > + > + file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags); > + > + dmabuf->file = file; > + > + mutex_init(&dmabuf->lock); > + INIT_LIST_HEAD(&dmabuf->attachments); > + > + return dmabuf; > +} > +EXPORT_SYMBOL_GPL(dma_buf_export); > + > + > +/** > + * dma_buf_fd - returns a file descriptor for the given dma_buf > + * @dmabuf: [in] pointer to dma_buf for which fd is required. > + * > + * On success, returns an associated 'fd'. Else, returns error. > + */ > +int dma_buf_fd(struct dma_buf *dmabuf) > +{ > + int error, fd; > + > + if (!dmabuf || !dmabuf->file) > + return -EINVAL; > + > + error = get_unused_fd(); > + if (error < 0) > + return error; > + fd = error; > + > + fd_install(fd, dmabuf->file); > + > + return fd; > +} > +EXPORT_SYMBOL_GPL(dma_buf_fd); > + > +/** > + * dma_buf_get - returns the dma_buf structure related to an fd > + * @fd: [in] fd associated with the dma_buf to be returned > + * > + * On success, returns the dma_buf structure associated with an fd; uses > + * file's refcounting done by fget to increase refcount. returns ERR_PTR > + * otherwise. > + */ > +struct dma_buf *dma_buf_get(int fd) > +{ > + struct file *file; > + > + file = fget(fd); > + > + if (!file) > + return ERR_PTR(-EBADF); > + > + if (!is_dma_buf_file(file)) { > + fput(file); > + return ERR_PTR(-EINVAL); > + } > + > + return file->private_data; > +} > +EXPORT_SYMBOL_GPL(dma_buf_get); > + > +/** > + * dma_buf_put - decreases refcount of the buffer > + * @dmabuf: [in] buffer to reduce refcount of > + * > + * Uses file's refcounting done implicitly by fput() > + */ > +void dma_buf_put(struct dma_buf *dmabuf) > +{ > + if (WARN_ON(!dmabuf || !dmabuf->file)) > + return; > + > + fput(dmabuf->file); > +} > +EXPORT_SYMBOL_GPL(dma_buf_put); > + > +/** > + * dma_buf_attach - Add the device to dma_buf's attachments list; optionally, > + * calls attach() of dma_buf_ops to allow device-specific attach functionality > + * @dmabuf: [in] buffer to attach device to. > + * @dev: [in] device to be attached. > + * > + * Returns struct dma_buf_attachment * for this attachment; may return negative > + * error codes. > + * > + */ > +struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, > + struct device *dev) > +{ > + struct dma_buf_attachment *attach; > + int ret; > + > + if (WARN_ON(!dmabuf || !dev || !dmabuf->ops)) > + return ERR_PTR(-EINVAL); > + > + attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL); > + if (attach == NULL) > + goto err_alloc; > + > + mutex_lock(&dmabuf->lock); > + > + attach->dev = dev; > + attach->dmabuf = dmabuf; > + if (dmabuf->ops->attach) { > + ret = dmabuf->ops->attach(dmabuf, dev, attach); > + if (ret) > + goto err_attach; > + } > + list_add(&attach->node, &dmabuf->attachments); > + > + mutex_unlock(&dmabuf->lock); > + return attach; > + > +err_alloc: > + return ERR_PTR(-ENOMEM); > +err_attach: > + kfree(attach); > + mutex_unlock(&dmabuf->lock); > + return ERR_PTR(ret); > +} > +EXPORT_SYMBOL_GPL(dma_buf_attach); > + > +/** > + * dma_buf_detach - Remove the given attachment from dmabuf's attachments list; > + * optionally calls detach() of dma_buf_ops for device-specific detach > + * @dmabuf: [in] buffer to detach from. > + * @attach: [in] attachment to be detached; is free'd after this call. > + * > + */ > +void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) > +{ > + if (WARN_ON(!dmabuf || !attach || !dmabuf->ops)) > + return; > + > + mutex_lock(&dmabuf->lock); > + list_del(&attach->node); > + if (dmabuf->ops->detach) > + dmabuf->ops->detach(dmabuf, attach); > + > + mutex_unlock(&dmabuf->lock); > + kfree(attach); > +} > +EXPORT_SYMBOL_GPL(dma_buf_detach); > + > +/** > + * dma_buf_map_attachment - Returns the scatterlist table of the attachment; > + * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the > + * dma_buf_ops. > + * @attach: [in] attachment whose scatterlist is to be returned > + * @direction: [in] direction of DMA transfer > + * > + * Returns sg_table containing the scatterlist to be returned; may return NULL > + * or ERR_PTR. > + * > + */ > +struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, > + enum dma_data_direction direction) > +{ > + struct sg_table *sg_table = ERR_PTR(-EINVAL); > + > + might_sleep(); > + > + if (WARN_ON(!attach || !attach->dmabuf || !attach->dmabuf->ops)) > + return ERR_PTR(-EINVAL); > + > + mutex_lock(&attach->dmabuf->lock); > + if (attach->dmabuf->ops->map_dma_buf) > + sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); > + mutex_unlock(&attach->dmabuf->lock); > + > + return sg_table; > +} > +EXPORT_SYMBOL_GPL(dma_buf_map_attachment); > + > +/** > + * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might > + * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of > + * dma_buf_ops. > + * @attach: [in] attachment to unmap buffer from > + * @sg_table: [in] scatterlist info of the buffer to unmap > + * > + */ > +void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, > + struct sg_table *sg_table) > +{ > + if (WARN_ON(!attach || !attach->dmabuf || !sg_table > + || !attach->dmabuf->ops)) > + return; > + > + mutex_lock(&attach->dmabuf->lock); > + if (attach->dmabuf->ops->unmap_dma_buf) > + attach->dmabuf->ops->unmap_dma_buf(attach, sg_table); > + mutex_unlock(&attach->dmabuf->lock); > + > +} > +EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > new file mode 100644 > index 0000000..f8ac076 > --- /dev/null > +++ b/include/linux/dma-buf.h > @@ -0,0 +1,176 @@ > +/* > + * Header file for dma buffer sharing framework. > + * > + * Copyright(C) 2011 Linaro Limited. All rights reserved. > + * Author: Sumit Semwal <sumit.semwal@xxxxxx> > + * > + * Many thanks to linaro-mm-sig list, and specially > + * Arnd Bergmann <arnd@xxxxxxxx>, Rob Clark <rob@xxxxxx> and > + * Daniel Vetter <daniel@xxxxxxxx> for their support in creation and > + * refining of this idea. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2 as published by > + * the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, but WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + * > + * You should have received a copy of the GNU General Public License along with > + * this program. If not, see <http://www.gnu.org/licenses/>. > + */ > +#ifndef __DMA_BUF_H__ > +#define __DMA_BUF_H__ > + > +#include <linux/file.h> > +#include <linux/err.h> > +#include <linux/device.h> > +#include <linux/scatterlist.h> > +#include <linux/list.h> > +#include <linux/dma-mapping.h> > + > +struct dma_buf; > +struct dma_buf_attachment; > + > +/** > + * struct dma_buf_ops - operations possible on struct dma_buf > + * @attach: [optional] allows different devices to 'attach' themselves to the > + * given buffer. It might return -EBUSY to signal that backing storage > + * is already allocated and incompatible with the requirements > + * of requesting device. > + * @detach: [optional] detach a given device from this buffer. > + * @map_dma_buf: returns list of scatter pages allocated, increases usecount > + * of the buffer. Requires atleast one attach to be called > + * before. Returned sg list should already be mapped into > + * _device_ address space. This call may sleep. May also return > + * -EINTR. Should return -EINVAL if attach hasn't been called yet. > + * @unmap_dma_buf: decreases usecount of buffer, might deallocate scatter > + * pages. > + * @release: release this buffer; to be called after the last dma_buf_put. > + */ > +struct dma_buf_ops { > + int (*attach)(struct dma_buf *, struct device *, > + struct dma_buf_attachment *); > + > + void (*detach)(struct dma_buf *, struct dma_buf_attachment *); > + > + /* For {map,unmap}_dma_buf below, any specific buffer attributes > + * required should get added to device_dma_parameters accessible > + * via dev->dma_params. > + */ > + struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *, > + enum dma_data_direction); > + void (*unmap_dma_buf)(struct dma_buf_attachment *, > + struct sg_table *); > + /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY > + * if the call would block. > + */ > + > + /* after final dma_buf_put() */ > + void (*release)(struct dma_buf *); > + > +}; > + > +/** > + * struct dma_buf - shared buffer object > + * @size: size of the buffer > + * @file: file pointer used for sharing buffers across, and for refcounting. > + * @attachments: list of dma_buf_attachment that denotes all devices attached. > + * @ops: dma_buf_ops associated with this buffer object. > + * @priv: exporter specific private data for this buffer object. > + */ > +struct dma_buf { > + size_t size; > + struct file *file; > + struct list_head attachments; > + const struct dma_buf_ops *ops; how about having sg_table here also? like this, struct sg_table *sgt; now dmabuf->priv could have duplicated values. I know that a private buffer object is set to dmabuf->priv when dma_buf_export function is called. but when xxx_acquire_dmabuf callback of vb2 side is called dmabuf->priv would have sg_table object returned from dmabuf->ops->map_dma_buf() again to release the sg_table with dmabuf->ops->unmap_dma_buf(). I'm not sure that this situation could induce some problem but anyway confusing. > + /* mutex to serialize list manipulation and other ops */ > + struct mutex lock; > + void *priv; > +}; > + > +/** > + * struct dma_buf_attachment - holds device-buffer attachment data > + * @dmabuf: buffer for this attachment. > + * @dev: device attached to the buffer. > + * @node: list of dma_buf_attachment. > + * @priv: exporter specific attachment data. > + * > + * This structure holds the attachment information between the dma_buf buffer > + * and its user device(s). The list contains one attachment struct per device > + * attached to the buffer. > + */ > +struct dma_buf_attachment { > + struct dma_buf *dmabuf; > + struct device *dev; > + struct list_head node; > + void *priv; > +}; > + > +#ifdef CONFIG_DMA_SHARED_BUFFER > +struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, > + struct device *dev); > +void dma_buf_detach(struct dma_buf *dmabuf, > + struct dma_buf_attachment *dmabuf_attach); > +struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops, > + size_t size, int flags); > +int dma_buf_fd(struct dma_buf *dmabuf); > +struct dma_buf *dma_buf_get(int fd); > +void dma_buf_put(struct dma_buf *dmabuf); > + > +struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *, > + enum dma_data_direction); > +void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *); > +#else > + > +static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, > + struct device *dev) > +{ > + return ERR_PTR(-ENODEV); > +} > + > +static inline void dma_buf_detach(struct dma_buf *dmabuf, > + struct dma_buf_attachment *dmabuf_attach) > +{ > + return; > +} > + > +static inline struct dma_buf *dma_buf_export(void *priv, > + struct dma_buf_ops *ops, > + size_t size, int flags) > +{ > + return ERR_PTR(-ENODEV); > +} > + > +static inline int dma_buf_fd(struct dma_buf *dmabuf) > +{ > + return -ENODEV; > +} > + > +static inline struct dma_buf *dma_buf_get(int fd) > +{ > + return ERR_PTR(-ENODEV); > +} > + > +static inline void dma_buf_put(struct dma_buf *dmabuf) > +{ > + return; > +} > + > +static inline struct sg_table *dma_buf_map_attachment( > + struct dma_buf_attachment *attach, enum dma_data_direction write) > +{ > + return ERR_PTR(-ENODEV); > +} > + > +static inline void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, > + struct sg_table *sg) > +{ > + return; > +} > + > +#endif /* CONFIG_DMA_SHARED_BUFFER */ > + > +#endif /* __DMA_BUF_H__ */ > -- > 1.7.5.4 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. 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