v4.19.13 snapshot.
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
new file mode 100644
index 0000000..1388447
--- /dev/null
+++ b/drivers/dma-buf/dma-buf.c
@@ -0,0 +1,1161 @@
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> 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/dma-fence.h>
+#include <linux/anon_inodes.h>
+#include <linux/export.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/poll.h>
+#include <linux/reservation.h>
+#include <linux/mm.h>
+
+#include <uapi/linux/dma-buf.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+struct dma_buf_list {
+ struct list_head head;
+ struct mutex lock;
+};
+
+static struct dma_buf_list db_list;
+
+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;
+
+ BUG_ON(dmabuf->vmapping_counter);
+
+ /*
+ * Any fences that a dma-buf poll can wait on should be signaled
+ * before releasing dma-buf. This is the responsibility of each
+ * driver that uses the reservation objects.
+ *
+ * If you hit this BUG() it means someone dropped their ref to the
+ * dma-buf while still having pending operation to the buffer.
+ */
+ BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
+
+ dmabuf->ops->release(dmabuf);
+
+ mutex_lock(&db_list.lock);
+ list_del(&dmabuf->list_node);
+ mutex_unlock(&db_list.lock);
+
+ if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])
+ reservation_object_fini(dmabuf->resv);
+
+ module_put(dmabuf->owner);
+ kfree(dmabuf);
+ return 0;
+}
+
+static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
+{
+ struct dma_buf *dmabuf;
+
+ if (!is_dma_buf_file(file))
+ return -EINVAL;
+
+ dmabuf = file->private_data;
+
+ /* check for overflowing the buffer's size */
+ if (vma->vm_pgoff + vma_pages(vma) >
+ dmabuf->size >> PAGE_SHIFT)
+ return -EINVAL;
+
+ return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
+{
+ struct dma_buf *dmabuf;
+ loff_t base;
+
+ if (!is_dma_buf_file(file))
+ return -EBADF;
+
+ dmabuf = file->private_data;
+
+ /* only support discovering the end of the buffer,
+ but also allow SEEK_SET to maintain the idiomatic
+ SEEK_END(0), SEEK_CUR(0) pattern */
+ if (whence == SEEK_END)
+ base = dmabuf->size;
+ else if (whence == SEEK_SET)
+ base = 0;
+ else
+ return -EINVAL;
+
+ if (offset != 0)
+ return -EINVAL;
+
+ return base + offset;
+}
+
+/**
+ * DOC: fence polling
+ *
+ * To support cross-device and cross-driver synchronization of buffer access
+ * implicit fences (represented internally in the kernel with &struct fence) can
+ * be attached to a &dma_buf. The glue for that and a few related things are
+ * provided in the &reservation_object structure.
+ *
+ * Userspace can query the state of these implicitly tracked fences using poll()
+ * and related system calls:
+ *
+ * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
+ * most recent write or exclusive fence.
+ *
+ * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
+ * all attached fences, shared and exclusive ones.
+ *
+ * Note that this only signals the completion of the respective fences, i.e. the
+ * DMA transfers are complete. Cache flushing and any other necessary
+ * preparations before CPU access can begin still need to happen.
+ */
+
+static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+ struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
+ unsigned long flags;
+
+ spin_lock_irqsave(&dcb->poll->lock, flags);
+ wake_up_locked_poll(dcb->poll, dcb->active);
+ dcb->active = 0;
+ spin_unlock_irqrestore(&dcb->poll->lock, flags);
+}
+
+static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
+{
+ struct dma_buf *dmabuf;
+ struct reservation_object *resv;
+ struct reservation_object_list *fobj;
+ struct dma_fence *fence_excl;
+ __poll_t events;
+ unsigned shared_count, seq;
+
+ dmabuf = file->private_data;
+ if (!dmabuf || !dmabuf->resv)
+ return EPOLLERR;
+
+ resv = dmabuf->resv;
+
+ poll_wait(file, &dmabuf->poll, poll);
+
+ events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
+ if (!events)
+ return 0;
+
+retry:
+ seq = read_seqcount_begin(&resv->seq);
+ rcu_read_lock();
+
+ fobj = rcu_dereference(resv->fence);
+ if (fobj)
+ shared_count = fobj->shared_count;
+ else
+ shared_count = 0;
+ fence_excl = rcu_dereference(resv->fence_excl);
+ if (read_seqcount_retry(&resv->seq, seq)) {
+ rcu_read_unlock();
+ goto retry;
+ }
+
+ if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
+ struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
+ __poll_t pevents = EPOLLIN;
+
+ if (shared_count == 0)
+ pevents |= EPOLLOUT;
+
+ spin_lock_irq(&dmabuf->poll.lock);
+ if (dcb->active) {
+ dcb->active |= pevents;
+ events &= ~pevents;
+ } else
+ dcb->active = pevents;
+ spin_unlock_irq(&dmabuf->poll.lock);
+
+ if (events & pevents) {
+ if (!dma_fence_get_rcu(fence_excl)) {
+ /* force a recheck */
+ events &= ~pevents;
+ dma_buf_poll_cb(NULL, &dcb->cb);
+ } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
+ dma_buf_poll_cb)) {
+ events &= ~pevents;
+ dma_fence_put(fence_excl);
+ } else {
+ /*
+ * No callback queued, wake up any additional
+ * waiters.
+ */
+ dma_fence_put(fence_excl);
+ dma_buf_poll_cb(NULL, &dcb->cb);
+ }
+ }
+ }
+
+ if ((events & EPOLLOUT) && shared_count > 0) {
+ struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
+ int i;
+
+ /* Only queue a new callback if no event has fired yet */
+ spin_lock_irq(&dmabuf->poll.lock);
+ if (dcb->active)
+ events &= ~EPOLLOUT;
+ else
+ dcb->active = EPOLLOUT;
+ spin_unlock_irq(&dmabuf->poll.lock);
+
+ if (!(events & EPOLLOUT))
+ goto out;
+
+ for (i = 0; i < shared_count; ++i) {
+ struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
+
+ if (!dma_fence_get_rcu(fence)) {
+ /*
+ * fence refcount dropped to zero, this means
+ * that fobj has been freed
+ *
+ * call dma_buf_poll_cb and force a recheck!
+ */
+ events &= ~EPOLLOUT;
+ dma_buf_poll_cb(NULL, &dcb->cb);
+ break;
+ }
+ if (!dma_fence_add_callback(fence, &dcb->cb,
+ dma_buf_poll_cb)) {
+ dma_fence_put(fence);
+ events &= ~EPOLLOUT;
+ break;
+ }
+ dma_fence_put(fence);
+ }
+
+ /* No callback queued, wake up any additional waiters. */
+ if (i == shared_count)
+ dma_buf_poll_cb(NULL, &dcb->cb);
+ }
+
+out:
+ rcu_read_unlock();
+ return events;
+}
+
+static long dma_buf_ioctl(struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ struct dma_buf *dmabuf;
+ struct dma_buf_sync sync;
+ enum dma_data_direction direction;
+ int ret;
+
+ dmabuf = file->private_data;
+
+ switch (cmd) {
+ case DMA_BUF_IOCTL_SYNC:
+ if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
+ return -EFAULT;
+
+ if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
+ return -EINVAL;
+
+ switch (sync.flags & DMA_BUF_SYNC_RW) {
+ case DMA_BUF_SYNC_READ:
+ direction = DMA_FROM_DEVICE;
+ break;
+ case DMA_BUF_SYNC_WRITE:
+ direction = DMA_TO_DEVICE;
+ break;
+ case DMA_BUF_SYNC_RW:
+ direction = DMA_BIDIRECTIONAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (sync.flags & DMA_BUF_SYNC_END)
+ ret = dma_buf_end_cpu_access(dmabuf, direction);
+ else
+ ret = dma_buf_begin_cpu_access(dmabuf, direction);
+
+ return ret;
+ default:
+ return -ENOTTY;
+ }
+}
+
+static const struct file_operations dma_buf_fops = {
+ .release = dma_buf_release,
+ .mmap = dma_buf_mmap_internal,
+ .llseek = dma_buf_llseek,
+ .poll = dma_buf_poll,
+ .unlocked_ioctl = dma_buf_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = dma_buf_ioctl,
+#endif
+};
+
+/*
+ * 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;
+}
+
+/**
+ * DOC: dma buf device access
+ *
+ * For device DMA access to a shared DMA buffer the usual sequence of operations
+ * is fairly simple:
+ *
+ * 1. The exporter defines his exporter instance using
+ * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
+ * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
+ * as a file descriptor by calling dma_buf_fd().
+ *
+ * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
+ * to share with: First the filedescriptor is converted to a &dma_buf using
+ * dma_buf_get(). Then the buffer is attached to the device using
+ * dma_buf_attach().
+ *
+ * Up to this stage the exporter is still free to migrate or reallocate the
+ * backing storage.
+ *
+ * 3. Once the buffer is attached to all devices userspace can initiate DMA
+ * access to the shared buffer. In the kernel this is done by calling
+ * dma_buf_map_attachment() and dma_buf_unmap_attachment().
+ *
+ * 4. Once a driver is done with a shared buffer it needs to call
+ * dma_buf_detach() (after cleaning up any mappings) and then release the
+ * reference acquired with dma_buf_get by calling dma_buf_put().
+ *
+ * For the detailed semantics exporters are expected to implement see
+ * &dma_buf_ops.
+ */
+
+/**
+ * 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.
+ * Additionally, provide a name string for exporter; useful in debugging.
+ *
+ * @exp_info: [in] holds all the export related information provided
+ * by the exporter. see &struct dma_buf_export_info
+ * for further details.
+ *
+ * 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.
+ *
+ * For most cases the easiest way to create @exp_info is through the
+ * %DEFINE_DMA_BUF_EXPORT_INFO macro.
+ */
+struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
+{
+ struct dma_buf *dmabuf;
+ struct reservation_object *resv = exp_info->resv;
+ struct file *file;
+ size_t alloc_size = sizeof(struct dma_buf);
+ int ret;
+
+ if (!exp_info->resv)
+ alloc_size += sizeof(struct reservation_object);
+ else
+ /* prevent &dma_buf[1] == dma_buf->resv */
+ alloc_size += 1;
+
+ if (WARN_ON(!exp_info->priv
+ || !exp_info->ops
+ || !exp_info->ops->map_dma_buf
+ || !exp_info->ops->unmap_dma_buf
+ || !exp_info->ops->release
+ || !exp_info->ops->map
+ || !exp_info->ops->mmap)) {
+ return ERR_PTR(-EINVAL);
+ }
+
+ if (!try_module_get(exp_info->owner))
+ return ERR_PTR(-ENOENT);
+
+ dmabuf = kzalloc(alloc_size, GFP_KERNEL);
+ if (!dmabuf) {
+ ret = -ENOMEM;
+ goto err_module;
+ }
+
+ dmabuf->priv = exp_info->priv;
+ dmabuf->ops = exp_info->ops;
+ dmabuf->size = exp_info->size;
+ dmabuf->exp_name = exp_info->exp_name;
+ dmabuf->owner = exp_info->owner;
+ init_waitqueue_head(&dmabuf->poll);
+ dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
+ dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
+
+ if (!resv) {
+ resv = (struct reservation_object *)&dmabuf[1];
+ reservation_object_init(resv);
+ }
+ dmabuf->resv = resv;
+
+ file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf,
+ exp_info->flags);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto err_dmabuf;
+ }
+
+ file->f_mode |= FMODE_LSEEK;
+ dmabuf->file = file;
+
+ mutex_init(&dmabuf->lock);
+ INIT_LIST_HEAD(&dmabuf->attachments);
+
+ mutex_lock(&db_list.lock);
+ list_add(&dmabuf->list_node, &db_list.head);
+ mutex_unlock(&db_list.lock);
+
+ return dmabuf;
+
+err_dmabuf:
+ kfree(dmabuf);
+err_module:
+ module_put(exp_info->owner);
+ return ERR_PTR(ret);
+}
+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.
+ * @flags: [in] flags to give to fd
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf, int flags)
+{
+ int fd;
+
+ if (!dmabuf || !dmabuf->file)
+ return -EINVAL;
+
+ fd = get_unused_fd_flags(flags);
+ if (fd < 0)
+ return fd;
+
+ 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().
+ *
+ * If, as a result of this call, the refcount becomes 0, the 'release' file
+ * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
+ * in turn, and frees the memory allocated for dmabuf when exported.
+ */
+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 pointer for this attachment. Attachments
+ * must be cleaned up by calling dma_buf_detach().
+ *
+ * Returns:
+ *
+ * A pointer to newly created &dma_buf_attachment on success, or a negative
+ * error code wrapped into a pointer on failure.
+ *
+ * Note that this can fail if the backing storage of @dmabuf is in a place not
+ * accessible to @dev, and cannot be moved to a more suitable place. This is
+ * indicated with the error code -EBUSY.
+ */
+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))
+ return ERR_PTR(-EINVAL);
+
+ attach = kzalloc(sizeof(*attach), GFP_KERNEL);
+ if (!attach)
+ return ERR_PTR(-ENOMEM);
+
+ attach->dev = dev;
+ attach->dmabuf = dmabuf;
+
+ mutex_lock(&dmabuf->lock);
+
+ if (dmabuf->ops->attach) {
+ ret = dmabuf->ops->attach(dmabuf, attach);
+ if (ret)
+ goto err_attach;
+ }
+ list_add(&attach->node, &dmabuf->attachments);
+
+ mutex_unlock(&dmabuf->lock);
+ return attach;
+
+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.
+ *
+ * Clean up a device attachment obtained by calling dma_buf_attach().
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+ if (WARN_ON(!dmabuf || !attach))
+ 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; returns ERR_PTR
+ * on error. May return -EINTR if it is interrupted by a signal.
+ *
+ * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
+ * the underlying backing storage is pinned for as long as a mapping exists,
+ * therefore users/importers should not hold onto a mapping for undue amounts of
+ * time.
+ */
+struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
+ enum dma_data_direction direction)
+{
+ struct sg_table *sg_table;
+
+ might_sleep();
+
+ if (WARN_ON(!attach || !attach->dmabuf))
+ return ERR_PTR(-EINVAL);
+
+ sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+ if (!sg_table)
+ sg_table = ERR_PTR(-ENOMEM);
+
+ 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
+ * @direction: [in] direction of DMA transfer
+ *
+ * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
+ */
+void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
+ struct sg_table *sg_table,
+ enum dma_data_direction direction)
+{
+ might_sleep();
+
+ if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+ return;
+
+ attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
+ direction);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
+
+/**
+ * DOC: cpu access
+ *
+ * There are mutliple reasons for supporting CPU access to a dma buffer object:
+ *
+ * - Fallback operations in the kernel, for example when a device is connected
+ * over USB and the kernel needs to shuffle the data around first before
+ * sending it away. Cache coherency is handled by braketing any transactions
+ * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
+ * access.
+ *
+ * To support dma_buf objects residing in highmem cpu access is page-based
+ * using an api similar to kmap. Accessing a dma_buf is done in aligned chunks
+ * of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which
+ * returns a pointer in kernel virtual address space. Afterwards the chunk
+ * needs to be unmapped again. There is no limit on how often a given chunk
+ * can be mapped and unmapped, i.e. the importer does not need to call
+ * begin_cpu_access again before mapping the same chunk again.
+ *
+ * Interfaces::
+ * void \*dma_buf_kmap(struct dma_buf \*, unsigned long);
+ * void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*);
+ *
+ * Implementing the functions is optional for exporters and for importers all
+ * the restrictions of using kmap apply.
+ *
+ * dma_buf kmap calls outside of the range specified in begin_cpu_access are
+ * undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on
+ * the partial chunks at the beginning and end but may return stale or bogus
+ * data outside of the range (in these partial chunks).
+ *
+ * For some cases the overhead of kmap can be too high, a vmap interface
+ * is introduced. This interface should be used very carefully, as vmalloc
+ * space is a limited resources on many architectures.
+ *
+ * Interfaces::
+ * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
+ * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
+ *
+ * The vmap call can fail if there is no vmap support in the exporter, or if
+ * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
+ * that the dma-buf layer keeps a reference count for all vmap access and
+ * calls down into the exporter's vmap function only when no vmapping exists,
+ * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
+ * provided by taking the dma_buf->lock mutex.
+ *
+ * - For full compatibility on the importer side with existing userspace
+ * interfaces, which might already support mmap'ing buffers. This is needed in
+ * many processing pipelines (e.g. feeding a software rendered image into a
+ * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
+ * framework already supported this and for DMA buffer file descriptors to
+ * replace ION buffers mmap support was needed.
+ *
+ * There is no special interfaces, userspace simply calls mmap on the dma-buf
+ * fd. But like for CPU access there's a need to braket the actual access,
+ * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
+ * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
+ * be restarted.
+ *
+ * Some systems might need some sort of cache coherency management e.g. when
+ * CPU and GPU domains are being accessed through dma-buf at the same time.
+ * To circumvent this problem there are begin/end coherency markers, that
+ * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
+ * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
+ * sequence would be used like following:
+ *
+ * - mmap dma-buf fd
+ * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
+ * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
+ * want (with the new data being consumed by say the GPU or the scanout
+ * device)
+ * - munmap once you don't need the buffer any more
+ *
+ * For correctness and optimal performance, it is always required to use
+ * SYNC_START and SYNC_END before and after, respectively, when accessing the
+ * mapped address. Userspace cannot rely on coherent access, even when there
+ * are systems where it just works without calling these ioctls.
+ *
+ * - And as a CPU fallback in userspace processing pipelines.
+ *
+ * Similar to the motivation for kernel cpu access it is again important that
+ * the userspace code of a given importing subsystem can use the same
+ * interfaces with a imported dma-buf buffer object as with a native buffer
+ * object. This is especially important for drm where the userspace part of
+ * contemporary OpenGL, X, and other drivers is huge, and reworking them to
+ * use a different way to mmap a buffer rather invasive.
+ *
+ * The assumption in the current dma-buf interfaces is that redirecting the
+ * initial mmap is all that's needed. A survey of some of the existing
+ * subsystems shows that no driver seems to do any nefarious thing like
+ * syncing up with outstanding asynchronous processing on the device or
+ * allocating special resources at fault time. So hopefully this is good
+ * enough, since adding interfaces to intercept pagefaults and allow pte
+ * shootdowns would increase the complexity quite a bit.
+ *
+ * Interface::
+ * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
+ * unsigned long);
+ *
+ * If the importing subsystem simply provides a special-purpose mmap call to
+ * set up a mapping in userspace, calling do_mmap with dma_buf->file will
+ * equally achieve that for a dma-buf object.
+ */
+
+static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+ enum dma_data_direction direction)
+{
+ bool write = (direction == DMA_BIDIRECTIONAL ||
+ direction == DMA_TO_DEVICE);
+ struct reservation_object *resv = dmabuf->resv;
+ long ret;
+
+ /* Wait on any implicit rendering fences */
+ ret = reservation_object_wait_timeout_rcu(resv, write, true,
+ MAX_SCHEDULE_TIMEOUT);
+ if (ret < 0)
+ return ret;
+
+ return 0;
+}
+
+/**
+ * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
+ * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
+ * preparations. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf: [in] buffer to prepare cpu access for.
+ * @direction: [in] length of range for cpu access.
+ *
+ * After the cpu access is complete the caller should call
+ * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
+ * it guaranteed to be coherent with other DMA access.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+ enum dma_data_direction direction)
+{
+ int ret = 0;
+
+ if (WARN_ON(!dmabuf))
+ return -EINVAL;
+
+ if (dmabuf->ops->begin_cpu_access)
+ ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
+
+ /* Ensure that all fences are waited upon - but we first allow
+ * the native handler the chance to do so more efficiently if it
+ * chooses. A double invocation here will be reasonably cheap no-op.
+ */
+ if (ret == 0)
+ ret = __dma_buf_begin_cpu_access(dmabuf, direction);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
+
+/**
+ * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
+ * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
+ * actions. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf: [in] buffer to complete cpu access for.
+ * @direction: [in] length of range for cpu access.
+ *
+ * This terminates CPU access started with dma_buf_begin_cpu_access().
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
+ enum dma_data_direction direction)
+{
+ int ret = 0;
+
+ WARN_ON(!dmabuf);
+
+ if (dmabuf->ops->end_cpu_access)
+ ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
+
+/**
+ * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
+ * same restrictions as for kmap and friends apply.
+ * @dmabuf: [in] buffer to map page from.
+ * @page_num: [in] page in PAGE_SIZE units to map.
+ *
+ * This call must always succeed, any necessary preparations that might fail
+ * need to be done in begin_cpu_access.
+ */
+void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
+{
+ WARN_ON(!dmabuf);
+
+ if (!dmabuf->ops->map)
+ return NULL;
+ return dmabuf->ops->map(dmabuf, page_num);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kmap);
+
+/**
+ * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
+ * @dmabuf: [in] buffer to unmap page from.
+ * @page_num: [in] page in PAGE_SIZE units to unmap.
+ * @vaddr: [in] kernel space pointer obtained from dma_buf_kmap.
+ *
+ * This call must always succeed.
+ */
+void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
+ void *vaddr)
+{
+ WARN_ON(!dmabuf);
+
+ if (dmabuf->ops->unmap)
+ dmabuf->ops->unmap(dmabuf, page_num, vaddr);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kunmap);
+
+
+/**
+ * dma_buf_mmap - Setup up a userspace mmap with the given vma
+ * @dmabuf: [in] buffer that should back the vma
+ * @vma: [in] vma for the mmap
+ * @pgoff: [in] offset in pages where this mmap should start within the
+ * dma-buf buffer.
+ *
+ * This function adjusts the passed in vma so that it points at the file of the
+ * dma_buf operation. It also adjusts the starting pgoff and does bounds
+ * checking on the size of the vma. Then it calls the exporters mmap function to
+ * set up the mapping.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
+ unsigned long pgoff)
+{
+ struct file *oldfile;
+ int ret;
+
+ if (WARN_ON(!dmabuf || !vma))
+ return -EINVAL;
+
+ /* check for offset overflow */
+ if (pgoff + vma_pages(vma) < pgoff)
+ return -EOVERFLOW;
+
+ /* check for overflowing the buffer's size */
+ if (pgoff + vma_pages(vma) >
+ dmabuf->size >> PAGE_SHIFT)
+ return -EINVAL;
+
+ /* readjust the vma */
+ get_file(dmabuf->file);
+ oldfile = vma->vm_file;
+ vma->vm_file = dmabuf->file;
+ vma->vm_pgoff = pgoff;
+
+ ret = dmabuf->ops->mmap(dmabuf, vma);
+ if (ret) {
+ /* restore old parameters on failure */
+ vma->vm_file = oldfile;
+ fput(dmabuf->file);
+ } else {
+ if (oldfile)
+ fput(oldfile);
+ }
+ return ret;
+
+}
+EXPORT_SYMBOL_GPL(dma_buf_mmap);
+
+/**
+ * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
+ * address space. Same restrictions as for vmap and friends apply.
+ * @dmabuf: [in] buffer to vmap
+ *
+ * This call may fail due to lack of virtual mapping address space.
+ * These calls are optional in drivers. The intended use for them
+ * is for mapping objects linear in kernel space for high use objects.
+ * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
+ */
+void *dma_buf_vmap(struct dma_buf *dmabuf)
+{
+ void *ptr;
+
+ if (WARN_ON(!dmabuf))
+ return NULL;
+
+ if (!dmabuf->ops->vmap)
+ return NULL;
+
+ mutex_lock(&dmabuf->lock);
+ if (dmabuf->vmapping_counter) {
+ dmabuf->vmapping_counter++;
+ BUG_ON(!dmabuf->vmap_ptr);
+ ptr = dmabuf->vmap_ptr;
+ goto out_unlock;
+ }
+
+ BUG_ON(dmabuf->vmap_ptr);
+
+ ptr = dmabuf->ops->vmap(dmabuf);
+ if (WARN_ON_ONCE(IS_ERR(ptr)))
+ ptr = NULL;
+ if (!ptr)
+ goto out_unlock;
+
+ dmabuf->vmap_ptr = ptr;
+ dmabuf->vmapping_counter = 1;
+
+out_unlock:
+ mutex_unlock(&dmabuf->lock);
+ return ptr;
+}
+EXPORT_SYMBOL_GPL(dma_buf_vmap);
+
+/**
+ * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
+ * @dmabuf: [in] buffer to vunmap
+ * @vaddr: [in] vmap to vunmap
+ */
+void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
+{
+ if (WARN_ON(!dmabuf))
+ return;
+
+ BUG_ON(!dmabuf->vmap_ptr);
+ BUG_ON(dmabuf->vmapping_counter == 0);
+ BUG_ON(dmabuf->vmap_ptr != vaddr);
+
+ mutex_lock(&dmabuf->lock);
+ if (--dmabuf->vmapping_counter == 0) {
+ if (dmabuf->ops->vunmap)
+ dmabuf->ops->vunmap(dmabuf, vaddr);
+ dmabuf->vmap_ptr = NULL;
+ }
+ mutex_unlock(&dmabuf->lock);
+}
+EXPORT_SYMBOL_GPL(dma_buf_vunmap);
+
+#ifdef CONFIG_DEBUG_FS
+static int dma_buf_debug_show(struct seq_file *s, void *unused)
+{
+ int ret;
+ struct dma_buf *buf_obj;
+ struct dma_buf_attachment *attach_obj;
+ struct reservation_object *robj;
+ struct reservation_object_list *fobj;
+ struct dma_fence *fence;
+ unsigned seq;
+ int count = 0, attach_count, shared_count, i;
+ size_t size = 0;
+
+ ret = mutex_lock_interruptible(&db_list.lock);
+
+ if (ret)
+ return ret;
+
+ seq_puts(s, "\nDma-buf Objects:\n");
+ seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\n",
+ "size", "flags", "mode", "count");
+
+ list_for_each_entry(buf_obj, &db_list.head, list_node) {
+ ret = mutex_lock_interruptible(&buf_obj->lock);
+
+ if (ret) {
+ seq_puts(s,
+ "\tERROR locking buffer object: skipping\n");
+ continue;
+ }
+
+ seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n",
+ buf_obj->size,
+ buf_obj->file->f_flags, buf_obj->file->f_mode,
+ file_count(buf_obj->file),
+ buf_obj->exp_name);
+
+ robj = buf_obj->resv;
+ while (true) {
+ seq = read_seqcount_begin(&robj->seq);
+ rcu_read_lock();
+ fobj = rcu_dereference(robj->fence);
+ shared_count = fobj ? fobj->shared_count : 0;
+ fence = rcu_dereference(robj->fence_excl);
+ if (!read_seqcount_retry(&robj->seq, seq))
+ break;
+ rcu_read_unlock();
+ }
+
+ if (fence)
+ seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
+ fence->ops->get_driver_name(fence),
+ fence->ops->get_timeline_name(fence),
+ dma_fence_is_signaled(fence) ? "" : "un");
+ for (i = 0; i < shared_count; i++) {
+ fence = rcu_dereference(fobj->shared[i]);
+ if (!dma_fence_get_rcu(fence))
+ continue;
+ seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
+ fence->ops->get_driver_name(fence),
+ fence->ops->get_timeline_name(fence),
+ dma_fence_is_signaled(fence) ? "" : "un");
+ }
+ rcu_read_unlock();
+
+ seq_puts(s, "\tAttached Devices:\n");
+ attach_count = 0;
+
+ list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
+ seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
+ attach_count++;
+ }
+
+ seq_printf(s, "Total %d devices attached\n\n",
+ attach_count);
+
+ count++;
+ size += buf_obj->size;
+ mutex_unlock(&buf_obj->lock);
+ }
+
+ seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
+
+ mutex_unlock(&db_list.lock);
+ return 0;
+}
+
+static int dma_buf_debug_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, dma_buf_debug_show, NULL);
+}
+
+static const struct file_operations dma_buf_debug_fops = {
+ .open = dma_buf_debug_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static struct dentry *dma_buf_debugfs_dir;
+
+static int dma_buf_init_debugfs(void)
+{
+ struct dentry *d;
+ int err = 0;
+
+ d = debugfs_create_dir("dma_buf", NULL);
+ if (IS_ERR(d))
+ return PTR_ERR(d);
+
+ dma_buf_debugfs_dir = d;
+
+ d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
+ NULL, &dma_buf_debug_fops);
+ if (IS_ERR(d)) {
+ pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
+ debugfs_remove_recursive(dma_buf_debugfs_dir);
+ dma_buf_debugfs_dir = NULL;
+ err = PTR_ERR(d);
+ }
+
+ return err;
+}
+
+static void dma_buf_uninit_debugfs(void)
+{
+ debugfs_remove_recursive(dma_buf_debugfs_dir);
+}
+#else
+static inline int dma_buf_init_debugfs(void)
+{
+ return 0;
+}
+static inline void dma_buf_uninit_debugfs(void)
+{
+}
+#endif
+
+static int __init dma_buf_init(void)
+{
+ mutex_init(&db_list.lock);
+ INIT_LIST_HEAD(&db_list.head);
+ dma_buf_init_debugfs();
+ return 0;
+}
+subsys_initcall(dma_buf_init);
+
+static void __exit dma_buf_deinit(void)
+{
+ dma_buf_uninit_debugfs();
+}
+__exitcall(dma_buf_deinit);