This patch introduces three new ioctls. They all should be called on a data endpoint (ie. not ep0). They are:
- FUNCTIONFS_DMABUF_ATTACH, which takes the file descriptor of a DMABUF object to attach to the endpoint.
- FUNCTIONFS_DMABUF_DETACH, which takes the file descriptor of the DMABUF to detach from the endpoint. Note that closing the endpoint's file descriptor will automatically detach all attached DMABUFs.
- FUNCTIONFS_DMABUF_TRANSFER, which requests a data transfer from / to the given DMABUF. Its argument is a structure that packs the DMABUF's file descriptor, the size in bytes to transfer (which should generally be set to the size of the DMABUF), and a 'flags' field which is unused for now. Before this ioctl can be used, the related DMABUF must be attached with FUNCTIONFS_DMABUF_ATTACH.
These three ioctls enable the FunctionFS code to transfer data between the USB stack and a DMABUF object, which can be provided by a driver from a completely different subsystem, in a zero-copy fashion.
Signed-off-by: Paul Cercueil paul@crapouillou.net Acked-by: Daniel Vetter daniel.vetter@ffwll.ch Acked-by: Christian König christian.koenig@amd.com
--- v2: - Make ffs_dma_resv_lock() static - Add MODULE_IMPORT_NS(DMA_BUF); - The attach/detach functions are now performed without locking the eps_lock spinlock. The transfer function starts with the spinlock unlocked, then locks it before allocating and queueing the USB transfer.
v3: - Inline to_ffs_dma_fence() which was called only once. - Simplify ffs_dma_resv_lock() - Add comment explaining why we unref twice in ffs_dmabuf_detach() - Document uapi struct usb_ffs_dmabuf_transfer_req and IOCTLs
v4: - Protect the DMABUF list with a mutex - Use incremental sequence number for the dma_fences - Unref attachments and DMABUFs in workers - Remove dead code in ffs_dma_resv_lock() - Fix non-block actually blocking - Use dma_fence_begin/end_signalling() - Add comment about cache-management and dma_buf_unmap_attachment() - Make sure dma_buf_map_attachment() is called with the dma-resv locked
v5: - Cache the dma_buf_attachment while the DMABUF is attached. - Use dma_buf_begin/end_access() to ensure that the DMABUF data will be coherent to the hardware. - Remove comment about cache-management and dma_buf_unmap_attachment(), since we now use dma_buf_begin/end_access(). - Added Christian's ACK - Select DMA_SHARED_BUFFER in Kconfig entry
v6: - Drop use of dma_buf_begin/end_access(). We now make the assumption that the devices attached to the DMABUFs must be coherent between themselves. The cache coherency issue is a tangential problem, and those functions can be re-introduced in a subsequent patchset. - Unqueue pending requests on detach. Otherwise, when closing the data endpoint the DMABUF will never be signaled. - Use list_for_each_entry_safe() in ffs_dmabuf_detach(), because there is a list_del() in there. - Use pr_vdebug() instead of pr_debug() - Rename ffs_dmabuf_unmap_work() -> ffs_dmabuf_cleanup() --- drivers/usb/gadget/Kconfig | 1 + drivers/usb/gadget/function/f_fs.c | 467 ++++++++++++++++++++++++++++ include/uapi/linux/usb/functionfs.h | 41 +++ 3 files changed, 509 insertions(+)
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig index b3592bcb0f96..566ff0b1282a 100644 --- a/drivers/usb/gadget/Kconfig +++ b/drivers/usb/gadget/Kconfig @@ -190,6 +190,7 @@ config USB_F_MASS_STORAGE tristate
config USB_F_FS + select DMA_SHARED_BUFFER tristate
config USB_F_UAC1 diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 491a1e0f4fa3..bffbc1dc651f 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -15,6 +15,9 @@ /* #define VERBOSE_DEBUG */
#include <linux/blkdev.h> +#include <linux/dma-buf.h> +#include <linux/dma-fence.h> +#include <linux/dma-resv.h> #include <linux/pagemap.h> #include <linux/export.h> #include <linux/fs_parser.h> @@ -43,6 +46,8 @@
#define FUNCTIONFS_MAGIC 0xa647361 /* Chosen by a honest dice roll ;) */
+MODULE_IMPORT_NS(DMA_BUF); + /* Reference counter handling */ static void ffs_data_get(struct ffs_data *ffs); static void ffs_data_put(struct ffs_data *ffs); @@ -124,6 +129,25 @@ struct ffs_ep { u8 num; };
+struct ffs_dmabuf_priv { + struct list_head entry; + struct kref ref; + struct ffs_data *ffs; + struct dma_buf_attachment *attach; + struct sg_table *sgt; + enum dma_data_direction dir; + spinlock_t lock; + u64 context; + struct usb_request *req; /* P: ffs->eps_lock */ + struct usb_ep *ep; /* P: ffs->eps_lock */ +}; + +struct ffs_dma_fence { + struct dma_fence base; + struct ffs_dmabuf_priv *priv; + struct work_struct work; +}; + struct ffs_epfile { /* Protects ep->ep and ep->req. */ struct mutex mutex; @@ -197,6 +221,11 @@ struct ffs_epfile { unsigned char isoc; /* P: ffs->eps_lock */
unsigned char _pad; + + /* Protects dmabufs */ + struct mutex dmabufs_mutex; + struct list_head dmabufs; /* P: dmabufs_mutex */ + atomic_t seqno; };
struct ffs_buffer { @@ -1271,10 +1300,58 @@ static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb, struct iov_iter *to) return res; }
+static void ffs_dmabuf_release(struct kref *ref) +{ + struct ffs_dmabuf_priv *priv = container_of(ref, struct ffs_dmabuf_priv, ref); + struct dma_buf_attachment *attach = priv->attach; + struct dma_buf *dmabuf = attach->dmabuf; + + pr_vdebug("FFS DMABUF release\n"); + dma_resv_lock(dmabuf->resv, NULL); + dma_buf_unmap_attachment(attach, priv->sgt, priv->dir); + dma_resv_unlock(dmabuf->resv); + + dma_buf_detach(attach->dmabuf, attach); + dma_buf_put(dmabuf); + kfree(priv); +} + +static void ffs_dmabuf_get(struct dma_buf_attachment *attach) +{ + struct ffs_dmabuf_priv *priv = attach->importer_priv; + + kref_get(&priv->ref); +} + +static void ffs_dmabuf_put(struct dma_buf_attachment *attach) +{ + struct ffs_dmabuf_priv *priv = attach->importer_priv; + + kref_put(&priv->ref, ffs_dmabuf_release); +} + static int ffs_epfile_release(struct inode *inode, struct file *file) { struct ffs_epfile *epfile = inode->i_private; + struct ffs_dmabuf_priv *priv, *tmp; + struct ffs_data *ffs = epfile->ffs; + + mutex_lock(&epfile->dmabufs_mutex); + + /* Close all attached DMABUFs */ + list_for_each_entry_safe(priv, tmp, &epfile->dmabufs, entry) { + /* Cancel any pending transfer */ + spin_lock_irq(&ffs->eps_lock); + if (priv->ep && priv->req) + usb_ep_dequeue(priv->ep, priv->req); + spin_unlock_irq(&ffs->eps_lock); + + list_del(&priv->entry); + ffs_dmabuf_put(priv->attach); + } + + mutex_unlock(&epfile->dmabufs_mutex);
__ffs_epfile_read_buffer_free(epfile); ffs_data_closed(epfile->ffs); @@ -1282,6 +1359,356 @@ ffs_epfile_release(struct inode *inode, struct file *file) return 0; }
+static void ffs_dmabuf_cleanup(struct work_struct *work) +{ + struct ffs_dma_fence *dma_fence = + container_of(work, struct ffs_dma_fence, work); + struct ffs_dmabuf_priv *priv = dma_fence->priv; + struct dma_buf_attachment *attach = priv->attach; + struct dma_fence *fence = &dma_fence->base; + + ffs_dmabuf_put(attach); + dma_fence_put(fence); +} + +static void ffs_dmabuf_signal_done(struct ffs_dma_fence *dma_fence, int ret) +{ + struct ffs_dmabuf_priv *priv = dma_fence->priv; + struct dma_fence *fence = &dma_fence->base; + bool cookie = dma_fence_begin_signalling(); + + dma_fence_get(fence); + fence->error = ret; + dma_fence_signal(fence); + dma_fence_end_signalling(cookie); + + /* + * The fence will be unref'd in ffs_dmabuf_cleanup. + * It can't be done here, as the unref functions might try to lock + * the resv object, which would deadlock. + */ + INIT_WORK(&dma_fence->work, ffs_dmabuf_cleanup); + queue_work(priv->ffs->io_completion_wq, &dma_fence->work); +} + +static void ffs_epfile_dmabuf_io_complete(struct usb_ep *ep, + struct usb_request *req) +{ + pr_vdebug("FFS: DMABUF transfer complete, status=%d\n", req->status); + ffs_dmabuf_signal_done(req->context, req->status); + usb_ep_free_request(ep, req); +} + +static const char *ffs_dmabuf_get_driver_name(struct dma_fence *fence) +{ + return "functionfs"; +} + +static const char *ffs_dmabuf_get_timeline_name(struct dma_fence *fence) +{ + return ""; +} + +static void ffs_dmabuf_fence_release(struct dma_fence *fence) +{ + struct ffs_dma_fence *dma_fence = + container_of(fence, struct ffs_dma_fence, base); + + kfree(dma_fence); +} + +static const struct dma_fence_ops ffs_dmabuf_fence_ops = { + .get_driver_name = ffs_dmabuf_get_driver_name, + .get_timeline_name = ffs_dmabuf_get_timeline_name, + .release = ffs_dmabuf_fence_release, +}; + +static int ffs_dma_resv_lock(struct dma_buf *dmabuf, bool nonblock) +{ + if (!nonblock) + return dma_resv_lock_interruptible(dmabuf->resv, NULL); + + if (!dma_resv_trylock(dmabuf->resv)) + return -EBUSY; + + return 0; +} + +static struct dma_buf_attachment * +ffs_dmabuf_find_attachment(struct ffs_epfile *epfile, struct dma_buf *dmabuf) +{ + struct device *dev = epfile->ffs->gadget->dev.parent; + struct dma_buf_attachment *attach = NULL; + struct ffs_dmabuf_priv *priv; + + mutex_lock(&epfile->dmabufs_mutex); + + list_for_each_entry(priv, &epfile->dmabufs, entry) { + if (priv->attach->dev == dev + && priv->attach->dmabuf == dmabuf) { + attach = priv->attach; + break; + } + } + + if (attach) + ffs_dmabuf_get(attach); + + mutex_unlock(&epfile->dmabufs_mutex); + + return attach ?: ERR_PTR(-EPERM); +} + +static int ffs_dmabuf_attach(struct file *file, int fd) +{ + bool nonblock = file->f_flags & O_NONBLOCK; + struct ffs_epfile *epfile = file->private_data; + struct usb_gadget *gadget = epfile->ffs->gadget; + struct dma_buf_attachment *attach; + struct ffs_dmabuf_priv *priv; + enum dma_data_direction dir; + struct sg_table *sg_table; + struct dma_buf *dmabuf; + int err; + + if (!gadget || !gadget->sg_supported) + return -EPERM; + + dmabuf = dma_buf_get(fd); + if (IS_ERR(dmabuf)) + return PTR_ERR(dmabuf); + + attach = dma_buf_attach(dmabuf, gadget->dev.parent); + if (IS_ERR(attach)) { + err = PTR_ERR(attach); + goto err_dmabuf_put; + } + + priv = kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) { + err = -ENOMEM; + goto err_dmabuf_detach; + } + + dir = epfile->in ? DMA_FROM_DEVICE : DMA_TO_DEVICE; + + err = ffs_dma_resv_lock(dmabuf, nonblock); + if (err) + goto err_free_priv; + + sg_table = dma_buf_map_attachment(attach, dir); + dma_resv_unlock(dmabuf->resv); + + if (IS_ERR(sg_table)) { + err = PTR_ERR(sg_table); + goto err_free_priv; + } + + attach->importer_priv = priv; + + priv->sgt = sg_table; + priv->dir = dir; + priv->ffs = epfile->ffs; + priv->attach = attach; + spin_lock_init(&priv->lock); + kref_init(&priv->ref); + priv->context = dma_fence_context_alloc(1); + + mutex_lock(&epfile->dmabufs_mutex); + list_add(&priv->entry, &epfile->dmabufs); + mutex_unlock(&epfile->dmabufs_mutex); + + return 0; + +err_free_priv: + kfree(priv); +err_dmabuf_detach: + dma_buf_detach(dmabuf, attach); +err_dmabuf_put: + dma_buf_put(dmabuf); + + return err; +} + +static int ffs_dmabuf_detach(struct file *file, int fd) +{ + struct ffs_epfile *epfile = file->private_data; + struct ffs_data *ffs = epfile->ffs; + struct device *dev = ffs->gadget->dev.parent; + struct ffs_dmabuf_priv *priv, *tmp; + struct dma_buf *dmabuf; + int ret = -EPERM; + + dmabuf = dma_buf_get(fd); + if (IS_ERR(dmabuf)) + return PTR_ERR(dmabuf); + + mutex_lock(&epfile->dmabufs_mutex); + + list_for_each_entry_safe(priv, tmp, &epfile->dmabufs, entry) { + if (priv->attach->dev == dev + && priv->attach->dmabuf == dmabuf) { + /* Cancel any pending transfer */ + spin_lock_irq(&ffs->eps_lock); + if (priv->ep && priv->req) + usb_ep_dequeue(priv->ep, priv->req); + spin_unlock_irq(&ffs->eps_lock); + + list_del(&priv->entry); + + /* Unref the reference from ffs_dmabuf_attach() */ + ffs_dmabuf_put(priv->attach); + ret = 0; + break; + } + } + + mutex_unlock(&epfile->dmabufs_mutex); + dma_buf_put(dmabuf); + + return ret; +} + +static int ffs_dmabuf_transfer(struct file *file, + const struct usb_ffs_dmabuf_transfer_req *req) +{ + bool nonblock = file->f_flags & O_NONBLOCK; + struct ffs_epfile *epfile = file->private_data; + struct dma_buf_attachment *attach; + struct ffs_dmabuf_priv *priv; + struct ffs_dma_fence *fence; + struct usb_request *usb_req; + struct dma_buf *dmabuf; + struct ffs_ep *ep; + bool cookie; + u32 seqno; + int ret; + + if (req->flags & ~USB_FFS_DMABUF_TRANSFER_MASK) + return -EINVAL; + + dmabuf = dma_buf_get(req->fd); + if (IS_ERR(dmabuf)) + return PTR_ERR(dmabuf); + + if (req->length > dmabuf->size || req->length == 0) { + ret = -EINVAL; + goto err_dmabuf_put; + } + + attach = ffs_dmabuf_find_attachment(epfile, dmabuf); + if (IS_ERR(attach)) { + ret = PTR_ERR(attach); + goto err_dmabuf_put; + } + + priv = attach->importer_priv; + + ep = ffs_epfile_wait_ep(file); + if (IS_ERR(ep)) { + ret = PTR_ERR(ep); + goto err_attachment_put; + } + + ret = ffs_dma_resv_lock(dmabuf, nonblock); + if (ret) + goto err_attachment_put; + + /* Make sure we don't have writers */ + if (!dma_resv_test_signaled(dmabuf->resv, DMA_RESV_USAGE_WRITE)) { + pr_vdebug("FFS WRITE fence is not signaled\n"); + ret = -EBUSY; + goto err_resv_unlock; + } + + /* If we're writing to the DMABUF, make sure we don't have readers */ + if (epfile->in && + !dma_resv_test_signaled(dmabuf->resv, DMA_RESV_USAGE_READ)) { + pr_vdebug("FFS READ fence is not signaled\n"); + ret = -EBUSY; + goto err_resv_unlock; + } + + ret = dma_resv_reserve_fences(dmabuf->resv, 1); + if (ret) + goto err_resv_unlock; + + fence = kmalloc(sizeof(*fence), GFP_KERNEL); + if (!fence) { + ret = -ENOMEM; + goto err_resv_unlock; + } + + fence->priv = priv; + + spin_lock_irq(&epfile->ffs->eps_lock); + + /* In the meantime, endpoint got disabled or changed. */ + if (epfile->ep != ep) { + ret = -ESHUTDOWN; + goto err_fence_put; + } + + usb_req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC); + if (!usb_req) { + ret = -ENOMEM; + goto err_fence_put; + } + + /* + * usb_ep_queue() guarantees that all transfers are processed in the + * order they are enqueued, so we can use a simple incrementing + * sequence number for the dma_fence. + */ + seqno = atomic_add_return(1, &epfile->seqno); + + dma_fence_init(&fence->base, &ffs_dmabuf_fence_ops, + &priv->lock, priv->context, seqno); + + dma_resv_add_fence(dmabuf->resv, &fence->base, + dma_resv_usage_rw(epfile->in)); + dma_resv_unlock(dmabuf->resv); + + /* Now that the dma_fence is in place, queue the transfer. */ + + usb_req->length = req->length; + usb_req->buf = NULL; + usb_req->sg = priv->sgt->sgl; + usb_req->num_sgs = sg_nents_for_len(priv->sgt->sgl, req->length); + usb_req->sg_was_mapped = true; + usb_req->context = fence; + usb_req->complete = ffs_epfile_dmabuf_io_complete; + + cookie = dma_fence_begin_signalling(); + ret = usb_ep_queue(ep->ep, usb_req, GFP_ATOMIC); + dma_fence_end_signalling(cookie); + if (!ret) { + priv->req = usb_req; + priv->ep = ep->ep; + } else { + pr_warn("FFS: Failed to queue DMABUF: %d\n", ret); + ffs_dmabuf_signal_done(fence, ret); + usb_ep_free_request(ep->ep, usb_req); + } + + spin_unlock_irq(&epfile->ffs->eps_lock); + dma_buf_put(dmabuf); + + return ret; + +err_fence_put: + spin_unlock_irq(&epfile->ffs->eps_lock); + dma_fence_put(&fence->base); +err_resv_unlock: + dma_resv_unlock(dmabuf->resv); +err_attachment_put: + ffs_dmabuf_put(attach); +err_dmabuf_put: + dma_buf_put(dmabuf); + + return ret; +} + static long ffs_epfile_ioctl(struct file *file, unsigned code, unsigned long value) { @@ -1292,6 +1719,44 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code, if (WARN_ON(epfile->ffs->state != FFS_ACTIVE)) return -ENODEV;
+ switch (code) { + case FUNCTIONFS_DMABUF_ATTACH: + { + int fd; + + if (copy_from_user(&fd, (void __user *)value, sizeof(fd))) { + ret = -EFAULT; + break; + } + + return ffs_dmabuf_attach(file, fd); + } + case FUNCTIONFS_DMABUF_DETACH: + { + int fd; + + if (copy_from_user(&fd, (void __user *)value, sizeof(fd))) { + ret = -EFAULT; + break; + } + + return ffs_dmabuf_detach(file, fd); + } + case FUNCTIONFS_DMABUF_TRANSFER: + { + struct usb_ffs_dmabuf_transfer_req req; + + if (copy_from_user(&req, (void __user *)value, sizeof(req))) { + ret = -EFAULT; + break; + } + + return ffs_dmabuf_transfer(file, &req); + } + default: + break; + } + /* Wait for endpoint to be enabled */ ep = ffs_epfile_wait_ep(file); if (IS_ERR(ep)) @@ -1869,6 +2334,8 @@ static int ffs_epfiles_create(struct ffs_data *ffs) for (i = 1; i <= count; ++i, ++epfile) { epfile->ffs = ffs; mutex_init(&epfile->mutex); + mutex_init(&epfile->dmabufs_mutex); + INIT_LIST_HEAD(&epfile->dmabufs); if (ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR) sprintf(epfile->name, "ep%02x", ffs->eps_addrmap[i]); else diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h index 078098e73fd3..9f88de9c3d66 100644 --- a/include/uapi/linux/usb/functionfs.h +++ b/include/uapi/linux/usb/functionfs.h @@ -86,6 +86,22 @@ struct usb_ext_prop_desc { __le16 wPropertyNameLength; } __attribute__((packed));
+/* Flags for usb_ffs_dmabuf_transfer_req->flags (none for now) */ +#define USB_FFS_DMABUF_TRANSFER_MASK 0x0 + +/** + * struct usb_ffs_dmabuf_transfer_req - Transfer request for a DMABUF object + * @fd: file descriptor of the DMABUF object + * @flags: one or more USB_FFS_DMABUF_TRANSFER_* flags + * @length: number of bytes used in this DMABUF for the data transfer. + * Should generally be set to the DMABUF's size. + */ +struct usb_ffs_dmabuf_transfer_req { + int fd; + __u32 flags; + __u64 length; +} __attribute__((packed)); + #ifndef __KERNEL__
/* @@ -290,6 +306,31 @@ struct usb_functionfs_event { #define FUNCTIONFS_ENDPOINT_DESC _IOR('g', 130, \ struct usb_endpoint_descriptor)
+/* + * Attach the DMABUF object, identified by its file descriptor, to the + * data endpoint. Returns zero on success, and a negative errno value + * on error. + */ +#define FUNCTIONFS_DMABUF_ATTACH _IOW('g', 131, int) +
+/* + * Detach the given DMABUF object, identified by its file descriptor, + * from the data endpoint. Returns zero on success, and a negative + * errno value on error. Note that closing the endpoint's file + * descriptor will automatically detach all attached DMABUFs. + */ +#define FUNCTIONFS_DMABUF_DETACH _IOW('g', 132, int) + +/* + * Enqueue the previously attached DMABUF to the transfer queue. + * The argument is a structure that packs the DMABUF's file descriptor, + * the size in bytes to transfer (which should generally correspond to + * the size of the DMABUF), and a 'flags' field which is unused + * for now. Returns zero on success, and a negative errno value on + * error. + */ +#define FUNCTIONFS_DMABUF_TRANSFER _IOW('g', 133, \ + struct usb_ffs_dmabuf_transfer_req)
#endif /* _UAPI__LINUX_FUNCTIONFS_H__ */