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
--- 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. --- drivers/usb/gadget/function/f_fs.c | 421 ++++++++++++++++++++++++++++ include/uapi/linux/usb/functionfs.h | 14 +- 2 files changed, 434 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 8da64f0fdef0..f5c609c83b36 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 +129,26 @@ struct ffs_ep { u8 num; };
+struct ffs_dmabuf_priv { + struct list_head entry; + struct kref ref; + struct dma_buf_attachment *attach; + spinlock_t lock; + u64 context; +}; + +struct ffs_dma_fence { + struct dma_fence base; + struct ffs_dmabuf_priv *priv; + struct sg_table *sgt; + enum dma_data_direction dir; +}; + +static inline struct ffs_dma_fence *to_ffs_dma_fence(struct dma_fence *fence) +{ + return container_of(fence, struct ffs_dma_fence, base); +} + struct ffs_epfile { /* Protects ep->ep and ep->req. */ struct mutex mutex; @@ -197,6 +222,8 @@ struct ffs_epfile { unsigned char isoc; /* P: ffs->eps_lock */
unsigned char _pad; + + struct list_head dmabufs; };
struct ffs_buffer { @@ -1292,19 +1319,374 @@ 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_debug("FFS DMABUF release\n"); + dma_buf_detach(attach->dmabuf, attach); + dma_buf_put(dmabuf); + + list_del(&priv->entry); + 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;
ENTER();
+ /* Close all attached DMABUFs */ + list_for_each_entry_safe(priv, tmp, &epfile->dmabufs, entry) { + ffs_dmabuf_put(priv->attach); + } + __ffs_epfile_read_buffer_free(epfile); ffs_data_closed(epfile->ffs);
return 0; }
+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; + + dma_fence_get(fence); + fence->error = ret; + dma_fence_signal(fence); + + dma_buf_unmap_attachment(priv->attach, dma_fence->sgt, dma_fence->dir); + dma_fence_put(fence); + ffs_dmabuf_put(priv->attach); +} + +static void ffs_epfile_dmabuf_io_complete(struct usb_ep *ep, + struct usb_request *req) +{ + ENTER(); + + pr_debug("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 = to_ffs_dma_fence(fence); + + 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) +{ + int ret; + + ret = dma_resv_lock_interruptible(dmabuf->resv, NULL); + if (ret) { + if (ret != -EDEADLK) + goto out; + if (nonblock) { + ret = -EBUSY; + goto out; + } + + ret = dma_resv_lock_slow_interruptible(dmabuf->resv, NULL); + } + +out: + return ret; +} + +static struct dma_buf_attachment * +ffs_dmabuf_find_attachment(struct device *dev, struct dma_buf *dmabuf, + bool nonblock) +{ + struct dma_buf_attachment *elm, *attach = NULL; + int ret; + + ret = ffs_dma_resv_lock(dmabuf, nonblock); + if (ret) + return ERR_PTR(ret); + + list_for_each_entry(elm, &dmabuf->attachments, node) { + if (elm->dev == dev) { + attach = elm; + break; + } + } + + if (attach) + ffs_dmabuf_get(elm); + + dma_resv_unlock(dmabuf->resv); + + return attach ?: ERR_PTR(-EPERM); +} + +static int ffs_dmabuf_attach(struct file *file, int fd) +{ + struct ffs_epfile *epfile = file->private_data; + struct usb_gadget *gadget = epfile->ffs->gadget; + struct dma_buf_attachment *attach; + struct ffs_dmabuf_priv *priv; + 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; + } + + attach->importer_priv = priv; + + priv->attach = attach; + spin_lock_init(&priv->lock); + kref_init(&priv->ref); + priv->context = dma_fence_context_alloc(1); + + list_add(&priv->entry, &epfile->dmabufs); + + return 0; + +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 usb_gadget *gadget = epfile->ffs->gadget; + bool nonblock = file->f_flags & O_NONBLOCK; + struct dma_buf_attachment *attach; + struct dma_buf *dmabuf; + int ret = 0; + + dmabuf = dma_buf_get(fd); + if (IS_ERR(dmabuf)) + return PTR_ERR(dmabuf); + + attach = ffs_dmabuf_find_attachment(gadget->dev.parent, + dmabuf, nonblock); + if (IS_ERR(attach)) { + ret = PTR_ERR(attach); + goto out_dmabuf_put; + } + + ffs_dmabuf_put(attach); + ffs_dmabuf_put(attach); + +out_dmabuf_put: + dma_buf_put(dmabuf); + return ret; +} + +static int ffs_dmabuf_transfer(struct file *file, + const struct usb_ffs_dmabuf_transfer_req *req) +{ + bool dma_to_ram, 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 ffs_dma_fence *fence; + struct usb_request *usb_req; + struct sg_table *sg_table; + struct dma_buf *dmabuf; + struct ffs_ep *ep; + 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(gadget->dev.parent, + dmabuf, nonblock); + if (IS_ERR(attach)) { + ret = PTR_ERR(attach); + goto err_dmabuf_put; + } + + priv = attach->importer_priv; + + if (epfile->in) + dir = DMA_FROM_DEVICE; + else + dir = DMA_TO_DEVICE; + + sg_table = dma_buf_map_attachment(attach, dir); + if (IS_ERR(sg_table)) { + ret = PTR_ERR(sg_table); + goto err_attachment_put; + } + + ep = ffs_epfile_wait_ep(file); + if (IS_ERR(ep)) { + ret = PTR_ERR(ep); + goto err_unmap_attachment; + } + + ret = ffs_dma_resv_lock(dmabuf, nonblock); + if (ret) + goto err_unmap_attachment; + + /* Make sure we don't have writers */ + if (!dma_resv_test_signaled(dmabuf->resv, DMA_RESV_USAGE_WRITE)) { + pr_debug("FFS WRITE fence is not signaled\n"); + ret = -EBUSY; + goto err_resv_unlock; + } + + dma_to_ram = dir == DMA_FROM_DEVICE; + + /* If we're writing to the DMABUF, make sure we don't have readers */ + if (dma_to_ram && + !dma_resv_test_signaled(dmabuf->resv, DMA_RESV_USAGE_READ)) { + pr_debug("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->sgt = sg_table; + fence->dir = dir; + fence->priv = priv; + + dma_fence_init(&fence->base, &ffs_dmabuf_fence_ops, + &priv->lock, priv->context, 0); + + spin_lock_irq(&epfile->ffs->eps_lock); + + /* In the meantime, endpoint got disabled or changed. */ + if (epfile->ep != ep) { + ret = -ESHUTDOWN; + goto err_spin_unlock; + } + + usb_req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC); + if (!usb_req) { + ret = -ENOMEM; + goto err_spin_unlock; + } + + dma_resv_add_fence(dmabuf->resv, &fence->base, + dma_resv_usage_rw(dma_to_ram)); + 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 = sg_table->sgl; + usb_req->num_sgs = sg_nents_for_len(sg_table->sgl, req->length); + usb_req->sg_was_mapped = true; + usb_req->context = fence; + usb_req->complete = ffs_epfile_dmabuf_io_complete; + + ret = usb_ep_queue(ep->ep, usb_req, GFP_ATOMIC); + if (ret) { + usb_ep_free_request(ep->ep, usb_req); + + spin_unlock_irq(&epfile->ffs->eps_lock); + + pr_warn("FFS: Failed to queue DMABUF: %d\n", ret); + ffs_dmabuf_signal_done(fence, ret); + goto out_dma_buf_put; + } + + spin_unlock_irq(&epfile->ffs->eps_lock); + +out_dma_buf_put: + dma_buf_put(dmabuf); + + return ret; + +err_spin_unlock: + spin_unlock_irq(&epfile->ffs->eps_lock); + dma_fence_put(&fence->base); +err_resv_unlock: + dma_resv_unlock(dmabuf->resv); +err_unmap_attachment: + dma_buf_unmap_attachment(attach, sg_table, dir); +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) { @@ -1317,6 +1699,44 @@ 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)) @@ -1931,6 +2351,7 @@ static int ffs_epfiles_create(struct ffs_data *ffs) for (i = 1; i <= count; ++i, ++epfile) { epfile->ffs = ffs; mutex_init(&epfile->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 d77ee6b65328..1412ab9f8ccc 100644 --- a/include/uapi/linux/usb/functionfs.h +++ b/include/uapi/linux/usb/functionfs.h @@ -84,6 +84,15 @@ 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 { + int fd; + __u32 flags; + __u64 length; +} __attribute__((packed)); + #ifndef __KERNEL__
/* @@ -288,6 +297,9 @@ struct usb_functionfs_event { #define FUNCTIONFS_ENDPOINT_DESC _IOR('g', 130, \ struct usb_endpoint_descriptor)
- +#define FUNCTIONFS_DMABUF_ATTACH _IOW('g', 131, int) +#define FUNCTIONFS_DMABUF_DETACH _IOW('g', 132, int) +#define FUNCTIONFS_DMABUF_TRANSFER _IOW('g', 133, \ + struct usb_ffs_dmabuf_transfer_req)
#endif /* _UAPI__LINUX_FUNCTIONFS_H__ */