[PATCH v2 0/3] usb: gadget: functionfs: DMABUF import interface

[PATCH v2 0/3] usb: gadget: functionfs: DMABUF import interface

[Paul Cercueil]

Hi,

This small patchset adds three new IOCTLs that can be used to attach,
detach, or transfer from/to a DMABUF object.

Changes since v1:
- patch [2/3] is new. I had to reuse a piece of code that was already
  duplicated in the driver, so I factorized the code.
- 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.

Cheers,
-Paul

Paul Cercueil (3):
  usb: gadget: Support already-mapped DMA SGs
  usb: gadget: functionfs: Factorize wait-for-endpoint code
  usb: gadget: functionfs: Add DMABUF import interface

 drivers/usb/gadget/function/f_fs.c  | 467 ++++++++++++++++++++++++++--
 drivers/usb/gadget/udc/core.c       |   7 +-
 include/linux/usb/gadget.h          |   2 +
 include/uapi/linux/usb/functionfs.h |  14 +-
 4 files changed, 468 insertions(+), 22 deletions(-)

-- 
2.39.2

[PATCH v2 1/3] usb: gadget: Support already-mapped DMA SGs

[Paul Cercueil]

Add a new 'sg_was_mapped' field to the struct usb_request. This field
can be used to indicate that the scatterlist associated to the USB
transfer has already been mapped into the DMA space, and it does not
have to be done internally.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 drivers/usb/gadget/udc/core.c | 7 ++++++-
 include/linux/usb/gadget.h    | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 23b0629a8774..5f2c4933769d 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -829,6 +829,11 @@ int usb_gadget_map_request_by_dev(struct device *dev,
 	if (req->length == 0)
 		return 0;
 
+	if (req->sg_was_mapped) {
+		req->num_mapped_sgs = req->num_sgs;
+		return 0;
+	}
+
 	if (req->num_sgs) {
 		int     mapped;
 
@@ -874,7 +879,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_map_request);
 void usb_gadget_unmap_request_by_dev(struct device *dev,
 		struct usb_request *req, int is_in)
 {
-	if (req->length == 0)
+	if (req->length == 0 || req->sg_was_mapped)
 		return;
 
 	if (req->num_mapped_sgs) {
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 00750f7020f3..9dd829b8974a 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -52,6 +52,7 @@ struct usb_ep;
  * @short_not_ok: When reading data, makes short packets be
  *     treated as errors (queue stops advancing till cleanup).
  * @dma_mapped: Indicates if request has been mapped to DMA (internal)
+ * @sg_was_mapped: Set if the scatterlist has been mapped before the request
  * @complete: Function called when request completes, so this request and
  *	its buffer may be re-used.  The function will always be called with
  *	interrupts disabled, and it must not sleep.
@@ -111,6 +112,7 @@ struct usb_request {
 	unsigned		zero:1;
 	unsigned		short_not_ok:1;
 	unsigned		dma_mapped:1;
+	unsigned		sg_was_mapped:1;
 
 	void			(*complete)(struct usb_ep *ep,
 					struct usb_request *req);
-- 
2.39.2

[PATCH v2 2/3] usb: gadget: functionfs: Factorize wait-for-endpoint code

[Paul Cercueil]

This exact same code was duplicated in two different places.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 drivers/usb/gadget/function/f_fs.c | 48 +++++++++++++++++-------------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index ddfc537c7526..8da64f0fdef0 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -947,31 +947,44 @@ static ssize_t __ffs_epfile_read_data(struct ffs_epfile *epfile,
 	return ret;
 }
 
-static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
+static struct ffs_ep *ffs_epfile_wait_ep(struct file *file)
 {
 	struct ffs_epfile *epfile = file->private_data;
-	struct usb_request *req;
 	struct ffs_ep *ep;
-	char *data = NULL;
-	ssize_t ret, data_len = -EINVAL;
-	int halt;
-
-	/* Are we still active? */
-	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
-		return -ENODEV;
+	int ret;
 
 	/* Wait for endpoint to be enabled */
 	ep = epfile->ep;
 	if (!ep) {
 		if (file->f_flags & O_NONBLOCK)
-			return -EAGAIN;
+			return ERR_PTR(-EAGAIN);
 
 		ret = wait_event_interruptible(
 				epfile->ffs->wait, (ep = epfile->ep));
 		if (ret)
-			return -EINTR;
+			return ERR_PTR(-EINTR);
 	}
 
+	return ep;
+}
+
+static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
+{
+	struct ffs_epfile *epfile = file->private_data;
+	struct usb_request *req;
+	struct ffs_ep *ep;
+	char *data = NULL;
+	ssize_t ret, data_len = -EINVAL;
+	int halt;
+
+	/* Are we still active? */
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	ep = ffs_epfile_wait_ep(file);
+	if (IS_ERR(ep))
+		return PTR_ERR(ep);
+
 	/* Do we halt? */
 	halt = (!io_data->read == !epfile->in);
 	if (halt && epfile->isoc)
@@ -1305,16 +1318,9 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
 		return -ENODEV;
 
 	/* Wait for endpoint to be enabled */
-	ep = epfile->ep;
-	if (!ep) {
-		if (file->f_flags & O_NONBLOCK)
-			return -EAGAIN;
-
-		ret = wait_event_interruptible(
-				epfile->ffs->wait, (ep = epfile->ep));
-		if (ret)
-			return -EINTR;
-	}
+	ep = ffs_epfile_wait_ep(file);
+	if (IS_ERR(ep))
+		return PTR_ERR(ep);
 
 	spin_lock_irq(&epfile->ffs->eps_lock);
 
-- 
2.39.2

[PATCH v2 3/3] usb: gadget: functionfs: Add DMABUF import interface

[Paul Cercueil]

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__ */
-- 
2.39.2

Re: [PATCH v2 0/3] usb: gadget: functionfs: DMABUF import interface

[Andrzej Pietrasiewicz]

Hi Paul,

W dniu 22.03.2023 o 10:21, Paul Cercueil pisze:
> Hi,
> 
> This small patchset adds three new IOCTLs that can be used to attach,
> detach, or transfer from/to a DMABUF object.
> 
> Changes since v1:
> - patch [2/3] is new. I had to reuse a piece of code that was already
>    duplicated in the driver, so I factorized the code.
> - 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.
> 

Can you share an example use case for these new features?
Is there a userspace that excercises the new ioctls?

Regards,

Andrzej

Re: [PATCH v2 0/3] usb: gadget: functionfs: DMABUF import interface

[Paul Cercueil]

Hi Andrzej,

Le vendredi 31 mars 2023 à 11:40 +0200, Andrzej Pietrasiewicz a écrit :
> Hi Paul,
> 
> W dniu 22.03.2023 o 10:21, Paul Cercueil pisze:
> > Hi,
> > 
> > This small patchset adds three new IOCTLs that can be used to
> > attach,
> > detach, or transfer from/to a DMABUF object.
> > 
> > Changes since v1:
> > - patch [2/3] is new. I had to reuse a piece of code that was
> > already
> >    duplicated in the driver, so I factorized the code.
> > - 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.
> > 
> 
> Can you share an example use case for these new features?
> Is there a userspace that excercises the new ioctls?

We use it at Analog Devices to share buffers between the IIO subsystem
and the USB stack, which makes it possible to stream data samples
between a host computer and high-speed transceivers as fast as
possible, in a zero-copy fashion.

This will be used by Libiio:
https://github.com/analogdevicesinc/libiio/pull/928/commits/dd348137ce371532fd952a2b249cfd96afaef7d1

The code that uses these IOCTLs is not yet merged to the "master"
branch, but will be as soon as this patchset is accepted.

Cheers,
-Paul