Re: [PATCH v5 2/3] net/9p/usbg: Add new usb gadget function transport

[Andrzej Pietrasiewicz]

Hi,

W dniu 28.05.2024 o 00:08, Michael Grzeschik pisze:
> Add the new gadget function for 9pfs transport. This function is
> defining an simple 9pfs transport interface that consists of one in and
> one out endpoint. The endpoints transmit and receive the 9pfs protocol
> payload when mounting a 9p filesystem over usb.
>
> Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>

Tested-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>

> ---
> v4 -> v5:
>    - remove instance from instance list on free
>    - bail out if no req was queued in disable
>    - free requests on disable
>    - use irqsave/restore in other functions then the completion handlers
>    - simplify the completion handlers
>    - reset tx_req pointer to NULL after the status update
>    - add unbind function
>    - use the right lock when protecting 9p requets
>    - refactor giveback of tx_request to extra function clear_tx
>    - enable endpoints once on set_alt
>    - only disable endpoints on unbind
>    - reset request pointers on free
>    - remove req_lock which is not necessary since only one transfer can
>      be queued for now
> v3 -> v4:
>    - implemented conn_cancel
>    - moved from mount_tag to device name like ffs does
>    - renamed function_list to usb9pfs_instance
>    - renamed usbg_function_list to usb9pfs_instance_list
>    - renamed rx/tx_fill to queue_rx/tx
>    - added use of retvals
>    - added locking comment over usb9pfs_transmit
>    - using if_else instead of two pathed switch calls
>    - fixed return values of completion handler
>    - using void pointer as parameter in rx_header
>    - added a missed req_put in rx_header
>    - removed extra disable function but call disable_ep directly
>    - repaired several return values
>    - remove the suspicious disable / enable path in usbg_create
> v2 -> v3: -
> v1 -> v2:
>    - move the driver to net/9p/trans_usbg.c
>    - fixed the commit title
>    - fix %zu usage in p9_debug for size_t type
>    - define functions static that are only used localy
>    - return 0 in alloc_requests
>    - use id_alloc_max instead of ida_simple_get
>    - call ida_free in usb9pfs_free_func
>    - call kfree for usb9pfs->tag and usb9pfs in usb9pfs_free_func
>    - add MODULE_ALIAS_9P to load this module automatic when mounting
>    - improved the documentation
>    - added depends on USB_GADGET in Kconfig
> ---
>   Documentation/filesystems/9p.rst |  17 +-
>   net/9p/Kconfig                   |   6 +
>   net/9p/Makefile                  |   4 +
>   net/9p/trans_usbg.c              | 974 +++++++++++++++++++++++++++++++++++++++
>   4 files changed, 1000 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst
> index 1e0e0bb6fdf91..10cf79dc287f8 100644
> --- a/Documentation/filesystems/9p.rst
> +++ b/Documentation/filesystems/9p.rst
> @@ -48,11 +48,25 @@ For server running on QEMU host with virtio transport::
>   
>   	mount -t 9p -o trans=virtio <mount_tag> /mnt/9
>   
> -where mount_tag is the tag associated by the server to each of the exported
> +where mount_tag is the tag generated by the server to each of the exported
>   mount points. Each 9P export is seen by the client as a virtio device with an
>   associated "mount_tag" property. Available mount tags can be
>   seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
>   
> +USBG Usage
> +==========
> +
> +To mount a 9p FS on a USB Host accessible via the gadget at runtime::
> +
> +	mount -t 9p -o trans=usbg,aname=/path/to/fs <device> /mnt/9
> +
> +To mount a 9p FS on a USB Host accessible via the gadget as root filesystem::
> +
> +	root=<device> rootfstype=9p rootflags=trans=usbg,cache=loose,uname=root,access=0,dfltuid=0,dfltgid=0,aname=/path/to/rootfs
> +
> +where <device> is the tag associated by the usb gadget transport.
> +It is defined by the configfs instance name.
> +
>   Options
>   =======
>   
> @@ -68,6 +82,7 @@ Options
>   			virtio	  connect to the next virtio channel available
>   				  (from QEMU with trans_virtio module)
>   			rdma	  connect to a specified RDMA channel
> +			usbg	  connect to a specified usb gadget channel
>   			========  ============================================
>   
>     uname=name	user name to attempt mount as on the remote server.  The
> diff --git a/net/9p/Kconfig b/net/9p/Kconfig
> index bcdab9c23b402..2d7e596e22c3f 100644
> --- a/net/9p/Kconfig
> +++ b/net/9p/Kconfig
> @@ -40,6 +40,12 @@ config NET_9P_XEN
>   	  This builds support for a transport for 9pfs between
>   	  two Xen domains.
>   
> +config NET_9P_USBG
> +	bool "9P USB Gadget Transport"
> +	depends on USB_GADGET
> +	help
> +	  This builds support for a transport for 9pfs over
> +	  usb gadget.
>   
>   config NET_9P_RDMA
>   	depends on INET && INFINIBAND && INFINIBAND_ADDR_TRANS
> diff --git a/net/9p/Makefile b/net/9p/Makefile
> index 1df9b344c30bd..22794a451c3f7 100644
> --- a/net/9p/Makefile
> +++ b/net/9p/Makefile
> @@ -4,6 +4,7 @@ obj-$(CONFIG_NET_9P_FD) += 9pnet_fd.o
>   obj-$(CONFIG_NET_9P_XEN) += 9pnet_xen.o
>   obj-$(CONFIG_NET_9P_VIRTIO) += 9pnet_virtio.o
>   obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
> +obj-$(CONFIG_NET_9P_USBG) += 9pnet_usbg.o
>   
>   9pnet-objs := \
>   	mod.o \
> @@ -23,3 +24,6 @@ obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
>   
>   9pnet_rdma-objs := \
>   	trans_rdma.o \
> +
> +9pnet_usbg-objs := \
> +	trans_usbg.o \
> diff --git a/net/9p/trans_usbg.c b/net/9p/trans_usbg.c
> new file mode 100644
> index 0000000000000..3a84097256837
> --- /dev/null
> +++ b/net/9p/trans_usbg.c
> @@ -0,0 +1,974 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * trans_usbg.c - USB peripheral usb9pfs configuration driver and transport.
> + *
> + * Copyright (C) 2024 Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
> + */
> +
> +/* Gadget usb9pfs only needs two bulk endpoints, and will use the usb9pfs
> + * transport to mount host exported filesystem via usb gadget.
> + */
> +
> +/*     +--------------------------+    |    +--------------------------+
> + *     |  9PFS mounting client    |    |    |  9PFS exporting server   |
> + *  SW |                          |    |    |                          |
> + *     |   (this:trans_usbg)      |    |    |(e.g. diod or nfs-ganesha)|
> + *     +-------------^------------+    |    +-------------^------------+
> + *                   |                 |                  |
> + * ------------------|------------------------------------|-------------
> + *                   |                 |                  |
> + *     +-------------v------------+    |    +-------------v------------+
> + *     |                          |    |    |                          |
> + *  HW |   USB Device Controller  <--------->   USB Host Controller    |
> + *     |                          |    |    |                          |
> + *     +--------------------------+    |    +--------------------------+
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/kernel.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/usb/composite.h>
> +#include <linux/usb/func_utils.h>
> +
> +#include <net/9p/9p.h>
> +#include <net/9p/client.h>
> +#include <net/9p/transport.h>
> +
> +#define DEFAULT_BUFLEN        16384
> +
> +struct f_usb9pfs {
> +	struct p9_client *client;
> +
> +	struct p9_req_t *p9_tx_req;
> +
> +	struct list_head tx_req_list;
> +
> +	/* 9p request lock for en/dequeue */
> +	spinlock_t lock;
> +
> +	struct usb_request *in_req;
> +	struct usb_request *out_req;
> +
> +	struct usb_ep *in_ep;
> +	struct usb_ep *out_ep;
> +
> +	unsigned int buflen;
> +
> +	struct usb_function function;
> +};
> +
> +static inline struct f_usb9pfs *func_to_usb9pfs(struct usb_function *f)
> +{
> +	return container_of(f, struct f_usb9pfs, function);
> +}
> +
> +struct f_usb9pfs_opts {
> +	struct usb_function_instance func_inst;
> +	unsigned int buflen;
> +
> +	struct f_usb9pfs_dev *dev;
> +
> +	/* Read/write access to configfs attributes is handled by configfs.
> +	 *
> +	 * This is to protect the data from concurrent access by read/write
> +	 * and create symlink/remove symlink.
> +	 */
> +	struct mutex lock;
> +	int refcnt;
> +};
> +
> +struct f_usb9pfs_dev {
> +	struct f_usb9pfs *usb9pfs;
> +	struct f_usb9pfs_opts *opts;
> +	char tag[41];
> +	bool inuse;
> +
> +	struct list_head usb9pfs_instance;
> +};
> +
> +static DEFINE_MUTEX(usb9pfs_lock);
> +static struct list_head usbg_instance_list;
> +
> +static int usb9pfs_queue_tx(struct f_usb9pfs *usb9pfs, struct usb_request *req,
> +			    gfp_t gfp_flags)
> +{
> +	struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
> +	int ret = -ENOMEM;
> +
> +	if (!(usb9pfs->p9_tx_req->tc.size % usb9pfs->in_ep->maxpacket))
> +		req->zero = 1;
> +
> +	req->buf = usb9pfs->p9_tx_req->tc.sdata;
> +	req->length = usb9pfs->p9_tx_req->tc.size;
> +
> +	dev_dbg(&cdev->gadget->dev, "%s usb9pfs send --> %d/%d, zero: %d\n",
> +		usb9pfs->in_ep->name, req->actual, req->length, req->zero);
> +
> +	ret = usb_ep_queue(usb9pfs->in_ep, req, gfp_flags);
> +
> +	dev_dbg(&cdev->gadget->dev, "tx submit --> %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int usb9pfs_queue_rx(struct f_usb9pfs *usb9pfs, struct usb_request *req,
> +			    gfp_t gfp_flags)
> +{
> +	struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
> +	int ret = -ENOMEM;
> +
> +	ret = usb_ep_queue(usb9pfs->out_ep, req, gfp_flags);
> +
> +	dev_dbg(&cdev->gadget->dev, "rx submit --> %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int usb9pfs_transmit(struct f_usb9pfs *usb9pfs)
> +{
> +	struct p9_req_t *p9_req = NULL;
> +	unsigned long flags;
> +	int ret = 0;
> +
> +	spin_lock_irqsave(&usb9pfs->lock, flags);
> +
> +	if (usb9pfs->p9_tx_req) {
> +		spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +		return -EBUSY;
> +	}
> +
> +	p9_req = list_first_entry_or_null(&usb9pfs->tx_req_list,
> +					  struct p9_req_t, req_list);
> +	if (!p9_req) {
> +		spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +		return -ENOENT;
> +	}
> +
> +	list_del(&p9_req->req_list);
> +
> +	usb9pfs->p9_tx_req = p9_req;
> +
> +	p9_req_get(usb9pfs->p9_tx_req);
> +
> +	ret = usb9pfs_queue_tx(usb9pfs, usb9pfs->in_req, GFP_ATOMIC);
> +
> +	spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +
> +	return ret;
> +}
> +
> +static void usb9pfs_tx_complete(struct usb_ep *ep, struct usb_request *req)
> +{
> +	struct f_usb9pfs *usb9pfs = ep->driver_data;
> +	struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
> +	int ret = 0;
> +
> +	if (req->status) {
> +		dev_err(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
> +			ep->name, req->status, req->actual, req->length);
> +		return;
> +	}
> +
> +	/* reset zero packages */
> +	req->zero = 0;
> +
> +	dev_dbg(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
> +		ep->name, req->status, req->actual, req->length);
> +
> +	WRITE_ONCE(usb9pfs->p9_tx_req->status, REQ_STATUS_SENT);
> +
> +	p9_req_put(usb9pfs->client, usb9pfs->p9_tx_req);
> +
> +	ret = usb9pfs_queue_rx(usb9pfs, usb9pfs->out_req, GFP_ATOMIC);
> +	if (ret)
> +		return;
> +
> +	return;
> +}
> +
> +static struct p9_req_t *usb9pfs_rx_header(struct f_usb9pfs *usb9pfs, void *buf)
> +{
> +	struct p9_req_t *p9_rx_req;
> +	struct p9_fcall	rc;
> +	int ret;
> +
> +	/* start by reading header */
> +	rc.sdata = buf;
> +	rc.offset = 0;
> +	rc.capacity = P9_HDRSZ;
> +	rc.size = P9_HDRSZ;
> +
> +	p9_debug(P9_DEBUG_TRANS, "mux %p got %zu bytes\n", usb9pfs,
> +		 rc.capacity - rc.offset);
> +
> +	ret = p9_parse_header(&rc, &rc.size, NULL, NULL, 0);
> +	if (ret) {
> +		p9_debug(P9_DEBUG_ERROR,
> +			 "error parsing header: %d\n", ret);
> +		return NULL;
> +	}
> +
> +	p9_debug(P9_DEBUG_TRANS,
> +		 "mux %p pkt: size: %d bytes tag: %d\n",
> +		 usb9pfs, rc.size, rc.tag);
> +
> +	p9_rx_req = p9_tag_lookup(usb9pfs->client, rc.tag);
> +	if (!p9_rx_req || p9_rx_req->status != REQ_STATUS_SENT) {
> +		p9_debug(P9_DEBUG_ERROR, "Unexpected packet tag %d\n", rc.tag);
> +		return NULL;
> +	}
> +
> +	if (rc.size > p9_rx_req->rc.capacity) {
> +		p9_debug(P9_DEBUG_ERROR,
> +			 "requested packet size too big: %d for tag %d with capacity %zd\n",
> +			 rc.size, rc.tag, p9_rx_req->rc.capacity);
> +		p9_req_put(usb9pfs->client, p9_rx_req);
> +		return NULL;
> +	}
> +
> +	if (!p9_rx_req->rc.sdata) {
> +		p9_debug(P9_DEBUG_ERROR,
> +			 "No recv fcall for tag %d (req %p), disconnecting!\n",
> +			 rc.tag, p9_rx_req);
> +		p9_req_put(usb9pfs->client, p9_rx_req);
> +		return NULL;
> +	}
> +
> +	return p9_rx_req;
> +}
> +
> +static void usb9pfs_rx_complete(struct usb_ep *ep, struct usb_request *req)
> +{
> +	struct f_usb9pfs *usb9pfs = ep->driver_data;
> +	struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
> +	struct p9_req_t *p9_rx_req;
> +	unsigned long flags;
> +
> +	if (req->status) {
> +		dev_err(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
> +			ep->name, req->status, req->actual, req->length);
> +		return;
> +	}
> +
> +	p9_rx_req = usb9pfs_rx_header(usb9pfs, req->buf);
> +	if (!p9_rx_req)
> +		return;
> +
> +	memcpy(p9_rx_req->rc.sdata, req->buf, req->actual);
> +
> +	p9_rx_req->rc.size = req->actual;
> +
> +	p9_client_cb(usb9pfs->client, p9_rx_req, REQ_STATUS_RCVD);
> +	p9_req_put(usb9pfs->client, p9_rx_req);
> +
> +	spin_lock_irqsave(&usb9pfs->lock, flags);
> +	usb9pfs->p9_tx_req = NULL;
> +
> +	spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +
> +	usb9pfs_transmit(usb9pfs);
> +
> +	return;
> +}
> +
> +static void disable_ep(struct usb_composite_dev *cdev, struct usb_ep *ep)
> +{
> +	int value;
> +
> +	value = usb_ep_disable(ep);
> +	if (value < 0)
> +		dev_info(&cdev->gadget->dev,
> +			 "disable %s --> %d\n", ep->name, value);
> +}
> +
> +static void disable_usb9pfs(struct f_usb9pfs *usb9pfs)
> +{
> +	struct usb_composite_dev *cdev =
> +		usb9pfs->function.config->cdev;
> +
> +	if (usb9pfs->in_req) {
> +		usb_ep_free_request(usb9pfs->in_ep, usb9pfs->in_req);
> +		usb9pfs->in_req = NULL;
> +	}
> +
> +	if (usb9pfs->out_req) {
> +		usb_ep_free_request(usb9pfs->out_ep, usb9pfs->out_req);
> +		usb9pfs->out_req = NULL;
> +	}
> +
> +	disable_ep(cdev, usb9pfs->in_ep);
> +	disable_ep(cdev, usb9pfs->out_ep);
> +	dev_dbg(&cdev->gadget->dev, "%s disabled\n",
> +		usb9pfs->function.name);
> +}
> +
> +static int alloc_requests(struct usb_composite_dev *cdev,
> +			  struct f_usb9pfs *usb9pfs)
> +{
> +	int ret = 0;
> +
> +	usb9pfs->in_req = usb_ep_alloc_request(usb9pfs->in_ep, GFP_ATOMIC);
> +	if (!usb9pfs->in_req) {
> +		ret = -ENOENT;
> +		goto fail;
> +	}
> +
> +	usb9pfs->out_req = alloc_ep_req(usb9pfs->out_ep, usb9pfs->buflen);
> +	if (!usb9pfs->out_req) {
> +		ret = -ENOENT;
> +		goto fail_in;
> +	}
> +
> +	usb9pfs->in_req->complete = usb9pfs_tx_complete;
> +	usb9pfs->out_req->complete = usb9pfs_rx_complete;
> +
> +	/* length will be set in complete routine */
> +	usb9pfs->in_req->context = usb9pfs;
> +	usb9pfs->out_req->context = usb9pfs;
> +
> +	return ret;
> +
> +fail_in:
> +	usb_ep_free_request(usb9pfs->in_ep, usb9pfs->in_req);
> +fail:
> +	return ret;
> +}
> +
> +static int enable_endpoint(struct usb_composite_dev *cdev,
> +			   struct f_usb9pfs *usb9pfs, struct usb_ep *ep)
> +{
> +	int ret;
> +
> +	ret = config_ep_by_speed(cdev->gadget, &usb9pfs->function, ep);
> +	if (ret)
> +		return ret;
> +
> +	ret = usb_ep_enable(ep);
> +	if (ret < 0)
> +		return ret;
> +
> +	ep->driver_data = usb9pfs;
> +
> +	return ret;
> +}
> +
> +static int
> +enable_usb9pfs(struct usb_composite_dev *cdev, struct f_usb9pfs *usb9pfs)
> +{
> +	int result = 0;
> +
> +	result = enable_endpoint(cdev, usb9pfs, usb9pfs->in_ep);
> +	if (result)
> +		goto out;
> +
> +	result = enable_endpoint(cdev, usb9pfs, usb9pfs->out_ep);
> +	if (result)
> +		goto disable_in;
> +
> +	result = alloc_requests(cdev, usb9pfs);
> +	if (result)
> +		goto disable_out;
> +
> +	dev_dbg(&cdev->gadget->dev, "%s enabled\n", usb9pfs->function.name);
> +	return 0;
> +
> +disable_out:
> +	usb_ep_disable(usb9pfs->out_ep);
> +disable_in:
> +	usb_ep_disable(usb9pfs->in_ep);
> +out:
> +	return result;
> +}
> +
> +static int p9_usbg_create(struct p9_client *client, const char *devname, char *args)
> +{
> +	struct usb_composite_dev *cdev;
> +	struct f_usb9pfs_dev *dev;
> +	struct f_usb9pfs_dev *tmp;
> +	struct f_usb9pfs *usb9pfs;
> +	struct usb_function *f;
> +	int ret = -ENOENT;
> +	int found = 0;
> +
> +	if (!devname)
> +		return -EINVAL;
> +
> +	mutex_lock(&usb9pfs_lock);
> +	list_for_each_entry_safe(dev, tmp, &usbg_instance_list, usb9pfs_instance) {
> +		if (!strncmp(devname, dev->tag, strlen(devname))) {
> +			if (!dev->inuse) {
> +				dev->inuse = true;
> +				found = 1;
> +				break;
> +			}
> +			ret = -EBUSY;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&usb9pfs_lock);
> +
> +	if (!found) {
> +		pr_err("no channels available for device %s\n", devname);
> +		return ret;
> +	}
> +
> +	usb9pfs = dev->usb9pfs;
> +	if (!usb9pfs)
> +		return -EINVAL;
> +
> +	INIT_LIST_HEAD(&usb9pfs->tx_req_list);
> +
> +	spin_lock_init(&usb9pfs->lock);
> +
> +	f = &usb9pfs->function;
> +	cdev = f->config->cdev;
> +
> +	client->trans = (void *)usb9pfs;
> +	client->status = Connected;
> +	usb9pfs->client = client;
> +
> +	client->trans_mod->maxsize = usb9pfs->buflen;
> +
> +	return 0;
> +}
> +
> +static void usb9pfs_clear_tx(struct f_usb9pfs *usb9pfs)
> +{
> +	struct p9_req_t *req;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&usb9pfs->lock, flags);
> +
> +	req = usb9pfs->p9_tx_req;
> +	if (!req) {
> +		spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +		return;
> +	}
> +
> +	if (!req->t_err)
> +		req->t_err = -ECONNRESET;
> +
> +	p9_client_cb(usb9pfs->client, req, REQ_STATUS_ERROR);
> +
> +	usb9pfs->p9_tx_req = NULL;
> +
> +	spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +}
> +
> +static void p9_usbg_close(struct p9_client *client)
> +{
> +	struct f_usb9pfs *usb9pfs;
> +	struct f_usb9pfs_dev *dev;
> +	struct f_usb9pfs_opts *opts;
> +
> +	if (!client)
> +		return;
> +
> +	usb9pfs = client->trans;
> +	if (!usb9pfs)
> +		return;
> +
> +	client->status = Disconnected;
> +
> +	usb9pfs_clear_tx(usb9pfs);
> +
> +	opts = container_of(usb9pfs->function.fi,
> +			    struct f_usb9pfs_opts, func_inst);
> +
> +	dev = opts->dev;
> +
> +	mutex_lock(&usb9pfs_lock);
> +	dev->inuse = false;
> +	mutex_unlock(&usb9pfs_lock);
> +}
> +
> +static int p9_usbg_request(struct p9_client *client, struct p9_req_t *p9_req)
> +{
> +	struct f_usb9pfs *usb9pfs = client->trans;
> +	unsigned long flags;
> +
> +	if (client->status != Connected)
> +		return -EBUSY;
> +
> +	spin_lock_irqsave(&usb9pfs->lock, flags);
> +	list_add_tail(&p9_req->req_list, &usb9pfs->tx_req_list);
> +	spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +
> +	return usb9pfs_transmit(usb9pfs);
> +}
> +
> +static int p9_usbg_cancel(struct p9_client *client, struct p9_req_t *req)
> +{
> +	struct f_usb9pfs *usb9pfs = client->trans;
> +	unsigned long flags;
> +	int ret = 1;
> +
> +	p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);
> +
> +	spin_lock_irqsave(&usb9pfs->lock, flags);
> +
> +	if (req->status == REQ_STATUS_UNSENT) {
> +		list_del(&req->req_list);
> +		WRITE_ONCE(req->status, REQ_STATUS_FLSHD);
> +		p9_req_put(client, req);
> +		ret = 0;
> +	}
> +	spin_unlock_irqrestore(&usb9pfs->lock, flags);
> +
> +	return ret;
> +}
> +
> +static struct p9_trans_module p9_usbg_trans = {
> +	.name = "usbg",
> +	.create = p9_usbg_create,
> +	.close = p9_usbg_close,
> +	.request = p9_usbg_request,
> +	.cancel = p9_usbg_cancel,
> +	.owner = THIS_MODULE,
> +};
> +
> +/*-------------------------------------------------------------------------*/
> +
> +#define USB_PROTOCOL_9PFS	0x09
> +
> +static struct usb_interface_descriptor usb9pfs_intf = {
> +	.bLength =		sizeof(usb9pfs_intf),
> +	.bDescriptorType =	USB_DT_INTERFACE,
> +
> +	.bNumEndpoints =	2,
> +	.bInterfaceClass =	USB_CLASS_VENDOR_SPEC,
> +	.bInterfaceSubClass =	USB_SUBCLASS_VENDOR_SPEC,
> +	.bInterfaceProtocol =   USB_PROTOCOL_9PFS,
> +
> +	/* .iInterface = DYNAMIC */
> +};
> +
> +/* full speed support: */
> +
> +static struct usb_endpoint_descriptor fs_usb9pfs_source_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bEndpointAddress =	USB_DIR_IN,
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +};
> +
> +static struct usb_endpoint_descriptor fs_usb9pfs_sink_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bEndpointAddress =	USB_DIR_OUT,
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +};
> +
> +static struct usb_descriptor_header *fs_usb9pfs_descs[] = {
> +	(struct usb_descriptor_header *)&usb9pfs_intf,
> +	(struct usb_descriptor_header *)&fs_usb9pfs_sink_desc,
> +	(struct usb_descriptor_header *)&fs_usb9pfs_source_desc,
> +	NULL,
> +};
> +
> +/* high speed support: */
> +
> +static struct usb_endpoint_descriptor hs_usb9pfs_source_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +	.wMaxPacketSize =	cpu_to_le16(512),
> +};
> +
> +static struct usb_endpoint_descriptor hs_usb9pfs_sink_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +	.wMaxPacketSize =	cpu_to_le16(512),
> +};
> +
> +static struct usb_descriptor_header *hs_usb9pfs_descs[] = {
> +	(struct usb_descriptor_header *)&usb9pfs_intf,
> +	(struct usb_descriptor_header *)&hs_usb9pfs_source_desc,
> +	(struct usb_descriptor_header *)&hs_usb9pfs_sink_desc,
> +	NULL,
> +};
> +
> +/* super speed support: */
> +
> +static struct usb_endpoint_descriptor ss_usb9pfs_source_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +	.wMaxPacketSize =	cpu_to_le16(1024),
> +};
> +
> +static struct usb_ss_ep_comp_descriptor ss_usb9pfs_source_comp_desc = {
> +	.bLength =		USB_DT_SS_EP_COMP_SIZE,
> +	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
> +	.bMaxBurst =		0,
> +	.bmAttributes =		0,
> +	.wBytesPerInterval =	0,
> +};
> +
> +static struct usb_endpoint_descriptor ss_usb9pfs_sink_desc = {
> +	.bLength =		USB_DT_ENDPOINT_SIZE,
> +	.bDescriptorType =	USB_DT_ENDPOINT,
> +
> +	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
> +	.wMaxPacketSize =	cpu_to_le16(1024),
> +};
> +
> +static struct usb_ss_ep_comp_descriptor ss_usb9pfs_sink_comp_desc = {
> +	.bLength =		USB_DT_SS_EP_COMP_SIZE,
> +	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
> +	.bMaxBurst =		0,
> +	.bmAttributes =		0,
> +	.wBytesPerInterval =	0,
> +};
> +
> +static struct usb_descriptor_header *ss_usb9pfs_descs[] = {
> +	(struct usb_descriptor_header *)&usb9pfs_intf,
> +	(struct usb_descriptor_header *)&ss_usb9pfs_source_desc,
> +	(struct usb_descriptor_header *)&ss_usb9pfs_source_comp_desc,
> +	(struct usb_descriptor_header *)&ss_usb9pfs_sink_desc,
> +	(struct usb_descriptor_header *)&ss_usb9pfs_sink_comp_desc,
> +	NULL,
> +};
> +
> +/* function-specific strings: */
> +static struct usb_string strings_usb9pfs[] = {
> +	[0].s = "usb9pfs input to output",
> +	{  }			/* end of list */
> +};
> +
> +static struct usb_gadget_strings stringtab_usb9pfs = {
> +	.language	= 0x0409,	/* en-us */
> +	.strings	= strings_usb9pfs,
> +};
> +
> +static struct usb_gadget_strings *usb9pfs_strings[] = {
> +	&stringtab_usb9pfs,
> +	NULL,
> +};
> +
> +/*-------------------------------------------------------------------------*/
> +
> +static int usb9pfs_func_bind(struct usb_configuration *c,
> +			     struct usb_function *f)
> +{
> +	struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
> +	struct f_usb9pfs_opts *opts;
> +	struct usb_composite_dev *cdev = c->cdev;
> +	int ret;
> +	int id;
> +
> +	/* allocate interface ID(s) */
> +	id = usb_interface_id(c, f);
> +	if (id < 0)
> +		return id;
> +	usb9pfs_intf.bInterfaceNumber = id;
> +
> +	id = usb_string_id(cdev);
> +	if (id < 0)
> +		return id;
> +	strings_usb9pfs[0].id = id;
> +	usb9pfs_intf.iInterface = id;
> +
> +	/* allocate endpoints */
> +	usb9pfs->in_ep = usb_ep_autoconfig(cdev->gadget,
> +					   &fs_usb9pfs_source_desc);
> +	if (!usb9pfs->in_ep)
> +		goto autoconf_fail;
> +
> +	usb9pfs->out_ep = usb_ep_autoconfig(cdev->gadget,
> +					    &fs_usb9pfs_sink_desc);
> +	if (!usb9pfs->out_ep)
> +		goto autoconf_fail;
> +
> +	/* support high speed hardware */
> +	hs_usb9pfs_source_desc.bEndpointAddress =
> +		fs_usb9pfs_source_desc.bEndpointAddress;
> +	hs_usb9pfs_sink_desc.bEndpointAddress =
> +		fs_usb9pfs_sink_desc.bEndpointAddress;
> +
> +	/* support super speed hardware */
> +	ss_usb9pfs_source_desc.bEndpointAddress =
> +		fs_usb9pfs_source_desc.bEndpointAddress;
> +	ss_usb9pfs_sink_desc.bEndpointAddress =
> +		fs_usb9pfs_sink_desc.bEndpointAddress;
> +
> +	ret = usb_assign_descriptors(f, fs_usb9pfs_descs, hs_usb9pfs_descs,
> +				     ss_usb9pfs_descs, ss_usb9pfs_descs);
> +	if (ret)
> +		return ret;
> +
> +	opts = container_of(f->fi, struct f_usb9pfs_opts, func_inst);
> +	opts->dev->usb9pfs = usb9pfs;
> +
> +	dev_dbg(&cdev->gadget->dev, "%s speed %s: IN/%s, OUT/%s\n",
> +		(gadget_is_superspeed(c->cdev->gadget) ? "super" :
> +		(gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full")),
> +			f->name, usb9pfs->in_ep->name, usb9pfs->out_ep->name);
> +
> +	return 0;
> +
> +autoconf_fail:
> +	ERROR(cdev, "%s: can't autoconfigure on %s\n",
> +	      f->name, cdev->gadget->name);
> +	return -ENODEV;
> +}
> +
> +static void usb9pfs_func_unbind(struct usb_configuration *c,
> +			     struct usb_function *f)
> +{
> +	struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
> +
> +	disable_usb9pfs(usb9pfs);
> +}
> +
> +static void usb9pfs_free_func(struct usb_function *f)
> +{
> +	struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
> +	struct f_usb9pfs_opts *opts;
> +
> +	kfree(usb9pfs);
> +
> +	opts = container_of(f->fi, struct f_usb9pfs_opts, func_inst);
> +
> +	mutex_lock(&opts->lock);
> +	opts->refcnt--;
> +	mutex_unlock(&opts->lock);
> +
> +	usb_free_all_descriptors(f);
> +}
> +
> +static int usb9pfs_set_alt(struct usb_function *f,
> +			   unsigned int intf, unsigned int alt)
> +{
> +	struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
> +	struct usb_composite_dev *cdev = f->config->cdev;
> +
> +	return enable_usb9pfs(cdev, usb9pfs);
> +}
> +
> +static void usb9pfs_disable(struct usb_function *f)
> +{
> +	struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
> +
> +	usb9pfs_clear_tx(usb9pfs);
> +}
> +
> +static struct usb_function *usb9pfs_alloc(struct usb_function_instance *fi)
> +{
> +	struct f_usb9pfs_opts *usb9pfs_opts;
> +	struct f_usb9pfs *usb9pfs;
> +
> +	usb9pfs = kzalloc(sizeof(*usb9pfs), GFP_KERNEL);
> +	if (!usb9pfs)
> +		return ERR_PTR(-ENOMEM);
> +
> +	usb9pfs_opts = container_of(fi, struct f_usb9pfs_opts, func_inst);
> +
> +	mutex_lock(&usb9pfs_opts->lock);
> +	usb9pfs_opts->refcnt++;
> +	mutex_unlock(&usb9pfs_opts->lock);
> +
> +	usb9pfs->buflen = usb9pfs_opts->buflen;
> +
> +	usb9pfs->function.name = "usb9pfs";
> +	usb9pfs->function.bind = usb9pfs_func_bind;
> +	usb9pfs->function.unbind = usb9pfs_func_unbind;
> +	usb9pfs->function.set_alt = usb9pfs_set_alt;
> +	usb9pfs->function.disable = usb9pfs_disable;
> +	usb9pfs->function.strings = usb9pfs_strings;
> +
> +	usb9pfs->function.free_func = usb9pfs_free_func;
> +
> +	return &usb9pfs->function;
> +}
> +
> +static inline struct f_usb9pfs_opts *to_f_usb9pfs_opts(struct config_item *item)
> +{
> +	return container_of(to_config_group(item), struct f_usb9pfs_opts,
> +			    func_inst.group);
> +}
> +
> +static inline struct f_usb9pfs_opts *fi_to_f_usb9pfs_opts(struct usb_function_instance *fi)
> +{
> +	return container_of(fi, struct f_usb9pfs_opts, func_inst);
> +}
> +
> +static void usb9pfs_attr_release(struct config_item *item)
> +{
> +	struct f_usb9pfs_opts *usb9pfs_opts = to_f_usb9pfs_opts(item);
> +
> +	usb_put_function_instance(&usb9pfs_opts->func_inst);
> +}
> +
> +static struct configfs_item_operations usb9pfs_item_ops = {
> +	.release		= usb9pfs_attr_release,
> +};
> +
> +static ssize_t f_usb9pfs_opts_buflen_show(struct config_item *item, char *page)
> +{
> +	struct f_usb9pfs_opts *opts = to_f_usb9pfs_opts(item);
> +	int result;
> +
> +	mutex_lock(&opts->lock);
> +	result = sprintf(page, "%d\n", opts->buflen);
> +	mutex_unlock(&opts->lock);
> +
> +	return result;
> +}
> +
> +static ssize_t f_usb9pfs_opts_buflen_store(struct config_item *item,
> +					   const char *page, size_t len)
> +{
> +	struct f_usb9pfs_opts *opts = to_f_usb9pfs_opts(item);
> +	int ret;
> +	u32 num;
> +
> +	mutex_lock(&opts->lock);
> +	if (opts->refcnt) {
> +		ret = -EBUSY;
> +		goto end;
> +	}
> +
> +	ret = kstrtou32(page, 0, &num);
> +	if (ret)
> +		goto end;
> +
> +	opts->buflen = num;
> +	ret = len;
> +end:
> +	mutex_unlock(&opts->lock);
> +	return ret;
> +}
> +
> +CONFIGFS_ATTR(f_usb9pfs_opts_, buflen);
> +
> +static struct configfs_attribute *usb9pfs_attrs[] = {
> +	&f_usb9pfs_opts_attr_buflen,
> +	NULL,
> +};
> +
> +static const struct config_item_type usb9pfs_func_type = {
> +	.ct_item_ops	= &usb9pfs_item_ops,
> +	.ct_attrs	= usb9pfs_attrs,
> +	.ct_owner	= THIS_MODULE,
> +};
> +
> +static struct f_usb9pfs_dev *_usb9pfs_do_find_dev(const char *tag)
> +{
> +	struct f_usb9pfs_dev *usb9pfs_dev;
> +	struct f_usb9pfs_dev *tmp;
> +
> +	if (!tag)
> +		return NULL;
> +
> +	list_for_each_entry_safe(usb9pfs_dev, tmp, &usbg_instance_list, usb9pfs_instance) {
> +		if (strcmp(usb9pfs_dev->tag, tag) == 0)
> +			return usb9pfs_dev;
> +	}
> +
> +	return NULL;
> +}
> +
> +static int usb9pfs_tag_instance(struct f_usb9pfs_dev *dev, const char *tag)
> +{
> +	struct f_usb9pfs_dev *existing;
> +	int ret = 0;
> +
> +	mutex_lock(&usb9pfs_lock);
> +	existing = _usb9pfs_do_find_dev(tag);
> +	if (!existing)
> +		strscpy(dev->tag, tag, ARRAY_SIZE(dev->tag));
> +	else if (existing != dev)
> +		ret = -EBUSY;
> +	mutex_unlock(&usb9pfs_lock);
> +
> +	return ret;
> +}
> +
> +static int usb9pfs_set_inst_tag(struct usb_function_instance *fi, const char *tag)
> +{
> +	if (strlen(tag) >= sizeof_field(struct f_usb9pfs_dev, tag))
> +		return -ENAMETOOLONG;
> +	return usb9pfs_tag_instance(fi_to_f_usb9pfs_opts(fi)->dev, tag);
> +}
> +
> +static void usb9pfs_free_instance(struct usb_function_instance *fi)
> +{
> +	struct f_usb9pfs_opts *usb9pfs_opts =
> +		container_of(fi, struct f_usb9pfs_opts, func_inst);
> +	struct f_usb9pfs_dev *dev = usb9pfs_opts->dev;
> +
> +	list_del(&dev->usb9pfs_instance);
> +	kfree(usb9pfs_opts);
> +}
> +
> +static struct usb_function_instance *usb9pfs_alloc_instance(void)
> +{
> +	struct f_usb9pfs_opts *usb9pfs_opts;
> +	struct f_usb9pfs_dev *dev;
> +
> +	usb9pfs_opts = kzalloc(sizeof(*usb9pfs_opts), GFP_KERNEL);
> +	if (!usb9pfs_opts)
> +		return ERR_PTR(-ENOMEM);
> +
> +	mutex_init(&usb9pfs_opts->lock);
> +
> +	usb9pfs_opts->func_inst.set_inst_name = usb9pfs_set_inst_tag;
> +	usb9pfs_opts->func_inst.free_func_inst = usb9pfs_free_instance;
> +
> +	usb9pfs_opts->buflen = DEFAULT_BUFLEN;
> +
> +	mutex_lock(&usb9pfs_lock);
> +	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> +	if (IS_ERR(dev)) {
> +		mutex_unlock(&usb9pfs_lock);
> +		kfree(usb9pfs_opts);
> +		return ERR_CAST(dev);
> +	}
> +	list_add_tail(&dev->usb9pfs_instance, &usbg_instance_list);
> +	mutex_unlock(&usb9pfs_lock);
> +
> +	usb9pfs_opts->dev = dev;
> +	dev->opts = usb9pfs_opts;
> +
> +	config_group_init_type_name(&usb9pfs_opts->func_inst.group, "",
> +				    &usb9pfs_func_type);
> +
> +	return &usb9pfs_opts->func_inst;
> +}
> +DECLARE_USB_FUNCTION(usb9pfs, usb9pfs_alloc_instance, usb9pfs_alloc);
> +
> +static int __init usb9pfs_modinit(void)
> +{
> +	int ret;
> +
> +	INIT_LIST_HEAD(&usbg_instance_list);
> +
> +	ret = usb_function_register(&usb9pfsusb_func);
> +	if (!ret)
> +		v9fs_register_trans(&p9_usbg_trans);
> +
> +	return ret;
> +}
> +
> +static void __exit usb9pfs_modexit(void)
> +{
> +	usb_function_unregister(&usb9pfsusb_func);
> +	v9fs_unregister_trans(&p9_usbg_trans);
> +}
> +
> +module_init(usb9pfs_modinit);
> +module_exit(usb9pfs_modexit);
> +
> +MODULE_ALIAS_9P("usbg");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("USB gadget 9pfs transport");
> +MODULE_AUTHOR("Michael Grzeschik");