path: root/net/9p/trans_usbg.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * trans_usbg.c - USB peripheral usb9pfs configuration driver and transport.
 *
 * Copyright (C) 2024 Michael Grzeschik <m.grzeschik@pengutronix.de>
 */

/* 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/cleanup.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs_context.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;

	/* 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;

	struct completion send;
	struct completion received;

	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 p9_req_t *p9_tx_req,
			    gfp_t gfp_flags)
{
	struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
	struct usb_request *req = usb9pfs->in_req;
	int ret;

	if (!(p9_tx_req->tc.size % usb9pfs->in_ep->maxpacket))
		req->zero = 1;

	req->buf = p9_tx_req->tc.sdata;
	req->length = p9_tx_req->tc.size;
	req->context = p9_tx_req;

	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);
	if (ret)
		req->context = NULL;

	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;

	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)
{
	int ret = 0;

	guard(spinlock_irqsave)(&usb9pfs->lock);

	ret = usb9pfs_queue_tx(usb9pfs, p9_req, GFP_ATOMIC);
	if (ret)
		return ret;

	list_del(&p9_req->req_list);

	p9_req_get(p9_req);

	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;
	struct p9_req_t *p9_tx_req = req->context;
	unsigned long flags;

	/* reset zero packages */
	req->zero = 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;
	}

	dev_dbg(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n