path: root/drivers/usb/gadget/function/u_ether.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * u_ether.c -- Ethernet-over-USB link layer utilities for Gadget stack
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2003-2004 Robert Schwebel, Benedikt Spranger
 * Copyright (C) 2008 Nokia Corporation
 */

/* #define VERBOSE_DEBUG */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/device.h>
#include <linux/ctype.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/if_vlan.h>
#include <linux/string_helpers.h>
#include <linux/usb/composite.h>

#include "u_ether.h"


/*
 * This component encapsulates the Ethernet link glue needed to provide
 * one (!) network link through the USB gadget stack, normally "usb0".
 *
 * The control and data models are handled by the function driver which
 * connects to this code; such as CDC Ethernet (ECM or EEM),
 * "CDC Subset", or RNDIS.  That includes all descriptor and endpoint
 * management.
 *
 * Link level addressing is handled by this component using module
 * parameters; if no such parameters are provided, random link level
 * addresses are used.  Each end of the link uses one address.  The
 * host end address is exported in various ways, and is often recorded
 * in configuration databases.
 *
 * The driver which assembles each configuration using such a link is
 * responsible for ensuring that each configuration includes at most one
 * instance of is network link.  (The network layer provides ways for
 * this single "physical" link to be used by multiple virtual links.)
 */

#define UETH__VERSION	"29-May-2008"

/* Experiments show that both Linux and Windows hosts allow up to 16k
 * frame sizes. Set the max MTU size to 15k+52 to prevent allocating 32k
 * blocks and still have efficient handling. */
#define GETHER_MAX_MTU_SIZE 15412
#define GETHER_MAX_ETH_FRAME_LEN (GETHER_MAX_MTU_SIZE + ETH_HLEN)

struct eth_dev {
	/* lock is held while accessing port_usb
	 */
	spinlock_t		lock;
	struct gether		*port_usb;

	struct net_device	*net;
	struct usb_gadget	*gadget;

	spinlock_t		req_lock;	/* guard {rx,tx}_reqs */
	struct list_head	tx_reqs, rx_reqs;
	atomic_t		tx_qlen;

	struct sk_buff_head	rx_frames;

	unsigned		qmult;

	unsigned		header_len;
	struct sk_buff		*(*wrap)(struct gether *, struct sk_buff *skb);
	int			(*unwrap)(struct gether *,
						struct sk_buff *skb,
						struct sk_buff_head *list);

	struct work_struct	work;

	unsigned long		todo;
#define	WORK_RX_MEMORY		0

	bool			zlp;
	bool			no_skb_reserve;
	bool			ifname_set;
	u8			host_mac[ETH_ALEN];
	u8			dev_mac[ETH_ALEN];
};

/*-------------------------------------------------------------------------*/

#define RX_EXTRA	20	/* bytes guarding against rx overflows */

#define DEFAULT_QLEN	2	/* double buffering by default */

/* use deeper queues at high/super speed */
static inline int qlen(struct usb_gadget *gadget, unsigned qmult)
{
	if (gadget->speed == USB_SPEED_HIGH || gadget->speed >= USB_SPEED_SUPER)
		return qmult * DEFAULT_QLEN;
	else
		return DEFAULT_QLEN;
}

/*-------------------------------------------------------------------------*/

/* NETWORK DRIVER HOOKUP (to the layer above this driver) */

static void eth_get_drvinfo(struct net_device *net, struct ethtool_drvinfo *p)
{
	struct eth_dev *dev = netdev_priv(net);

	strscpy(p->driver, "g_ether", sizeof(p->driver));
	strscpy(p->version, UETH__VERSION, sizeof(p->version));
	strscpy(p->fw_version, dev->gadget->name, sizeof(p->fw_version));
	strscpy(p->bus_info, dev_name(&dev->gadget->dev), sizeof(p->bus_info));
}

/* REVISIT can also support:
 *   - WOL (by tracking suspends and issuing remote wakeup)
 *   - msglevel (implies updated messaging)
 *   - ... probably more ethtool ops
 */

static const struct ethtool_ops ops = {
	.get_drvinfo = eth_get_drvinfo,
	.get_link = ethtool_op_get_link,
};

static void defer_kevent(struct eth_dev *dev, int flag)
{
	if (test_and_set_bit(flag, &dev->todo))
		return;
	if (!schedule_work(&dev->work))
		ERROR(dev, "kevent %d may have been dropped\n", flag);
	else
		DBG(dev, "kevent %d scheduled\n", flag);
}

static void rx_complete