path: root/drivers/net/usb/qmi_wwan.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2012  Bjørn Mork <bjorn@mork.no>
 *
 * The probing code is heavily inspired by cdc_ether, which is:
 * Copyright (C) 2003-2005 by David Brownell
 * Copyright (C) 2006 by Ole Andre Vadla Ravnas (ActiveSync)
 */

#include <linux/module.h>
#include <linux/sched/signal.h>
#include <linux/netdevice.h>
#include <linux/ethtool.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/kstrtox.h>
#include <linux/mii.h>
#include <linux/rtnetlink.h>
#include <linux/usb.h>
#include <linux/usb/cdc.h>
#include <linux/usb/usbnet.h>
#include <linux/usb/cdc-wdm.h>
#include <linux/u64_stats_sync.h>

/* This driver supports wwan (3G/LTE/?) devices using a vendor
 * specific management protocol called Qualcomm MSM Interface (QMI) -
 * in addition to the more common AT commands over serial interface
 * management
 *
 * QMI is wrapped in CDC, using CDC encapsulated commands on the
 * control ("master") interface of a two-interface CDC Union
 * resembling standard CDC ECM.  The devices do not use the control
 * interface for any other CDC messages.  Most likely because the
 * management protocol is used in place of the standard CDC
 * notifications NOTIFY_NETWORK_CONNECTION and NOTIFY_SPEED_CHANGE
 *
 * Alternatively, control and data functions can be combined in a
 * single USB interface.
 *
 * Handling a protocol like QMI is out of the scope for any driver.
 * It is exported as a character device using the cdc-wdm driver as
 * a subdriver, enabling userspace applications ("modem managers") to
 * handle it.
 *
 * These devices may alternatively/additionally be configured using AT
 * commands on a serial interface
 */

/* driver specific data */
struct qmi_wwan_state {
	struct usb_driver *subdriver;
	atomic_t pmcount;
	unsigned long flags;
	struct usb_interface *control;
	struct usb_interface *data;
};

enum qmi_wwan_flags {
	QMI_WWAN_FLAG_RAWIP = 1 << 0,
	QMI_WWAN_FLAG_MUX = 1 << 1,
	QMI_WWAN_FLAG_PASS_THROUGH = 1 << 2,
};

enum qmi_wwan_quirks {
	QMI_WWAN_QUIRK_DTR = 1 << 0,	/* needs "set DTR" request */
};

struct qmimux_hdr {
	u8 pad;
	u8 mux_id;
	__be16 pkt_len;
};

struct qmimux_priv {
	struct net_device *real_dev;
	u8 mux_id;
};

static int qmimux_open(struct net_device *dev)
{
	struct qmimux_priv *priv = netdev_priv(dev);
	struct net_device *real_dev = priv->real_dev;

	if (!(priv->real_dev->flags & IFF_UP))
		return -ENETDOWN;

	if (netif_carrier_ok(real_dev))
		netif_carrier_on(dev);
	return 0;
}

static int qmimux_stop(struct net_device *dev)
{
	netif_carrier_off(dev);
	return 0;
}

static netdev_tx_t qmimux_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct qmimux_priv *priv = netdev_priv(dev);
	unsigned int len = skb->len;
	struct qmimux_hdr *hdr;
	netdev_tx_t ret;

	hdr = skb_push(skb, sizeof(struct qmimux_hdr));
	hdr->pad = 0;
	hdr->mux_id = priv->mux_id;
	hdr->pkt_len = cpu_to_be16(len);
	skb->dev = priv->real_dev;
	ret = dev_queue_xmit(skb);

	if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN))
		dev_sw_netstats_tx_add(dev, 1, len);
	else
		dev->stats.tx_dropped++;

	return ret;
}

static const struct net_device_ops qmimux_netdev_ops = {
	.ndo_open        = qmimux_open,
	.ndo_stop        = qmimux_stop,
	.ndo_start_xmit  = qmimux_start_xmit,
};

static void qmimux_setup(struct net_device *dev)
{
	dev->header_ops      = NULL;  /* No header */
	dev->type            = ARPHRD_NONE;
	dev->hard_header_len = 0;
	dev->addr_len        = 0;
	dev->flags           = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
	dev->netdev_ops      = &qmimux_netdev_ops;
	dev->mtu             = 1500;
	dev->pcpu_stat_type  = NETDEV_PCPU_STAT_TSTATS;
	dev->needs_free_netdev = true;
}

static struct net_device *qmimux_find_dev(struct usbnet *dev, u8 mux_id)
{
	struct qmimux_priv *priv;
	struct list_head *iter;
	struct net_device *ldev;

	rcu_read_lock();
	netdev_for_each_upper_dev_rcu(dev->net, ldev, iter) {
		priv = netdev_priv(ldev);
		if (priv->mux_id == mux_id) {
			rcu_read_unlock();
			return ldev;
		}
	}
	rcu_read_unlock();
	return NULL;
}

static bool qmimux_has_slaves(struct usbnet *dev)
{
	return !list_empty(&dev->net->adj_list.upper);
}

static int qmimux_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
{
	unsigned int len, offset = 0, pad_len, pkt_len;
	struct qmimux_hdr *hdr;
	struct net_device *net;
	struct sk_buff *skbn;
	u8 qmimux_hdr_sz = sizeof(*hdr);

	while (offset + qmimux_hdr_sz < skb->len) {
		hdr = (struct qmimux_hdr *)(skb->data + offset);
		len = be16_to_cpu(hdr->pkt_len);

		/* drop the packet, bogus length */
		if (offset + len + qmimux_hdr_sz > skb->len)
			return 0;

		/* control packet, we do not know what to do */
		if (hdr->pad & 0x80)
			goto skip;

		/* extract padding length and check for valid length info */
		pad_len = hdr->pad & 0x3f;
		if (len == 0 || pad_len >= len)
			goto skip;
		pkt_len = len