caif: Add support for CAIF over CDC NCM USB interface

NCM 1.0 does not support anything but Ethernet framing, hence
CAIF payload will be put into Ethernet frames.

Discovery is based on fixed USB vendor 0x04cc (ST-Ericsson),
product-id 0x230f (NCM). In this variant only CAIF payload is sent over
the NCM interface.

The CAIF stack (cfusbl.c) will when USB interface register first check if
we got a CDC NCM USB interface with the right VID, PID.
It will then read the device's Ethernet address and create a 'template'
Ethernet TX header, using a broadcast address as the destination address,
and EthType 0x88b5 (802.1 Local Experimental - vendor specific).

A protocol handler for 0x88b5 is setup for reception of CAIF frames from
the CDC NCM USB interface.

Signed-off-by: Sjur Brændeland <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/caif/Kconfig

···
 	If you select to build it as a built-in then the main CAIF device must
 	also be a built-in.
 	If unsure say Y.
+
+config CAIF_USB
+	tristate "CAIF USB support"
+	depends on CAIF
+	default n
+	---help---
+	Say Y if you are using CAIF over USB CDC NCM.
+	This can be either built-in or a loadable module,
+	If you select to build it as a built-in then the main CAIF device must
+	also be a built-in.
+	If unsure say N.

net/caif/Makefile

···
 obj-$(CONFIG_CAIF) += caif.o
 obj-$(CONFIG_CAIF_NETDEV) += chnl_net.o
 obj-$(CONFIG_CAIF) += caif_socket.o
+obj-$(CONFIG_CAIF_USB) += caif_usb.o
 
 export-y := caif.o

net/caif/caif_dev.c

···
 	if (rcv_func)
 		*rcv_func = receive;
 }
+EXPORT_SYMBOL(caif_enroll_dev);
 
 /* notify Caif of device events */
 static int caif_device_notify(struct notifier_block *me, unsigned long what,

net/caif/caif_usb.c

···
+/*
+ * CAIF USB handler
+ * Copyright (C) ST-Ericsson AB 2011
+ * Author:	Sjur Brendeland/[e-mail]
+ * License terms: GNU General Public License (GPL) version 2
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/usbnet.h>
+#include <net/netns/generic.h>
+#include <net/caif/caif_dev.h>
+#include <net/caif/caif_layer.h>
+#include <net/caif/cfpkt.h>
+#include <net/caif/cfcnfg.h>
+
+MODULE_LICENSE("GPL");
+
+#define CFUSB_PAD_DESCR_SZ 1	/* Alignment descriptor length */
+#define CFUSB_ALIGNMENT 4	/* Number of bytes to align. */
+#define CFUSB_MAX_HEADLEN (CFUSB_PAD_DESCR_SZ + CFUSB_ALIGNMENT-1)
+#define STE_USB_VID 0x04cc	/* USB Product ID for ST-Ericsson */
+#define STE_USB_PID_CAIF 0x2306	/* Product id for CAIF Modems */
+
+struct cfusbl {
+	struct cflayer layer;
+	u8 tx_eth_hdr[ETH_HLEN];
+};
+
+static bool pack_added;
+
+static int cfusbl_receive(struct cflayer *layr, struct cfpkt *pkt)
+{
+	u8 hpad;
+
+	/* Remove padding. */
+	cfpkt_extr_head(pkt, &hpad, 1);
+	cfpkt_extr_head(pkt, NULL, hpad);
+	return layr->up->receive(layr->up, pkt);
+}
+
+static int cfusbl_transmit(struct cflayer *layr, struct cfpkt *pkt)
+{
+	struct caif_payload_info *info;
+	u8 hpad;
+	u8 zeros[CFUSB_ALIGNMENT];
+	struct sk_buff *skb;
+	struct cfusbl *usbl = container_of(layr, struct cfusbl, layer);
+
+	skb = cfpkt_tonative(pkt);
+
+	skb_reset_network_header(skb);
+	skb->protocol = htons(ETH_P_IP);
+
+	info = cfpkt_info(pkt);
+	hpad = (info->hdr_len + CFUSB_PAD_DESCR_SZ) & (CFUSB_ALIGNMENT - 1);
+
+	if (skb_headroom(skb) < ETH_HLEN + CFUSB_PAD_DESCR_SZ + hpad) {
+		pr_warn("Headroom to small\n");
+		kfree_skb(skb);
+		return -EIO;
+	}
+	memset(zeros, 0, hpad);
+
+	cfpkt_add_head(pkt, zeros, hpad);
+	cfpkt_add_head(pkt, &hpad, 1);
+	cfpkt_add_head(pkt, usbl->tx_eth_hdr, sizeof(usbl->tx_eth_hdr));
+	return layr->dn->transmit(layr->dn, pkt);
+}
+
+static void cfusbl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
+					int phyid)
+{
+	if (layr->up && layr->up->ctrlcmd)
+		layr->up->ctrlcmd(layr->up, ctrl, layr->id);
+}
+
+struct cflayer *cfusbl_create(int phyid, u8 ethaddr[ETH_ALEN],
+					u8 braddr[ETH_ALEN])
+{
+	struct cfusbl *this = kmalloc(sizeof(struct cfusbl), GFP_ATOMIC);
+
+	if (!this) {
+		pr_warn("Out of memory\n");
+		return NULL;
+	}
+	caif_assert(offsetof(struct cfusbl, layer) == 0);
+
+	memset(this, 0, sizeof(struct cflayer));
+	this->layer.receive = cfusbl_receive;
+	this->layer.transmit = cfusbl_transmit;
+	this->layer.ctrlcmd = cfusbl_ctrlcmd;
+	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "usb%d", phyid);
+	this->layer.id = phyid;
+
+	/*
+	 * Construct TX ethernet header:
+	 *	0-5	destination address
+	 *	5-11	source address
+	 *	12-13	protocol type
+	 */
+	memcpy(&this->tx_eth_hdr[ETH_ALEN], braddr, ETH_ALEN);
+	memcpy(&this->tx_eth_hdr[ETH_ALEN], ethaddr, ETH_ALEN);
+	this->tx_eth_hdr[12] = cpu_to_be16(ETH_P_802_EX1) & 0xff;
+	this->tx_eth_hdr[13] = (cpu_to_be16(ETH_P_802_EX1) >> 8) & 0xff;
+	pr_debug("caif ethernet TX-header dst:%pM src:%pM type:%02x%02x\n",
+			this->tx_eth_hdr, this->tx_eth_hdr + ETH_ALEN,
+			this->tx_eth_hdr[12], this->tx_eth_hdr[13]);
+
+	return (struct cflayer *) this;
+}
+
+static struct packet_type caif_usb_type __read_mostly = {
+	.type = cpu_to_be16(ETH_P_802_EX1),
+};
+
+static int cfusbl_device_notify(struct notifier_block *me, unsigned long what,
+			      void *arg)
+{
+	struct net_device *dev = arg;
+	struct caif_dev_common common;
+	struct cflayer *layer, *link_support;
+	struct usbnet	*usbnet = netdev_priv(dev);
+	struct usb_device	*usbdev = usbnet->udev;
+	struct ethtool_drvinfo drvinfo;
+
+	/*
+	 * Quirks: High-jack ethtool to find if we have a NCM device,
+	 * and find it's VID/PID.
+	 */
+	if (dev->ethtool_ops == NULL || dev->ethtool_ops->get_drvinfo == NULL)
+		return 0;
+
+	dev->ethtool_ops->get_drvinfo(dev, &drvinfo);
+	if (strncmp(drvinfo.driver, "cdc_ncm", 7) != 0)
+		return 0;
+
+	pr_debug("USB CDC NCM device VID:0x%4x PID:0x%4x\n",
+		le16_to_cpu(usbdev->descriptor.idVendor),
+		le16_to_cpu(usbdev->descriptor.idProduct));
+
+	/* Check for VID/PID that supports CAIF */
+	if (!(le16_to_cpu(usbdev->descriptor.idVendor) == STE_USB_VID &&
+		le16_to_cpu(usbdev->descriptor.idProduct) == STE_USB_PID_CAIF))
+		return 0;
+
+	if (what == NETDEV_UNREGISTER)
+		module_put(THIS_MODULE);
+
+	if (what != NETDEV_REGISTER)
+		return 0;
+
+	__module_get(THIS_MODULE);
+
+	memset(&common, 0, sizeof(common));
+	common.use_frag = false;
+	common.use_fcs = false;
+	common.use_stx = false;
+	common.link_select = CAIF_LINK_HIGH_BANDW;
+	common.flowctrl = NULL;
+
+	link_support = cfusbl_create(dev->ifindex, dev->dev_addr,
+					dev->broadcast);
+
+	if (!link_support)
+		return -ENOMEM;
+
+	if (dev->num_tx_queues > 1)
+		pr_warn("USB device uses more than one tx queue\n");
+
+	caif_enroll_dev(dev, &common, link_support, CFUSB_MAX_HEADLEN,
+			&layer, &caif_usb_type.func);
+	if (!pack_added)
+		dev_add_pack(&caif_usb_type);
+	pack_added = 1;
+
+	strncpy(layer->name, dev->name,
+			sizeof(layer->name) - 1);
+	layer->name[sizeof(layer->name) - 1] = 0;
+
+	return 0;
+}
+
+static struct notifier_block caif_device_notifier = {
+	.notifier_call = cfusbl_device_notify,
+	.priority = 0,
+};
+
+static int __init cfusbl_init(void)
+{
+	return register_netdevice_notifier(&caif_device_notifier);
+}
+
+static void __exit cfusbl_exit(void)
+{
+	unregister_netdevice_notifier(&caif_device_notifier);
+	dev_remove_pack(&caif_usb_type);
+}
+
+module_init(cfusbl_init);
+module_exit(cfusbl_exit);

net/caif/cfpkt_skbuff.c

···
 	return (struct cfpkt *) skb;
 }
 
-
 struct cfpkt *cfpkt_fromnative(enum caif_direction dir, void *nativepkt)
 {
 	struct cfpkt *pkt = skb_to_pkt(nativepkt);
···
 	kfree_skb(skb);
 }
 
-
 inline bool cfpkt_more(struct cfpkt *pkt)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	return skb->len > 0;
 }
-
 
 int cfpkt_peek_head(struct cfpkt *pkt, void *data, u16 len)
 {
···
 		memcpy(data, from, len);
 	return 0;
 }
+EXPORT_SYMBOL(cfpkt_extr_head);
 
 int cfpkt_extr_trail(struct cfpkt *pkt, void *dta, u16 len)
 {
···
 	return 0;
 }
 
-
 int cfpkt_pad_trail(struct cfpkt *pkt, u16 len)
 {
 	return cfpkt_add_body(pkt, NULL, len);
 }
-
 
 int cfpkt_add_body(struct cfpkt *pkt, const void *data, u16 len)
 {
···
 	memcpy(to, data, len);
 	return 0;
 }
-
+EXPORT_SYMBOL(cfpkt_add_head);
 
 inline int cfpkt_add_trail(struct cfpkt *pkt, const void *data, u16 len)
 {
 	return cfpkt_add_body(pkt, data, len);
 }
 
-
 inline u16 cfpkt_getlen(struct cfpkt *pkt)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	return skb->len;
 }
-
 
 inline u16 cfpkt_iterate(struct cfpkt *pkt,
 			    u16 (*iter_func)(u16, void *, u16),
···
 	}
 	return iter_func(data, pkt->skb.data, cfpkt_getlen(pkt));
 }
-
 
 int cfpkt_setlen(struct cfpkt *pkt, u16 len)
 {
···
 {
 	return (struct caif_payload_info *)&pkt_to_skb(pkt)->cb;
 }
+EXPORT_SYMBOL(cfpkt_info);