net: usb: qmi_wwan: New driver for Huawei QMI based WWAN devices

Some WWAN LTE/3G devices based on chipsets from Qualcomm provide
near standard CDC ECM interfaces in addition to the usual serial
interfaces.   The Huawei E392/E398 are examples of such devices.

These typically cannot be fully configured using AT commands
over a serial interface.  It is necessary to speak the proprietary
Qualcomm MSM Interface (QMI) protocol to the device to enable the
ethernet proxy functionality.

The devices embed the QMI protocol in CDC on the control interface,
using standard CDC commands and notifications. The do not otherwise
use CDC commands for the ethernet function.  This driver does
therefore not need access to any other aspects of the control
interface than the descriptors attached to it.

Another driver, cdc-wdm, will provide userspace access to the
QMI protocol independently of this driver.  To facilitate this,
this driver avoids binding to the control interface, and uses
only the associated data interface after parsing the common CDC
functional descriptors on the control interface.

You will want both the cdc-wdm and option drivers as companions to
this driver, to have full access to all interfaces and protocols
exported by the device.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 228 insertions, 0 deletions

diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
new file mode 100644
index 00000000000..739e6de7abc
--- /dev/null
+++ b/drivers/net/usb/qmi_wwan.c
@@ -0,0 +1,228 @@
+/*
+ * Copyright (c) 2012  Bjørn Mork <bjorn@mork.no>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/ethtool.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+
+/* The name of the CDC Device Management driver */
+#define DM_DRIVER "cdc_wdm"
+
+/*
+ * 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
+ *
+ * Handling a protocol like QMI is out of the scope for any driver.
+ * It can be exported as a character device using the cdc-wdm driver,
+ * which will enable userspace applications ("modem managers") to
+ * handle it.  This may be required to use the network interface
+ * provided by the driver.
+ *
+ * These devices may alternatively/additionally be configured using AT
+ * commands on any of the serial interfaces driven by the option driver
+ *
+ * This driver binds only to the data ("slave") interface to enable
+ * the cdc-wdm driver to bind to the control interface.  It still
+ * parses the CDC functional descriptors on the control interface to
+ *  a) verify that this is indeed a handled interface (CDC Union
+ *     header lists it as slave)
+ *  b) get MAC address and other ethernet config from the CDC Ethernet
+ *     header
+ *  c) enable user bind requests against the control interface, which
+ *     is the common way to bind to CDC Ethernet Control Model type
+ *     interfaces
+ *  d) provide a hint to the user about which interface is the
+ *     corresponding management interface
+ */
+
+static int qmi_wwan_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+	int status = -1;
+	struct usb_interface *control = NULL;
+	u8 *buf = intf->cur_altsetting->extra;
+	int len = intf->cur_altsetting->extralen;
+	struct usb_interface_descriptor *desc = &intf->cur_altsetting->desc;
+	struct usb_cdc_union_desc *cdc_union = NULL;
+	struct usb_cdc_ether_desc *cdc_ether = NULL;
+	u32 required = 1 << USB_CDC_HEADER_TYPE | 1 << USB_CDC_UNION_TYPE;
+	u32 found = 0;
+
+	/*
+	 * assume a data interface has no additional descriptors and
+	 * that the control and data interface are numbered
+	 * consecutively - this holds for the Huawei device at least
+	 */
+	if (len == 0 && desc->bInterfaceNumber > 0) {
+		control = usb_ifnum_to_if(dev->udev, desc->bInterfaceNumber - 1);
+		if (!control)
+			goto err;
+
+		buf = control->cur_altsetting->extra;
+		len = control->cur_altsetting->extralen;
+		dev_dbg(&intf->dev, "guessing \"control\" => %s, \"data\" => this\n",
+			dev_name(&control->dev));
+	}
+
+	while (len > 3) {
+		struct usb_descriptor_header *h = (void *)buf;
+
+		/* ignore any misplaced descriptors */
+		if (h->bDescriptorType != USB_DT_CS_INTERFACE)
+			goto next_desc;
+
+		/* buf[2] is CDC descriptor subtype */
+		switch (buf[2]) {
+		case USB_CDC_HEADER_TYPE:
+			if (found & 1 << USB_CDC_HEADER_TYPE) {
+				dev_dbg(&intf->dev, "extra CDC header\n");
+				goto err;
+			}
+			if (h->bLength != sizeof(struct usb_cdc_header_desc)) {
+				dev_dbg(&intf->dev, "CDC header len %u\n", h->bLength);
+				goto err;
+			}
+			break;
+		case USB_CDC_UNION_TYPE:
+			if (found & 1 << USB_CDC_UNION_TYPE) {
+				dev_dbg(&intf->dev, "extra CDC union\n");
+				goto err;
+			}
+			if (h->bLength != sizeof(struct usb_cdc_union_desc)) {
+				dev_dbg(&intf->dev, "CDC union len %u\n", h->bLength);
+				goto err;
+			}
+			cdc_union = (struct usb_cdc_union_desc *)buf;
+			break;
+		case USB_CDC_ETHERNET_TYPE:
+			if (found & 1 << USB_CDC_ETHERNET_TYPE) {
+				dev_dbg(&intf->dev, "extra CDC ether\n");
+				goto err;
+			}
+			if (h->bLength != sizeof(struct usb_cdc_ether_desc)) {
+				dev_dbg(&intf->dev, "CDC ether len %u\n",  h->bLength);
+				goto err;
+			}
+			cdc_ether = (struct usb_cdc_ether_desc *)buf;
+			break;
+		}
+
+		/*
+		 * Remember which CDC functional descriptors we've seen.  Works
+		 * for all types we care about, of which USB_CDC_ETHERNET_TYPE
+		 * (0x0f) is the highest numbered
+		 */
+		if (buf[2] < 32)
+			found |= 1 << buf[2];
+
+next_desc:
+		len -= h->bLength;
+		buf += h->bLength;
+	}
+
+	/* did we find all the required ones? */
+	if ((found & required) != required) {
+		dev_err(&intf->dev, "CDC functional descriptors missing\n");
+		goto err;
+	}
+
+	/* give the user a helpful hint if trying to bind to the wrong interface */
+	if (cdc_union && desc->bInterfaceNumber == cdc_union->bMasterInterface0) {
+		dev_err(&intf->dev, "leaving \"control\" interface for " DM_DRIVER " - try binding to %s instead!\n",
+			dev_name(&usb_ifnum_to_if(dev->udev, cdc_union->bSlaveInterface0)->dev));
+		goto err;
+	}
+
+	/* errors aren't fatal - we can live with the dynamic address */
+	if (cdc_ether) {
+		dev->hard_mtu = le16_to_cpu(cdc_ether->wMaxSegmentSize);
+		usbnet_get_ethernet_addr(dev, cdc_ether->iMACAddress);
+	}
+
+	/* success! point the user to the management interface */
+	if (control)
+		dev_info(&intf->dev, "Use \"" DM_DRIVER "\" for QMI interface %s\n",
+			dev_name(&control->dev));
+
+	/* XXX: add a sysfs symlink somewhere to help management applications find it? */
+
+	/* collect bulk endpoints now that we know intf == "data" interface */
+	status = usbnet_get_endpoints(dev, intf);
+
+err:
+	return status;
+}
+
+/* stolen from cdc_ether.c */
+static int qmi_wwan_manage_power(struct usbnet *dev, int on)
+{
+	dev->intf->needs_remote_wakeup = on;
+	return 0;
+}
+
+static const struct driver_info	qmi_wwan_info = {
+	.description	= "QMI speaking wwan device",
+	.flags		= FLAG_WWAN,
+	.bind		= qmi_wwan_bind,
+	.manage_power	= qmi_wwan_manage_power,
+};
+
+#define HUAWEI_VENDOR_ID	0x12D1
+
+static const struct usb_device_id products[] = {
+{
+	/* Huawei E392, E398 and possibly others sharing both device id and more... */
+	.match_flags        = USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_INT_INFO,
+	.idVendor           = HUAWEI_VENDOR_ID,
+	.bInterfaceClass    = USB_CLASS_VENDOR_SPEC,
+	.bInterfaceSubClass = 1,
+	.bInterfaceProtocol = 8, /* NOTE: This is the *slave* interface of the CDC Union! */
+	.driver_info        = (unsigned long)&qmi_wwan_info,
+}, {
+},	/* END */
+};
+MODULE_DEVICE_TABLE(usb, products);
+
+static struct usb_driver qmi_wwan_driver = {
+	.name		      = "qmi_wwan",
+	.id_table	      = products,
+	.probe		      =	usbnet_probe,
+	.disconnect	      = usbnet_disconnect,
+	.suspend	      = usbnet_suspend,
+	.resume		      =	usbnet_resume,
+	.reset_resume         = usbnet_resume,
+	.supports_autosuspend = 1,
+};
+
+static int __init qmi_wwan_init(void)
+{
+	return usb_register(&qmi_wwan_driver);
+}
+module_init(qmi_wwan_init);
+
+static void __exit qmi_wwan_exit(void)
+{
+	usb_deregister(&qmi_wwan_driver);
+}
+module_exit(qmi_wwan_exit);
+
+MODULE_AUTHOR("Bjørn Mork <bjorn@mork.no>");
+MODULE_DESCRIPTION("Qualcomm MSM Interface (QMI) WWAN driver");
+MODULE_LICENSE("GPL");