This adds a new configfs attribute named `use_ms_rndiscmp`. It is a
boolean value that is used to select the class/subclass/protocol used
by the RNDIS function interface association descriptor. By default,
this is 0x02 (Comm), 0x06 (Ethernet), 0xff (None). When the
use_ms_rndiscmp attribute is set to true, the values 0xef (Misc),
0x04 (RNDIS), 0x01 (Ethernet) will be used instead. This class/subclass/
protocol combination is recognized by the rndiscmp.inf file in Windows
Vista and newer and will cause Windows to load the correct RNDIS driver
without the need for a custom (signed) .inf file.

Signed-off-by: David Lechner <da...@lechnology.com>
---
 .../ABI/testing/configfs-usb-gadget-rndis          |  3 ++
 drivers/usb/gadget/function/f_rndis.c              | 48 ++++++++++++++++++++++
 drivers/usb/gadget/function/u_rndis.h              |  1 +
 include/uapi/linux/usb/misc.h                      | 14 +++++++
 4 files changed, 66 insertions(+)
 create mode 100644 include/uapi/linux/usb/misc.h

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-rndis 
b/Documentation/ABI/testing/configfs-usb-gadget-rndis
index e32879b..bb4b5a85 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-rndis
+++ b/Documentation/ABI/testing/configfs-usb-gadget-rndis
@@ -12,3 +12,6 @@ Description:
                                Ethernet over USB link
                dev_addr        - MAC address of device's end of this
                                Ethernet over USB link
+               use_ms_rndiscmp - Use the MS Windows rndiscmp.inf compatible
+                               class 0xEF, subclass 0x04, protocol 0x01
+                               instead of the default 0x02/0x06/0x00.
diff --git a/drivers/usb/gadget/function/f_rndis.c 
b/drivers/usb/gadget/function/f_rndis.c
index 16562e4..b92f4f4 100644
--- a/drivers/usb/gadget/function/f_rndis.c
+++ b/drivers/usb/gadget/function/f_rndis.c
@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/etherdevice.h>
+#include <linux/usb/misc.h>
 
 #include <linux/atomic.h>
 
@@ -692,6 +693,18 @@ rndis_bind(struct usb_configuration *c, struct 
usb_function *f)
        }
 
        /*
+        * Starting with Vista, Windows will match this Class/SubClass/Protocol
+        * with rndiscmp.inf and load the proper driver without the need for a
+        * custom .inf.
+        * Ref: https://msdn.microsoft.com/library/ff538820(v=vs.85).aspx
+        */
+       if (rndis_opts->use_ms_rndiscmp) {
+               rndis_iad_descriptor.bFunctionClass = USB_CLASS_MISC;
+               rndis_iad_descriptor.bFunctionSubClass = 
USB_MISC_SUBCLASS_RNDIS;
+               rndis_iad_descriptor.bFunctionProtocol = 
USB_MISC_RNDIS_PROTO_ENET;
+       }
+
+       /*
         * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
         * configurations are bound in sequence with list_for_each_entry,
         * in each configuration its functions are bound in sequence
@@ -866,11 +879,46 @@ USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(rndis);
 /* f_rndis_opts_ifname */
 USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(rndis);
 
+static ssize_t
+rndis_opts_use_ms_rndiscmp_show(struct config_item *item, char *page)
+{
+       struct f_rndis_opts *opts = to_f_rndis_opts(item);
+       int ret;
+
+       mutex_lock(&opts->lock);
+       ret = sprintf(page, "%d\n", opts->use_ms_rndiscmp);
+       mutex_unlock(&opts->lock);
+
+       return ret;
+}
+
+static ssize_t
+rndis_opts_use_ms_rndiscmp_store(struct config_item *item, const char *page,
+                                size_t len)
+{
+       struct f_rndis_opts *opts = to_f_rndis_opts(item);
+       int ret;
+       bool use;
+
+       mutex_lock(&opts->lock);
+       ret = strtobool(page, &use);
+       if (!ret) {
+               opts->use_ms_rndiscmp = use;
+               ret = len;
+       }
+       mutex_unlock(&opts->lock);
+
+       return ret;
+}
+
+CONFIGFS_ATTR(rndis_opts_, use_ms_rndiscmp);
+
 static struct configfs_attribute *rndis_attrs[] = {
        &rndis_opts_attr_dev_addr,
        &rndis_opts_attr_host_addr,
        &rndis_opts_attr_qmult,
        &rndis_opts_attr_ifname,
+       &rndis_opts_attr_use_ms_rndiscmp,
        NULL,
 };
 
diff --git a/drivers/usb/gadget/function/u_rndis.h 
b/drivers/usb/gadget/function/u_rndis.h
index 4eafd50..03f241f 100644
--- a/drivers/usb/gadget/function/u_rndis.h
+++ b/drivers/usb/gadget/function/u_rndis.h
@@ -25,6 +25,7 @@ struct f_rndis_opts {
        struct net_device               *net;
        bool                            bound;
        bool                            borrowed_net;
+       bool                            use_ms_rndiscmp;
 
        struct usb_os_desc              rndis_os_desc;
        char                            rndis_ext_compat_id[16];
diff --git a/include/uapi/linux/usb/misc.h b/include/uapi/linux/usb/misc.h
new file mode 100644
index 0000000..a6661f6
--- /dev/null
+++ b/include/uapi/linux/usb/misc.h
@@ -0,0 +1,14 @@
+/*
+ * USB Miscellaneous Device Class definitions
+ *
+ * Ref: http://www.usb.org/developers/defined_class/#BaseClassEFh
+ */
+
+#ifndef __UAPI_LINUX_USB_MISC_H
+#define __UAPI_LINUX_USB_MISC_H
+
+#define USB_MISC_SUBCLASS_RNDIS                        0x04
+
+#define USB_MISC_RNDIS_PROTO_ENET              0x01
+
+#endif /* __UAPI_LINUX_USB_MISC_H */
-- 
2.7.4

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