4 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 3210540f8bd3..237acab169dd 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -131,6 +131,7 @@ Code  Seq#(hex)	Include File		Comments
 'H'     40-4F   sound/hdspm.h           conflict!
 'H'     40-4F   sound/hdsp.h            conflict!
 'H'     90      sound/usb/usx2y/usb_stream.h
+'H'     A0      uapi/linux/usb/cdc-wdm.h
 'H'     C0-F0   net/bluetooth/hci.h     conflict!
 'H'     C0-DF   net/bluetooth/hidp/hidp.h       conflict!
 'H'     C0-DF   net/bluetooth/cmtp/cmtp.h       conflict!
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 122d056d96d5..8a230f0ef77c 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -13,6 +13,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/ioctl.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -644,6 +645,22 @@ static int wdm_release(struct inode *inode, struct file *file)
         return 0;
 }
 
+static long wdm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        struct wdm_device *desc = file->private_data;
+        int rv = 0;
+
+        switch (cmd) {
+        case IOCTL_WDM_MAX_COMMAND:
+                if (copy_to_user((void __user *)arg, &desc->wMaxCommand, sizeof(desc->wMaxCommand)))
+                        rv = -EFAULT;
+                break;
+        default:
+                rv = -ENOTTY;
+        }
+        return rv;
+}
+
 static const struct file_operations wdm_fops = {
         .owner =        THIS_MODULE,
         .read =         wdm_read,
@@ -652,6 +669,8 @@ static const struct file_operations wdm_fops = {
         .flush =        wdm_flush,
         .release =      wdm_release,
         .poll =         wdm_poll,
+        .unlocked_ioctl = wdm_ioctl,
+        .compat_ioctl = wdm_ioctl,
         .llseek =       noop_llseek,
 };
 
diff --git a/include/linux/usb/cdc-wdm.h b/include/linux/usb/cdc-wdm.h
index 719c332620fa..0b3f4295c025 100644
--- a/include/linux/usb/cdc-wdm.h
+++ b/include/linux/usb/cdc-wdm.h
@@ -11,6 +11,8 @@
 #ifndef __LINUX_USB_CDC_WDM_H
 #define __LINUX_USB_CDC_WDM_H
 
+#include <uapi/linux/usb/cdc-wdm.h>
+
 extern struct usb_driver *usb_cdc_wdm_register(struct usb_interface *intf,
                                         struct usb_endpoint_descriptor *ep,
                                         int bufsize,
diff --git a/include/uapi/linux/usb/cdc-wdm.h b/include/uapi/linux/usb/cdc-wdm.h
new file mode 100644
index 000000000000..f03134feebd6
--- /dev/null
+++ b/include/uapi/linux/usb/cdc-wdm.h
@@ -0,0 +1,21 @@
+/*
+ * USB CDC Device Management userspace API definitions
+ *
+ * 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.
+ */
+
+#ifndef _UAPI__LINUX_USB_CDC_WDM_H
+#define _UAPI__LINUX_USB_CDC_WDM_H
+
+/*
+ * This IOCTL is used to retrieve the wMaxCommand for the device,
+ * defining the message limit for both reading and writing.
+ *
+ * For CDC WDM functions this will be the wMaxCommand field of the
+ * Device Management Functional Descriptor.
+ */
+#define IOCTL_WDM_MAX_COMMAND _IOR('H', 0xA0, __u16)
+
+#endif /* _UAPI__LINUX_USB_CDC_WDM_H */