[PATCH] USB: otg hub support is optional

USB OTG devices are not required to support external hubs.  This adds a
configuration option to disable that support.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 14 insertions, 0 deletions

diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index ff03184da403..a08787e253aa 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -99,4 +99,11 @@ config USB_OTG_WHITELIST
           normal Linux-USB hosts do (other than the warning), and is
           convenient for many stages of product development.
 
+config USB_OTG_BLACKLIST_HUB
+        bool "Disable external hubs"
+        depends on USB_OTG
+        help
+          If you say Y here, then Linux will refuse to enumerate
+          external hubs.  OTG hosts are allowed to reduce hardware
+          and software costs by not supporting external hubs.
 
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3c76f7e17c0c..0c87f73f2933 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -836,6 +836,13 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
         desc = intf->cur_altsetting;
         hdev = interface_to_usbdev(intf);
 
+#ifdef  CONFIG_USB_OTG_BLACKLIST_HUB
+        if (hdev->parent) {
+                dev_warn(&intf->dev, "ignoring external hub\n");
+                return -ENODEV;
+        }
+#endif
+
         /* Some hubs have a subclass of 1, which AFAICT according to the */
         /*  specs is not defined, but it works */
         if ((desc->desc.bInterfaceSubClass != 0) &&