netdev - [PATCH v2 net-next 11/13] net: cdc_ncm: do not bind to NCM compatible MBIM devices

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Message-Id: <1350939400-27209-12-git-send-email-bjorn@mork.no>
Date:	Mon, 22 Oct 2012 22:56:38 +0200
From:	Bjørn Mork <bjorn@...k.no>
To:	netdev@...r.kernel.org
Cc:	linux-usb@...r.kernel.org, Oliver Neukum <oliver@...kum.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexey Orishko <alexey.orishko@...il.com>,
	Greg Suarez <gpsuarez2512@...il.com>,
	"Fangxiaozhi (Franko)" <fangxiaozhi@...wei.com>,
	Dan Williams <dcbw@...hat.com>,
	Aleksander Morgado <aleksander@...edo.com>,
	Bjørn Mork <bjorn@...k.no>,
	Greg Suarez <gsuarez@...thmicro.com>
Subject: [PATCH v2 net-next 11/13] net: cdc_ncm: do not bind to NCM compatible MBIM devices

The MBIM specification allows a MBIM device to disguise
itself as NCM for backwards compatibility, using additional
altsettings with different subclass (control) or protocol
(data):

C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=0d Prot=00 Driver=cdc_mbim
E:  Ad=81(I) Atr=03(Int.) MxPS=  64 Ivl=7ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=02(comm.) Sub=0e Prot=00 Driver=cdc_mbim
E:  Ad=81(I) Atr=03(Int.) MxPS=  64 Ivl=7ms
I:  If#= 1 Alt= 0 #EPs= 0 Cls=0a(data ) Sub=00 Prot=01 Driver=cdc_mbim
I:  If#= 1 Alt= 1 #EPs= 2 Cls=0a(data ) Sub=00 Prot=01 Driver=cdc_mbim
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms
I:* If#= 1 Alt= 2 #EPs= 2 Cls=0a(data ) Sub=00 Prot=02 Driver=cdc_mbim
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms

If the MBIM driver is enabled then that should have priority
for devices providing such a NCM 1.0 backward compatibility
mode.

Signed-off-by: Bjørn Mork <bjorn@...k.no>
Signed-off-by: Greg Suarez <gsuarez@...thmicro.com>
---
 drivers/net/usb/cdc_ncm.c |   27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 17b4ba0..0ed03b1 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -563,6 +563,33 @@ static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	int ret;
 
+	/* The MBIM spec defines a NCM compatible default altsetting,
+	 * which we may have matched:
+	 *
+	 *  "Functions that implement both NCM 1.0 and MBIM (an
+	 *   “NCM/MBIM function”) according to this recommendation
+	 *   shall provide two alternate settings for the
+	 *   Communication Interface.  Alternate setting 0, and the
+	 *   associated class and endpoint descriptors, shall be
+	 *   constructed according to the rules given for the
+	 *   Communication Interface in section 5 of [USBNCM10].
+	 *   Alternate setting 1, and the associated class and
+	 *   endpoint descriptors, shall be constructed according to
+	 *   the rules given in section 6 (USB Device Model) of this
+	 *   specification."
+	 *
+	 * Do not bind to such interfaces, allowing cdc_mbim to handle
+	 * them
+	 */
+#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
+	if ((intf->num_altsetting == 2) &&
+	    !usb_set_interface(dev->udev,
+			       intf->cur_altsetting->desc.bInterfaceNumber,
+			       CDC_NCM_COMM_ALTSETTING_MBIM) &&
+	    cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
+		return -ENODEV;
+#endif
+
 	/* NCM data altsetting is always 1 */
 	ret = cdc_ncm_bind_common(dev, intf, 1);
 
-- 
1.7.10.4

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