net: cdc_ncm/cdc_mbim: rework probing of NCM/MBIM functions

The NCM class match in the cdc_mbim driver is confusing and
cause unexpected behaviour. The USB core guarantees that a
USB interface is in altsetting 0 when probing starts. This
means that devices implementing a NCM 1.0 backwards
compatible MBIM function (a "NCM/MBIM function") always hit
the NCM entry in the cdc_mbim driver match table. Such
functions will never match any of the MBIM entries.

This causes unexpeced behaviour for cases where the NCM and
MBIM entries are differet, which is currently the case for
all except Ericsson devices.

Improve the probing of NCM/MBIM functions by looking up the
device again in the cdc_mbim match table after switching to
the MBIM identity.

The shared altsetting selection is updated to better
accommodate the new probing logic, returning the preferred
altsetting for the control interface instead of the data
interface. The control interface altsetting update is moved
to the cdc_mbim driver. It is never necessary to change the
control interface altsetting for NCM.

Cc: Greg Suarez <gsuarez@smithmicro.com>
Reported by: Yu-an Shih <yshih@nvidia.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 44b38b92236a..55b6feead93b 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -121,7 +121,7 @@ struct cdc_ncm_ctx {
 	u16 connected;
 };
 
-u8 cdc_ncm_select_altsetting(struct usbnet *dev, struct usb_interface *intf);
+u8 cdc_ncm_select_altsetting(struct usb_interface *intf);
 int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting);
 void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf);
 struct sk_buff *cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign);