From: Bjørn Mork <bjorn@xxxxxxx> Date: Thu, 12 Sep 2019 10:42:00 +0200 > A Mediatek based smartphone owner reports problems with USB > tethering in Linux. The verbose USB listing shows a rndis_host > interface pair (e0/01/03 + 10/00/00), but the driver fails to > bind with > > [ 355.960428] usb 1-4: bad CDC descriptors > > The problem is a failsafe test intended to filter out ACM serial > functions using the same 02/02/ff class/subclass/protocol as RNDIS. > The serial functions are recognized by their non-zero bmCapabilities. > > No RNDIS function with non-zero bmCapabilities were known at the time > this failsafe was added. But it turns out that some Wireless class > RNDIS functions are using the bmCapabilities field. These functions > are uniquely identified as RNDIS by their class/subclass/protocol, so > the failing test can safely be disabled. The same applies to the two > types of Misc class RNDIS functions. > > Applying the failsafe to Communication class functions only retains > the original functionality, and fixes the problem for the Mediatek based > smartphone. > > Tow examples of CDC functional descriptors with non-zero bmCapabilities > from Wireless class RNDIS functions are: ... > The Mediatek example is believed to apply to most smartphones with > Mediatek firmware. The ZTE example is most likely also part of a larger > family of devices/firmwares. > > Suggested-by: Lars Melin <larsm17@xxxxxxxxx> > Signed-off-by: Bjørn Mork <bjorn@xxxxxxx> Applied and queued up for -stable, thanks.
