Re: [PATCH net-next] qmi_wwan: set FLAG_SEND_ZLP to avoid network initiated disconnect

On Thu, Dec 14, 2017 at 07:55:50PM +0100, Bjørn Mork wrote:

It has been reported that the dummy byte we add to avoid
ZLPs can be forwarded by the modem to the PGW/GGSN, and that
some operators will drop the connection if this happens.

In theory, QMI devices are based on CDC ECM and should as such
both support ZLPs and silently ignore the dummy byte.  The latter
assumption failed.  Let's test out the first.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
---
I am a bit worried about the effect of this change on all the
devices I can't test myself. But trying it is the only way we
can ever find out....

flag zlp is tested with pids: 9034,9048,904c,9075, 908E,9079,
908A,909F and 90A4. In general, qualcomm usb firmware can
handle zlps.