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

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Message-ID: <20171214213959.GC21058@vskrishn2-linux.qualcomm.com>
Date:   Thu, 14 Dec 2017 13:39:59 -0800
From:   Vamsi Samavedam <vskrishn@...eaurora.org>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     netdev@...r.kernel.org, linux-usb@...r.kernel.org
Subject: 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@...k.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.