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

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Message-ID: <87374df0kj.fsf@miraculix.mork.no>
Date:   Thu, 14 Dec 2017 22:42:52 +0100
From:   Bjørn Mork <bjorn@...k.no>
To:     Vamsi Samavedam <vskrishn@...eaurora.org>
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

Vamsi Samavedam <vskrishn@...eaurora.org> writes:

> 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.

Thanks.  That's very good to know.


Bjørn