netdev - Re:Re: [RFC PATCH v2 0/6] net: wwan: add NMEA port type support

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Message-ID: <e8d7bab.2987.19936a78b86.Coremail.slark_xiao@163.com>
Date: Thu, 11 Sep 2025 10:42:53 +0800 (CST)
From: "Slark Xiao" <slark_xiao@....com>
To: "Loic Poulain" <loic.poulain@....qualcomm.com>
Cc: "Sergey Ryazanov" <ryazanov.s.a@...il.com>,
	"Johannes Berg" <johannes@...solutions.net>,
	"Andrew Lunn" <andrew+netdev@...n.ch>,
	"Eric Dumazet" <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	"Jakub Kicinski" <kuba@...nel.org>,
	"Paolo Abeni" <pabeni@...hat.com>, netdev@...r.kernel.org,
	"Muhammad Nuzaihan" <zaihan@...ealasia.net>,
	"Qiang Yu" <quic_qianyu@...cinc.com>,
	"Manivannan Sadhasivam" <mani@...nel.org>,
	"Johan Hovold" <johan@...nel.org>
Subject: Re:Re: [RFC PATCH v2 0/6] net: wwan: add NMEA port type support


At 2025-06-30 15:30:14, "Loic Poulain" <loic.poulain@....qualcomm.com> wrote:
>Hi Sergey,
>
>
>On Sun, Jun 29, 2025 at 12:07 PM Sergey Ryazanov <ryazanov.s.a@...il.com> wrote:
>>
>> Hi Loic,
>>
>> On 6/29/25 05:50, Loic Poulain wrote:
>> > Hi Sergey,
>> >
>> > On Tue, Jun 24, 2025 at 11:39 PM Sergey Ryazanov <ryazanov.s.a@...il.com> wrote:
>> >> The series introduces a long discussed NMEA port type support for the
>> >> WWAN subsystem. There are two goals. From the WWAN driver perspective,
>> >> NMEA exported as any other port type (e.g. AT, MBIM, QMI, etc.). From
>> >> user space software perspective, the exported chardev belongs to the
>> >> GNSS class what makes it easy to distinguish desired port and the WWAN
>> >> device common to both NMEA and control (AT, MBIM, etc.) ports makes it
>> >> easy to locate a control port for the GNSS receiver activation.
>> >>
>> >> Done by exporting the NMEA port via the GNSS subsystem with the WWAN
>> >> core acting as proxy between the WWAN modem driver and the GNSS
>> >> subsystem.
>> >>
>> >> The series starts from a cleanup patch. Then two patches prepares the
>> >> WWAN core for the proxy style operation. Followed by a patch introding a
>> >> new WWNA port type, integration with the GNSS subsystem and demux. The
>> >> series ends with a couple of patches that introduce emulated EMEA port
>> >> to the WWAN HW simulator.
>> >>
>> >> The series is the product of the discussion with Loic about the pros and
>> >> cons of possible models and implementation. Also Muhammad and Slark did
>> >> a great job defining the problem, sharing the code and pushing me to
>> >> finish the implementation. Many thanks.
>> >>
>> >> Comments are welcomed.
>> >>
>> >> Slark, Muhammad, if this series suits you, feel free to bundle it with
>> >> the driver changes and (re-)send for final inclusion as a single series.
>> >>
>> >> Changes RFCv1->RFCv2:
>> >> * Uniformly use put_device() to release port memory. This made code less
>> >>    weird and way more clear. Thank you, Loic, for noticing and the fix
>> >>    discussion!
>> >
>> > I think you can now send that series without the RFC tag. It looks good to me.
>>
>> Thank you for reviewing it. Do you think it makes sense to introduce new
>> API without an actual user? Ok, we have two drivers potentially ready to
>> use GNSS port type, but they are not yet here. That is why I have send
>> as RFC. On another hand, testing with simulator has not revealed any
>> issue and GNSS port type implementation looks ready to be merged.
>
>Right, we need a proper user for it, I think some MHI PCIe modems already
>have this NMEA port available, so it can easily be added to this PR. For sure
>we will need someone to test this.
>
Hi Loic, Sergey,
Any update about this topic?
If you want to test it, we can provide some help on this. Also, I think the quicinc
center may also do some test. You can contact it with Mani for further details.

Thanks

>> Let's wait a month or so and if no actual driver patch going to be send,
>> then I will resend as formal patch to have the functionality in the
>> kernel in advance.
>
>ack.
>
>Regards,
>Loic