netdev - Re: [PATCH] Add NMEA GPS character device for PCIe MHI Quectel Module to read NMEA statements.

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Message-ID: <aea78599-0d3f-42d9-8f3e-0e90c37a31b8@gmail.com>
Date: Thu, 2 Jan 2025 19:18:46 +0200
From: Sergey Ryazanov <ryazanov.s.a@...il.com>
To: Muhammad Nuzaihan <zaihan@...ealasia.net>
Cc: netdev@...r.kernel.org, Loic Poulain <loic.poulain@...aro.org>,
 Johannes Berg <johannes@...solutions.net>, Andrew Lunn <andrew@...n.ch>,
 Slark Xiao <slark_xiao@....com>
Subject: Re: [PATCH] Add NMEA GPS character device for PCIe MHI Quectel Module
 to read NMEA statements.

Hi Muhammad and welcome to netdev,

On 01.01.2025 23:12, Muhammad Nuzaihan wrote:
> Hi netdev,
> 
> I made a mistake in choosing AT mode IPC, which is incorrect. For NMEA 
> streams it should use LOOPBACK for IPC. If it uses AT, i noticed that 
> using gpsd will cause intermittent IOCTL errors which is caused when 
> gpsd wants to write to the device.
> 
> Attached is the patch.

Do you had a chance to check this discussion: 
https://lore.kernel.org/all/CAMZdPi_MF=-AjTaBZ_HxtwpbQK5+WwR9eXsSvnvK_-O30ff+Tw@mail.gmail.com/

To summarize, an NMEA port suppose to be exported through the GNSS 
subsystem to properly indicate the device class. Still, the port needs 
to be exported through the WWAN subsystem to facilitate a corresponding 
control port discovery. Looks like that the WWAN changes going to be a 
bit more tricky.

> Thank you.
> 
> Signed-off-by: Muhammad Nuzaihan Bin Kamal Luddin <zaihan@...ealasia.net>
> 
> On Thu, Jan 2 2025 at 02:34:03 AM +0800, Muhammad Nuzaihan 
> <zaihan@...ealasia.net> wrote:
>> Hi netdev,
>>
>> I am using a Quectel RM520N-GL *PCIe* (not USB) module which uses the 
>> MHI interface.
>>
>> In /devices/pci0000:00/0000:00:1c.6/0000:08:00.0/mhi0 i can see 
>> "mhi0_NMEA" but the actual NMEA device is missing in /dev and needs a 
>> character device to be useful with tty programs.
>>
>> NMEA statements are a stream of GPS information which is used to tell 
>> the current device location in the console (like minicom).
>>
>> Attached is the patch to ensure a device is registered (as /dev/ 
>> wwan0nmea0) so this device will stream GPS NMEA statements and can be 
>> used to be read by popular GPS tools like gpsd and then tracking with 
>> cgps, xgps, QGIS, etc.
>>
>> Regards,
>> Muhammad Nuzaihan
>>
>> Signed-off-by: Muhammad Nuzaihan Bin Kamal Luddin <zaihan@...ealasia.net>
>>
>