linux-kernel - Re: [PATCH 1/6] tty: n_gsm: Add support for serdev drivers

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Message-ID: <b9220ab2-0992-41d0-abef-f9ec6e306af1@gmail.com>
Date: Thu, 19 Dec 2024 09:45:56 +0200
From: Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To: Pavel Machek <pavel@....cz>, Johan Hovold <johan@...nel.org>
Cc: Tony Lindgren <tony@...mide.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Rob Herring <robh@...nel.org>, Alan Cox <gnomes@...rguk.ukuu.org.uk>,
 Lee Jones <lee.jones@...aro.org>, Jiri Slaby <jslaby@...e.cz>,
 Merlijn Wajer <merlijn@...zup.org>, Peter Hurley <peter@...leysoftware.com>,
 Sebastian Reichel <sre@...nel.org>, linux-serial@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-omap@...r.kernel.org, phone-devel@...r.kernel.org
Subject: Re: [PATCH 1/6] tty: n_gsm: Add support for serdev drivers

Hi,

...

On 29.11.20 г. 22:51 ч., Pavel Machek wrote:
>>
>> It looks like you may also have a problem with tty hangups, which serdev
>> does not support currently. There are multiple paths in n_gsm which can
>> trigger a hangup (e.g. based on remote input) and would likely lead to a
>> crash
> 
> I don't believe we need to support hangups for the Droid 4, but
> obviously it would be good not to crash. But I don't know where to
> start looking, do you have any hints?
> 

I changed the patch so it calls tty_port_register_device_serdev, ported 
gnss driver to use serdev_device, got it working:

root@...uan-droid4:~# cat /dev/gnss0
$GPGGA,,,,,,0,,,,,,,,*66
$GNGNS,,,,,,NN,,,,,,*53
$GNGNS,,,,,,NN,,,,,,*53
$GNGNS,,,,,,NN,,,,,,*53
$GPVTG,,T,,M,,N,,K,N*2C
$GPRMC,,V,,,,,,,,,,N*53
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GLGSV,1,1,01,255,,,37*52
$GPGGA,,,,,,0,,,,,,,,*66
$GNGNS,,,,,,NN,,,,,,*53
$GNGNS,,,,,,NN,,,,,,*53
$GNGNS,,,,,,NN,,,,,,*53

However, I get:

gsmtty gsmtty4: tty_hangup: tty->count(1) != (#fd's(0) + #kopen's(0))

when closing /dev/gnss0

Any hint what shall be implemented in serdev to properly handle hangups? 
Or, shall I ignore that warning?

Regards,
Ivo