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

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Message-ID: <dcdc22f2-587e-4879-a987-71c92c0149e9@suse.cz>
Date: Thu, 19 Dec 2024 08:53:47 +0100
From: Jiri Slaby <jslaby@...e.cz>
To: Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>, 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>, 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

On 19. 12. 24, 8:45, Ivaylo Dimitrov wrote:
> 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? 

Without code, no.

> Or, shall I ignore that warning?

Definitely not.

thanks,
-- 
js
suse labs