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

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Date:   Fri, 1 May 2020 22:31:30 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.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
Subject: Re: [PATCH 1/6] tty: n_gsm: Add support for serdev drivers

Hi!

> We can make use of serdev drivers to do simple device drivers for
> TS 27.010 chanels, and we can handle vendor specific protocols on top
> of TS 27.010 with serdev drivers.
> 
> So far this has been tested with Motorola droid4 where there is a custom
> packet numbering protocol on top of TS 27.010 for the MDM6600 modem.
> 
> I initially though about adding the serdev support into a separate file,
> but that will take some refactoring of n_gsm.c. And I'd like to have
> things working first. Then later on we might want to consider splitting
> n_gsm.c into three pieces for core, tty and serdev parts. And then maybe
> the serdev related parts can be just moved to live under something like
> drivers/tty/serdev/protocol/ngsm.c.
> 
> Signed-off-by: Tony Lindgren <tony@...mide.com>

If you fix error path below, you can add:

Reviewed-by: Pavel Machek <pavel@....cz> 

> +static struct gsm_dlci *gsd_dlci_get(struct gsm_serdev *gsd, int line,
> +				     bool allocate)
> +{
> +	struct gsm_mux *gsm;
> +	struct gsm_dlci *dlci;
> +
> +	if (!gsd || !gsd->gsm)
> +		return ERR_PTR(-ENODEV);
> +
> +	gsm = gsd->gsm;
> +
> +	if (line < 1 || line >= 63)
> +		return ERR_PTR(-EINVAL);
> +
> +	mutex_lock(&gsm->mutex);
...
> +	dlci = gsm_dlci_alloc(gsm, line);
> +	if (!dlci) {
> +		gsm = ERR_PTR(-ENOMEM);
> +		goto unlock;

dlci = , or you get nice crash.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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