linux-kernel - Re: [PATCH v3 1/3] leds: triggers: provide led_trigger_register

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Date:   Sat, 12 May 2018 20:59:28 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Pavel Machek <pavel@....cz>
Cc:     linux-arm-kernel@...ts.infradead.org,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>, linux-can@...r.kernel.org,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-serial@...r.kernel.org, Jiri Slaby <jslaby@...e.com>,
        Robin Murphy <robin.murphy@....com>, linux-leds@...r.kernel.org
Subject: Re: [PATCH v3 1/3] leds: triggers: provide
 led_trigger_register_format()

On Thu, May 10, 2018 at 01:22:29PM +0200, Pavel Machek wrote:
> On Thu 2018-05-10 13:21:01, Pavel Machek wrote:
> > Hi!
> > 
> > > This allows one to simplify drivers that provide a trigger with a
> > > non-constant name (e.g. one trigger per device with the trigger name
> > > depending on the device's name).
> > > 
> > > Internally the memory the name member of struct led_trigger points to
> > > now always allocated dynamically instead of just taken from the caller.
> > > 
> > > The function led_trigger_rename_static() must be changed accordingly and
> > > was renamed to led_trigger_rename() for consistency, with the only user
> > > adapted.
> > 
> > Well, I'm not sure if we want to have _that_ many trigger. Trigger
> > interface is going to become.. "interesting".
> > 
> > We have 4K limit on total number of triggers. We use rather strange
> > interface to select trigger.
> > 
> > > @@ -115,13 +115,13 @@ static int can_led_notifier(struct notifier_block *nb, unsigned long msg,
> > >  
> > >  	if (msg == NETDEV_CHANGENAME) {
> > >  		snprintf(name, sizeof(name), "%s-tx", netdev->name);
> > > -		led_trigger_rename_static(name, priv->tx_led_trig);
> > > +		led_trigger_rename(priv->tx_led_trig, name);
> > >  
> > >  		snprintf(name, sizeof(name), "%s-rx", netdev->name);
> > > -		led_trigger_rename_static(name, priv->rx_led_trig);
> > > +		led_trigger_rename(priv->rx_led_trig, name);
> > >  
> > >  		snprintf(name, sizeof(name), "%s-rxtx", netdev->name);
> > > -		led_trigger_rename_static(name, priv->rxtx_led_trig);
> > > +		led_trigger_rename(priv->rxtx_led_trig, name);
> > >  	}
> > >  
> > 
> > I know this is not your fault, but if you have a space or "[]" in
> > netdev names, confusing things will happen.
> 
> Hmm. If we are doing this we really should check trigger names for
> forbidden characters. At least "[] " should be forbidden.

I think you don't expect me to change the patch, but to make this
explicit: My patch doesn't make this problem worse, so this would be an
orthogonal change and doesn't affect this one.

Spaces don't seem to be allowed in netdev names:

uwe@...rus:~$ sudo ip link set wlp3s0 name 'la la'
Error: argument "la la" is wrong: "name" not a valid ifname

(Didn't check if only ip forbids that, of if that is a kernel policy.) I
could rename my device to "lala[]" though.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |