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List:       devicetree
Subject:    Re: [PATCH v3 2/2] i2c: Add GPIO-based hotplug gate
From:       Michał_Mirosław <mirq-linux () rere ! qmqm ! pl>
Date:       2023-07-31 23:01:43
Message-ID: ZMg9VwKxXBm94YRl () qmqm ! qmqm ! pl
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On Mon, Jul 31, 2023 at 12:11:47AM +0200, Michał Mirosław wrote:
> On Sun, Jul 30, 2023 at 10:25:07PM +0200, Andi Shyti wrote:
> > On Sat, Jul 29, 2023 at 07:08:57PM +0300, Svyatoslav Ryhel wrote:
> > > +static int i2c_hotplug_activate(struct i2c_hotplug_priv *priv)
> [...]
> > > +{
> > > +	int ret;
> > > +
> > > +	if (priv->adap.algo_data)
> > > +		return 0;
> [...]
> > > +	ret = i2c_add_adapter(&priv->adap);
> > > +	if (!ret)
> > > +		priv->adap.algo_data = (void *)1;
> > 
> > You want to set algo_data to "1" in order to keep the
> > activate/deactivate ordering.
> > 
> > But if we fail to add the adapter, what's the point to keep it
> > active?
> 
> The code above does "if we added the adapter, remember we did so".
> IOW, if we failed to add the adapter we don't set the mark so that
> the next interrupt edge can trigger another try. Also we prevent
> trying to remove an adapter we didn't successfully add.

Maybe the function's name is misleading? We could find a better one.
Activation/deactivation in this driver means "initialize/shutdown the
hotplugged bus" and is done in response to an edge (triggering an
interrupt) of the hotplug-detect signal.

Best Regards
Michał Mirosław
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