linux-kernel - Re: [RFC/PATCH 2/5] device property: introduce notion of subnodes for legacy boards

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Message-ID: <20180924072953.GH11965@kuha.fi.intel.com>
Date:   Mon, 24 Sep 2018 10:29:53 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        linux-input@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [RFC/PATCH 2/5] device property: introduce notion of subnodes
 for legacy boards

On Fri, Sep 21, 2018 at 04:33:36PM -0700, Dmitry Torokhov wrote:
> On Thu, Sep 20, 2018 at 01:16:48PM +0300, Heikki Krogerus wrote:
> > On Wed, Sep 19, 2018 at 10:13:26AM -0700, Dmitry Torokhov wrote:
> > > > > diff --git a/drivers/base/pset_property.c b/drivers/base/pset_property.c
> > > > > index 08ecc13080ae..63f2377aefe8 100644
> > > > > --- a/drivers/base/pset_property.c
> > > > > +++ b/drivers/base/pset_property.c
> > > > > @@ -18,6 +18,11 @@ struct property_set {
> > > > >  	struct device *dev;
> > > > >  	struct fwnode_handle fwnode;
> > > > >  	const struct property_entry *properties;
> > > > > +
> > > > > +	struct property_set *parent;
> > > > > +	/* Entry in parent->children list */
> > > > > +	struct list_head child_node;
> > > > > +	struct list_head children;
> > > > 
> > > > Add
> > > > 
> > > >         const char *name;
> > > > 
> > > > and you can implement also pset_get_named_child_node().
> > > 
> > > Or
> > > 	char name[];
> > > 
> > > to avoid separate allocation.
> > 
> > Let's not do that, especially if you are planning on exporting this
> > structure.
> 
> Can you please elaborate why? Not using pointer saves us 4/8 bytes +
> however much memory we need for bookkeeping for the extra chunk. Given
> that majority of pset nodes are unnamed this seems wasteful.
> 
> > If the name is coming from .rodata, there is no need to
> > allocate anything for the name. Check kstrdup_const().
> 
> The data is most likely coming as __initconst so we do need to copy it.

OK, I did not consider that. Yes, it makes sense to always copy.

Thanks,

-- 
heikki