linux-kernel - Re: [PATCH 1/3] of: always populate a root node

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Date:   Tue, 3 May 2022 17:38:29 +0200
From:   Clément Léger <clement.leger@...tlin.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Allan Nielsen <allan.nielsen@...rochip.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Steen Hegelund <steen.hegelund@...rochip.com>,
        Thomas Petazzoni <thomas.petazonni@...tlin.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Andrew Lunn <andrew@...n.ch>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 1/3] of: always populate a root node

Le Tue, 3 May 2022 08:45:11 -0500,
Rob Herring <robh@...nel.org> a écrit :

> On Wed, Apr 27, 2022 at 11:45:00AM +0200, Clément Léger wrote:
> > When enabling CONFIG_OF on a platform where of_root is not populated by
> > firmware, we end up without a root node. In order to apply overlays and
> > create subnodes of the root node, we need one. This commit creates an
> > empty root node if not present.  
> 
> The existing unittest essentially does the same thing for running the 
> tests on non-DT systems. It should be modified to use this support 
> instead. Maybe that's just removing the unittest code that set of_root.

Acked, I'll try the unit test on my system.

> 
> I expect Frank will have some comments.
> 
> > Co-developed-by: Rob Herring <robh@...nel.org>
> > Signed-off-by: Rob Herring <robh@...nel.org>
> > Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> > ---
> >  drivers/of/base.c | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index e7d92b67cb8a..6b8584c39f73 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -177,6 +177,19 @@ void __init of_core_init(void)
> >  		pr_err("failed to register existing nodes\n");
> >  		return;
> >  	}
> > +
> > +	if (!of_root) {
> > +		of_root = kzalloc(sizeof(*of_root), GFP_KERNEL);
> > +		if (!of_root) {
> > +			mutex_unlock(&of_mutex);
> > +			pr_err("failed to create root node\n");
> > +			return;
> > +		}
> > +
> > +		of_root->full_name = "/";
> > +		of_node_init(of_root);
> > +	}
> > +
> >  	for_each_of_allnodes(np) {
> >  		__of_attach_node_sysfs(np);
> >  		if (np->phandle && !phandle_cache[of_phandle_cache_hash(np->phandle)])
> > @@ -185,8 +198,7 @@ void __init of_core_init(void)
> >  	mutex_unlock(&of_mutex);
> >  
> >  	/* Symlink in /proc as required by userspace ABI */
> > -	if (of_root)
> > -		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
> > +	proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
> >  }
> >  
> >  static struct property *__of_find_property(const struct device_node *np,
> > -- 
> > 2.34.1
> > 
> >   



-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com