linux-kernel - [PATCH 2/4] of: property: Do not link to disabled devices

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Message-Id: <20200415150550.28156-3-nsaenzjulienne@suse.de>
Date:   Wed, 15 Apr 2020 17:05:47 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     saravanak@...gle.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] of: property: Do not link to disabled devices

When creating a consumer/supplier relationship between two devices, make
sure the supplier node is actually active. Otherwise this will create a
device link that will never be fulfilled. This, in the worst case
scenario, will hang the system during boot.

Note that, in practice, the fact that a device-tree represented
consumer/supplier relationship isn't fulfilled will not prevent devices
from successfully probing.

Fixes: a3e1d1a7f5fc ("of: property: Add functional dependency link from DT bindings")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
---
 drivers/of/property.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index a8c2b13521b27..487685ff8bb19 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1052,6 +1052,13 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
 		return -ENODEV;
 	}
 
+	/* Don't allow linking a device node as consumer of a disabled node */
+	if (!of_device_is_available(sup_np)) {
+		dev_dbg(dev, "Not linking to %pOFP - Not available\n", sup_np);
+		of_node_put(sup_np);
+		return -ENODEV;
+	}
+
 	/*
 	 * Don't allow linking a device node as a consumer of one of its
 	 * descendant nodes. By definition, a child node can't be a functional
-- 
2.26.0