[PATCH v3 2/2] of: property: Do not link to disabled devices

From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: saravanak@google.com, linux-kernel@vger.kernel.org,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: devicetree@vger.kernel.org,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: [PATCH v3 2/2] of: property: Do not link to disabled devices
Date: Mon, 20 Apr 2020 14:01:02 +0200	[thread overview]
Message-ID: <20200420120101.31405-3-nsaenzjulienne@suse.de> (raw)
In-Reply-To: <20200420120101.31405-1-nsaenzjulienne@suse.de>

When creating a consumer/supplier relationship between two devices,
make sure the supplier node is actually active. Otherwise this will
create a link relationship 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@suse.de>

---

Changes since v2:
 - Correct code comment
 - Use already available return handling code

Changes since v1:
 - Move availability check into the compatible search code and stop if
   node disabled

 drivers/of/property.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index dc034eb45defd..7bcf31ba717d8 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1045,8 +1045,20 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
 	 * Find the device node that contains the supplier phandle.  It may be
 	 * @sup_np or it may be an ancestor of @sup_np.
 	 */
-	while (sup_np && !of_find_property(sup_np, "compatible", NULL))
+	while (sup_np) {
+
+		/* Don't allow linking to a disabled supplier */
+		if (!of_device_is_available(sup_np)) {
+			of_node_put(sup_np);
+			sup_np = NULL;
+		}
+
+		if (of_find_property(sup_np, "compatible", NULL))
+			break;
+
 		sup_np = of_get_next_parent(sup_np);
+	}
+
 	if (!sup_np) {
 		dev_dbg(dev, "Not linking to %pOFP - No device\n", tmp_np);
 		return -ENODEV;
-- 
2.26.0

