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From:   Herve Codina <herve.codina@bootlin.com>
To:     Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Peter Rosin <peda@axentia.se>
Cc:     linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        Allan Nielsen <allan.nielsen@microchip.com>,
        Horatiu Vultur <horatiu.vultur@microchip.com>,
        Steen Hegelund <steen.hegelund@microchip.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Herve Codina <herve.codina@bootlin.com>
Subject: [PATCH 1/3] i2c: muxes: i2c-mux-pinctrl: Use of_get_i2c_adapter_by_node()
Date:   Thu, 19 Oct 2023 09:35:28 +0200
Message-ID: <20231019073533.386563-2-herve.codina@bootlin.com>
In-Reply-To: <20231019073533.386563-1-herve.codina@bootlin.com>
References: <20231019073533.386563-1-herve.codina@bootlin.com>
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i2c-mux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
i2c_put_adapter(). These pair alone is not correct to properly lock the
I2C parent adapter.

Indeed, i2c_put_adapter() decrements the module refcount while
of_find_i2c_adapter_by_node() does not increment it. This leads to an
overflow over zero of the parent adapter user counter.

Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
correctly the module refcount.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/i2c/muxes/i2c-mux-pinctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pinctrl.c b/drivers/i2c/muxes/i2c-mux-pinctrl.c
index 18236b9fa14a..6ebca7bfd8a2 100644
--- a/drivers/i2c/muxes/i2c-mux-pinctrl.c
+++ b/drivers/i2c/muxes/i2c-mux-pinctrl.c
@@ -62,7 +62,7 @@ static struct i2c_adapter *i2c_mux_pinctrl_parent_adapter(struct device *dev)
 		dev_err(dev, "Cannot parse i2c-parent\n");
 		return ERR_PTR(-ENODEV);
 	}
-	parent = of_find_i2c_adapter_by_node(parent_np);
+	parent = of_get_i2c_adapter_by_node(parent_np);
 	of_node_put(parent_np);
 	if (!parent)
 		return ERR_PTR(-EPROBE_DEFER);
-- 
2.41.0