| Message ID | 20231019073533.386563-3-herve.codina@bootlin.com |
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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 2/3] i2c: muxes: i2c-demux-pinctrl: Use
of_get_i2c_adapter_by_node()
Date: Thu, 19 Oct 2023 09:35:29 +0200
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| Series |
Fix i2c mux module refcount issues
|
|
Commit Message
Herve Codina
Oct. 19, 2023, 7:35 a.m. UTC
i2c-demux-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-demux-pinctrl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Comments
Hi! 2023-10-19 at 09:35, Herve Codina wrote: > i2c-demux-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. Perhaps "... underflow of the parent module refcount."? > > 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> Good find! Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver") Acked-by: Peter Rosin <peda@axentia.se> Cheers, Peter > --- > drivers/i2c/muxes/i2c-demux-pinctrl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c > index 22f2280eab7f..9f2e4aa28159 100644 > --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c > +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c > @@ -61,7 +61,7 @@ static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 ne > if (ret) > goto err; > > - adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np); > + adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np); > if (!adap) { > ret = -ENODEV; > goto err_with_revert;
Hi Peter, On Thu, 19 Oct 2023 11:26:14 +0200 Peter Rosin <peda@axentia.se> wrote: > Hi! > > 2023-10-19 at 09:35, Herve Codina wrote: > > i2c-demux-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. > > Perhaps "... underflow of the parent module refcount."? Will be changed in the next iteration > > > > > 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> > > Good find! > > Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver") > Acked-by: Peter Rosin <peda@axentia.se> > Will be added in the next iteration. Thanks for the review, Hervé
diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c index 22f2280eab7f..9f2e4aa28159 100644 --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c @@ -61,7 +61,7 @@ static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 ne if (ret) goto err; - adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np); + adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np); if (!adap) { ret = -ENODEV; goto err_with_revert;