Re: [PATCH v2 3/3] i2c: muxes: i2c-mux-gpmux: Use of_get_i2c_adapter_by_node()

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 19 Oct 2023 12:10:16 +0200
Herve Codina <herve.codina@bootlin.com> wrote:

> i2c-mux-gpmux 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
> underflow of the parent module refcount.
> 
> Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
> 
> Fixes: ac8498f0ce53 ("i2c: i2c-mux-gpmux: new driver")
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> Acked-by: Peter Rosin <peda@axentia.se>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/i2c/muxes/i2c-mux-gpmux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-gpmux.c b/drivers/i2c/muxes/i2c-mux-gpmux.c
> index baccf4bfaf02..8305661e1253 100644
> --- a/drivers/i2c/muxes/i2c-mux-gpmux.c
> +++ b/drivers/i2c/muxes/i2c-mux-gpmux.c
> @@ -52,7 +52,7 @@ static struct i2c_adapter *mux_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);