Re: [PATCH v2 3/7] i2c: implement rescan

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 09.03.23 12:52, Sascha Hauer wrote:
> struct device::rescan is called by the core to let the subsystem rescan
> the controllers device node. Implement that for I2C. Ahmad recently
> implemented the struct device::detect hook for the very same purpose.
> The downside of that approach was that device_detect() had to be called
> manually and that either needs knowledge which device actually has
> updated device nodes, or all devices were detected, like unrelated USB
> or MMC/SD devices. The rescan hook doesn't need that manual detect call,
> so just drop the I2C detect implementation in favour for implementing
> rescan.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/i2c/i2c.c | 20 +++++---------------
>  1 file changed, 5 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/i2c/i2c.c b/drivers/i2c/i2c.c
> index efcad29342..df89b8fb65 100644
> --- a/drivers/i2c/i2c.c
> +++ b/drivers/i2c/i2c.c
> @@ -471,15 +471,7 @@ int of_i2c_register_devices_by_node(struct device_node *node)
>  	return 0;
>  }
>  
> -static int i2c_bus_detect(struct device *dev)
> -{
> -	struct i2c_adapter *adap = container_of(dev, struct i2c_adapter, dev);
> -
> -	of_i2c_register_devices(adap);
> -	return 0;
> -}
> -
> -static int i2c_hw_detect(struct device *dev)
> +static void i2c_hw_rescan(struct device *dev)
>  {
>  	struct i2c_adapter *adap;
>  
> @@ -489,8 +481,6 @@ static int i2c_hw_detect(struct device *dev)
>  		of_i2c_register_devices(adap);
>  		break;
>  	}
> -
> -	return 0;
>  }
>  
>  /**
> @@ -720,7 +710,6 @@ int i2c_add_numbered_adapter(struct i2c_adapter *adapter)
>  	}
>  
>  	adapter->dev.id = adapter->nr;
> -	adapter->dev.detect = i2c_bus_detect;
>  	dev_set_name(&adapter->dev, "i2c");
>  
>  	ret = register_device(&adapter->dev);
> @@ -732,11 +721,12 @@ int i2c_add_numbered_adapter(struct i2c_adapter *adapter)
>  	/* populate children from any i2c device tables */
>  	scan_boardinfo(adapter);
>  
> +	of_i2c_register_devices(adapter);

I think this would fail for a non-OF I2C contoller on a CONFIG_OFTREE=y system,
because the function doesn't guard against !CONFIG_OFTREE. Just move it into
the if clause below.

> +
>  	hw_dev = adapter->dev.parent;
>  	if (hw_dev && dev_of_node(hw_dev)) {
> -		if (!hw_dev->detect)
> -			hw_dev->detect = i2c_hw_detect;
> -		i2c_hw_detect(hw_dev);
> +		if (!hw_dev->rescan)
> +			hw_dev->rescan = i2c_hw_rescan;
>  	}
>  
>  	return 0;

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