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

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Mar 09, 2023 at 02:02:09PM +0100, Ahmad Fatoum wrote:
> 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.

This is not equivalent as of_i2c_register_devices() uses
adap->dev.of_node whereas the if clause below uses adapter->dev.parent->of_node.

Ideally this should be the same, but for now I think I'll just
revert to what has been done before the i2c_hw_detect patches
which adding a check in of_i2c_register_devices().

Sascha

> 
> > +
> >  	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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> 

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