Re: [PATCH v3 2/2] i2c: Add i2c_device_get_match_data() callback

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Aug 01, 2023 at 10:28:38PM +0300, Andy Shevchenko wrote:
> On Tue, Aug 01, 2023 at 06:03:18PM +0100, Biju Das wrote:
> > Add i2c_device_get_match_data() callback to struct bus_type().
> > 
> > While at it, introduced i2c_get_match_data_helper() to avoid code
> > duplication with i2c_get_match_data().
> 
> Have you used --patience when prepared the patch for sending?
> 
> ...
> 
> > -const void *i2c_get_match_data(const struct i2c_client *client)
> > +static const void *i2c_get_match_data_helper(const struct i2c_driver *driver,
> > +					     const struct i2c_client *client)
> >  {
> 
> > -	struct i2c_driver *driver = to_i2c_driver(client->dev.driver);
> 
> Does it make sense to remove and add an additional parameter? In one case it's
> a copy, in another it probably the same, just hidden in the code.
> 
> >  	const struct i2c_device_id *match;
> > +
> > +	match = i2c_match_id(driver->id_table, client);
> > +	if (!match)
> > +		return NULL;
> > +
> > +	return (const void *)match->driver_data;
> > +}
> > +
> > +static const void *i2c_device_get_match_data(const struct device *dev)
> > +{
> > +	/* TODO: use i2c_verify_client() when it accepts const pointer */
> > +	const struct i2c_client *client = (dev->type == &i2c_client_type) ?
> > +					  to_i2c_client(dev) : NULL;
> >  	const void *data;
> 
> > +	if (!dev->driver)
> > +		return NULL;
> 
> When can this be true?

It is not guaranteed that the function is always called on a device
bound to a driver (even though we normally expect this to be the case).

> 
> > +	data = i2c_get_match_data_helper(to_i2c_driver(dev->driver), client);
> > +	if (data)
> > +		return data;
> >  
> > -		data = (const void *)match->driver_data;
> > +	if (dev->driver->of_match_table) {
> > +		const struct of_device_id *match;
> > +
> > +		match = i2c_of_match_device_sysfs(dev->driver->of_match_table,
> > +						  (struct i2c_client *)client);

Can we make i2c_of_match_device_sysfs() take a const pointer to a
client? Casting away constness is something that we should avoid.

> > +		if (match)
> > +			data = match->data;
> >  	}
> >  
> >  	return data;
> >  }
> 
> ...
> 
> > -static const struct of_device_id*
> > +const struct of_device_id*
> 
> While here, add a missing space after of_device_id.
> 
> ...
> 
> > +const struct of_device_id*
> 
> Ditto.
> 
> Or use below (weird) style in case it occurs more often than usual one.
> 
> > +i2c_of_match_device_sysfs(const struct of_device_id *matches,
> > +			  struct i2c_client *client);
> > +
> >  const struct of_device_id
> >  *i2c_of_match_device(const struct of_device_id *matches,
> >  		     struct i2c_client *client);
> 
> ...
> 
> > +static inline const struct of_device_id
> > +*i2c_of_match_device(const struct of_device_id *matches,
> 
> As per above.

Was it supposed to be i2c_of_match_device_sysfs()? Also, this should be
in drivers/i2c/i2c-core.h, not in public header.

Thanks.

-- 
Dmitry