Re: [PATCH 2/3] rtc: isl1208: Support more chip variations

[Trent Piepho <tpiepho@impinj.com>]

On Sun, 2019-02-10 at 22:12 +0100, Alexandre Belloni wrote:
> +};
> > +MODULE_DEVICE_TABLE(i2c, isl1208_id);
> > +
> > +static const struct of_device_id isl1208_of_match[] = {
> > +	{ .compatible = "isil,isl1208", .data = &isl1208_configs[TYPE_ISL1208] },
> > +	{ .compatible = "isil,isl1209", .data = &isl1208_configs[TYPE_ISL1209] },
> 
> This compatible needs to be documented.

I see isil,isl1219 escaped documentation when it was added too.  I'll
add both to rtc.txt.

> >  
> >  	return handled ? IRQ_HANDLED : IRQ_NONE;
> > @@ -743,6 +778,19 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
> >  		return -ENOMEM;
> >  	i2c_set_clientdata(client, isl1208);
> >  
> > +	/* Determine which chip we have */
> > +	if (client->dev.of_node) {
> > +		const struct of_device_id *match =
> > +			of_match_node(isl1208_of_match, client->dev.of_node);
> > +		if (!match)
> 
> This will never happen, else the driver would not be probed.

If there was a driver_override ability with i2c, like PCI and SPI, then
it would be possible.

> 
> > +			return -EINVAL;
> > +		isl1208->config = match->data;
> 
> Maybe you should use of_device_get_match_data anyway.

Yes, of_device_get_match_data() would be better.  Not sure why I didn't
find that.

Interestingly, I see could have just depended on id->driver_data being
set even in the OF case, as the i2c-core code always sets it.  But it
look to be deprecated and i2c clients should provide a probe_new method
that does not provide an i2c_device_id.  I'm not sure if that's
entirely better, as every i2c client that cares will need to re-
implement the code to look up by device name and/or OF node and/or
ACPI.

> 
> > +	} else {
> > +		if (id->driver_data >= ISL_LAST_ID)
> > +			return -EINVAL;
> 
> This should be -ENODEV.

There's quite a few drivers that return EINVAL when the driver_data
appears to be incorrect.  But some also return ENODEV.