Re: [RFC PATCH v2 07/16] gpio: Add support for unified device properties interface

[Arnd Bergmann]

On Tuesday 23 September 2014 18:25:01 Rafael J. Wysocki wrote:
> The problem is iteration over child nodes of a given one where there
> may not be struct device objects.
> 
> For example (from patch [2/16]):
> 
> +int acpi_for_each_child_node(struct acpi_device *adev,
> +                             int (*fn)(struct fw_dev_node *fdn, void *data),
> +                             void *data)
> +{
> +       struct acpi_device *child;
> +       int ret = 0;
> +
> +       list_for_each_entry(child, &adev->children, node) {
> +               struct fw_dev_node fdn = { .acpi_node = child, };
> +
> +               ret = fn(&fdn, data);
> +               if (ret)
> +                       break;
> +       }
> +       return ret;
> +}
> 
> and then fn() can be made work for both DTs and ACPI.  Without this we'd
> need to have two versions of fn(), one for DTs and one for ACPI (and possibly
> more for some other FW protocols), which isn't necessary in general (and
> duplicates code etc.). 
> 
> That actually is used by some patches down in the series (eg. [10/16]).
> 

Ok, I understand what you are doing now.

Looking at the example you point to (http://www.spinics.net/lists/devicetree/msg49502.html), I still feel
that this is adding more abstraction than what is good for us, and
I'd be happier with an implementation of gpio_leds_create() that
has a bit more duplication and less abstraction.

The important part should be that the driver-side interface is
sensible, other than that an implementation like

static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
{
	if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node)
		return gpio_leds_create_of(pdev);
	else if (IS_ENABLED(CONFIG_ACPI))
		return gpio_leds_create_of(acpi);
	return ERR_PTR(-ENXIO);
}

would keep either side of it relatively simple, by leaving out the
indirect function calls and new for_each_available_child_of_node()
macro.

How many other users of fw_dev_node do you have at the moment?

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/