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

Arnd Bergmann
2014-09-23T16:26:07Z

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
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