linux-kernel - Re: [PATCH v5 09/12] Driver core: Unified interface for firmware node properties

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Date:	Sat, 18 Oct 2014 11:35:21 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>, devicetree@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v5 09/12] Driver core: Unified interface for firmware node properties

On Friday 17 October 2014 14:14:53 Rafael J. Wysocki wrote:
> +/**
> + * fwnode_property_present - check if a property of a firmware node is present
> + * @fwnode: Firmware node whose property to check
> + * @propname: Name of the property
> + */
> +bool fwnode_property_present(struct fwnode_handle *fwnode, const char *propname)
> +{
> +       if (is_of_node(fwnode))
> +               return of_property_read_bool(of_node(fwnode), propname);
> +       else if (is_acpi_node(fwnode))
> +               return !acpi_dev_prop_get(acpi_node(fwnode), propname, NULL);
> +
> +       return false;
> +}
> +EXPORT_SYMBOL_GPL(fwnode_property_present);
> 

Should this be

		return acpi_dev_prop_get(acpi_node(fwnode), propname, NULL);

without the '!'?

I'm also unsure about the '_present' vs '_read_bool' naming. IIRC we had
a long debate about this before we decided on 'read_bool' for DT, and
I don't really want to start a new debate, but being consistent would
be nice.

We could of course have

static inline bool fwnode_property_read_bool(struct fwnode_handle *fwnode, const char *propname)
{
	return fwnode_property_present(fwnode, propname);
}

which is completely redundant, but would help for drivers using the
interface to document whether we are checking for bool property that
we expect to be either empty or absent (_get_bool), vs checking for
the presence of a non-empty property (_present).

	Arnd
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