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

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Message-ID: <CACxGe6vhtFrpcnmw5LtzwVTjqkTS1v4f=TsqJ7x-LBdSu9j-tw@mail.gmail.com>
Date:	Mon, 20 Oct 2014 16:55:08 +0200
From:	Grant Likely <grant.likely@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.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" <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 Mon, Oct 20, 2014 at 4:19 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 20 October 2014 01:46:00 Rafael J. Wysocki wrote:
>>
>> > Something like:
>> >
>> > #define define_fwnode_accessors(__type, __devprop_type) \
>> > int device_property_read_##__type(struct device *dev, \
>> >                               const char *propname, __type *val) \
>> > { \
>> >       if (IS_ENABLED(CONFIG_OF) && dev->of_node) \
>> >               return of_property_read_##__type(dev->of_node, propname, val); \
>> >       return acpi_dev_prop_read(ACPI_COMPANION(dev), propname, \
>> >                                 __devprop_type, val); \
>> > } \
>> > int fwnode_property_read_##__type(struct fwnode_handle *fwnode, \
>> >                               const char *propname, __type *val) \
>> > { \
>> >       if (IS_ENABLED(CONFIG_OF) && is_of_node(fwnode)) \
>> >               return of_property_read_##__type(of_node(fwnode), propname, val); \
>> >       else if (IS_ENABLED(CONFIG_ACPI) && is_acpi_node(fwnode)) \
>> >               return acpi_dev_prop_read(acpi_node(fwnode), propname, \
>> >                                         __devprop_type, val); \
>> >       return -ENXIO; \
>> > }
>> >
>> > define_fwnode_accessors(u8, DEV_PROP_U8);
>> > define_fwnode_accessors(u16, DEV_PROP_U16);
>> > define_fwnode_accessors(u32, DEV_PROP_U32);
>> > define_fwnode_accessors(u64, DEV_PROP_U64);
>> >
>> > That significantly reduces the code size for these things.
>>
>> So I was considering to do that, but eventually decided not to, because (1)
>> adding kerneldoc comments to such things looks odd and (2) (which IMO is
>> more important) this breaks LXR (for example, the thing at lxr.free-electrons.com
>> that some people, including me in particular, occasionally use to check how things
>> are defined).  And even if you used the old good grep to look for a definition of
>> fwnode_property_read_u8, say, this wouldn't work exactly as expected I'm afraid.
>
> Agreed, I'd also prefer your proposed code over Grant's macros.
>
>> I would very much like to retain the headers at least for this reason, if that's
>> not a big deal.
>>
>> What I can do, however, is to use macros for generating the bodies of those
>> functions.
>
> Yes, just don't do any concatenation to generate the names of the called
> functions, i.e.
>
>         return fwnode_call(of_property_read_u32, acpi_dev_prop_read, DEV_PROP_U32, node, propname, val);
>
> is better than
>
>         return fwnode_call(u32, DEV_PROP_U32, node, propname, val);
>
> because it's easier to understand the call chain.

Sounds reasonable. I've got no problem with that.

g.
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