linux-kernel - Re: [PATCH v1 06/10] device property: switch to use UUID API

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Date:	Fri, 26 Feb 2016 16:11:37 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Lv Zheng <lv.zheng@...el.com>, Mark Brown <broonie@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-efi@...r.kernel.org,
	linux-api@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v1 06/10] device property: switch to use UUID API

On Thu, 2016-02-18 at 01:03 +0100, Rafael J. Wysocki wrote:
> On Wednesday, February 17, 2016 02:17:24 PM Andy Shevchenko wrote:
> > Switch to use a generic UUID API instead of custom approach. It
> > allows to
> > define UUIDs, compare them, and validate.

[]

> > +static const uuid_le ads_uuid =
> > +	UUID_LE(0xdbb8e3e6, 0x5886, 0x4ba6,
> > +		0x87, 0x95, 0x13, 0x19, 0xf5, 0x2a, 0x96, 0x6b);
> >  
> >  static bool acpi_enumerate_nondev_subnodes(acpi_handle scope,
> >  					   const union acpi_object
> > *desc,
> > @@ -138,7 +136,7 @@ static bool
> > acpi_enumerate_nondev_subnodes(acpi_handle scope,
> >  		    || links->type != ACPI_TYPE_PACKAGE)
> >  			break;
> >  
> > -		if (memcmp(uuid->buffer.pointer, ads_uuid,
> > sizeof(ads_uuid)))
> > +		if (uuid_le_cmp(*(uuid_le *)uuid->buffer.pointer,
> > ads_uuid))
> 
> Maybe it's too late, but I don't quite understand the pointer
> manipulations here.
> 
> I can see why you need a type conversion (although it looks ugly),
> but why do you
> need to dereference it too?

The function takes that kind of type on input. The other variants are
not compiled.
Perhaps we better change uuid_{lb}e_cmp() first to take normal
pointers, though I think the initial idea was to get type checking at
compile time.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy