linux-kernel - Question on FIELD_PREP() for static array

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Date:   Wed, 10 Oct 2018 18:16:32 +0100
From:   John Garry <john.garry@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>, <johannes@...solutions.net>,
        <jakub.kicinski@...ronome.com>, <yamada.masahiro@...ionext.com>,
        Arnd Bergmann <arnd@...db.de>, <viro@...iv.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Question on FIELD_PREP() for static array

(to: get_maintainers -f include/linux/bitfield.h)

Hi,

I would like to use FIELD_PREP() macro for assigning a static array, 
like this:
function()
{
	static u32 val[2] = {FIELD_PREP(GENMASK_ULL(10, 0), 5), 0};

}

However the compiler complains of non-const expression:
./include/linux/bitfield.h:88:2: error: initializer element is not constant
    ({        \

Specifically it doesn't like the __BF_FIELD_CHECK() in FIELD_PREP().

Any ideas on compiler trickery we could do with the FIELD_PREP() 
definition to avoid this issue (i.e. enforce the check but only use the 
constant value)?

Thanks in advance,
John