linux-kernel - Re: [RFC PATCH v2 02/12] of: Allow scripts/dtc/libfdt to be used from kernel code

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Date:	Sat, 5 Mar 2011 19:24:09 +1100
From:	David Gibson <david@...son.dropbear.id.au>
To:	David Daney <ddaney@...iumnetworks.com>
Cc:	linux-mips@...ux-mips.org, ralf@...ux-mips.org,
	devicetree-discuss@...ts.ozlabs.org, grant.likely@...retlab.ca,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 02/12] of: Allow scripts/dtc/libfdt to be used
 from kernel code

On Fri, Mar 04, 2011 at 11:42:14AM -0800, David Daney wrote:
> Signed-off-by: David Daney <ddaney@...iumnetworks.com>
[snip]
> --- /dev/null
> +++ b/lib/libfdt/libfdt_env.h
> @@ -0,0 +1,21 @@
> +#ifndef _LIBFDT_ENV_H
> +#define _LIBFDT_ENV_H
> +
> +#include <linux/string.h>
> +
> +#define _B(n)	((unsigned long long)((uint8_t *)&x)[n])
> +static inline uint32_t fdt32_to_cpu(uint32_t x)
> +{
> +	return (_B(0) << 24) | (_B(1) << 16) | (_B(2) << 8) | _B(3);
> +}
> +#define cpu_to_fdt32(x) fdt32_to_cpu(x)
> +
> +static inline uint64_t fdt64_to_cpu(uint64_t x)
> +{
> +	return (_B(0) << 56) | (_B(1) << 48) | (_B(2) << 40) | (_B(3) << 32)
> +		| (_B(4) << 24) | (_B(5) << 16) | (_B(6) << 8) | _B(7);
> +}
> +#define cpu_to_fdt64(x) fdt64_to_cpu(x)
> +#undef _B

Ah, yuck.  I only used those nasty macros in the userspace version of
libfdt_env.h because bytesex.h is such a portability nightmare.  The
kernel already has cpu_to_be{32,64}(), and the fdt byteswapping
functions should just be aliased to them.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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