linux-kernel - Re: [RFC][PATCH] Add primitives for manipulating bitfields both in host- and fixed-endian.

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Date:   Thu, 14 Dec 2017 21:07:13 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] Add primitives for manipulating bitfields both in
 host- and fixed-endian.

Looks great to me!

On Fri, 15 Dec 2017 02:33:43 +0000, Al Viro wrote:
> The following primitives are defined in linux/bitfield.h:
> 
> * u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
>   bitfield specified by @field in little-endian 32bit value @val and
>   converts it to host-endian.
> 
> * void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
>   the contents of the bitfield specified by @field in little-endian
>   32bit object pointet to by *p with the value of @v.  New value is
>   given in host-endian and stored as little-endian.
> 
> * __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
>   ({__le32 tmp = old; le32p_replace_bits(&old, v, field); tmp;})
>   In other words, instead of modifying an object in memory, it takes
>   the initial value and returns the modified one.

the current macros take filed/mask as first param, not sure if it's
worth maintaining the order