Message-ID: <52DB9B39.9090502@meshcoding.com>
Date: Sun, 19 Jan 2014 10:30:33 +0100
From: Antonio Quartulli <antonio@meshcoding.com>
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To: James Hogan <james.hogan@imgtec.com>
CC: Chen Gang <gang.chen.5i5j@gmail.com>, David Miller <davem@davemloft.net>,
        mareklindner@neomailbox.ch, sw@simonwunderlich.de,
        b.a.t.m.a.n@lists.open-mesh.org, netdev <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-metag@vger.kernel.org
Subject: Re: [PATCH linux-next] net: batman-adv: use "__packed __aligned(2)"
 for each structure instead of "__packed(2)" region
References: <52DA65F4.5070501@gmail.com> <52DA7B9E.4040202@meshcoding.com> <4915262.qEFumRrH4p@radagast>
In-Reply-To: <4915262.qEFumRrH4p@radagast>
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On 19/01/14 02:10, James Hogan wrote:
>=20
> It appears that the following gcc patch adds support for #pragma pack:
> http://gcc.gnu.org/ml/gcc-patches/2006-10/msg01115.html
>=20
> I gave it a quick spin on metag gcc (which is unfortunately stuck on an=
 old=20
> version) and it seems to fix my simple test case so that #pragma pack(2=
)=20
> becomes equivalent to __packed __aligned(2) (for sizeof and __alignof__=
).
>=20

Then I personally think that it is better to fix metag gcc instead of
changing the kernel.

Actually there are many different spots where "#pragma pack" is used.
batman-adv is just the only one having compile time checks for structure
sizes.

>=20
> However, the __packed and __aligned are linux specific macros to abstra=
ct=20
> compiler details, whereas #pragma pack appears to be a compiler-specifi=
c WIN32=20
> style equivalent to GCC's __attribute__((packed)) and=20
> __attribute__((aligned(2))) (these are what __packed and __aligned use =
in=20
> compiler-gcc.h).
>=20
> Therefore I believe using the Linux abstractions is still more correct =
here.

If you really think so, I'd suggest to grep in the kernel and catch all
the other occurrences of "#pragma pack" and change them all (assuming
that using __attribute__((aligned(2))) is the way to go).

Cheers,


--=20
Antonio Quartulli


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