From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Brandewie Subject: Re: [sodaville] [PATCH 3/4] of/dtc: force dtb size to modulo 32 bytes Date: Thu, 11 Nov 2010 17:01:16 -0800 Message-ID: <4CDC91DC.7030407@gmail.com> References: <4CDC8EA3.6080608@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4CDC8EA3.6080608-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: "H. Peter Anvin" Cc: sodaville-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, arjan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org List-Id: devicetree@vger.kernel.org On 11/11/2010 04:47 PM, H. Peter Anvin wrote: > On 11/11/2010 04:03 PM, dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote: >> From: Dirk Brandewie >> >> This patch forces the size of the DTB to be modulo 32 bytes. This is >> needed to support linking multiple DTB's into a single section in the >> image. GCC wants structures to be 32 byte aligned without this change >> DTB's after the first in the section may not be properly aligned so >> the flat tree parsing code will fall over. >> >> Signed-off-by: Dirk Brandewie > > I don't think 32 is a universal number; it should depend on the ABI. On > x86, for one thing, I'm pretty sure that there is no particular > alignment requirements beyond the natural alignment of the data items, > for example. > > Although 32 is probably conservative on any platform, please flag the > origin of this with a comment, or make it a constant defined in a header > file... otherwise, if this breaks for whatever reason it'll be near > impossible to find. > I will change . = ALIGN(32); to STRUCT_ALIGN(); from vmlinux.lds.h: /* * Align to a 32 byte boundary equal to the * alignment gcc 4.5 uses for a struct */ #define STRUCT_ALIGN() . = ALIGN(32) --Dirk