From mboxrd@z Thu Jan 1 00:00:00 1970 From: Albert ARIBAUD Date: Thu, 02 Dec 2010 20:32:09 +0100 Subject: [U-Boot] [PATCH] omap3evm: Clean-up EVM detection code. In-Reply-To: <20101202185136.499ACEA6600@gemini.denx.de> References: <1291288812-12653-1-git-send-email-premi@ti.com> <20101202113726.2C683EA6600@gemini.denx.de> <4CF7896B.5090007@free.fr> <20101202120141.30416EA6600@gemini.denx.de> <4CF7922B.3020504@free.fr> <20101202135804.3BACFEA6600@gemini.denx.de> <4CF7C7F4.6030803@free.fr> <20101202185136.499ACEA6600@gemini.denx.de> Message-ID: <4CF7F439.3020102@free.fr> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Le 02/12/2010 19:51, Wolfgang Denk a ?crit : > Dear Albert ARIBAUD, > > In message<4CF7C7F4.6030803@free.fr> you wrote: >> >>> Well, an u8 is as good a data type as any other. The available range >>> of 0...255 seems more than sufficient to store the needed >>> information, so why should I waste 4 bytes of storage when a single >>> byte is sufficient as well? >> >> You don't necessarily use only one byte when declaring an u8 instead of >> an int, because the next declaration may have alignment requirements >> that will cause the compiler to skip bytes after the u8. Besides, u8 is > > The compiler / linker may (or may not) optimize this and collect > variables of similar alignment. An "int foo;" is likely to end in > .bss segment, while an "char foo;" will probably show up in .sbss - I > don;t know how good or bad the current situation for ARM is, but I'm > sure it is improving (look for example at all the microoptimizations > done by Linaro). There is only a single .bss for ARM. >> not "as good a data type" as any other, it is a specific data type >> whereas 'int' is the native data type of the platform, supposed to be >> the most natural to deal with for the cpu -- 32-bit for an ARM. > > Can an ARM CPU not read1s and write single bytes, too? It can, but for many of its operations, it can only work with 32-bit data. > Let's stop this here. Understood. > Best regards, > > Wolfgang Denk Amicalement, -- Albert.