From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcel Date: Sat, 15 May 2010 17:26:57 +0200 Subject: [Buildroot] endian issue In-Reply-To: References: <201005151547.02656.korgull@home.nl> <1273933182.28330.87.camel@coalu.atr> Message-ID: <201005151726.58323.korgull@home.nl> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net On Saturday 15 May 2010 04:43:29 pm Grant Edwards wrote: > On 2010-05-15, Lionel Landwerlin wrote: > > Le samedi 15 mai 2010 ?? 15:47 +0200, Marcel a ??crit : > >> I'm using an Atmel sam9g45 using buildroot with linux 2.6.33. > >> > >> I currently have most of my things working but run into an issue which > >> is endian related. > > > > The endianness configuration of your processor isn't something you > > can usually change 'on-the-fly'. It's usually set up early in the > > boot process. > > While the endian configuration of the ARM9 core can be changed, the > AT91 peripherals are little-endian. In theory, he should be able to > run the ARM9 core in big-endian mode, but a running uC core without > any working peripherals is surprisingly useless. > > > So you have to choose whether you want to compile all your system in > > big or little endian, you can select that from the buildroot > > architecture configuration (arm -> little, armeb -> big, for > > example). > > In this case, he has to choose little-endian. That's very clear. > [I've never seen an ARM-based uController that had peripherals with > configurable endianess -- are there any?] > > >> Is there any way to compile my package in big-endian mode from > >> buildroot? Or is there another way I should force this? > > > > You can't select that for 1 package, it's for the whole system or > > nothing. Otherwise, the smartest approch would be to make endian > > detection (at compile time or at running time) to adapt your > > processing algorithm. > > Yep, the OP's should driver should return data in host-order. > > Otherwise, he'll have to suffer the guilt of knowing that a few years > from now some poor sod who inherits the code will have a stroke from > the effort required to resist the urge to track down the OP and slap > him silly. If I wish to do that, how do I detect the endianness of a sytem and do I need to reformat my data in my drivers for this ? If so, isn't that a pure waste of cpu cycles for the sake of reusable code ? If I can do this without any speed sacrifice than I will do it, if not....than it's simply not an option for this system. Best regards, Marcel