From mboxrd@z Thu Jan 1 00:00:00 1970 From: Detlev Zundel Date: Fri, 15 Oct 2004 20:55:18 +0200 Subject: [U-Boot-Users] how to program a bootloader In-Reply-To: (Mildred Frisco's message of "Thu, 14 Oct 2004 15:34:59 +0800") References: Message-ID: <871xfzyfop.fsf@deepthought.outer.space.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Mildred, > This might not be the exact list for this but hope some here would be > able to help me. Is there a step-by-step guide on how to program a > bootloader? The u-boot bootloader (or other linux bootloader) is a > very big program to study. I would like to know how to program the > basics and concepts. > Thanks. Well look at it this way - what does a bootloader do? - Initialize the hardware - Setup everything so the booted program finds what it needs - What abilities are needed to do this in a comfortable way? Well there's your requirements ;) Now find the relevant hardware and software documentation to write a program doing just that. The complexity of U-Boot is due to supporting many different platforms. Try studing the code relevant for _one single_ board and you have an excellent object to study. For a somewhat more detailed specification read the docs about the available U-Boot commands in the DULG documentation. Most commands are there because they serve a purpose necessary for a comfortable working of a bootloader. Read the README in the toplevel directory to read more about the "invisible parts" of U-Boot. But remember that studying a working fully fledged boot loader can be somewhat irritating if you just want to see clearly the basic concepts. On the other hand there is _nothing better_ to study than such a Free Software project that has features needed and added by a community much larger than most closed software development teams. Cheers Detlev -- "It's amazing I won. I was running against peace, prosperity, and incumbency." -- George H.W. Bush, 06/14/2001, talking to Swedish prime minister Goran Perrson, unaware that a live tv camera was still on