From 96f4672d44d8cfaf058c827d8fb8a74e9a5689ff Mon Sep 17 00:00:00 2001 From: Sascha Hauer Date: Thu, 5 Jul 2007 21:40:46 +0200 Subject: Documentation update --- README.u2 | 155 +++++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 108 insertions(+), 47 deletions(-) (limited to 'README.u2') diff --git a/README.u2 b/README.u2 index 26138e60c7..e77092b224 100644 --- a/README.u2 +++ b/README.u2 @@ -7,8 +7,69 @@ today's embedded systems, seen from a user's point of view. Nevertheless, there are quite some design flaws which turned out over the last years and we think that they cannot be solved in a production tree. So this tree tries to do several things right - without caring -about losing support for old boards. So if you aim at stability at this -time, stay with the official U-Boot releases. +about losing support for old boards. + +General features include: + +- A posix based file API + inside U-Boot the usual open/close/read/write/lseek functions are used. + This makes it familiar to everyone who has programmed under unix systems. + +- usual shell commands like ls/cd/mkdir/echo/cat,... + +- The environment is not a variable store anymore, but a file store. It has + currently some limitations, of course. The environment is not a real + read/write filesystem, it is more like a tar archive, or even more like + an ar archive, because it cannot handle directories. The saveenv command + saves the files under a certain directory (by default /env) in persistent + storage (by default /dev/env0). There is a counterpart called loadenv, too. + +- Real filesystem support + The loader starts up with mounting a ramdisk on /. Then a devfs is mounted + on /dev allowing the user (or shell commands) to access devices. Apart from + these two filesystems there is currently one filesystem ported: cramfs. One + can mount it with the usual mount command. + +- device/driver model + Devices are no longer described by defines in the config file. Instead + there are devices which can be registered in the board .c file or + dynamically allocated. Drivers will match upon the devices automatically. + +- clocksource support + Timekeeping has been simplified by the use of the Linux clocksource API. + Only one function is needed for a new board, no [gs]et_timer[masked]() or + reset_timer[masked]() functions. + +- Kconfig and Kernel build system + Only targets which are really needed get recompiled. Parallel builds are + no problem anymore. This also removes the need for many many ifdefs in + the code. + +- simulation target + U-Boot can be compiled to run under Linux. While this is rather useless + in real world this is a great debugging and development aid. New features + can be easily developped and tested on long train journeys and started + under gdb. There is a console driver for linux which emulates a serial + device and a tap based ethernet driver. Linux files can be mapped to + devices under U-Boot to emulate storage devices. + +- device parameter support + Each device can have a unlimited number of parameters. They can be accessed + on the command line with .="...", for example + 'eth0.ip=192.168.0.7' or 'echo $eth0.ip' + +- initcalls + hooks in the startup process can be archieved with *_initcall() directives + in each file. + +- getopt + There is a small getopt implementation. Some commands got really + complicated (both in code and in usage) due to the fact that U-Boot only + allowed positional parameters. + +- editor + Scripts can be edited with a small editor. This editor has no features + except the ones really needed: moving the cursor and typing characters. Building U-Boot @@ -22,7 +83,8 @@ kernel. For the examples below, we use the User Mode U-Boot implementation, which is a port of U-Boot to the Linux userspace. This makes it possible to test drive the code without having real hardware. So for this test -scenario, ARCH=linux is the valid architecture selection. +scenario, ARCH=linux is the valid architecture selection. This currently +only works on ia32 hosts and partly on x86-64. Selection of the architecture and the cross compiler can be done in two ways. You can either specify it using the environment variables ARCH @@ -57,7 +119,7 @@ U-Boot usually needs an environment for storing the configuation data. You can generate an environment using the example environment contained in examples/environment: - # ./scripts/ubootenv -s examples/environment/ env.bin + # ./scripts/ubootenv -s -p 0x10000 examples/environment/ env.bin To get some files to play with you can generate a cramfs image: # mkcramfs somedir/ cramfs.bin @@ -80,61 +142,60 @@ load it to /env. It then executes /env/init if it exists. If you have loaded the example environment U-Boot will show you a menu asking for your settings. +If you have started U-Boot as root you will find a new tap device on your +host which you can configure using ifconfig. Once you configured U-Boots +network settings accordingly you can do a ping or tftpboot. +If you have mapped a cramfs image try mounting it with -FIXME: cfi currently doesn't work with um-uboot + # mkdir /cram + # mount /dev/fd0 cramfs /cram +Memory can be examined as usual using md/mw commands. They both understand +the -f option to tell the commands that they should work on the +specified files instead of /dev/mem which holds the complete address space. +Note that if you call 'md /dev/fd0' (without -f) U-Boot will segfault on +the host, because it will interpret /dev/fd0 as a number. -Commands --------- +Directory layout +---------------- -devinfo -addpart -pwd -cd -ls -cat -tftpboot FIXME: order? -tftpboot /dev/nor0.1 -erase -f /dev/nor0.1 -help -edit -> ctrl-c ctrl-d -md -f /dev/nor0.1 -exec /env/init FIXME: doesn't work yet -saveenv (makes /env persistent) -> /dev/env0 -printenv -mount +Most of the directory layout is based upon the Linux Kernel: -Shell ------ +arch/*/ -> contains architecture specific parts +arch/*/mach-*/ -> SoC specific code -- doesn't have switch/case yet -- only one variable space -[ ] add variable space +drivers/serial -> drivers +drivers/net +drivers/... -Drivers -------- +include/asm-* -> architecture specific includes +include/asm-*/arch-* -> SoC specific includes -/dev -serial -partition -environment -> /env; /env/init +fs/ -> filesystem support and filesystem drivers -Design ------- +lib/ -> generic library functions (getopt, readline and the + like) + +common/ -> common stuff + +commands/ -> many things previously in common/cmd_*, one command + per file + +net/ -> Networking stuff -include/driver.h -board/scb9328.c -include/param.h: each device can have parameters; can be changed on -runtime; get/set can be overwritten by implementation. +scripts/ -> Kconfig system -- xfunctions: do panic if error -- proposed design: - arch/ - arch/arm/cpu-arm920t/ - arch/arm/board-.../ - board/ is obsolete +Documentation/ -> -- arch/*/Makefile is central makefile +There is still the old directory layout in the tree which of course should be +merged in one way or the other: +lib_*/ -> currently unused +cpu/* -> currently unsused +post/ -> untouched +nand_spl/ -> untouched +dtt/ -> untouched +disk/ -> untouched +documentation/ -> untouched -- cgit v1.2.3