[U-Boot-Users] 回复: [U-Boot-Users] U-Boot-NG ?
Songmao Tian
kingkongmao at gmail.com
Fri Jul 6 08:39:29 CEST 2007
I can't reach the links in my network, what a pity, are they still valid?
2007/7/3, Sascha Hauer <s.hauer at pengutronix.de>:
> Hi,
>
> I just prepared a git repository for our U-Boot-NG proposal. Do a
>
> git clone http://iocaste.extern.pengutronix.de/git/U-Boot-NG.git
>
> (no native git support at the moment)
>
> There is also a tarball snapshot available here:
>
> http://pengutronix.de/software/ptxdist/temporary-src/U-Boot-NG-20070702.tar.gz
>
> This is only a temporary place for the source, further development should
> probably either be done on Wolgangs server or some other dedicated
> server.
> The tree is based on vanilla U-Boot-1.2.0.
>
> As a starting point I've included the README in this mail. It's also
> included in the source tree under README.u2. Further documentation can be
> found under Documentation/ and of course in the code ;)
>
> Regards,
> Sascha Hauer
>
>
> U2Boot
> ------
>
> This is u2boot, our proposal for a next generation of the famous U-Boot
> bootloader. U-Boot offers an excellent choice as a bootloader for
> 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.
>
> 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 <devid>.<param>="...", 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
> ---------------
>
> U-Boot uses the Linux kernel's build system. It consists of two parts:
> the makefile infrastructure (kbuild), plus a configuration system
> (kconfig). So building U-Boot is very similar to building the Linux
> 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. 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
> and CROSS_COMPILE, or you can create the soft links cross_arch and
> cross_compile pointing to your architecture and compiler. For ARCH=linux
> we do not need a cross compiler so it is sufficient to specify the
> architecture:
>
> # ln -s linux cross_arch
>
> In order to configure the various aspects of U-Boot, start the U-Boot
> configuration system:
>
> # make menuconfig
>
> This command starts a menu box and lets you select all the different
> options available for your architecture. Once the configuration was
> finished (you can simulate this by using the standard demo config file
> with 'make linux_defconfig'), there is a .config file in the toplevel
> directory of the sourcode.
>
> Once U-Boot is configured, we can start the compilation
>
> # make
>
> If everything goes well, the result is a file called uboot:
>
> # ls -l uboot
> -rwxr-xr-x 1 rsc ptx 114073 Jun 26 22:34 uboot
>
> 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
>
> To get some files to play with you can generate a cramfs image:
> # mkcramfs somedir/ cramfs.bin
>
> The U-Boot image is a normal Linux executable, so it can be started
> just like every other program:
>
> # ./uboot -e env.bin -i cramfs.bin
>
> U-Boot 2.0.0-trunk (Jun 26 2007 - 22:34:38)
>
> loading environment from /dev/env0
> uboot> /
>
> Specifying -[ie] <file> tells U-Boot to map the file as a device
> under /dev. Files given with '-e' will appear as /dev/env[n]. Files
> given with '-i' will appear as /dev/fd[n].
> If U-Boot finds a valid configuration sector on /dev/env0 it will
> 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
>
> # mkdir /cram
> # mount /dev/fd0 cramfs /cram
>
> Memory can be examined as usual using md/mw commands. They both understand
> the -f <file> 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.
>
> Directory layout
> ----------------
>
> Most of the directory layout is based upon the Linux Kernel:
>
> arch/*/ -> contains architecture specific parts
> arch/*/mach-*/ -> SoC specific code
>
> drivers/serial -> drivers
> drivers/net
> drivers/...
>
> include/asm-* -> architecture specific includes
> include/asm-*/arch-* -> SoC specific includes
>
> fs/ -> filesystem support and filesystem drivers
>
> 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
>
> scripts/ -> Kconfig system
>
> Documentation/ ->
>
> 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
>
>
>
> --
> Pengutronix - Linux Solutions for Science and Industry
> Entwicklungszentrum Nord http://www.pengutronix.de
>
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