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This How-To is meant to be a starting point for people to learn how access to the uboot environment from userspace.
This is my first wiki page so please be benevolent with the formatting :-)
In order to modify the uboot environment variables from userspace we will need a program called fw_setenv, we can compile this program ourselves from the u-boot sources, follow the instructions in this wiki page and then proceed to compile with (don't modify the .h file as it says in the tools/env/README file):
make env
This will give us fw_printenv, in order to get fw_setenv we just have to change the name of the file. Magic!!
cp fw_printenv fw_setenv
The next thing we will need is the fw_env.config file with the appropiate settings for our board. Here comes the confusion :-)
In this file you have to specify:
Ok, so in order to get all this information the easyest thing is to read it from dmesg or from /proc/mtd
cat /proc/mtd
All my initial confusion comes from using an incorrect kernel, my first tries where with 2.6.28.10 and the driver used to read mtd was NAND, in the kernel configuration file I only had :
CONFIG_MTD_NAND=y
being the output of /proc/mtd:
dev: size erasesize name mtd0: 00080000 00040000 "X-Loader"mtd1: 001e0000 00040000 "U-Boot"mtd2: 00020000 00040000 "U-Boot Env"mtd3: 00500000 00040000 "Kernel"mtd4: 1f880000 00040000 "File System"
through "dmesg" I could see this line indicating something was wrong:
[ 1174.517120] Creating 5 MTD partitions on "omap2-onenand":[ 1174.522552] 0x00000000-0x00080000 : "X-Loader"[ 1174.528381] 0x00080000-0x00260000 : "U-Boot"[ 1174.533508] 0x00260000-0x00280000 : "U-Boot Env"[ 1174.538177] mtd: partition "U-Boot Env" doesn't start on an erase block boundary -- force read-only[ 1174.548126] 0x00280000-0x00780000 : "Kernel"[ 1174.553192] 0x00780000-0x20000000 : "File System"
But if we use the aproppiate kernel, in my case 2.6.33.7-0 with the onenand driver instead of the nand driver:
CONFIG_MTD_ONENAND=y
The output of /proc/mtd is different:
dev: size erasesize namemtd0: 00080000 00040000 "X-Loader"mtd1: 00180000 00040000 "U-Boot"mtd2: 00080000 00040000 "Environment"mtd3: 00300000 00040000 "Kernel"mtd4: 1fa80000 00040000 "File System"
Now we can fill in all the values we needed (that's what I thought)
Pretty easy right? wrong!!! The right values are:
I figured these out by reading different posts and by trial and error, but I still don't understand the environment size value or the flash sector size, I can imagine the device offset is 0 if you specify /dev/mtd2 but I'd be great if someone could edit this page and point out why are this the correct values.
In order to give it a try is better to poke with fw_printenv than with fw_setenv, because the first one just tries to read, so go ahead and try it:
fw_printenv
this should output something like:
ethact=smc911x-0distro=pokyproject=poky-image-satoipaddr=192.168.254.254netmask=255.255.255.0gatewayip=192.168.254.10serverip=192.168.254.10addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}::eth0:mmc-boot=mmc init 0; if fatload mmc 0 80000000 boot.ini; then source; else if fatload mmc 0 80000000 uImage; then run mmc-bootargs; bootm; fi; fionenand-bootargs=setenv bootargs ${bootargs-base} root=/dev/mtdblock4 rootfstype=jffs2 ; run addiponenand-boot=run onenand-bootargs; onenand read 80000000 280000 400000 ; bootm 80000000nfs-bootargs=setenv bootargs ${bootargs-base} root=/dev/nfs nfsroot=${serverip}:/srv/nfs/${distro}/${project}/${machine} ; run addipnfs-boot=if ping ${serverip}; then run nfs-bootargs; tftp 0x80000000 ${distro}/${project}/${machine}/uImage; bootm; fi;machine=igep0020mmc-bootargs=setenv bootargs ${bootargs-base} root=/dev/mmcblk0p2 rw rootwait dieid=${dieid#}dieid#=638a00040000000004036abc07016018mpurate=110stdin=serialstdout=serialstderr=serialbootargs-base=mem=512M console=ttyS2,115200n8 console=tty0 omapfb.mode=dvi:1024x768MR-16@60 mpurate=110bootcmd=run onenand-boot; run mmc-boot; if you get something like:
Warning: Bad CRC, using default environmentbootcmd=bootp; setenv bootargs root=/dev/nfs nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}::off; bootmbootdelay=5baudrate=115200 it means the values in /etc/fw_env.config are not correct, so don't even try fw_setenv
Now that we found out the correct values for /etc/fw_env.config you can just use fw_setenv with the same syntax as if you were in u-boot command line, to assing a value don't use "=" but a space.
./fw_setenv test 1234
then fw_printenv should output
test=1234
notice we didn't need to use saveenv as we would do in u-boot command line.
That's it!!
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There is a set of .
tools/env, which can be built with command: make env
For building against older versions of the headers (meaning before v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to make:
make MTD_VERSION=old env
The resulting binary is called fw_printenv, but actually includes support for setting environment variables too. To achieve this, the binary behaves according to the name it is invoked as, so you will have to create a link called fw_setenv to fw_printenv.
These tools work exactly like the U-Boot commands printenv resp. setenv You can either build these tools with a fixed configuration selected at compile time, or you can configure the tools using the /etc/fw_env.config configuration file in your target root filesystem. Here is an example configuration file:
# Configuration file for fw_(printenv/saveenv) utility.# Up to two entries are valid, in this case the redundand# environment sector is assumed present.########################################################################## For TQM8xxL modules:########################################################################## MTD device name Device offset Env. size Flash sector size/dev/mtd0 0x8000 0x4000 0x4000/dev/mtd0 0xC000 0x4000 0x4000########################################################################## For NSCU:########################################################################## MTD device name Device offset Env. size Flash sector size#/dev/mtd1 0x0000 0x8000 0x20000#/dev/mtd2 0x0000 0x8000 0x20000########################################################################## For LWMON########################################################################## MTD device name Device offset Env. size Flash sector size#/dev/mtd1 0x0000 0x2000 0x40000
代码分析：
README：
This is a demo implementation of a Linux command line tool to access
the U-Boot's environment variables.For the run-time utiltity configuration uncomment the line
#define CONFIG_FILE "/etc/fw_env.config" in fw_env.h.这个有误，应该是用配置文件时，不要注释掉这个宏
See comments in the fw_env.config file for definitions for the
particular board.Configuration can also be done via #defines in the fw_env.h file. The
following lines are relevant:#define HAVE_REDUND /* For systems with 2 env sectors */
#define DEVICE1_NAME "/dev/mtd1" #define DEVICE2_NAME "/dev/mtd2" #define DEVICE1_OFFSET 0x0000 #define ENV1_SIZE 0x4000 #define DEVICE1_ESIZE 0x4000 #define DEVICE2_OFFSET 0x0000 #define ENV2_SIZE 0x4000 #define DEVICE2_ESIZE 0x4000Current configuration matches the environment layout of the TRAB
board.HAVE_REDUND是用来环境变量备份用的
Un-define HAVE_REDUND, if you want to use the utlities on a system
that does not have support for redundant environment enabled. If HAVE_REDUND is undefined, DEVICE2_NAME is ignored, as is ENV2_SIZE and DEVICE2_ESIZE.The DEVICEx_NAME constants define which MTD character devices are to
be used to access the environment.The DEVICEx_OFFSET constants define the environment offset within the
MTD character device.ENVx_SIZE defines the size in bytes taken by the environment, which
may be less then flash sector size, if the environment takes less then 1 sector.DEVICEx_ESIZE defines the size of the first sector in the flash
partition where the environment resides.
DEVICEx_NAME设备名
DEVICEx_OFFSET设备中环境变量的偏移
ENVx_SIZE 环境变量大小，可能比1sector小
查看环境变量大小：
pri查看
Environment size: 1560/4092 bytes
include/configs/mv_kv.h
#define CFG_ENV_SIZE 0x1000
所以大小是0x1000
查看环境变量偏移：
#define CFG_MONITOR_LEN (512 << 10) /* Reserve 512 kB for Monitor */ uboot镜像长度 0x80000 =512k
//uboot的基址和环境变量的基址
#define CFG_MONITOR_BASE (CFG_FLASH_BASE) #define CFG_ENV_ADDR (CFG_MONITOR_BASE + CFG_MONITOR_LEN) 环境变量开始位置#define CFG_ENV_SIZE 0x1000 //4k
环境变量从0x80000开始 到0x80000+0x1000
根据CFG_ENV_ADDR 知道环境变量偏移是0x80000
查看erasesize
/opt/qtmarvell/mvqt/tools # cat /proc/mtd
dev: size erasesize name mtd0: 00100000 00010000 "uboot" mtd1: 00700000 00010000 "linux-root"
编译fw_printenv:
下载u-boot-2011.03.tar.bz2
根目录下：
make env HOSTCC=arm-mv5sft-linux-gnueabi-gcc
ln -s fw_printenv fw_setenv
修改fw_env.config ，根据上面的信息：
/opt/qtmarvell/mvqt/tools # cat fw_env.config
# Configuration file for fw_(printenv/saveenv) utility. # Up to two entries are valid, in this case the redundant # environment sector is assumed present. # Notice, that the "Number of sectors" is ignored on NOR.# MTD device name Device offset Env. size Flash sector size Number of sectors
/dev/mtd0 0x80000 0x1000 0x10000转载地址：http://qsgxf.baihongyu.com/