doc: Move environment documentation to rST
Move this from the README to rST format. Drop i2cfast since it is obviously obsolete and breaks the formatting. Other changes and improvements are in a following patch. Signed-off-by: Simon Glass <sjg@chromium.org> Acked-by: Marek Behún <marek.behun@nic.cz>
This commit is contained in:
Simon Glass
Tom Rini
parent
79c0e8a935
commit
ea754aa565
328
README
328
README
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@ -2966,334 +2966,6 @@ TODO.
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For now: just type "help <command>".
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Environment Variables:
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======================
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U-Boot supports user configuration using Environment Variables which
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can be made persistent by saving to Flash memory.
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Environment Variables are set using "setenv", printed using
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"printenv", and saved to Flash using "saveenv". Using "setenv"
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without a value can be used to delete a variable from the
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environment. As long as you don't save the environment you are
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working with an in-memory copy. In case the Flash area containing the
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environment is erased by accident, a default environment is provided.
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Some configuration options can be set using Environment Variables.
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List of environment variables (most likely not complete):
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baudrate - see CONFIG_BAUDRATE
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bootdelay - see CONFIG_BOOTDELAY
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bootcmd - see CONFIG_BOOTCOMMAND
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bootargs - Boot arguments when booting an RTOS image
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bootfile - Name of the image to load with TFTP
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bootm_low - Memory range available for image processing in the bootm
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command can be restricted. This variable is given as
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a hexadecimal number and defines lowest address allowed
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for use by the bootm command. See also "bootm_size"
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environment variable. Address defined by "bootm_low" is
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also the base of the initial memory mapping for the Linux
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kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
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bootm_mapsize.
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bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
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This variable is given as a hexadecimal number and it
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defines the size of the memory region starting at base
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address bootm_low that is accessible by the Linux kernel
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during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
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as the default value if it is defined, and bootm_size is
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used otherwise.
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bootm_size - Memory range available for image processing in the bootm
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command can be restricted. This variable is given as
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a hexadecimal number and defines the size of the region
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allowed for use by the bootm command. See also "bootm_low"
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environment variable.
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bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
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updatefile - Location of the software update file on a TFTP server, used
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by the automatic software update feature. Please refer to
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documentation in doc/README.update for more details.
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autoload - if set to "no" (any string beginning with 'n'),
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"bootp" will just load perform a lookup of the
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configuration from the BOOTP server, but not try to
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load any image using TFTP
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autostart - if set to "yes", an image loaded using the "bootp",
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"rarpboot", "tftpboot" or "diskboot" commands will
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be automatically started (by internally calling
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"bootm")
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If set to "no", a standalone image passed to the
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"bootm" command will be copied to the load address
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(and eventually uncompressed), but NOT be started.
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This can be used to load and uncompress arbitrary
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data.
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fdt_high - if set this restricts the maximum address that the
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flattened device tree will be copied into upon boot.
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For example, if you have a system with 1 GB memory
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at physical address 0x10000000, while Linux kernel
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only recognizes the first 704 MB as low memory, you
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may need to set fdt_high as 0x3C000000 to have the
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device tree blob be copied to the maximum address
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of the 704 MB low memory, so that Linux kernel can
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access it during the boot procedure.
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If this is set to the special value 0xFFFFFFFF then
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the fdt will not be copied at all on boot. For this
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to work it must reside in writable memory, have
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sufficient padding on the end of it for u-boot to
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add the information it needs into it, and the memory
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must be accessible by the kernel.
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fdtcontroladdr- if set this is the address of the control flattened
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device tree used by U-Boot when CONFIG_OF_CONTROL is
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defined.
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i2cfast - (PPC405GP|PPC405EP only)
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if set to 'y' configures Linux I2C driver for fast
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mode (400kHZ). This environment variable is used in
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initialization code. So, for changes to be effective
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it must be saved and board must be reset.
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initrd_high - restrict positioning of initrd images:
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If this variable is not set, initrd images will be
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copied to the highest possible address in RAM; this
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is usually what you want since it allows for
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maximum initrd size. If for some reason you want to
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make sure that the initrd image is loaded below the
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CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
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variable to a value of "no" or "off" or "0".
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Alternatively, you can set it to a maximum upper
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address to use (U-Boot will still check that it
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does not overwrite the U-Boot stack and data).
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For instance, when you have a system with 16 MB
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RAM, and want to reserve 4 MB from use by Linux,
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you can do this by adding "mem=12M" to the value of
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the "bootargs" variable. However, now you must make
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sure that the initrd image is placed in the first
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12 MB as well - this can be done with
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setenv initrd_high 00c00000
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If you set initrd_high to 0xFFFFFFFF, this is an
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indication to U-Boot that all addresses are legal
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for the Linux kernel, including addresses in flash
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memory. In this case U-Boot will NOT COPY the
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ramdisk at all. This may be useful to reduce the
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boot time on your system, but requires that this
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feature is supported by your Linux kernel.
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ipaddr - IP address; needed for tftpboot command
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loadaddr - Default load address for commands like "bootp",
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"rarpboot", "tftpboot", "loadb" or "diskboot"
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loads_echo - see CONFIG_LOADS_ECHO
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serverip - TFTP server IP address; needed for tftpboot command
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bootretry - see CONFIG_BOOT_RETRY_TIME
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bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
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bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
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ethprime - controls which interface is used first.
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ethact - controls which interface is currently active.
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For example you can do the following
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=> setenv ethact FEC
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=> ping 192.168.0.1 # traffic sent on FEC
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=> setenv ethact SCC
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=> ping 10.0.0.1 # traffic sent on SCC
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ethrotate - When set to "no" U-Boot does not go through all
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available network interfaces.
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It just stays at the currently selected interface.
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netretry - When set to "no" each network operation will
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either succeed or fail without retrying.
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When set to "once" the network operation will
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fail when all the available network interfaces
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are tried once without success.
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Useful on scripts which control the retry operation
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themselves.
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npe_ucode - set load address for the NPE microcode
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silent_linux - If set then Linux will be told to boot silently, by
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changing the console to be empty. If "yes" it will be
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made silent. If "no" it will not be made silent. If
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unset, then it will be made silent if the U-Boot console
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is silent.
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tftpsrcp - If this is set, the value is used for TFTP's
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UDP source port.
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tftpdstp - If this is set, the value is used for TFTP's UDP
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destination port instead of the Well Know Port 69.
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tftpblocksize - Block size to use for TFTP transfers; if not set,
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we use the TFTP server's default block size
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tftptimeout - Retransmission timeout for TFTP packets (in milli-
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seconds, minimum value is 1000 = 1 second). Defines
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when a packet is considered to be lost so it has to
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be retransmitted. The default is 5000 = 5 seconds.
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Lowering this value may make downloads succeed
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faster in networks with high packet loss rates or
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with unreliable TFTP servers.
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tftptimeoutcountmax - maximum count of TFTP timeouts (no
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unit, minimum value = 0). Defines how many timeouts
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can happen during a single file transfer before that
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transfer is aborted. The default is 10, and 0 means
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'no timeouts allowed'. Increasing this value may help
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downloads succeed with high packet loss rates, or with
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unreliable TFTP servers or client hardware.
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tftpwindowsize - if this is set, the value is used for TFTP's
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window size as described by RFC 7440.
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This means the count of blocks we can receive before
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sending ack to server.
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vlan - When set to a value < 4095 the traffic over
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Ethernet is encapsulated/received over 802.1q
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VLAN tagged frames.
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bootpretryperiod - Period during which BOOTP/DHCP sends retries.
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Unsigned value, in milliseconds. If not set, the period will
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be either the default (28000), or a value based on
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CONFIG_NET_RETRY_COUNT, if defined. This value has
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precedence over the valu based on CONFIG_NET_RETRY_COUNT.
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memmatches - Number of matches found by the last 'ms' command, in hex
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memaddr - Address of the last match found by the 'ms' command, in hex,
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or 0 if none
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mempos - Index position of the last match found by the 'ms' command,
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in units of the size (.b, .w, .l) of the search
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zbootbase - (x86 only) Base address of the bzImage 'setup' block
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zbootaddr - (x86 only) Address of the loaded bzImage, typically
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BZIMAGE_LOAD_ADDR which is 0x100000
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The following image location variables contain the location of images
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used in booting. The "Image" column gives the role of the image and is
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not an environment variable name. The other columns are environment
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variable names. "File Name" gives the name of the file on a TFTP
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server, "RAM Address" gives the location in RAM the image will be
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loaded to, and "Flash Location" gives the image's address in NOR
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flash or offset in NAND flash.
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*Note* - these variables don't have to be defined for all boards, some
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boards currently use other variables for these purposes, and some
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boards use these variables for other purposes.
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Image File Name RAM Address Flash Location
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----- --------- ----------- --------------
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u-boot u-boot u-boot_addr_r u-boot_addr
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Linux kernel bootfile kernel_addr_r kernel_addr
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device tree blob fdtfile fdt_addr_r fdt_addr
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ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
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The following environment variables may be used and automatically
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updated by the network boot commands ("bootp" and "rarpboot"),
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depending the information provided by your boot server:
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bootfile - see above
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dnsip - IP address of your Domain Name Server
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dnsip2 - IP address of your secondary Domain Name Server
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gatewayip - IP address of the Gateway (Router) to use
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hostname - Target hostname
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ipaddr - see above
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netmask - Subnet Mask
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rootpath - Pathname of the root filesystem on the NFS server
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serverip - see above
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There are two special Environment Variables:
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serial# - contains hardware identification information such
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as type string and/or serial number
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ethaddr - Ethernet address
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These variables can be set only once (usually during manufacturing of
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the board). U-Boot refuses to delete or overwrite these variables
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once they have been set once.
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Further special Environment Variables:
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ver - Contains the U-Boot version string as printed
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with the "version" command. This variable is
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readonly (see CONFIG_VERSION_VARIABLE).
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Please note that changes to some configuration parameters may take
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only effect after the next boot (yes, that's just like Windoze :-).
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Callback functions for environment variables:
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---------------------------------------------
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For some environment variables, the behavior of u-boot needs to change
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when their values are changed. This functionality allows functions to
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be associated with arbitrary variables. On creation, overwrite, or
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deletion, the callback will provide the opportunity for some side
|
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effect to happen or for the change to be rejected.
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The callbacks are named and associated with a function using the
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U_BOOT_ENV_CALLBACK macro in your board or driver code.
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These callbacks are associated with variables in one of two ways. The
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static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
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in the board configuration to a string that defines a list of
|
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associations. The list must be in the following format:
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||||
entry = variable_name[:callback_name]
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list = entry[,list]
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|
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If the callback name is not specified, then the callback is deleted.
|
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Spaces are also allowed anywhere in the list.
|
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Callbacks can also be associated by defining the ".callbacks" variable
|
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with the same list format above. Any association in ".callbacks" will
|
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override any association in the static list. You can define
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CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
|
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".callbacks" environment variable in the default or embedded environment.
|
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If CONFIG_REGEX is defined, the variable_name above is evaluated as a
|
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regular expression. This allows multiple variables to be connected to
|
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the same callback without explicitly listing them all out.
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The signature of the callback functions is:
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int callback(const char *name, const char *value, enum env_op op, int flags)
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* name - changed environment variable
|
||||
* value - new value of the environment variable
|
||||
* op - operation (create, overwrite, or delete)
|
||||
* flags - attributes of the environment variable change, see flags H_* in
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include/search.h
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|
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The return value is 0 if the variable change is accepted and 1 otherwise.
|
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|
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Note for Redundant Ethernet Interfaces:
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=======================================
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|
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|
|
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381
doc/usage/environment.rst
Normal file
381
doc/usage/environment.rst
Normal file
|
|
@ -0,0 +1,381 @@
|
|||
.. SPDX-License-Identifier: GPL-2.0+
|
||||
|
||||
Environment Variables
|
||||
=====================
|
||||
|
||||
U-Boot supports user configuration using Environment Variables which
|
||||
can be made persistent by saving to Flash memory.
|
||||
|
||||
Environment Variables are set using "setenv", printed using
|
||||
"printenv", and saved to Flash using "saveenv". Using "setenv"
|
||||
without a value can be used to delete a variable from the
|
||||
environment. As long as you don't save the environment you are
|
||||
working with an in-memory copy. In case the Flash area containing the
|
||||
environment is erased by accident, a default environment is provided.
|
||||
|
||||
Some configuration options can be set using Environment Variables.
|
||||
|
||||
List of environment variables (most likely not complete):
|
||||
|
||||
baudrate
|
||||
see CONFIG_BAUDRATE
|
||||
|
||||
bootdelay
|
||||
see CONFIG_BOOTDELAY
|
||||
|
||||
bootcmd
|
||||
see CONFIG_BOOTCOMMAND
|
||||
|
||||
bootargs
|
||||
Boot arguments when booting an RTOS image
|
||||
|
||||
bootfile
|
||||
Name of the image to load with TFTP
|
||||
|
||||
bootm_low
|
||||
Memory range available for image processing in the bootm
|
||||
command can be restricted. This variable is given as
|
||||
a hexadecimal number and defines lowest address allowed
|
||||
for use by the bootm command. See also "bootm_size"
|
||||
environment variable. Address defined by "bootm_low" is
|
||||
also the base of the initial memory mapping for the Linux
|
||||
kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
|
||||
bootm_mapsize.
|
||||
|
||||
bootm_mapsize
|
||||
Size of the initial memory mapping for the Linux kernel.
|
||||
This variable is given as a hexadecimal number and it
|
||||
defines the size of the memory region starting at base
|
||||
address bootm_low that is accessible by the Linux kernel
|
||||
during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
|
||||
as the default value if it is defined, and bootm_size is
|
||||
used otherwise.
|
||||
|
||||
bootm_size
|
||||
Memory range available for image processing in the bootm
|
||||
command can be restricted. This variable is given as
|
||||
a hexadecimal number and defines the size of the region
|
||||
allowed for use by the bootm command. See also "bootm_low"
|
||||
environment variable.
|
||||
|
||||
bootstopkeysha256, bootdelaykey, bootstopkey
|
||||
See README.autoboot
|
||||
|
||||
updatefile
|
||||
Location of the software update file on a TFTP server, used
|
||||
by the automatic software update feature. Please refer to
|
||||
documentation in doc/README.update for more details.
|
||||
|
||||
autoload
|
||||
if set to "no" (any string beginning with 'n'),
|
||||
"bootp" will just load perform a lookup of the
|
||||
configuration from the BOOTP server, but not try to
|
||||
load any image using TFTP
|
||||
|
||||
autostart
|
||||
if set to "yes", an image loaded using the "bootp",
|
||||
"rarpboot", "tftpboot" or "diskboot" commands will
|
||||
be automatically started (by internally calling
|
||||
"bootm")
|
||||
|
||||
If set to "no", a standalone image passed to the
|
||||
"bootm" command will be copied to the load address
|
||||
(and eventually uncompressed), but NOT be started.
|
||||
This can be used to load and uncompress arbitrary
|
||||
data.
|
||||
|
||||
fdt_high
|
||||
if set this restricts the maximum address that the
|
||||
flattened device tree will be copied into upon boot.
|
||||
For example, if you have a system with 1 GB memory
|
||||
at physical address 0x10000000, while Linux kernel
|
||||
only recognizes the first 704 MB as low memory, you
|
||||
may need to set fdt_high as 0x3C000000 to have the
|
||||
device tree blob be copied to the maximum address
|
||||
of the 704 MB low memory, so that Linux kernel can
|
||||
access it during the boot procedure.
|
||||
|
||||
If this is set to the special value 0xFFFFFFFF then
|
||||
the fdt will not be copied at all on boot. For this
|
||||
to work it must reside in writable memory, have
|
||||
sufficient padding on the end of it for u-boot to
|
||||
add the information it needs into it, and the memory
|
||||
must be accessible by the kernel.
|
||||
|
||||
fdtcontroladdr
|
||||
if set this is the address of the control flattened
|
||||
device tree used by U-Boot when CONFIG_OF_CONTROL is
|
||||
defined.
|
||||
|
||||
initrd_high
|
||||
restrict positioning of initrd images:
|
||||
If this variable is not set, initrd images will be
|
||||
copied to the highest possible address in RAM; this
|
||||
is usually what you want since it allows for
|
||||
maximum initrd size. If for some reason you want to
|
||||
make sure that the initrd image is loaded below the
|
||||
CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
|
||||
variable to a value of "no" or "off" or "0".
|
||||
Alternatively, you can set it to a maximum upper
|
||||
address to use (U-Boot will still check that it
|
||||
does not overwrite the U-Boot stack and data).
|
||||
|
||||
For instance, when you have a system with 16 MB
|
||||
RAM, and want to reserve 4 MB from use by Linux,
|
||||
you can do this by adding "mem=12M" to the value of
|
||||
the "bootargs" variable. However, now you must make
|
||||
sure that the initrd image is placed in the first
|
||||
12 MB as well - this can be done with::
|
||||
|
||||
setenv initrd_high 00c00000
|
||||
|
||||
If you set initrd_high to 0xFFFFFFFF, this is an
|
||||
indication to U-Boot that all addresses are legal
|
||||
for the Linux kernel, including addresses in flash
|
||||
memory. In this case U-Boot will NOT COPY the
|
||||
ramdisk at all. This may be useful to reduce the
|
||||
boot time on your system, but requires that this
|
||||
feature is supported by your Linux kernel.
|
||||
|
||||
ipaddr
|
||||
IP address; needed for tftpboot command
|
||||
|
||||
loadaddr
|
||||
Default load address for commands like "bootp",
|
||||
"rarpboot", "tftpboot", "loadb" or "diskboot"
|
||||
|
||||
loads_echo
|
||||
see CONFIG_LOADS_ECHO
|
||||
|
||||
serverip
|
||||
TFTP server IP address; needed for tftpboot command
|
||||
|
||||
bootretry
|
||||
see CONFIG_BOOT_RETRY_TIME
|
||||
|
||||
bootdelaykey
|
||||
see CONFIG_AUTOBOOT_DELAY_STR
|
||||
|
||||
bootstopkey
|
||||
see CONFIG_AUTOBOOT_STOP_STR
|
||||
|
||||
ethprime
|
||||
controls which interface is used first.
|
||||
|
||||
ethact
|
||||
controls which interface is currently active.
|
||||
For example you can do the following::
|
||||
|
||||
=> setenv ethact FEC
|
||||
=> ping 192.168.0.1 # traffic sent on FEC
|
||||
=> setenv ethact SCC
|
||||
=> ping 10.0.0.1 # traffic sent on SCC
|
||||
|
||||
ethrotate
|
||||
When set to "no" U-Boot does not go through all
|
||||
available network interfaces.
|
||||
It just stays at the currently selected interface.
|
||||
|
||||
netretry
|
||||
When set to "no" each network operation will
|
||||
either succeed or fail without retrying.
|
||||
When set to "once" the network operation will
|
||||
fail when all the available network interfaces
|
||||
are tried once without success.
|
||||
Useful on scripts which control the retry operation
|
||||
themselves.
|
||||
|
||||
npe_ucode
|
||||
set load address for the NPE microcode
|
||||
|
||||
silent_linux
|
||||
If set then Linux will be told to boot silently, by
|
||||
changing the console to be empty. If "yes" it will be
|
||||
made silent. If "no" it will not be made silent. If
|
||||
unset, then it will be made silent if the U-Boot console
|
||||
is silent.
|
||||
|
||||
tftpsrcp
|
||||
If this is set, the value is used for TFTP's
|
||||
UDP source port.
|
||||
|
||||
tftpdstp
|
||||
If this is set, the value is used for TFTP's UDP
|
||||
destination port instead of the Well Know Port 69.
|
||||
|
||||
tftpblocksize
|
||||
Block size to use for TFTP transfers; if not set,
|
||||
we use the TFTP server's default block size
|
||||
|
||||
tftptimeout
|
||||
Retransmission timeout for TFTP packets (in milli-
|
||||
seconds, minimum value is 1000 = 1 second). Defines
|
||||
when a packet is considered to be lost so it has to
|
||||
be retransmitted. The default is 5000 = 5 seconds.
|
||||
Lowering this value may make downloads succeed
|
||||
faster in networks with high packet loss rates or
|
||||
with unreliable TFTP servers.
|
||||
|
||||
tftptimeoutcountmax
|
||||
maximum count of TFTP timeouts (no
|
||||
unit, minimum value = 0). Defines how many timeouts
|
||||
can happen during a single file transfer before that
|
||||
transfer is aborted. The default is 10, and 0 means
|
||||
'no timeouts allowed'. Increasing this value may help
|
||||
downloads succeed with high packet loss rates, or with
|
||||
unreliable TFTP servers or client hardware.
|
||||
|
||||
tftpwindowsize
|
||||
if this is set, the value is used for TFTP's
|
||||
window size as described by RFC 7440.
|
||||
This means the count of blocks we can receive before
|
||||
sending ack to server.
|
||||
|
||||
vlan
|
||||
When set to a value < 4095 the traffic over
|
||||
Ethernet is encapsulated/received over 802.1q
|
||||
VLAN tagged frames.
|
||||
|
||||
bootpretryperiod
|
||||
Period during which BOOTP/DHCP sends retries.
|
||||
Unsigned value, in milliseconds. If not set, the period will
|
||||
be either the default (28000), or a value based on
|
||||
CONFIG_NET_RETRY_COUNT, if defined. This value has
|
||||
precedence over the valu based on CONFIG_NET_RETRY_COUNT.
|
||||
|
||||
memmatches
|
||||
Number of matches found by the last 'ms' command, in hex
|
||||
|
||||
memaddr
|
||||
Address of the last match found by the 'ms' command, in hex,
|
||||
or 0 if none
|
||||
|
||||
mempos
|
||||
Index position of the last match found by the 'ms' command,
|
||||
in units of the size (.b, .w, .l) of the search
|
||||
|
||||
zbootbase
|
||||
(x86 only) Base address of the bzImage 'setup' block
|
||||
|
||||
zbootaddr
|
||||
(x86 only) Address of the loaded bzImage, typically
|
||||
BZIMAGE_LOAD_ADDR which is 0x100000
|
||||
|
||||
|
||||
Image locations
|
||||
---------------
|
||||
|
||||
The following image location variables contain the location of images
|
||||
used in booting. The "Image" column gives the role of the image and is
|
||||
not an environment variable name. The other columns are environment
|
||||
variable names. "File Name" gives the name of the file on a TFTP
|
||||
server, "RAM Address" gives the location in RAM the image will be
|
||||
loaded to, and "Flash Location" gives the image's address in NOR
|
||||
flash or offset in NAND flash.
|
||||
|
||||
*Note* - these variables don't have to be defined for all boards, some
|
||||
boards currently use other variables for these purposes, and some
|
||||
boards use these variables for other purposes.
|
||||
|
||||
================= ============== ================ ==============
|
||||
Image File Name RAM Address Flash Location
|
||||
================= ============== ================ ==============
|
||||
u-boot u-boot u-boot_addr_r u-boot_addr
|
||||
Linux kernel bootfile kernel_addr_r kernel_addr
|
||||
device tree blob fdtfile fdt_addr_r fdt_addr
|
||||
ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
|
||||
================= ============== ================ ==============
|
||||
|
||||
|
||||
Automatically updated variables
|
||||
-------------------------------
|
||||
|
||||
The following environment variables may be used and automatically
|
||||
updated by the network boot commands ("bootp" and "rarpboot"),
|
||||
depending the information provided by your boot server:
|
||||
|
||||
========= ===================================================
|
||||
Variable Notes
|
||||
========= ===================================================
|
||||
bootfile see above
|
||||
dnsip IP address of your Domain Name Server
|
||||
dnsip2 IP address of your secondary Domain Name Server
|
||||
gatewayip IP address of the Gateway (Router) to use
|
||||
hostname Target hostname
|
||||
ipaddr See above
|
||||
netmask Subnet Mask
|
||||
rootpath Pathname of the root filesystem on the NFS server
|
||||
serverip see above
|
||||
========= ===================================================
|
||||
|
||||
|
||||
Special environment variables
|
||||
-----------------------------
|
||||
|
||||
There are two special Environment Variables:
|
||||
|
||||
serial#
|
||||
contains hardware identification information such as type string and/or
|
||||
serial number
|
||||
ethaddr
|
||||
Ethernet address
|
||||
|
||||
These variables can be set only once (usually during manufacturing of
|
||||
the board). U-Boot refuses to delete or overwrite these variables
|
||||
once they have been set once.
|
||||
|
||||
Also:
|
||||
|
||||
ver
|
||||
Contains the U-Boot version string as printed
|
||||
with the "version" command. This variable is
|
||||
readonly (see CONFIG_VERSION_VARIABLE).
|
||||
|
||||
Please note that changes to some configuration parameters may take
|
||||
only effect after the next boot (yes, that's just like Windoze :-).
|
||||
|
||||
|
||||
Callback functions for environment variables
|
||||
--------------------------------------------
|
||||
|
||||
For some environment variables, the behavior of u-boot needs to change
|
||||
when their values are changed. This functionality allows functions to
|
||||
be associated with arbitrary variables. On creation, overwrite, or
|
||||
deletion, the callback will provide the opportunity for some side
|
||||
effect to happen or for the change to be rejected.
|
||||
|
||||
The callbacks are named and associated with a function using the
|
||||
U_BOOT_ENV_CALLBACK macro in your board or driver code.
|
||||
|
||||
These callbacks are associated with variables in one of two ways. The
|
||||
static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
|
||||
in the board configuration to a string that defines a list of
|
||||
associations. The list must be in the following format::
|
||||
|
||||
entry = variable_name[:callback_name]
|
||||
list = entry[,list]
|
||||
|
||||
If the callback name is not specified, then the callback is deleted.
|
||||
Spaces are also allowed anywhere in the list.
|
||||
|
||||
Callbacks can also be associated by defining the ".callbacks" variable
|
||||
with the same list format above. Any association in ".callbacks" will
|
||||
override any association in the static list. You can define
|
||||
CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
|
||||
".callbacks" environment variable in the default or embedded environment.
|
||||
|
||||
If CONFIG_REGEX is defined, the variable_name above is evaluated as a
|
||||
regular expression. This allows multiple variables to be connected to
|
||||
the same callback without explicitly listing them all out.
|
||||
|
||||
The signature of the callback functions is::
|
||||
|
||||
int callback(const char *name, const char *value, enum env_op op, int flags)
|
||||
|
||||
* name - changed environment variable
|
||||
* value - new value of the environment variable
|
||||
* op - operation (create, overwrite, or delete)
|
||||
* flags - attributes of the environment variable change, see flags H_* in
|
||||
include/search.h
|
||||
|
||||
The return value is 0 if the variable change is accepted and 1 otherwise.
|
||||
Loading…
Reference in New Issue
Block a user