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 ---

(no changes since v6)

Changes in v6: - Move all updates to a separate patch

Changes in v5: - Minor updates as suggested by Wolfgang

Changes in v4: - Add new patch to move environment documentation to rST

README | 328 -------------------------------- doc/usage/environment.rst | 381 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 381 insertions(+), 328 deletions(-) create mode 100644 doc/usage/environment.rst

diff --git a/README b/README index 840b192aae5..f20bc38a41c 100644 --- a/README +++ b/README @@ -2999,334 +2999,6 @@ TODO. For now: just type "help <command>".

-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. - - i2cfast - (PPC405GP|PPC405EP only) - if set to 'y' configures Linux I2C driver for fast - mode (400kHZ). This environment variable is used in - initialization code. So, for changes to be effective - it must be saved and board must be reset. - - 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 - -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 - -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: - - 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 - - -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. - - -Further special Environment Variables: - - 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. - - Note for Redundant Ethernet Interfaces: =======================================

diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst new file mode 100644 index 00000000000..7a733b44556 --- /dev/null +++ b/doc/usage/environment.rst @@ -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.

Make various updates suggested during review of the rST conversion.

Signed-off-by: Simon Glass sjg@chromium.org Reviewed-by: Marek Behún marek.behun@nic.cz Suggested-by: Wolfgang Denk wd@denx.de ---

(no changes since v7)

Changes in v7: - A few more tweaks

Changes in v6: - Move all updates to a separate patch - More updates and improvements

Changes in v5: - Minor updates as suggested by Wolfgang

Changes in v4: - Add new patch to move environment documentation to rST

doc/usage/environment.rst | 36 +++++++++++++++++++++++++++--------- doc/usage/index.rst | 1 + 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst index adf2e067b58..a3eddbaaf2e 100644 --- a/doc/usage/environment.rst +++ b/doc/usage/environment.rst @@ -4,16 +4,20 @@ Environment Variables =====================

U-Boot supports user configuration using Environment Variables which -can be made persistent by saving to Flash memory. +can be made persistent by saving to persistent storage, for example flash +memory.

-Environment Variables are set using "setenv", printed using -"printenv", and saved to Flash using "saveenv". Using "setenv" +Environment Variables are set using "env set" (alias "setenv"), printed using +"env print" (alias "printenv"), and saved to persistent storage using +"env save" (alias "saveenv"). Using "env set" without a value can be used to delete a variable from the -environment. As long as you don't save the environment you are +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. +Some configuration is controlled by Environment Variables, so that setting the +variable can adjust the behaviour of U-Boot (e.g. autoboot delay, autoloading +from tftp).

Text-based Environment ---------------------- @@ -90,16 +94,24 @@ environment but work is underway to address this. List of environment variables -----------------------------

+Some configuration options can be set using Environment Variables. In many cases +the value in the default environment comes from a CONFIG option - see +`include/env_default.h`) for this. + This is most-likely not complete:

baudrate - see CONFIG_BAUDRATE + Current baud rate used by the serial console. The built-in value is set by + CONFIG_BAUDRATE (see `drivers/serial/Kconfig`)

bootdelay - see CONFIG_BOOTDELAY + Current autoboot delay. The built-in value is set by CONFIG_BOOTDELAY (see + `common/Kconfig`)

bootcmd - see CONFIG_BOOTCOMMAND + Defines a command string that is automatically executed when no character + is read on the console interface within a cetain boot delay after reset. + The built-in value is set by CONFIG_BOOTCOMMAND (see `common/Kconfig`)

bootargs Boot arguments when booting an RTOS image @@ -145,7 +157,7 @@ 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 + load any image using TFTP or DHCP.

autostart if set to "yes", an image loaded using the "bootp", @@ -311,6 +323,8 @@ vlan Ethernet is encapsulated/received over 802.1q VLAN tagged frames.

+ Note: This appears not to be used in U-Boot. See `README.VLAN`. + bootpretryperiod Period during which BOOTP/DHCP sends retries. Unsigned value, in milliseconds. If not set, the period will @@ -352,6 +366,10 @@ flash or offset in NAND flash. boards currently use other variables for these purposes, and some boards use these variables for other purposes.

+Also note that most of these variables are just a commonly used set of variable +names, used in some other variable definitions, but are not hard-coded anywhere +in U-Boot code. + ================= ============== ================ ============== Image File Name RAM Address Flash Location ================= ============== ================ ============== diff --git a/doc/usage/index.rst b/doc/usage/index.rst index 356f2a56181..1a79d1c03eb 100644 --- a/doc/usage/index.rst +++ b/doc/usage/index.rst @@ -5,6 +5,7 @@ Use U-Boot :maxdepth: 1

dfu + environment fdt_overlays fit netconsole