Make various updates suggested during review of the rST conversion.
Signed-off-by: Simon Glass sjg@chromium.org Suggested-by: Wolfgang Denk wd@denx.de ---
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 | 35 ++++++++++++++++++++++++++--------- doc/usage/index.rst | 1 + 2 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst index 76915484b85..ef9cd20715a 100644 --- a/doc/usage/environment.rst +++ b/doc/usage/environment.rst @@ -5,16 +5,20 @@ 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 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).
The default environment is created in `include/env_default.h`, and can be augmented by various `CONFIG` defines. See that file for details. In @@ -68,18 +72,25 @@ Example:: echo CONFIG_SYS_BOARD boot failed - please check your image echo Load address is CONFIG_SYS_LOAD_ADDR
-Some configuration options can be set using 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. +
List of environment variables (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 @@ -125,7 +136,7 @@ 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", @@ -291,6 +302,8 @@ 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 @@ -332,6 +345,10 @@ 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