From: Simon Glass <sjg@chromium.org>
To: U-Boot Mailing List <u-boot@lists.denx.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>,
Tom Rini <trini@konsulko.com>, Wolfgang Denk <wd@denx.de>,
Simon Glass <sjg@chromium.org>
Subject: [PATCH v6 6/7] doc: Improve environment documentation
Date: Thu, 14 Oct 2021 12:22:56 -0600 [thread overview]
Message-ID: <20211014182257.468649-5-sjg@chromium.org> (raw)
In-Reply-To: <20211014182257.468649-1-sjg@chromium.org>
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
--
2.33.0.1079.g6e70778dc9-goog
next prev parent reply other threads:[~2021-10-14 18:24 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 18:22 [PATCH v6 0/7] env: Allow environment in text files Simon Glass
2021-10-14 18:22 ` [PATCH v6 1/7] binman: Allow timeout to occur in the image or its section Simon Glass
2021-10-14 18:22 ` [PATCH v6 2/7] sandbox: Drop distro_boot Simon Glass
2021-10-14 18:22 ` [PATCH v6 3/7] doc: Move environment documentation to rST Simon Glass
2021-10-14 18:22 ` [PATCH v6 4/7] env: Allow U-Boot scripts to be placed in a .env file Simon Glass
2021-10-15 14:32 ` Wolfgang Denk
2021-10-15 15:15 ` Simon Glass
2021-10-18 11:58 ` Wolfgang Denk
2021-10-18 13:37 ` Tom Rini
2021-10-18 14:10 ` Wolfgang Denk
2021-10-18 14:24 ` Tom Rini
2021-10-19 10:33 ` Wolfgang Denk
2021-10-18 18:12 ` Simon Glass
2021-10-19 10:38 ` Wolfgang Denk
2021-10-18 18:12 ` Simon Glass
2021-10-19 10:46 ` Wolfgang Denk
2021-10-19 14:11 ` Simon Glass
2021-10-19 16:09 ` Wolfgang Denk
2021-10-19 16:14 ` Simon Glass
2021-10-14 18:22 ` [PATCH v6 5/7] sandbox: Use a text-based environment Simon Glass
2021-10-14 18:22 ` Simon Glass [this message]
2021-10-14 18:22 ` [PATCH v6 7/7] bootm: Tidy up use of autostart env var Simon Glass
2021-10-15 14:45 ` Wolfgang Denk
2021-10-24 19:53 ` Simon Glass
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