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Environment callbacks can already be configured from Kconfig with CONFIG_ENV_CALLBACK_LIST_STATIC, but static environment flags still require board headers to define CFG_ENV_FLAGS_LIST_STATIC. Add CONFIG_ENV_FLAGS_LIST_STATIC and use it as the only board-provided static environment flags list. Convert the remaining default-config users from CFG_ENV_FLAGS_LIST_STATIC to defconfig settings and drop the legacy header macro from ENV_FLAGS_LIST_STATIC. Move the environment flags format documentation out of README and into the developer environment documentation. Include the format in the Kconfig help as well. This lets boards configure writeable-list policy and type validation from defconfig without adding a config header solely for env flags. This preserves the behavior of default configs. Header-only cases that were inactive in upstream defconfigs are not converted into defconfig entries: iot2050 can add its list when enabling ENV_WRITEABLE_LIST, and smegw01 can add mmcdev:dw support if the unlocked SYS_BOOT_LOCKED=n configuration is needed. Signed-off-by: James Hilliard <james.hilliard1@gmail.com> Reviewed-by: Tom Rini <trini@konsulko.com> Reviewed-by: Simon Glass <sjg@chromium.org> Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com> Reviewed-by: Walter Schweizer <walter.schweizer@siemens.com>
92 lines
3.2 KiB
ReStructuredText
92 lines
3.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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Environment implementation
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==========================
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See :doc:`../usage/environment` for usage information.
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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 defconfig via menuconfig 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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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
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* value - new value of the environment variable
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* op - operation (create, overwrite, or delete)
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* flags - attributes of the environment variable change, see flags H_* in
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include/search.h
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The return value is 0 if the variable change is accepted and 1 otherwise.
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Flags for environment variables
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-------------------------------
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Environment flags validate the values given to environment variables and
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restrict how environment variables can be changed.
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The static list is configured with CONFIG_ENV_FLAGS_LIST_STATIC. The list
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must be in the following format::
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type_attribute = [s|d|x|b|i|m]
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access_attribute = [a|r|o|c|w]
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attributes = type_attribute[access_attribute]
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entry = variable_name[:attributes]
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list = entry[,list]
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The type attributes are:
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* s - String (default)
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* d - Decimal
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* x - Hexadecimal
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* b - Boolean ([1yYtT|0nNfF])
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* i - IP address, if networking is enabled
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* m - MAC address, if networking is enabled
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The access attributes are:
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* a - Any (default)
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* r - Read-only
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* o - Write-once
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* c - Change-default
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* w - Writeable, if CONFIG_ENV_WRITEABLE_LIST is enabled
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CONFIG_ENV_FLAGS_LIST_DEFAULT defines the ``.flags`` variable in the
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default or embedded environment. Any association in ``.flags`` overrides
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an association in the static list.
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If CONFIG_REGEX is defined, the variable name is evaluated as a regular
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expression. This allows multiple variables to define the same flags without
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explicitly listing them all.
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