Config.in.legacy: update description for developers

The existing comments in Config.in.legacy are not entirely in-line with
current practice. The comments implies that BR2_LEGACY should not be set when
the conversion from old-to-new symbol can be done automatically using the
appropriate 'select' statements. However, none of the existing legacy options
does it this way. Moreover, I think it's intentional that the user is notified
of the change, so that the removal of the legacy options in later buildroot
versions no longer poses a problem.
Additionally, the comments now describe how to handle string options.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Thomas De Schampheleire 2013-09-02 22:07:50 +02:00 committed by Peter Korsgaard
parent 0764b1cf45
commit f8c56f5f62

View File

@ -1,13 +1,9 @@
#
# Config.in.legacy - support for backward compatibility
#
# When an existing Config.in symbol is removed, it should be added again in this
# file, and take appropriate action to approximate backward compatibility. If
# there is an equivalent (set of) new symbols, these can just be select'ed by
# the old symbol. This makes sure that running 'make oldconfig' will make things
# "just work" when upgrading to a new buildroot version. If the change is too
# fundamental and cannot be fixed by a simple select, then the old symbol should
# select BR2_LEGACY. If that symbol is set, the build will issue an error.
# When an existing Config.in symbol is removed, it should be added again in
# this file, and take appropriate action to approximate backward compatibility.
# This will make the transition for the user more convenient.
#
# When adding legacy symbols to this file, add them to the front. The oldest
# symbols will be removed again after about two years.
@ -15,6 +11,46 @@
# The symbol should be copied as-is from the place where it was previously
# defined, but the help text should be removed or replaced with something that
# explains how to fix it.
#
# For bool options, the old symbol should select BR2_LEGACY, so that the user
# is informed at build-time about selected legacy options.
# If there is an equivalent (set of) new symbols, these should be select'ed by
# the old symbol for backwards compatibility.
#
# For string options, it is not possible to directly select another symbol. In
# this case, a hidden wrap bool option has to be added, that defaults to y if
# the old string is not set at its default value. The wrap symbol should select
# BR2_LEGACY.
# If the original symbol has been renamed, the new symbol should use the value
# of the old symbol as default. This requires a change outside of
# Config.in.legacy, and this should be clearly marked as such below, so that
# removal of legacy options also include the removal of these external
# references.
#
# [Example: renaming a string option from FOO to BAR]
# original symbol:
# config BR2_FOO_STRING
# string "Some foo string"
#
# becomes:
# config BR2_BAR_STRING
# string "Some bar string"
# default BR2_FOO_STRING if BR2_FOO_STRING != "" # legacy
#
# and in Config.in.legacy:
# config BR2_FOO_STRING
# string "The foo string has been renamed"
# help
# <suitable help text>
#
# config BR2_FOO_STRING_WRAP
# bool
# default y if BR2_FOO_STRING != ""
# select BR2_LEGACY
#
# # Note: BR2_FOO_STRING is still referenced from package/foo/Config.in
#
# [End of example]
config BR2_LEGACY
bool