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| -rw-r--r-- | meta/conf/machine/include/README | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/meta/conf/machine/include/README b/meta/conf/machine/include/README index 65d09428a8..6c390adeee 100644 --- a/meta/conf/machine/include/README +++ b/meta/conf/machine/include/README @@ -1,6 +1,9 @@ 2012/03/30 - Mark Hatle <mark.hatle@windriver.com> - Initial Revision + +Introduction +============ The individual CPU, and ABI tunings are contained in this directory. A number of local and global variables are used to control the way the tunings are setup and how they work together to specify an optimized @@ -79,3 +82,19 @@ configured in the same way that TUNE_CCARGS is. BASE_LIB_tune-<tune> - The "/lib" location for a specific ABI. This is used in a multilib configuration to place the libraries in the correct, non-conflicting locations. + + +Best Practice +============= +The tune infrastructure is designed to be hierarchical. When writing a +new tune file for a "fast-forward" CPU architecture (one that supports +everything from a previous generation), it is recommended to require the +previous generation tune file and specify PACKAGE_EXTRA_ARCHS using the +previous generation's override and appending the new tune. Note that +only one previous tune file should be included to avoid mutiple includes +of the base arch which could lead to a broken configuration due to +multiple prepend and append assignments. + +For example, for x86, there is a common x86/arch-x86.inc which is +included in the base i586 tune file. The core2 tune builds +on that, and corei7 builds on core2. |