From d029e786b56b1e38fc5ac7243ba61672f47a7e18 Mon Sep 17 00:00:00 2001 From: Scott Rifenbark Date: Mon, 28 Jan 2013 11:18:25 -0600 Subject: kernel-dev: Added new appendix for kernel concepts. (From yocto-docs rev: e25465c6d177a27d3dee742ebc958ae30f968ffa) Signed-off-by: Scott Rifenbark Signed-off-by: Richard Purdie --- .../kernel-dev/kernel-dev-concepts-appx.xml | 89 ++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 documentation/kernel-dev/kernel-dev-concepts-appx.xml (limited to 'documentation/kernel-dev') diff --git a/documentation/kernel-dev/kernel-dev-concepts-appx.xml b/documentation/kernel-dev/kernel-dev-concepts-appx.xml new file mode 100644 index 0000000000..d78d2dc86c --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-concepts-appx.xml @@ -0,0 +1,89 @@ + %poky; ] > + + +Advanced Kernel Concepts + +
+ Yocto Project Kernel Development and Maintenance + + Kernels available through the Yocto Project, like other kernels, are based off the Linux + kernel releases from . + At the beginning of a major development cycle, the Yocto Project team + chooses its kernel based on factors such as release timing, the anticipated release + timing of final upstream kernel.org versions, and Yocto Project + feature requirements. + Typically, the kernel chosen is in the + final stages of development by the community. + In other words, the kernel is in the release + candidate or "rc" phase and not yet a final release. + But, by being in the final stages of external development, the team knows that the + kernel.org final release will clearly be within the early stages of + the Yocto Project development window. + + + This balance allows the team to deliver the most up-to-date kernel + possible, while still ensuring that the team has a stable official release for + the baseline Linux kernel version. + + + The ultimate source for kernels available through the Yocto Project are released kernels + from kernel.org. + In addition to a foundational kernel from kernel.org, the + kernels available contain a mix of important new mainline + developments, non-mainline developments (when there is no alternative), + Board Support Package (BSP) developments, + and custom features. + These additions result in a commercially released Yocto Project Linux kernel that caters + to specific embedded designer needs for targeted hardware. + + + Once a kernel is officially released, the Yocto Project team goes into + their next development cycle, or upward revision (uprev) cycle, while still + continuing maintenance on the released kernel. + It is important to note that the most sustainable and stable way + to include feature development upstream is through a kernel uprev process. + Back-porting hundreds of individual fixes and minor features from various + kernel versions is not sustainable and can easily compromise quality. + + + During the uprev cycle, the Yocto Project team uses an ongoing analysis of + kernel development, BSP support, and release timing to select the best + possible kernel.org version. + The team continually monitors community kernel + development to look for significant features of interest. + The team does consider back-porting large features if they have a significant advantage. + User or community demand can also trigger a back-port or creation of new + functionality in the Yocto Project baseline kernel during the uprev cycle. + + + Generally speaking, every new kernel both adds features and introduces new bugs. + These consequences are the basic properties of upstream kernel development and are + managed by the Yocto Project team's kernel strategy. + It is the Yocto Project team's policy to not back-port minor features to the released kernel. + They only consider back-porting significant technological jumps - and, that is done + after a complete gap analysis. + The reason for this policy is that back-porting any small to medium sized change + from an evolving kernel can easily create mismatches, incompatibilities and very + subtle errors. + + + These policies result in both a stable and a cutting + edge kernel that mixes forward ports of existing features and significant and critical + new functionality. + Forward porting functionality in the kernels available through the Yocto Project kernel + can be thought of as a "micro uprev." + The many “micro uprevs” produce a kernel version with a mix of + important new mainline, non-mainline, BSP developments and feature integrations. + This kernel gives insight into new features and allows focused + amounts of testing to be done on the kernel, which prevents + surprises when selecting the next major uprev. + The quality of these cutting edge kernels is evolving and the kernels are used in leading edge + feature and BSP development. + +
+ + -- cgit v1.2.3-54-g00ecf