diff options
Diffstat (limited to 'documentation/kernel-dev')
-rw-r--r-- | documentation/kernel-dev/kernel-dev-advanced.xml | 658 |
1 files changed, 0 insertions, 658 deletions
diff --git a/documentation/kernel-dev/kernel-dev-advanced.xml b/documentation/kernel-dev/kernel-dev-advanced.xml index adfd774a41..df3f30141a 100644 --- a/documentation/kernel-dev/kernel-dev-advanced.xml +++ b/documentation/kernel-dev/kernel-dev-advanced.xml | |||
@@ -38,30 +38,6 @@ | |||
38 | together as needed, but maintain them in only one place. | 38 | together as needed, but maintain them in only one place. |
39 | Similar logic applies to source changes. | 39 | Similar logic applies to source changes. |
40 | </para> | 40 | </para> |
41 | |||
42 | <para> | ||
43 | Original Text: | ||
44 | <literallayout class='monospaced'> | ||
45 | In addition to configuration fragments and patches, the Yocto Project kernel | ||
46 | tools support rich metadata which you can use to define complex policies and | ||
47 | BSP support. The purpose of the metadata and the tools to manage it, known as | ||
48 | the kern-tools (kern-tools-native_git.bb), is to assist in managing the | ||
49 | complexity of the configuration and sources in support of multiple BSPs and | ||
50 | Linux kernel types. | ||
51 | |||
52 | In particular, the kernel tools allow you to specify only what you must, and | ||
53 | nothing more. Where a complete Linux kernel .config includes all the | ||
54 | automatically selected CONFIG options, the configuration fragments only need to | ||
55 | contain the highest level visible CONFIG options as presented by the Linux | ||
56 | kernel menuconfig system. This reduces your maintenance effort and allows you | ||
57 | to further separate your configuration in ways that make sense for your project. | ||
58 | A common split is policy and hardware. For example, all your kernels may support | ||
59 | the proc and sys filesystems, but only specific boards will require sound, USB, | ||
60 | or specific drivers. Specifying these individually allows you to aggregate them | ||
61 | together as needed, but maintain them in only one place. Similar logic applies | ||
62 | to source changes. | ||
63 | </literallayout> | ||
64 | </para> | ||
65 | </section> | 41 | </section> |
66 | 42 | ||
67 | <section id='using-kernel-metadata-in-a-recipe'> | 43 | <section id='using-kernel-metadata-in-a-recipe'> |
@@ -197,88 +173,6 @@ to source changes. | |||
197 | releases of the Yocto Project. | 173 | releases of the Yocto Project. |
198 | </note> | 174 | </note> |
199 | </para> | 175 | </para> |
200 | |||
201 | <para> | ||
202 | Original Text. | ||
203 | <literallayout class='monospaced'> | ||
204 | The metadata provided with any linux-yocto style Linux kernel sources must | ||
205 | define a BSP that corresponds to the definition laid out in the recipe. A BSP | ||
206 | consists of an aggregation of kernel policy and hardware specific feature | ||
207 | enablement. This can be influenced from within the recipe. | ||
208 | |||
209 | Every linux-yocto style recipe must define the following variables: | ||
210 | |||
211 | KMACHINE | ||
212 | |||
213 | KMACHINE is typically set to the same value as used within the recipe-space BSP | ||
214 | definition, such as "routerstationpro" or "fri2". However, multiple BSPs can | ||
215 | reuse the same KMACHINE name if they are built using the same BSP description | ||
216 | (see 3.3.5). The meta-intel "fri2" and "fri2-noemgd" are good examples of such | ||
217 | a situation where each specifies KMACHINE as "fri2". | ||
218 | |||
219 | They may optionally define the following variables: | ||
220 | KBRANCH | ||
221 | KERNEL_FEATURES | ||
222 | KBRANCH_DEFAULT | ||
223 | LINUX_KERNEL_TYPE | ||
224 | |||
225 | KBRANCH_DEFAULT defines the default source branch within the Linux kernel source | ||
226 | repository to be used to build the Linux kernel. It is used as the default value | ||
227 | for KBRANCH which may define an alternate branch, typically with a machine | ||
228 | override, such as: | ||
229 | |||
230 | KBRANCH_fri2 = "standard/fri2" | ||
231 | |||
232 | Unless you specify otherwise, KBRANCH_DEFAULT is initialized to "master". | ||
233 | |||
234 | LINUX_KERNEL_TYPE defines the kernel type to be used in assembling the | ||
235 | configuration and defaults to "standard" if you do not specify otherwise. | ||
236 | Together with KMACHINE, this defines the search arguments used by the Yocto | ||
237 | Project Linux kernel tools to find the appropriate description within the | ||
238 | metadata with which to build out the sources and configuration. The linux-yocto | ||
239 | recipes define "standard", "tiny", and "preempt-rt" kernel types. See 3.3.4 for | ||
240 | more information on kernel types. | ||
241 | |||
242 | During the build, the kern-tools will search for the BSP description file that | ||
243 | most closely matches the KMACHINE and LINUX_KERNEL_TYPE passed in from the | ||
244 | recipe. It will use the first BSP description it finds matching both variables. | ||
245 | Failing that it will issue a warning such as the following: | ||
246 | |||
247 | WARNING: Can't find any BSP hardware or required configuration fragments. | ||
248 | WARNING: Looked at meta/cfg/broken/fri2-broken/hdw_frags.txt and | ||
249 | meta/cfg/broken/fri2-broken/required_frags.txt in directory: | ||
250 | meta/cfg/broken/fri2-broken | ||
251 | |||
252 | In this example KMACHINE was set to "fri2-broken" and LINUX_KERNEL_TYPE | ||
253 | was set to "broken". | ||
254 | |||
255 | It will then search first for the KMACHINE and then | ||
256 | for the LINUX_KERNEL_TYPE. If it cannot find a partial match, it will use the | ||
257 | sources from the KBRANCH and any configuration specified in the SRC_URI. | ||
258 | |||
259 | KERNEL_FEATURES can be used to include features (configuration fragments, | ||
260 | patches, or both) that are not already included by the KMACHINE and | ||
261 | LINUX_KERNEL_TYPE combination. To include a feature specified as | ||
262 | "features/netfilter.scc" for example, specify: | ||
263 | |||
264 | KERNEL_FEATURES += "features/netfilter.scc" | ||
265 | |||
266 | To include a feature called "cfg/sound.scc" just for the qemux86 machine, | ||
267 | specify: | ||
268 | |||
269 | KERNEL_FEATURES_append_qemux86 = "cfg/sound.scc" | ||
270 | |||
271 | The value of the entries in KERNEL_FEATURES are dependent on their location | ||
272 | within the metadata itself. The examples here are taken from the | ||
273 | linux-yocto-3.4 repository where "features" and "cfg" are subdirectories of the | ||
274 | metadata directory. For details, see 3.3. | ||
275 | |||
276 | Note: The processing of the these variables has evolved some between the | ||
277 | 0.9 and 1.3 releases of the Yocto Project and associated | ||
278 | kern-tools sources. The above is accurate for 1.3 and later | ||
279 | releases of the Yocto Project. | ||
280 | </literallayout> | ||
281 | </para> | ||
282 | </section> | 176 | </section> |
283 | 177 | ||
284 | <section id='kernel-metadata-location'> | 178 | <section id='kernel-metadata-location'> |
@@ -315,31 +209,6 @@ metadata directory. For details, see 3.3. | |||
315 | more efficient outside of the BitBake environment. | 209 | more efficient outside of the BitBake environment. |
316 | </para> | 210 | </para> |
317 | 211 | ||
318 | <para> | ||
319 | Original Text: | ||
320 | <literallayout class='monospaced'> | ||
321 | This meta-data can be defined along with the Linux kernel recipe (recipe-space) | ||
322 | as partially described in section 2.2 as well as within the Linux kernel sources | ||
323 | themselves (in-tree). | ||
324 | |||
325 | Where you choose to store the meta-data depends on what you want to do and how | ||
326 | you intend to work. If you are unfamiliar with the Linux kernel and only wish | ||
327 | to apply a config and possibly a couple of patches provided to you by others, | ||
328 | you may find the recipe-space mechanism to be easier to work with. This is also | ||
329 | a good approach if you are working with Linux kernel sources you do not control | ||
330 | or if you just don't want to maintain a Linux kernel git repository on your own. | ||
331 | |||
332 | If you are doing active kernel development and are already maintaining a Linux | ||
333 | kernel git repository of your own, you may find it more convenient to work with | ||
334 | the meta-data in the same repository as the Linux kernel sources. This can make | ||
335 | iterative development of the Linux kernel more efficient outside of the BitBake | ||
336 | environment. | ||
337 | |||
338 | Regardless of where the meta-data is stored, the syntax as | ||
339 | described in the following sections applies equally. | ||
340 | </literallayout> | ||
341 | </para> | ||
342 | |||
343 | <section id='recipe-space-metadata'> | 212 | <section id='recipe-space-metadata'> |
344 | <title>Recipe-Space Metadata</title> | 213 | <title>Recipe-Space Metadata</title> |
345 | 214 | ||
@@ -386,35 +255,6 @@ described in the following sections applies equally. | |||
386 | value when changing the content of files not explicitly listed | 255 | value when changing the content of files not explicitly listed |
387 | in the <filename>SRC_URI</filename>. | 256 | in the <filename>SRC_URI</filename>. |
388 | </para> | 257 | </para> |
389 | |||
390 | <para> | ||
391 | Original text: | ||
392 | <literallayout class='monospaced'> | ||
393 | When stored in recipe-space, the meta-data files reside in a directory hierarchy | ||
394 | below FILESEXTRAPATHS, which is typically set to ${THISDIR}/${PN} for a | ||
395 | linux-yocto or linux-yocto-custom derived Linux kernel recipe. See 2.2. | ||
396 | |||
397 | By way of example, a trivial tree of meta-data stored in recipe-space within a | ||
398 | BSP layer might look like the following: | ||
399 | |||
400 | meta/ | ||
401 | `-- recipes-kernel | ||
402 | `-- linux | ||
403 | `-- linux-yocto | ||
404 | |-- bsp-standard.scc | ||
405 | |-- bsp.cfg | ||
406 | `-- standard.cfg | ||
407 | |||
408 | When the meta-data is stored in recipe-space, you must take steps to ensure | ||
409 | BitBake has the necessary information to decide which files to fetch and when | ||
410 | they need to be fetched again. | ||
411 | |||
412 | It is only necessary to specify the .scc files on the SRC_URI; BitBake will | ||
413 | parse them and fetch any files referenced in the .scc files by the include, | ||
414 | patch, or kconf commands. Because of this, it is necessary to bump the recipe PR | ||
415 | value when changing the content of files not explicitly listed in the SRC_URI. | ||
416 | </literallayout> | ||
417 | </para> | ||
418 | </section> | 258 | </section> |
419 | 259 | ||
420 | <section id='in-tree-metadata'> | 260 | <section id='in-tree-metadata'> |
@@ -474,48 +314,6 @@ value when changing the content of files not explicitly listed in the SRC_URI. | |||
474 | $ git commit --allow-empty -m "Create orphan meta branch" | 314 | $ git commit --allow-empty -m "Create orphan meta branch" |
475 | </literallayout> | 315 | </literallayout> |
476 | </para> | 316 | </para> |
477 | |||
478 | <para> | ||
479 | Original text: | ||
480 | <literallayout class='monospaced'> | ||
481 | When stored in-tree, the meta-data files reside in the "meta" directory of the | ||
482 | Linux kernel sources. They may be present in the same branch as the sources, | ||
483 | such as "master", or in their own orphan branch, typically named "meta". An | ||
484 | orphan branch in git is a branch with unique history and content to the other | ||
485 | branches in the repository. This is useful to track meta-data changes | ||
486 | independently from the sources of the Linux kernel, while still keeping them | ||
487 | together in the same repository. For the purposes of this document, we will | ||
488 | discuss all in-tree meta-data as residing below the "meta/cfg/kernel-cache" | ||
489 | directory. | ||
490 | |||
491 | By way of example, a trivial tree of meta-data stored in a custom Linux kernel | ||
492 | git repository might look like the following: | ||
493 | |||
494 | meta/ | ||
495 | `-- cfg | ||
496 | `-- kernel-cache | ||
497 | |-- bsp-standard.scc | ||
498 | |-- bsp.cfg | ||
499 | `-- standard.cfg | ||
500 | |||
501 | To use a specific branch for the meta-data, specify the branch in the KMETA | ||
502 | variable in your Linux kernel recipe, for example: | ||
503 | |||
504 | KMETA = "meta" | ||
505 | |||
506 | To use the same branch as the sources, set KMETA to the empty string: | ||
507 | |||
508 | KMETA = "" | ||
509 | |||
510 | If you are working with your own sources and want to create an orphan meta | ||
511 | branch, you can do so using the following commands from within your Linux kernel | ||
512 | git repository: | ||
513 | |||
514 | $ git checkout --orphan meta | ||
515 | $ git rm -rf . | ||
516 | $ git commit --allow-empty -m "Create orphan meta branch" | ||
517 | </literallayout> | ||
518 | </para> | ||
519 | </section> | 317 | </section> |
520 | </section> | 318 | </section> |
521 | 319 | ||
@@ -635,66 +433,6 @@ git repository: | |||
635 | Metadata <link linkend='in-tree-metadata'>in-tree</link>. | 433 | Metadata <link linkend='in-tree-metadata'>in-tree</link>. |
636 | </para> | 434 | </para> |
637 | 435 | ||
638 | <para> | ||
639 | Original text: | ||
640 | <literallayout class='monospaced'> | ||
641 | The Yocto Project Linux kernel tools meta-data consists of three primary types | ||
642 | of files: scc* description files, configuration fragments, and patches. The scc | ||
643 | files define variables and include or otherwise reference any of the three file | ||
644 | types. The description files are used to aggregate all types of meta-data into | ||
645 | what ultimately describes the sources and the configuration required to build a | ||
646 | Linux kernel tailored to a specific machine. | ||
647 | |||
648 | The scc description files are used to define two fundamental types of meta-data: | ||
649 | o Features | ||
650 | o BSPs | ||
651 | |||
652 | Features aggregate sources in the form of patches and configuration in the form | ||
653 | of configuration fragments into a modular reusable unit. Features are used to | ||
654 | implement conceptually separate meta-data descriptions like pure configuration | ||
655 | fragments, simple patches, complex features, and kernel types (ktypes). Kernel | ||
656 | types define general kernel features and policy to be reused in the BSPs. | ||
657 | |||
658 | BSPs define hardware-specific features and aggregate them with kernel types to | ||
659 | form the final description of what will be assembled and built. | ||
660 | |||
661 | While the meta-data syntax does not enforce any logical separation of | ||
662 | configuration fragments, patches, features or kernel types, best practices | ||
663 | dictate a logical separation of these types of meta-data. The following | ||
664 | meta-data file hierarchy is recommended: | ||
665 | |||
666 | <base>/ | ||
667 | bsp/ | ||
668 | cfg/ | ||
669 | features/ | ||
670 | ktypes/ | ||
671 | patches/ | ||
672 | |||
673 | The bsp directory should contain the BSP descriptions, described in detail in | ||
674 | 3.3.5. The remaining directories all contain "features"; the separation is meant | ||
675 | to aid in conceptualizing their intended usage. A simple guide to determine | ||
676 | where your scc description file should go is as follows. If it contains only | ||
677 | configuration fragments, it belongs in cfg. If it contains only source-code | ||
678 | fixes, it belongs in patches. If it encapsulates a major feature, often | ||
679 | combining sources and configurations, it belongs in features. If it aggregates | ||
680 | non-hardware configuration and patches in order to define a base kernel policy | ||
681 | or major kernel type to be reused across multiple BSPs, it belongs in ktypes. | ||
682 | The line between these can easily become blurred, especially as out-of-tree | ||
683 | features are slowly merged upstream over time. Also remember that this is purely | ||
684 | logical organization and has no impact on the functionality of the meta-data as | ||
685 | all of cfg, features, patches, and ktypes, contain "features" as far as the | ||
686 | Yocto Project Linux kernel tools are concerned. | ||
687 | |||
688 | Paths used in meta-data files are relative to <base> which is either | ||
689 | FILESEXTRAPATHS if you are creating meta-data in recipe-space (see 3.2.1), or | ||
690 | meta/cfg/kernel-cache/ if you are creating meta-data in-tree (see 3.2.2). | ||
691 | |||
692 | * scc stands for Series Configuration Control, but the naming has less | ||
693 | significance in the current implementation of the tooling than it had in the | ||
694 | past. Consider it to be a description file. | ||
695 | </literallayout> | ||
696 | </para> | ||
697 | |||
698 | <section id='configuration'> | 436 | <section id='configuration'> |
699 | <title>Configuration</title> | 437 | <title>Configuration</title> |
700 | 438 | ||
@@ -757,45 +495,6 @@ meta/cfg/kernel-cache/ if you are creating meta-data in-tree (see 3.2.2). | |||
757 | $ bitbake linux-yocto -c kernel_configcheck -f | 495 | $ bitbake linux-yocto -c kernel_configcheck -f |
758 | </literallayout> | 496 | </literallayout> |
759 | </para> | 497 | </para> |
760 | |||
761 | <para> | ||
762 | Original text: | ||
763 | <literallayout class='monospaced'> | ||
764 | The simplest unit of meta-data is the configuration-only feature. It consists of | ||
765 | one or more Linux kernel configuration parameters in a .cfg file (as described | ||
766 | in section XYZ) and an scc file describing the fragment. The SMP fragment | ||
767 | included in the linux-yocto-3.4 git repository consists of the following two | ||
768 | files: | ||
769 | |||
770 | cfg/smp.scc: | ||
771 | define KFEATURE_DESCRIPTION "Enable SMP" | ||
772 | kconf hardware smp.cfg | ||
773 | |||
774 | cfg/smp.cfg: | ||
775 | CONFIG_SMP=y | ||
776 | CONFIG_SCHED_SMT=y | ||
777 | |||
778 | See 2.3.1 for details on creating configuration fragments. | ||
779 | |||
780 | KFEATURE_DESCRIPTION provides a short description of the fragment, the | ||
781 | primary use is for higher level tooling, such as the Yocto Project BSP Tools | ||
782 | (TODO:Citation). | ||
783 | |||
784 | The "kconf" command is used to include the actual configuration fragment in an | ||
785 | scc file, and the "hardware" keyword identifies the fragment as being hardware | ||
786 | enabling, as opposed to general policy (which would use the keyword | ||
787 | "non-hardware"). The distinction is made for the benefit of the configuration | ||
788 | validation tools which will warn you if a hardware fragment overrides a policy | ||
789 | set by a non-hardware fragment. | ||
790 | |||
791 | As described in 2.3.1, the following bitbake command can be used to audit your | ||
792 | configuration: | ||
793 | |||
794 | $ bitbake linux-yocto -c kernel_configcheck -f | ||
795 | |||
796 | The description file can include multiple kconf statements, one per fragment. | ||
797 | </literallayout> | ||
798 | </para> | ||
799 | </section> | 498 | </section> |
800 | 499 | ||
801 | <section id='patches'> | 500 | <section id='patches'> |
@@ -826,23 +525,6 @@ The description file can include multiple kconf statements, one per fragment. | |||
826 | The description file can include multiple patch statements, | 525 | The description file can include multiple patch statements, |
827 | one per patch. | 526 | one per patch. |
828 | </para> | 527 | </para> |
829 | |||
830 | <para> | ||
831 | Original text: | ||
832 | <literallayout class='monospaced'> | ||
833 | Patches are described in a very similar way to configuration fragments (see | ||
834 | 3.3.1). Instead of a .cfg file, they work with source patches. A typical patch | ||
835 | includes a description file and the patch itself: | ||
836 | |||
837 | patches/mypatch.scc: | ||
838 | patch mypatch.patch | ||
839 | |||
840 | patches/mypatch.patch: | ||
841 | <typical patch created with 'diff -Nurp' or 'git format-patch'> | ||
842 | |||
843 | The description file can include multiple patch statements, one per patch. | ||
844 | </literallayout> | ||
845 | </para> | ||
846 | </section> | 528 | </section> |
847 | 529 | ||
848 | <section id='features'> | 530 | <section id='features'> |
@@ -881,33 +563,6 @@ The description file can include multiple patch statements, one per patch. | |||
881 | See the "<link linkend='using-kernel-metadata-in-a-recipe'>Using Kernel Metadata in a Recipe</link>" | 563 | See the "<link linkend='using-kernel-metadata-in-a-recipe'>Using Kernel Metadata in a Recipe</link>" |
882 | section earlier in the manual. | 564 | section earlier in the manual. |
883 | </para> | 565 | </para> |
884 | |||
885 | <para> | ||
886 | Original text: | ||
887 | <literallayout class='monospaced'> | ||
888 | Features are a combination of configuration fragments and patches, or, more | ||
889 | accurately, configuration fragments and patches are simple forms of a feature, a | ||
890 | more complex meta-data type. In addition to the kconf and patch commands, | ||
891 | features often aggregate description files with the include command. | ||
892 | |||
893 | A hypothetical example of a feature description file might look like the | ||
894 | following: | ||
895 | |||
896 | features/myfeature.scc | ||
897 | define KFEATURE_DESCRIPTION "Enable myfeature" | ||
898 | |||
899 | patch 0001-myfeature-core.patch | ||
900 | patch 0002-myfeature-interface.patch | ||
901 | |||
902 | include cfg/myfeature_dependency.scc | ||
903 | kconf non-hardware myfeature.cfg | ||
904 | |||
905 | Features are typically less granular than configuration fragments and are more | ||
906 | likely than configurations fragments and patches to be the types of things you | ||
907 | will want to specify in the KERNEL_FEATURES variable of the Linux kernel recipe | ||
908 | (see 3.1). | ||
909 | </literallayout> | ||
910 | </para> | ||
911 | </section> | 566 | </section> |
912 | 567 | ||
913 | <section id='kernel-types'> | 568 | <section id='kernel-types'> |
@@ -1003,58 +658,6 @@ will want to specify in the KERNEL_FEATURES variable of the Linux kernel recipe | |||
1003 | See the "<link linkend='bsp-descriptions'>BSP Descriptions</link>" | 658 | See the "<link linkend='bsp-descriptions'>BSP Descriptions</link>" |
1004 | section for more information. | 659 | section for more information. |
1005 | </note> | 660 | </note> |
1006 | |||
1007 | <para> | ||
1008 | Original text: | ||
1009 | <literallayout class='monospaced'> | ||
1010 | Kernel types, or ktypes, are used to aggregate all non-hardware configuration | ||
1011 | fragments together with any patches you want to use for all Linux kernel builds | ||
1012 | of the specified ktype. In short, ktypes are where you define a high-level | ||
1013 | kernel policy. Syntactically, however, they are no different than features (see | ||
1014 | 3.3.3). preempt-rt, and tiny. The ktype is selected by the LINUX_KERNEL_TYPE | ||
1015 | variable in the recipe (see 3.1). | ||
1016 | |||
1017 | By way of example, the linux-yocto-3.4 tree defines three ktypes: standard, | ||
1018 | tiny, and preempt-rt. The standard kernel type includes the generic Linux kernel | ||
1019 | policy of the Yocto Project linux-yocto kernel recipes. This includes things | ||
1020 | like which filesystems, which networking options, which core kernel features, | ||
1021 | and which debugging and tracing optoins are supported. The preempt-rt kernel | ||
1022 | type applies the PREEMPT_RT patches and the configuration options required to | ||
1023 | build a real-time Linux kernel. It inherits from standard. The tiny kernel type | ||
1024 | is independent from the standard configuration and defines a bare minimum | ||
1025 | configuration meant to serve as a base for very small Linux kernels. Tiny does | ||
1026 | not currently include any source changes, but it may in the future. | ||
1027 | |||
1028 | The standard ktype is defined by standard.scc: | ||
1029 | # Include this kernel type fragment to get the standard features and | ||
1030 | # configuration values. | ||
1031 | |||
1032 | # Include all standard features | ||
1033 | include standard-nocfg.scc | ||
1034 | |||
1035 | kconf non-hardware standard.cfg | ||
1036 | |||
1037 | # individual cfg block section | ||
1038 | include cfg/fs/devtmpfs.scc | ||
1039 | include cfg/fs/debugfs.scc | ||
1040 | include cfg/fs/btrfs.scc | ||
1041 | include cfg/fs/ext2.scc | ||
1042 | include cfg/fs/ext3.scc | ||
1043 | include cfg/fs/ext4.scc | ||
1044 | |||
1045 | include cfg/net/ipv6.scc | ||
1046 | include cfg/net/ip_nf.scc | ||
1047 | include cfg/net/ip6_nf.scc | ||
1048 | include cfg/net/bridge.scc | ||
1049 | |||
1050 | As with any scc file, a ktype definition can aggregate other scc files with the | ||
1051 | include command, or directly pull in configuration fragments and patches with | ||
1052 | the kconf and patch commands, respectively. | ||
1053 | |||
1054 | Note: It is not strictly necessary to create a ktype scc file. The BSP file can | ||
1055 | define the ktype implicitly with a "define KTYPE myktype" line. See 3.3.5. | ||
1056 | </literallayout> | ||
1057 | </para> | ||
1058 | </section> | 661 | </section> |
1059 | 662 | ||
1060 | <section id='bsp-descriptions'> | 663 | <section id='bsp-descriptions'> |
@@ -1246,130 +849,6 @@ Note: It is not strictly necessary to create a ktype scc file. The BSP file can | |||
1246 | Of these variables, only the <filename>KTYPE</filename> has changed. | 849 | Of these variables, only the <filename>KTYPE</filename> has changed. |
1247 | It is now set to "tiny". | 850 | It is now set to "tiny". |
1248 | </para> | 851 | </para> |
1249 | |||
1250 | <para> | ||
1251 | Original text: | ||
1252 | <literallayout class='monospaced'> | ||
1253 | BSP descriptions combine kernel types (see 3.3.4) with hardware-specific | ||
1254 | features (see 3.3.3). The hardware specific portion is typically defined | ||
1255 | independently, and then aggregated with each supported kernel type. Consider a | ||
1256 | simple example: | ||
1257 | |||
1258 | mybsp.scc: | ||
1259 | define KMACHINE mybsp | ||
1260 | define KTYPE standard | ||
1261 | define KARCH i386 | ||
1262 | |||
1263 | kconf mybsp.cfg | ||
1264 | |||
1265 | Every BSP description should include the definition of the KMACHINE, KTYPE, and | ||
1266 | KARCH variables. These variables allow the build-system to identify this | ||
1267 | description as meeting the criteria set by the recipe being built. This | ||
1268 | particular description can be said to support the "mybsp" machine for the | ||
1269 | "standard" kernel type and the "i386" architecture. Note that there is no hard | ||
1270 | link between the KTYPE and a ktype description file. If you do not have kernel | ||
1271 | types defined in your meta-data, you only need to ensure that the recipe | ||
1272 | LINUX_KERNEL_TYPE and the KTYPE here match. | ||
1273 | |||
1274 | NOTE: future versions of the tooling make the specification of KTYPE in the BSP | ||
1275 | optional. | ||
1276 | |||
1277 | If you did want to separate your kernel policy from your hardware configuration, | ||
1278 | you could do so by specifying a kernel type, such as "standard" (see 3.3.4) and | ||
1279 | including that description in the BSP description. You might also have multiple | ||
1280 | hardware configurations that you aggregate into a single hardware description | ||
1281 | file which you could include here, rather than referencing a single .cfg file. | ||
1282 | Consider the following: | ||
1283 | |||
1284 | mybsp.scc: | ||
1285 | define KMACHINE mybsp | ||
1286 | define KTYPE standard | ||
1287 | define KARCH i386 | ||
1288 | |||
1289 | include standard.scc | ||
1290 | include mybsp.scc | ||
1291 | |||
1292 | In the above example standard.scc aggregates all the configuration fragments, | ||
1293 | patches, and features that make up your standard kernel policy whereas mybsp.scc | ||
1294 | aggregates all those necessary to support the hardware available on the mybsp | ||
1295 | machine. For information on how to break a complete .config into the various | ||
1296 | fragments, see 2.3.1. | ||
1297 | |||
1298 | Many real-world examples are more complex. Like any other scc file, BSP | ||
1299 | descriptions can aggregate features. Consider the Fish River Island II (fri2) | ||
1300 | BSP definitions from the linux-yocto-3.4 repository: | ||
1301 | |||
1302 | fri2.scc: | ||
1303 | kconf hardware fri2.cfg | ||
1304 | |||
1305 | include cfg/x86.scc | ||
1306 | include features/eg20t/eg20t.scc | ||
1307 | include cfg/dmaengine.scc | ||
1308 | include features/ericsson-3g/f5521gw.scc | ||
1309 | include features/power/intel.scc | ||
1310 | include cfg/efi.scc | ||
1311 | include features/usb/ehci-hcd.scc | ||
1312 | include features/usb/ohci-hcd.scc | ||
1313 | include features/iwlwifi/iwlwifi.scc | ||
1314 | |||
1315 | The fri2.scc description file includes a hardware configuration fragment | ||
1316 | (fri2.cfg) specific to the fri2 BSP as well as several more general | ||
1317 | configuration fragments and features enabling hardware found on the fri2. This | ||
1318 | description is then included in each of the three machine-ktype descriptions | ||
1319 | (standard, preempt-rt, and tiny). Consider the fri2 standard description: | ||
1320 | |||
1321 | fri2-standard.scc: | ||
1322 | define KMACHINE fri2 | ||
1323 | define KTYPE standard | ||
1324 | define KARCH i386 | ||
1325 | |||
1326 | include ktypes/standard/standard.scc | ||
1327 | branch fri2 | ||
1328 | |||
1329 | git merge emgd-1.14 | ||
1330 | |||
1331 | include fri2.scc | ||
1332 | |||
1333 | # Extra fri2 configs above the minimal defined in fri2.scc | ||
1334 | include cfg/efi-ext.scc | ||
1335 | include features/drm-emgd/drm-emgd.scc | ||
1336 | include cfg/vesafb.scc | ||
1337 | |||
1338 | # default policy for standard kernels | ||
1339 | include cfg/usb-mass-storage.scc | ||
1340 | |||
1341 | Note the "include fri2.scc" line about midway through the file. By defining all | ||
1342 | hardware enablement common to the BSP for all kernel types, duplication is | ||
1343 | significantly reduced. | ||
1344 | |||
1345 | This description introduces a few more variables and commands worthy of further | ||
1346 | discussion. Note the "branch" command which is used to create a | ||
1347 | machine-specific branch into which source changes can be applied. With this | ||
1348 | branch set up, the "git merge" command uses the git SCM to merge in a feature | ||
1349 | branch "emgd-1.14". This could also be handled with the patch command, but for | ||
1350 | commonly used features such as this, feature branches can be a convenient | ||
1351 | mechanism (see 3.5). | ||
1352 | |||
1353 | Next consider the fri2 tiny description: | ||
1354 | |||
1355 | fri2-tiny.scc: | ||
1356 | define KMACHINE fri2 | ||
1357 | define KTYPE tiny | ||
1358 | define KARCH i386 | ||
1359 | |||
1360 | include ktypes/tiny/tiny.scc | ||
1361 | branch fri2 | ||
1362 | |||
1363 | include fri2.scc | ||
1364 | |||
1365 | As you might expect, the tiny description includes quite a bit less. In fact, | ||
1366 | it includes only the minimal policy defined by the tiny ktype and the | ||
1367 | hardware-specific configuration required for boot and the most basic | ||
1368 | functionality of the system as defined in the base fri2 description file. Note | ||
1369 | again the three critical variables: KMACHINE, KTYPE, and KARCH. Of these, only | ||
1370 | the KTYPE has changed, now set to "tiny". | ||
1371 | </literallayout> | ||
1372 | </para> | ||
1373 | </section> | 852 | </section> |
1374 | </section> | 853 | </section> |
1375 | 854 | ||
@@ -1521,86 +1000,6 @@ the KTYPE has changed, now set to "tiny". | |||
1521 | would have to create a file and a directory named "standard". | 1000 | would have to create a file and a directory named "standard". |
1522 | </note> | 1001 | </note> |
1523 | </para> | 1002 | </para> |
1524 | |||
1525 | <para> | ||
1526 | Original text: | ||
1527 | <literallayout class='monospaced'> | ||
1528 | Section 3.1 introduced the KBRANCH variable which defines the source branch to | ||
1529 | use from the Linux kernel git repository you are using. Many linux-yocto-custom | ||
1530 | derived recipes will be using Linux kernel sources with only a single branch: | ||
1531 | "master". However, when you are working with multiple boards and architectures, | ||
1532 | you are likely to run into the situation where a series of patches are needed | ||
1533 | for one board to boot. Sometimes these patches are works in progress or | ||
1534 | fundamentally wrong, yet still necessary for specific boards. In these | ||
1535 | situations, you most likely do not want to include these patches in every kernel | ||
1536 | you build. You have a couple of options. | ||
1537 | |||
1538 | First, you could encapsulate these patches in a feature description and only | ||
1539 | include them in the BSP description for the board(s) that require them (see | ||
1540 | 3.3.2 and 3.3.5). | ||
1541 | |||
1542 | Alternatively, you can create a branch in your Linux kernel sources and apply | ||
1543 | the patches there. You can then specify this new branch as the KBRANCH to use | ||
1544 | for this board. You can do this in the recipe with the KBRANCH variable: | ||
1545 | |||
1546 | KBRANCH = "mynewbranch" | ||
1547 | |||
1548 | or in the BSP description using the "branch" command: | ||
1549 | |||
1550 | mybsp.scc: | ||
1551 | define KMACHINE mybsp | ||
1552 | define KTYPE standard | ||
1553 | define KARCH i386 | ||
1554 | include standard.scc | ||
1555 | |||
1556 | branch mynewbranchIf you are actively | ||
1557 | working on board support, you may find that working within a branch is more | ||
1558 | practical than trying to continually reintegrate your patches into a feature. On | ||
1559 | the other hand, if you are simply reusing some patches from an external tree and | ||
1560 | are not working on them, you may find the encapsulated feature to be appropriate | ||
1561 | as it does not require the additional complexity of branching in your Linux | ||
1562 | kernel sources | ||
1563 | |||
1564 | include mybsp.scc | ||
1565 | |||
1566 | The decision of which approach to take, feature or branch, is entirely up to you | ||
1567 | and depends on what works best for your development model. If you are actively | ||
1568 | working on board support, you may find that working within a branch is more | ||
1569 | practical than trying to continually reintegrate your patches into a feature. On | ||
1570 | the other hand, if you are simply reusing some patches from an external tree and | ||
1571 | are not working on them, you may find the encapsulated feature to be appropriate | ||
1572 | as it does not require the additional complexity of branching in your Linux | ||
1573 | kernel sources. | ||
1574 | |||
1575 | If you are supporting multiple boards and architectures and find yourself with | ||
1576 | numerous branches, you might consider using a hierarchical branching system | ||
1577 | similar to what the linux-yocto Linux kernel repositories use: | ||
1578 | |||
1579 | <common>/<ktype>/<machine> | ||
1580 | |||
1581 | If you had two ktypes, standard and small for instance, and three machines, your | ||
1582 | git tree might look like this: | ||
1583 | |||
1584 | common/base | ||
1585 | common/standard/base | ||
1586 | common/standard/machine_a | ||
1587 | common/standard/machine_b | ||
1588 | common/standard/machine_c | ||
1589 | common/small/base | ||
1590 | common/small/machine_a | ||
1591 | |||
1592 | This organization can help clarify the relationship of the branches to | ||
1593 | each other. In this case, "common/standard/machine_a" would include everything in | ||
1594 | "common/base" and "common/standard/base". The "standard" and "small" branches | ||
1595 | add sources specific to those kernel types that for whatever reason are not | ||
1596 | appropriate for the other branches. | ||
1597 | |||
1598 | Note: The "base" branches are an artifact of the way git manages its data | ||
1599 | internally on the filesystem: it will not allow you to use | ||
1600 | "common/standard" and "common/standard/machine_a" because it would have to | ||
1601 | create a file and a directory named "standard". | ||
1602 | </literallayout> | ||
1603 | </para> | ||
1604 | </section> | 1003 | </section> |
1605 | 1004 | ||
1606 | <section id='feature-branches'> | 1005 | <section id='feature-branches'> |
@@ -1631,30 +1030,6 @@ Note: The "base" branches are an artifact of the way git manages its data | |||
1631 | include mybsp-hw.scc | 1030 | include mybsp-hw.scc |
1632 | </literallayout> | 1031 | </literallayout> |
1633 | </para> | 1032 | </para> |
1634 | |||
1635 | <para> | ||
1636 | Original text: | ||
1637 | <literallayout class='monospaced'> | ||
1638 | During active development a new feature, it can be more efficient to work with | ||
1639 | that feature as a branch, rather than as a set of patches which have to be | ||
1640 | regularly updated. The Yocto Project Linux kernel tools provide for this with | ||
1641 | the "git merge" command. | ||
1642 | |||
1643 | To merge a feature branch into a BSP, insert the "git merge" command after any | ||
1644 | branch commands: | ||
1645 | |||
1646 | mybsp.scc: | ||
1647 | define KMACHINE mybsp | ||
1648 | define KTYPE standard | ||
1649 | define KARCH i386 | ||
1650 | include standard.scc | ||
1651 | |||
1652 | branch mynewbranch | ||
1653 | git merge myfeature | ||
1654 | |||
1655 | include mybsp.scc | ||
1656 | </literallayout> | ||
1657 | </para> | ||
1658 | </section> | 1033 | </section> |
1659 | </section> | 1034 | </section> |
1660 | 1035 | ||
@@ -1687,39 +1062,6 @@ mybsp.scc: | |||
1687 | Applies the patch to the current Git branch.</para></listitem> | 1062 | Applies the patch to the current Git branch.</para></listitem> |
1688 | </itemizedlist> | 1063 | </itemizedlist> |
1689 | </para> | 1064 | </para> |
1690 | |||
1691 | <para> | ||
1692 | Original text: | ||
1693 | <literallayout class='monospaced'> | ||
1694 | * branch [ref] | ||
1695 | |||
1696 | Create a new branch relative to the current branch (typically ${KTYPE}) using | ||
1697 | the currently checked-out branch, or "ref" if specified. | ||
1698 | |||
1699 | TODO: Bruce, we need to clarify the "relative to the current branch" bit. | ||
1700 | |||
1701 | * define | ||
1702 | |||
1703 | Define variables, such as KMACHINE, KTYPE, KARCH, and KFEATURE_DESCRIPTION. | ||
1704 | |||
1705 | * include SCC_FILE | ||
1706 | |||
1707 | Include an scc file in the current file. It will be parsed as if inserted | ||
1708 | inline. | ||
1709 | |||
1710 | * kconf [hardware|non-hardware] CFG_FILE | ||
1711 | |||
1712 | Queue a configuration fragment for merging into the final Linux .config file. | ||
1713 | |||
1714 | * merge (or "git merge") GIT_BRANCH | ||
1715 | |||
1716 | Merge the feature branch into the current branch. | ||
1717 | |||
1718 | * patch PATCH_FILE | ||
1719 | |||
1720 | Apply the patch to the current git branch. | ||
1721 | </literallayout> | ||
1722 | </para> | ||
1723 | </section> | 1065 | </section> |
1724 | 1066 | ||
1725 | </chapter> | 1067 | </chapter> |