diff options
Diffstat (limited to 'documentation')
| -rw-r--r-- | documentation/kernel-dev/kernel-dev-advanced.xml | 147 |
1 files changed, 82 insertions, 65 deletions
diff --git a/documentation/kernel-dev/kernel-dev-advanced.xml b/documentation/kernel-dev/kernel-dev-advanced.xml index 87819903bb..c069ddfb08 100644 --- a/documentation/kernel-dev/kernel-dev-advanced.xml +++ b/documentation/kernel-dev/kernel-dev-advanced.xml | |||
| @@ -188,7 +188,7 @@ to source changes. | |||
| 188 | and "cfg" are subdirectories within the | 188 | and "cfg" are subdirectories within the |
| 189 | <filename>meta/cfg/kernel-cache</filename> directory. | 189 | <filename>meta/cfg/kernel-cache</filename> directory. |
| 190 | For more information, see the | 190 | For more information, see the |
| 191 | "<link linkend='metadata-syntax'>Metadata Syntax</link>" section. | 191 | "<link linkend='kernel-metadata-syntax'>Kernel Metadata Syntax</link>" section. |
| 192 | <note> | 192 | <note> |
| 193 | The processing of the these variables has evolved some between the | 193 | The processing of the these variables has evolved some between the |
| 194 | 0.9 and 1.3 releases of the Yocto Project and associated | 194 | 0.9 and 1.3 releases of the Yocto Project and associated |
| @@ -421,24 +421,27 @@ value when changing the content of files not explicitly listed in the SRC_URI. | |||
| 421 | <title>In-Tree Metadata</title> | 421 | <title>In-Tree Metadata</title> |
| 422 | 422 | ||
| 423 | <para> | 423 | <para> |
| 424 | When stored in-tree, the metadata files reside in the | 424 | When stored in-tree, the kernel Metadata files reside in the |
| 425 | "meta" directory of the Linux kernel sources. | 425 | <filename>meta</filename> directory of the Linux kernel sources. |
| 426 | They may be present in the same branch as the sources, | 426 | The <filename>meta</filename> directory can be present in the |
| 427 | such as "master", or in their own orphan branch, | 427 | same repository branch as the sources, |
| 428 | typically named "meta". | 428 | such as "master", or <filename>meta</filename> can be its own |
| 429 | An orphan branch in Git is a branch with unique history and | 429 | orphan branch. |
| 430 | content to the other branches in the repository. | 430 | <note> |
| 431 | This is useful to track metadata changes independently from the | 431 | An orphan branch in Git is a branch with unique history and |
| 432 | sources of the Linux kernel, while still keeping them | 432 | content to the other branches in the repository. |
| 433 | together in the same repository. | 433 | Orphan branches are useful to track Metadata changes |
| 434 | independently from the sources of the Linux kernel, while | ||
| 435 | still keeping them together in the same repository. | ||
| 436 | </note> | ||
| 434 | For the purposes of this document, we will discuss all | 437 | For the purposes of this document, we will discuss all |
| 435 | in-tree metadata as residing below the | 438 | in-tree Metadata as residing below the |
| 436 | <filename>meta/cfg/kernel-cache</filename> directory. | 439 | <filename>meta/cfg/kernel-cache</filename> directory. |
| 437 | </para> | 440 | </para> |
| 438 | 441 | ||
| 439 | <para> | 442 | <para> |
| 440 | By way of example, a trivial tree of metadata stored in a custom | 443 | Following is an example that shows how a trivial tree of Metadata |
| 441 | Linux kernel Git repository might look like the following: | 444 | is stored in a custom Linux kernel Git repository: |
| 442 | <literallayout class='monospaced'> | 445 | <literallayout class='monospaced'> |
| 443 | meta/ | 446 | meta/ |
| 444 | `-- cfg | 447 | `-- cfg |
| @@ -450,20 +453,21 @@ value when changing the content of files not explicitly listed in the SRC_URI. | |||
| 450 | </para> | 453 | </para> |
| 451 | 454 | ||
| 452 | <para> | 455 | <para> |
| 453 | To use a specific branch for the metadata, specify the branch | 456 | To use a branch different from where the sources reside, |
| 454 | in the <filename>KMETA</filename> variable in your Linux kernel | 457 | specify the branch in the <filename>KMETA</filename> variable |
| 455 | recipe, for example: | 458 | in your Linux kernel recipe. |
| 459 | Here is an example: | ||
| 456 | <literallayout class='monospaced'> | 460 | <literallayout class='monospaced'> |
| 457 | KMETA = "meta" | 461 | KMETA = "meta" |
| 458 | </literallayout> | 462 | </literallayout> |
| 459 | To use the same branch as the sources, set | 463 | To use the same branch as the sources, set |
| 460 | <filename>KMETA</filename> to the empty string: | 464 | <filename>KMETA</filename> to an empty string: |
| 461 | <literallayout class='monospaced'> | 465 | <literallayout class='monospaced'> |
| 462 | KMETA = "" | 466 | KMETA = "" |
| 463 | </literallayout> | 467 | </literallayout> |
| 464 | If you are working with your own sources and want to create an | 468 | If you are working with your own sources and want to create an |
| 465 | orphan <filename>meta</filename> branch, you can do so using the | 469 | orphan <filename>meta</filename> branch, use these commands |
| 466 | following commands from within your Linux kernel Git repository: | 470 | from within your Linux kernel Git repository: |
| 467 | <literallayout class='monospaced'> | 471 | <literallayout class='monospaced'> |
| 468 | $ git checkout --orphan meta | 472 | $ git checkout --orphan meta |
| 469 | $ git rm -rf . | 473 | $ git rm -rf . |
| @@ -515,32 +519,33 @@ git repository: | |||
| 515 | </section> | 519 | </section> |
| 516 | </section> | 520 | </section> |
| 517 | 521 | ||
| 518 | <section id='metadata-syntax'> | 522 | <section id='kernel-metadata-syntax'> |
| 519 | <title>Metadata Syntax</title> | 523 | <title>Kernel Metadata Syntax</title> |
| 520 | 524 | ||
| 521 | <para> | 525 | <para> |
| 522 | The Yocto Project Linux kernel tools metadata consists of three | 526 | The kernel Metadata consists of three primary types of files: |
| 523 | primary types of files: <filename>scc</filename> | 527 | <filename>scc</filename> |
| 524 | <footnote> | 528 | <footnote> |
| 525 | <para> | 529 | <para> |
| 526 | <filename>scc</filename> stands for Series Configuration | 530 | <filename>scc</filename> stands for Series Configuration |
| 527 | Control, but the naming has less significance in the | 531 | Control, but the naming has less significance in the |
| 528 | current implementation of the tooling than it had in the | 532 | current implementation of the tooling than it had in the |
| 529 | past. | 533 | past. |
| 530 | Consider it to be a description file. | 534 | Consider <filename>scc</filename> files to be description files. |
| 531 | </para> | 535 | </para> |
| 532 | </footnote> | 536 | </footnote> |
| 533 | description files, configuration fragments, and patches. | 537 | description files, configuration fragments, and patches. |
| 534 | The <filename>scc</filename> files define variables and include or | 538 | The <filename>scc</filename> files define variables and include or |
| 535 | otherwise reference any of the three file types. | 539 | otherwise reference any of the three file types. |
| 536 | The description files are used to aggregate all types of metadata into | 540 | The description files are used to aggregate all types of kernel |
| 541 | Metadata into | ||
| 537 | what ultimately describes the sources and the configuration required | 542 | what ultimately describes the sources and the configuration required |
| 538 | to build a Linux kernel tailored to a specific machine. | 543 | to build a Linux kernel tailored to a specific machine. |
| 539 | </para> | 544 | </para> |
| 540 | 545 | ||
| 541 | <para> | 546 | <para> |
| 542 | The <filename>scc</filename> description files are used to define two | 547 | The <filename>scc</filename> description files are used to define two |
| 543 | fundamental types of metadata: | 548 | fundamental types of kernel Metadata: |
| 544 | <itemizedlist> | 549 | <itemizedlist> |
| 545 | <listitem><para>Features</para></listitem> | 550 | <listitem><para>Features</para></listitem> |
| 546 | <listitem><para>Board Support Packages (BSPs)</para></listitem> | 551 | <listitem><para>Board Support Packages (BSPs)</para></listitem> |
| @@ -549,12 +554,12 @@ git repository: | |||
| 549 | 554 | ||
| 550 | <para> | 555 | <para> |
| 551 | Features aggregate sources in the form of patches and configuration | 556 | Features aggregate sources in the form of patches and configuration |
| 552 | in the form of configuration fragments into a modular reusable unit. | 557 | fragments into a modular reusable unit. |
| 553 | Features are used to implement conceptually separate metadata | 558 | You can use features to implement conceptually separate kernel |
| 554 | descriptions like pure configuration fragments, simple patches, | 559 | Metadata descriptions such as pure configuration fragments, |
| 555 | complex features, and kernel types (ktypes). | 560 | simple patches, complex features, and kernel types. |
| 556 | Kernel types define general kernel features and policy to be reused | 561 | <link linkend='kernel-types'>Kernel types</link> define general |
| 557 | in the BSPs. | 562 | kernel features and policy to be reused in the BSPs. |
| 558 | </para> | 563 | </para> |
| 559 | 564 | ||
| 560 | <para> | 565 | <para> |
| @@ -563,10 +568,11 @@ git repository: | |||
| 563 | </para> | 568 | </para> |
| 564 | 569 | ||
| 565 | <para> | 570 | <para> |
| 566 | While the metadata syntax does not enforce any logical separation of | 571 | While the kernel Metadata syntax does not enforce any logical |
| 567 | configuration fragments, patches, features or kernel types, best | 572 | separation of configuration fragments, patches, features or kernel |
| 568 | practices dictate a logical separation of these types of meta-data. | 573 | types, best practices dictate a logical separation of these types |
| 569 | The following metadata file hierarchy is recommended: | 574 | of Metadata. |
| 575 | The following Metadata file hierarchy is recommended: | ||
| 570 | <literallayout class='monospaced'> | 576 | <literallayout class='monospaced'> |
| 571 | <base>/ | 577 | <base>/ |
| 572 | bsp/ | 578 | bsp/ |
| @@ -578,44 +584,55 @@ git repository: | |||
| 578 | </para> | 584 | </para> |
| 579 | 585 | ||
| 580 | <para> | 586 | <para> |
| 581 | The <filename>bsp</filename> directory should contain the | 587 | The <filename>bsp</filename> directory contains the |
| 582 | BSP descriptions, described in detail in section 3.3.5. | 588 | <link linkend='bsp-descriptions'>BSP descriptions</link>. |
| 583 | The remaining directories all contain "features"; the separation | 589 | The remaining directories all contain "features". |
| 584 | is meant to aid in conceptualizing their intended usage. | 590 | Separating <filename>bsp</filename> from the rest of the structure |
| 585 | A simple guide to determine where your <filename>scc</filename> | 591 | aids conceptualizing intended usage. |
| 586 | description file should go is as follows. | 592 | </para> |
| 587 | If it contains only configuration fragments, it belongs in | 593 | |
| 588 | <filename>cfg</filename>. | 594 | <para> |
| 589 | If it contains only source-code fixes, it belongs in | 595 | Use these guidelines to help place your <filename>scc</filename> |
| 590 | <filename>patches</filename>. | 596 | description files within the structure: |
| 591 | If it encapsulates a major feature, often combining sources and | 597 | <itemizedlist> |
| 592 | configurations, it belongs in <filename>features</filename>. | 598 | <listitem><para>If your file contains |
| 593 | If it aggregates non-hardware configuration and patches | 599 | only configuration fragments, place the file in |
| 594 | in order to define a base kernel policy or major kernel type to | 600 | <filename>cfg</filename>.</para></listitem> |
| 595 | be reused across multiple BSPs, it belongs in | 601 | <listitem><para>If your file contains |
| 596 | <filename>ktypes</filename>. | 602 | only source-code fixes, place the file in |
| 603 | <filename>patches</filename>.</para></listitem> | ||
| 604 | <listitem><para>If your file encapsulates | ||
| 605 | a major feature, often combining sources and configurations, | ||
| 606 | place the file in <filename>features</filename>. | ||
| 607 | </para></listitem> | ||
| 608 | <listitem><para>If your file aggregates | ||
| 609 | non-hardware configuration and patches in order to define a | ||
| 610 | base kernel policy or major kernel type to be reused across | ||
| 611 | multiple BSPs, place the file in <filename>ktypes</filename>. | ||
| 612 | </para></listitem> | ||
| 613 | </itemizedlist> | ||
| 597 | </para> | 614 | </para> |
| 598 | 615 | ||
| 599 | <para> | 616 | <para> |
| 600 | The lines between these can easily become blurred, especially as | 617 | These distinctions can easily become blurred - especially as |
| 601 | out-of-tree features are slowly merged upstream over time. | 618 | out-of-tree features slowly merge upstream over time. |
| 602 | Also remember that this is purely logical organization and has | 619 | Also, remember that how the description files are placed is |
| 603 | no impact on the functionality of the metadata as | 620 | a purely logical organization and has no impact on the functionality |
| 604 | all of <filename>cfg</filename>, <filename>features</filename>, | 621 | of the kernel Metadata. |
| 605 | <filename>patches</filename>, and <filename>ktypes</filename>, | 622 | There is no impact because all of <filename>cfg</filename>, |
| 606 | contain "features" as far as the Yocto Project Linux kernel | 623 | <filename>features</filename>, <filename>patches</filename>, and |
| 624 | <filename>ktypes</filename>, contain "features" as far as the kernel | ||
| 607 | tools are concerned. | 625 | tools are concerned. |
| 608 | </para> | 626 | </para> |
| 609 | 627 | ||
| 610 | <para> | 628 | <para> |
| 611 | Paths used in metadata files are relative to | 629 | Paths used in kernel Metadata files are relative to |
| 612 | <filename><base></filename>, which is either | 630 | <filename><base></filename>, which is either |
| 613 | <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> | 631 | <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> |
| 614 | if you are creating metadata in recipe-space as described in | 632 | if you are creating Metadata in |
| 615 | section "<link linkend='recipe-space-metadata'>Recipe-Space Metadata</link>", | 633 | <link linkend='recipe-space-metadata'>recipe-space</link>, |
| 616 | or <filename>meta/cfg/kernel-cache/</filename> if you are creating | 634 | or <filename>meta/cfg/kernel-cache/</filename> if you are creating |
| 617 | metadata in-tree as described in | 635 | Metadata <link linkend='in-tree-metadata'>in-tree</link>. |
| 618 | the "<link linkend='in-tree-metadata'>In-Tree Metadata</link>" section. | ||
| 619 | </para> | 636 | </para> |
| 620 | 637 | ||
| 621 | <para> | 638 | <para> |
