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documentation/poky-ref-manual/ref-variables.xml: New KMACHINE gloss entry

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Created a new glossary entry for the KMACHINE variable.  I used
Bruce Ashfield as my resource for understanding this variable.

(From yocto-docs rev: 1069ddb3fe0b3bd00ba651b51419354258ae57d3)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2012-07-20 10:24:47 -07:00
committed by Richard Purdie
parent 15b96762f1
commit 3b4c9331df
1 changed files with 88 additions and 0 deletions
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documentation/poky-ref-manual/ref-variables.xml
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@@ -1128,6 +1128,94 @@ recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR = "r2"
</glossdef>
</glossentry>
<glossentry id='var-KMACHINE'><glossterm>KMACHINE</glossterm>
<glossdef>
<para>
The machine as known by the kernel.
Sometimes the machine name used by the kernel does not match the machine name
used by the OpenEmbedded build system.
For example, the machine name that the OpenEmbedded build system understands as
<filename>qemuarm</filename> goes by a different name in the Linux Yocto kernel.
The kernel understands that machine as <filename>arm_versatile926ejs</filename>.
For cases like these, the <filename>KMACHINE</filename> variable maps the
kernel machine name to the OpenEmbedded build system machine name.
</para>
<para>
Kernel machine names are initially defined in the
<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink> in
the <filename>meta/cfg/kernel-cache/bsp/&lt;bsp_name&gt;/&lt;bsp-name&gt;-&lt;kernel-type&gt;.scc</filename> file.
For example, in the <filename>linux-yocto-3.4</filename> kernel in the
<filename>meta/cfg/kernel-cache/bsp/cedartrail/cedartrail-standard.scc</filename> file,
has the following:
<literallayout class='monospaced'>
define KMACHINE cedartrail
define KTYPE standard
define KARCH i386
include ktypes/standard
branch cedartrail
include cedartrail.scc
</literallayout>
You can see that the kernel understands the machine name for the Cedar Trail BSP as
<filename>cedartrail</filename>.
</para>
<para>
If you look in the Cedar Trail BSP layer in the <filename>meta-intel</filename> source
repository at <filename>meta-cedartrail/recipes-kernel/linux/linux-yocto_3.0.bbappend</filename>,
you will find the following statements among others:
<literallayout class='monospaced'>
COMPATIBLE_MACHINE_cedartrail = "cedartrail"
KMACHINE_cedartrail = "cedartrail"
KBRANCH_cedartrail = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail += "bsp/cedartrail/cedartrail-pvr-merge.scc"
KERNEL_FEATURES_append_cedartrail += "cfg/efi-ext.scc"
COMPATIBLE_MACHINE_cedartrail-nopvr = "cedartrail"
KMACHINE_cedartrail-nopvr = "cedartrail"
KBRANCH_cedartrail-nopvr = "yocto/standard/cedartrail"
KERNEL_FEATURES_append_cedartrail-nopvr += " cfg/smp.scc"
</literallayout>
The <filename>KMACHINE</filename> statements in the kernel's append file make sure that
the OpenEmbedded build system and the Yocto Linux kernel understand the same machine
names.
</para>
<para>
This append file uses two <filename>KMACHINE</filename> statements.
The first is not really necessary but does ensure that the machine known to the
OpenEmbedded build system as <filename>cedartrail</filename> maps to the machine
in the kernel also known as <filename>cedartrail</filename>:
<literallayout class='monospaced'>
KMACHINE_cedartrail = "cedartrail"
</literallayout>
</para>
<para>
The second statement is a good example of why the <filename>KMACHINE</filename> variable
is needed.
In this example, the OpenEmbedded build system uses the <filename>cedartrail-nopvr</filename>
machine name to refer to the Cedar Trail BSP that does not support the propriatory
PowerVR driver.
The kernel, however, uses the machine name <filename>cedartrail</filename>.
Thus, the append file must map the <filename>cedartrail-nopvr</filename> machine name to
the kernel's <filename>cedartrail</filename> name:
<literallayout class='monospaced'>
KMACHINE_cedartrail-nopvr = "cedartrail"
</literallayout>
</para>
<para>
BSPs that ship with the Yocto Project release provide all mappings between the Yocto
Project kernel machine names and the OpenEmbedded machine names.
Be sure to use the <filename>KMACHINE</filename> if you create a BSP and the machine
name you use is different than that used in the kernel.
</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv id='var-glossary-l'><title>L</title>