Blame - yocto-poky/documentation/bsp-guide/bsp.xml - stefanberger/openbmc

"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-yocto-layer-script'>Creating a General Layer Using the yocto-layer Script</ulink>"

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section in the Yocto Project Development Guide.

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</note>

</para>

<para>

The next sections provide a concrete starting point to expand on a few points that

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might not be immediately obvious or that could use further explanation.

</para>

</section>

<title>Creating a new BSP Layer Using the yocto-bsp Script</title>

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<para>

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The <filename>yocto-bsp</filename> script creates a new

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by the Yocto Project, as well as QEMU versions of the same.

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The default mode of the script's operation is to prompt you for information needed

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to generate the BSP layer.

</para>

<para>

For the current set of BSPs, the script prompts you for various important

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parameters such as:

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<listitem><para>The kernel to use</para></listitem>

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<listitem><para>The branch of that kernel to use (or re-use)</para></listitem>

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<listitem><para>Whether or not to use X, and if so, which drivers to use</para></listitem>

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<listitem><para>Whether to turn on SMP</para></listitem>

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<listitem><para>Whether the BSP has a keyboard</para></listitem>

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<listitem><para>Whether the BSP has a touchscreen</para></listitem>

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<listitem><para>Remaining configurable items associated with the BSP</para></listitem>

</itemizedlist>

</para>

<para>

You use the <filename>yocto-bsp create</filename> sub-command to create

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a new BSP layer.

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This command requires you to specify a particular kernel architecture

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(<filename>karch</filename>) on which to base the BSP.

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Assuming you have sourced the environment, you can use the

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<filename>yocto-bsp list karch</filename> sub-command to list the

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architectures available for BSP creation as follows:

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$ yocto-bsp list karch

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Architectures available:

qemu

mips64

powerpc

x86_64

arm

mips

i386

</literallayout>

</para>

<para>

The remainder of this section presents an example that uses

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<filename>myarm</filename> as the machine name and <filename>qemu</filename>

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as the machine architecture.

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Of the available architectures, <filename>qemu</filename> is the only architecture

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that causes the script to prompt you further for an actual architecture.

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In every other way, this architecture is representative of how creating a BSP for

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an actual machine would work.

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The reason the example uses this architecture is because it is an emulated architecture

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and can easily be followed without requiring actual hardware.

</para>

<para>

As the <filename>yocto-bsp create</filename> command runs, default values for

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the prompts appear in brackets.

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Pressing enter without supplying anything on the command line or pressing enter

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with an invalid response causes the script to accept the default value.

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Once the script completes, the new <filename>meta-myarm</filename> BSP layer

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is created in the current working directory.

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This example assumes you have sourced the

setup script.

</para>

<para>

Following is the complete example:

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$ yocto-bsp create myarm qemu

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Checking basic git connectivity...

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Done.

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Which qemu architecture would you like to use? [default: i386]

1) i386 (32-bit)

2) x86_64 (64-bit)

3) ARM (32-bit)

4) PowerPC (32-bit)

5) MIPS (32-bit)

6) MIPS64 (64-bit)

3

Would you like to use the default (3.19) kernel? (y/n) [default: y] y

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Do you need a new machine branch for this BSP (the alternative is to re-use an existing branch)? [y/n] [default: y]

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Getting branches from remote repo git://git.yoctoproject.org/linux-yocto-3.19.git...

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Please choose a machine branch to base your new BSP branch on: [default: standard/base]

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1) standard/arm-versatile-926ejs

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2) standard/base

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3) standard/beagleboard

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4) standard/beaglebone

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5) standard/ck

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6) standard/common-pc

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7) standard/crownbay

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8) standard/edgerouter

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9) standard/fsl-mpc8315e-rdb

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10) standard/mti-malta32

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11) standard/mti-malta64

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12) standard/qemuarm64

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13) standard/qemuppc

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1

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Would you like SMP support? (y/n) [default: y]

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Does your BSP have a touchscreen? (y/n) [default: n]

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Does your BSP have a keyboard? (y/n) [default: y]

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New qemu BSP created in meta-myarm

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</literallayout>

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Take a closer look at the example now:

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<listitem><para>For the QEMU architecture,

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the script first prompts you for which emulated architecture to use.

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In the example, we use the ARM architecture.

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</para></listitem>

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<listitem><para>The script then prompts you for the kernel.

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The default 3.19 kernel is acceptable.

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So, the example accepts the default.

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If you enter 'n', the script prompts you to further enter the kernel

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you do want to use.</para></listitem>

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<listitem><para>Next, the script asks whether you would like to have a new

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branch created especially for your BSP in the local

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<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Linux Yocto Kernel</ulink>

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Git repository .

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If not, then the script re-uses an existing branch.</para>

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<para>In this example, the default (or "yes") is accepted.

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Thus, a new branch is created for the BSP rather than using a common, shared

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branch.

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The new branch is the branch committed to for any patches you might later add.

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The reason a new branch is the default is that typically

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new BSPs do require BSP-specific patches.

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The tool thus assumes that most of time a new branch is required.

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</para></listitem>

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<listitem><para>Regardless of which choice you make in the previous step,

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you are now given the opportunity to select a particular machine branch on

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which to base your new BSP-specific machine branch

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(or to re-use if you had elected to not create a new branch).

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Because this example is generating an ARM-based BSP, the example

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uses <filename>#1</filename> at the prompt, which selects the ARM-versatile branch.

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</para></listitem>

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<listitem><para>The remainder of the prompts are routine.

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Defaults are accepted for each.</para></listitem>

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<listitem><para>By default, the script creates the new BSP Layer in the

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current working directory of the

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<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>,

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(i.e. <filename>poky/build</filename>).

</para></listitem>

</orderedlist>

</para>

<para>

Once the BSP Layer is created, you must add it to your

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<filename>bblayers.conf</filename> file.

Here is an example:

BBLAYERS = ? " \

/usr/local/src/yocto/meta \

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/usr/local/src/yocto/meta-yocto \

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/usr/local/src/yocto/meta-yocto-bsp \

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/usr/local/src/yocto/meta-myarm \

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"

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BBLAYERS_NON_REMOVABLE ?= " \

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/usr/local/src/yocto/meta \

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/usr/local/src/yocto/meta-yocto \

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"

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</literallayout>

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Adding the layer to this file allows the build system to build the BSP and

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the <filename>yocto-kernel</filename> tool to be able to find the layer and

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other Metadata it needs on which to operate.

</para>

</section>

<title>Managing Kernel Patches and Config Items with yocto-kernel</title>

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<para>

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Assuming you have created a <link linkend='bsp-layers'>BSP Layer</link> using

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<filename>yocto-bsp</filename></link> and you added it to your

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<ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>

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variable in the <filename>bblayers.conf</filename> file, you can now use

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the <filename>yocto-kernel</filename> script to add patches and configuration

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items to the BSP's kernel.

</para>

<para>

The <filename>yocto-kernel</filename> script allows you to add, remove, and list patches

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and kernel config settings to a BSP's kernel

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<filename>.bbappend</filename> file.

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All you need to do is use the appropriate sub-command.

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Recall that the easiest way to see exactly what sub-commands are available

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is to use the <filename>yocto-kernel</filename> built-in help as follows:

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$ yocto-kernel --help

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Usage:

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Modify and list Yocto BSP kernel config items and patches.

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usage: yocto-kernel [--version] [--help] COMMAND [ARGS]

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Current 'yocto-kernel' commands are:

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config list List the modifiable set of bare kernel config options for a BSP

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config add Add or modify bare kernel config options for a BSP

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config rm Remove bare kernel config options from a BSP

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patch list List the patches associated with a BSP

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patch add Patch the Yocto kernel for a BSP

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patch rm Remove patches from a BSP

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feature list List the features used by a BSP

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feature add Have a BSP use a feature

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feature rm Have a BSP stop using a feature

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features list List the features available to BSPs

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feature describe Describe a particular feature

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feature create Create a new BSP-local feature

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feature destroy Remove a BSP-local feature

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See 'yocto-kernel help COMMAND' for more information on a specific command.

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Options:

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--version show program's version number and exit

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-h, --help show this help message and exit

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-D, --debug output debug information

</literallayout>

</para>

<para>

The <filename>yocto-kernel patch add</filename> sub-command allows you to add a

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patch to a BSP.

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The following example adds two patches to the <filename>myarm</filename> BSP:

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$ yocto-kernel patch add myarm ~/test.patch

Added patches:

test.patch

$ yocto-kernel patch add myarm ~/yocto-testmod.patch

Added patches:

yocto-testmod.patch

</literallayout>

<note>Although the previous example adds patches one at a time, it is possible

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to add multiple patches at the same time.</note>

</para>

<para>

You can verify patches have been added by using the

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<filename>yocto-kernel patch list</filename> sub-command.

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Here is an example:

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$ yocto-kernel patch list myarm

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The current set of machine-specific patches for myarm is:

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1) test.patch

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2) yocto-testmod.patch

</literallayout>

</para>

<para>

You can also use the <filename>yocto-kernel</filename> script to

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remove a patch using the <filename>yocto-kernel patch rm</filename> sub-command.

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Here is an example:

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$ yocto-kernel patch rm myarm

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Specify the patches to remove:

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1) test.patch

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2) yocto-testmod.patch

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Removed patches:

test.patch

</literallayout>

</para>

<para>

Again, using the <filename>yocto-kernel patch list</filename> sub-command,

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you can verify that the patch was in fact removed:

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$ yocto-kernel patch list myarm

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The current set of machine-specific patches for myarm is:

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1) yocto-testmod.patch

</literallayout>

</para>

<para>

In a completely similar way, you can use the <filename>yocto-kernel config add</filename>

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sub-command to add one or more kernel config item settings to a BSP.

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The following commands add a couple of config items to the

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<filename>myarm</filename> BSP:

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$ yocto-kernel config add myarm CONFIG_MISC_DEVICES=y

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Added item:

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CONFIG_MISC_DEVICES=y

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$ yocto-kernel config add myarm CONFIG_YOCTO_TESTMOD=y

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Added item:

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CONFIG_YOCTO_TESTMOD=y

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</literallayout>

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<note>

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Although the previous example adds config items one at a time, it is possible

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to add multiple config items at the same time.

</note>

</para>

<para>

You can list the config items now associated with the BSP.

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Doing so shows you the config items you added as well as others associated

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with the BSP:

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$ yocto-kernel config list myarm

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The current set of machine-specific kernel config items for myarm is:

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1) CONFIG_MISC_DEVICES=y

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2) CONFIG_YOCTO_TESTMOD=y

</literallayout>

</para>

<para>

Finally, you can remove one or more config items using the

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<filename>yocto-kernel config rm</filename> sub-command in a manner

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completely analogous to <filename>yocto-kernel patch rm</filename>.

</para>

</section>

</section>

</chapter>