[yocto] understanding recipes

[Scott Garman]

On 01/26/2012 08:44 AM, jfabernathy wrote:
> I'm trying to understand the concept of creating a recipe and having it
> included in the build I do.
>
> For example, suppose I want to create the meta-intel/meta-cedartrail BSP
> with the core-image-minimal image, but I wanted to include hello world
> as shown in 3.1.2 Autotooled Package section of the Poky reference Manual.
>
> Where do I put the recipe file? I'm guessing a recipe-jfa directory at
> the same level as the meta-cedartrail recipe-core, recipe-kernel,
> recipe-graphic, recipe-bsp?

Hi Jim,

The best way to do this is to create your own layer, and keep all of 
your customizations there.

You'd put this in a directory, say meta-jfa with something like the 
following:

meta-jfa/
meta-jfa/conf/layer.conf
meta-jfa/recipes-jfa/helloworld/helloworld.bb

where your layer.conf file would look like:

# We have a conf and classes directory, add to BBPATH
BBPATH := "${BBPATH}:${LAYERDIR}"

# We have a packages directory, add to BBFILES
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
             ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "jfa"
BBFILE_PATTERN_jfa := "^${LAYERDIR}/"
BBFILE_PRIORITY_jfa = "5"

Then point your build's bblayers.conf file to include the path to your 
meta-jfa/ directory.

>
> I'm also assuming that helloworld.bb file would contain:
>
> DESCRIPTION = "GNU Helloworld application"
> SECTION = "examples"
> LICENSE = "GPLv2+"
> LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
> PR = "r0"
>
> SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
>
> inherit autotools gettext
>
>
> So where do the values of ${GNU_MIRROR|, and ${PV} get set correctly?

Those examples are defined in the bitbake classes you have in your base 
layers.

> And what does the following line do or require me to do:
>
> LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"

This was answered in another post.

> Is this all that is needed to get helloworld put into /usr/bin so it can
> be executed at the command line when the image is booted?

You'd also need to add the helloworld package to your image file. The 
simplest way to do this is to add EXTRA_IMAGE_FEATURES += "helloworld" 
in your build's local.conf file.

I think the above should be accurate enough w/o testing it myself.

Scott

-- 
Scott Garman
Embedded Linux Engineer - Yocto Project
Intel Open Source Technology Center