bitbake 如何在构建过程中搜索配方？

Question

I am trying to find out that how bitbake search for recipe in build process? For example, I have a recipe something like below:

DESCRIPTION = "PetaLinux GSTREAMER supported packages"

inherit packagegroup

GSTREAMER_PACKAGES = " \
    gstreamer1.0 \
    gstreamer1.0-python \
    gstreamer1.0-meta-base \
    gstreamer1.0-plugins-base \
    gstreamer1.0-plugins-good \
    gstreamer1.0-plugins-bad \
    gstreamer1.0-rtsp-server \
    gst-shark \
    gstd \
    gst-perf \
    gst-interpipes \
    "
GSTREAMER_PACKAGES_append_zynqmp = " gstreamer1.0-omx"

RDEPENDS_${PN} = "${GSTREAMER_PACKAGES}"

When I searched gstreamer1.0 related recipe in yocto layers, I found two recipe, one of them is gstreamer1.0_1.16.1.bb in meta layer, and the other is gstreamer1.0_%.bbappend in meta-petalinux layer.

Both of these layers was added to the BBLAYERS in bblayers.conf file and the priorities that spesified with BBFILE_PRIORITY_ * in related layer's layer.conf file is same.

So, Which recipe will be used in build process in that case? What is the recipe lookup rules in yocto?

I changed somethings to understand the behaviour: For example,

1. I entered the invalid github URL that spesified in gstreamer1.0_%.bbappend recipe. When I tried to build the linux system, I encountered with an error. Thats fine.
2. Then I corrected the github URL in this recipe and entered invalid source code address that spesified in gstreamer1.0_1.16.1.bb recipe. When I tried to build linux system, process finished successfully.
3. Then I increased the priority of meta layer. I supposed to encounter with an error in this case but again build process finished successfully.

Could you please help me to understand this behaviour?

Thanks.

Answer 1

You have two different files: a .bb and a .bbappend .

A .bb is the base recipe of one (or multiple) packages. It generally describe how to fetch, configure, compile, install files in a package for your target.

A .bbappend file is an 'append' file. It allows a meta (here meta-petalinux) to modify an existing recipe in another meta without copying it. A .bbappend can modify any steps of the bb file: source fetch, configure, compile, install...

You can for example create your own bbappend of Gstreamer, to enable pango (disbaled by default on my Yocto). The bbappend filename is gstreamer1.0-plugins-base_%.bbappend and only contains PACKAGECONFIG_append = "pango"

The Yocto Manual can give you more information on bbappend files here .