12-01, 17:30–18:00 (UTC), Langdale
A typical software product build with Yocto Project makes use of several different metadata layers. These layers may be maintained by hardware manufacturers, software/service companies, or individual hobby developers. Naturally there is some variation in layer quality and compatibility - some layers play well with each other while others are in practice mutually exclusive. For example, misbehaving layers may force the selection of particular machine or distro or make unwanted changes to recipes defined in other layers. This can result in broken builds (often with confusing error messages) or subtle runtime errors and crashes which may be difficult to debug.
As a layer author you can apply straightforward design principles to maximise the compatibility of your layer, or at least to ensure that useful error messages are given if you layer is used incorrectly. Following these principles effectively requires a good understanding of how variables, tasks, distro features and overrides work within the Yocto Project.
This talk will collect the knowledge required to design and implement high quality Yocto Project layers. Attention will be given to proper use of bbappends, conditionals, distro & machine features and sanity checks. Examples of well behaved layers will also be highlighted. Information presented in the previous edition of this talk will be updated to target the Langdale (4.1) and Kirkstone (4.0, LTS) releases.
Paul Barker is an Embedded Linux & Open Source professional. He has been an active member of the Yocto Project community since 2013. He has contributed to the project in many ways, including maintaining the opkg package manager during 2013-2015 and presenting at several previous
Yocto Project summit events. He is currently working as Principal Software Engineer for SanCloud Ltd, maintaining the meta-sancloud BSP layer and other software components.