Apertis is meant as a very flexible baseline to base a variety of different product and product types. This flexibility not only in the software selection used, but also in the hardware platforms, boards and features.
As Apertis aims to cater to a variety of use-cases and hardware platforms (with each platform providing its own balance of performance and features), developers are free to pick the hardware platform that provides the best match to their requirements. As an example, currently there are two big flavours of images targetted towards devices:
- Target Images: The “default” images with a reference HMI implementation. Expects hardware features like a 3D capable graphics system, touchscreen, hardware video decoding to be utilised.
- Minimal Images: GUI-less images with a minimal footprint (though images can be scaled down further if that's required). Only relies on network connectivity and generally has far lower resource demands.
Finally to make it possible to support various boards, it is critical that the integration of hardware support is done in a very consistent way using a consistent set of interfaces. This prevents the need for big, and potentially conflicting, adaptions in the generic parts of the software stack.
Adding Hardware Support
Typically the end-goal of adding hardware support is either to:
- Build new images for it (e.g. a new board)
- Add support for it to one or more existing images (e.g. add support for a previously unsupported USB modem).
In either case the first step is to add the hardware support into the relevant (Debian) package or introduce new (Debian) packages with support. For example, for a new modem family support might need to be added to ofono, but only ofono. However for a new board a selection of packages and package update will be required (e.g. kernel, bootloader, firmware, graphics stack).
For more information about the requirements with respect to hardware enabling see the Hardware Enablement page.
Once the hardware support is available in packages and accepted in the mainline distribution the next step is to make those available in images if applicable.
If the additional support doesn't require a new package (e.g. an ofono plugin for a modem which is included in the ofono package), no further work needs to done as such a package will already be installed on all relevant image types.
However, in case the new hardware support does require new packages or if it's specific to a board or a platform, image integration is the next step. Apertis takes a two step approach to building images:
- Generate an OSpack: A root file system containing all generic software for a particular image type and hardware architecture (e.g. target OSpack, containing the HMI stack for the arm architecture).
- Apply a hardware pack: A combination of hardware specific packages (e.g. bootloader, kernel, graphics stack if not generic) and configuration metadata (partition layout, bootloader setup information etc), that are combined with the OS pack to generate a hardware specific image.
If the new hardware support can be used on various boards (e.g. support for an certain type of USB device/dongle), the package should be added to the ospack such that it's available for all images of that type. If however, it's specific to a board then such a packages would be added to the hwpack (making it only available for that specific boardboard), of course if the board is completely new for Apertis a new hardware pack should be created.
More information about image building in can be found on Image building.