Yocto: sharing the sstate cache and download directories

When developing projects based on Yocto Project / OpenEmbedded, a quite common practice is to have multiple build environments in different directories: one per product, or one for each development branch, or for other scenarios. Each build environment could have different layers, a different configuration, or just using a different version of the source code.

With default settings, different build directories result in duplicated storage for the downloaded source code and build artifacts, as well as duplicated time for downloading the sources and to build everything. This can be troublesome for large projects.

Fortunately, the bitbake build engine can share both the downloaded source code and the intermediate build results across multiple build directories, saving build time and disk space.

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A Tegra20 parallel camera capture driver heading for the mainline Linux kernel

Over the past year Bootlin engineer Luca Ceresoli has been working to add a device driver for the parallel camera interface of the NVIDIA Tegra20 System on Chip into the mainline Linux kernel.

The main challenge faced during this work has been the lack of documentation. So the work has been based on a driver from an NVIDIA BSP, forked from a 3.1 kernel (which has been released back in 2011!). The old driver code base needed a huge rework, being largely rewritten, and not only because of the changes in 10+ years of kernel development.

The mainline kernel already has a driver for CSI capture on Tegra210, albeit in staging. The two hardware components have some common functionality, thus to avoid code duplication Luca augmented the existing driver and generalized the code implementing common areas instead of adding a new driver. This posed the additional challenge of not breaking functionality on another SoC, based on a different architecture and using a different video bus… all without access to such other hardware!

Luca just resent version 4 of the patch series implementing this.

If you have a device using Tegra20 parallel capture or Tegra210 CSI video capture, this is a great opportunity to test the code and report your findings! And in case you don’t have the hardware, you’d still be very welcome in reviewing the patches.

Finally, if you have access to the Tegra20 documentation, we’d love to know: the driver could possibly be improved with good knowledge of the hardware.

Fixing reboot in ZynqMP PMU Firmware

Thanks to community contributions, our engineer Luca Ceresoli has recently published a fix to the zynqmp-pmufw-builder repository that allows building a fully working PMU Firmware binary. Rebooting had previously been broken for a long time.

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