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HACKING.md

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You can run Cadmium inside qemu if you built image into file:

qemu-system-aarch64 -M virt -cpu cortex-a57 -kernel tmp/linux-arm64/arch/arm64/boot/Image -nographic -m 2G -serial mon:stdio -append "console=ttyAMA0,115200 root=/dev/vda3" -drive file=cd.img,if=virtio,format=raw

Explamantions of common env vars:

  • $TARGET is target device, krane, kevin or other
  • $ROOTFS represents target linux rootfs, Cadmium is made to be independent of rootfs
  • $CADMIUMROOT is root directory of Cadmium containing board/, kernel/, fs/, tmp/ etc. directories

Various hacks that were used:

  • /dev/mmcblk?: On Duet, Linux kernel randomly switches eMMC device between mmcblk0 and mmcblk1, therefore a wildcard has to be used
  • eMMC installation script has been split in 3 parts:
  • install-to-emmc-begin, which sets up partitioning, firmware and kernel
  • install-to-emmc-middle, which installs rootfs. this should be as small as possible
  • install-to-emmc-end, which sets up rootfs in order to make it easier to use(user accounts and cadmium-specific configs)
  • kernel/build has krane-specific kernel source :(

What directory has what:

  • board/$TARGET/ is for stuff specific to one device, usually: config files, dts configuration, kernel patches and firmware
  • fs/ is for building rootfs that can be used on target device
  • fs/$ROOTFS is for parts that are rootfs-specific
  • kernel/ contains only kernel-specific files, including scripts to test whether built kernel works or not
  • bootfw/ has scripts to set up kernel and partition layout

Random notes:

  • MMSYS sits between everything related to multimedia

boardinfo file in board:

  • BASEBOARD is "reference" board for family of chromebooks or common ancestor
  • BOARD is the target board, for example: kevin, krane
  • TYPE is type of device, laptop, tablet, convertible-laptop is laptop with 360° hinge, convertible-tablet is tablet with keyboard attachment or handheld

boardinfo file in baseboard:

  • ARCH uses kernel's naming, arm, arm64 etc.
  • ARCH_UNAME is what appears in uname -m, armv7l, aarch64 etc.
  • ARCH_DEB is whatever debian calls the architecture of device, armhf, arm64
  • YES ALL THIS ARCH STUFF IS A GIANT MESS
  • CROSS_COMPILE is self-explanatory
  • SOC - self explanatory
  • BOOTFW is boot firmware of device, chromebooks use depthcharge