On Wed, Nov 25, 2020 at 06:57:07AM -0800, mturney@codeaurora.org wrote:
On 2020-11-24 03:05, Andy Pont wrote:
Hello,
Is there an idiots guide to the definitions in devicetree.cb? Trying to make sense of the USB and PCIe configuration stuff.
I don't know if these qualify as part of an idiots guide, but I found these links especially useful when learning devicetree (all from elinux.org):
Device Tree Reference: https://elinux.org/Device_Tree_Reference Device Tree Usage: https://elinux.org/Device_Tree_Usage Device Tree Mysteries: https://elinux.org/Device_Tree_Mysteries
No, these are unfortunately not suitable, because they are about the OpenFirmware-derived Devicetree format. The devicetree.cb format used in coreboot is different, albeit serving a similar purpose (hardware description and configuration).
One important detail about the devicetree.cb format is that a "chip" statement specifies a file path to a chip.h file that defines a struct (e.g. "chip soc/intel/skylake" -> src/soc/intel/skylake/chip.h), and a "register" statement sets a member of that struct to a particular value (as far as I understand it).
Jonathan Neuschäfer