Section 3 of this document defines some interfaces how a boot loader could forward a command line *or* a device tree to the kernel: http://wiki.prplfoundation.org/w/images/4/42/UHI_Reference_Manual.pdf This allows only a device tree *or* a command line, not both. The Linux kernel also supports an appended device tree. In this case the early code overwrites the fw_args to look like the boot loader added a device tree. This is done when CONFIG_MIPS_RAW_APPENDED_DTB is activated. The problem is when we use an appended device tree and the boot loader adds some important information in the kernel command line. In this case the command line gets overwritten and we do not get this information. This is the case for some lantiq devices were the boot loader provides the mac address to the kernel via the kernel command line. My proposal to solve this problem is to extend the interface and add a option to provide the kernel command line *and* a device tree from the boot loader to the kernel. a) use fw_arg0 ($a0) = -2 and fill the unused registers fw_arg2 ($a2) and fw_arg3 ($a3) with argv and envp. b) add a new boot protocol $a0 = -3 with $a1 = DT address, $a2 = argv and $a3 = envp. I would prefer solution b). This way we would not loose the kernel command line when appending a device tree and this could also be used by the boot loader if someone wants to. Should I send a patch for this? Hauke
