On Wednesday, July 13, 2016 6:58:32 PM CEST Mark Rutland wrote: > > > we may want to remove unnecessary devices and even add a dedicated > > storage device for storing a core dump image. > > I suspect that bringing up a minimal number of devices is better > controlled by a cmdline option. In general, figuring out what is > necessary and what is not is going to be board specific, so hacking the > FW tables (DTB or ACPI) is not a very portable/reliable approach. > > Do we actually add devices in practice? More so than the above that > requires special knowledge of the platform (including things that were > not described in the boot DTB). > > In the ACPI case modifying a DTB alone is not sufficient to change the > information regarding devices, as those won't be described in the DTB. > It's not possible to convert ACPI to DTB in general. A more likely scenario would be replacing ACPI tables with a DTB that describes the platform in order to use devices that the ACPI tables don't contain. > > - Say, booting BE kernel on ACPI LE kernel > > In this case, there is no useful dtb in the kernel. > If the platform only has ACPI, then you cannot boot a BE kernel to begin > with. As above one cannot convert ACPI to DTB, so one would need > extensive platform knowledge for this to work. I think what he meant was to pass a DTB to the kexec kernel in order to run BE, while the original kernel can only run LE due to ACPI. If you boot a LE kernel using DTB, the same DTB should work for a kexec boot for a BE kernel. Arnd
