On 12-02-21, 12:07, Masahiro Yamada wrote: > BTW, I do not know how to use overlay. > Do we apply overlay in the build time? Ideally it can be applied at both build time and runtime, but we haven't allowed the runtime way until now in kernel. This patchset is all about applying it at build time. > If so, I do not know what the benefit of overlay is. > Or is this just for build testing? For now the main benefit of using them is that we can keep stuff in separate files without including each other. For example a primary board may or may not have an extension board connected to it. Without overlays we will have this many dtbs for this simple case: 1. primary.dtb 2. extension.dtb 3. primary-includes-extension.dtb With overlays we will have the first two. Now the same extension can be applied to lots of boards and multiple extensions can be applied to the same primary board. This just complicates the process of managing dtbs. > I just thought this was done in the boot time, > for example, in U-Boot or something. Yes, bootloader can do it as well. -- viresh
