ARM: default machine descriptor for multiplatform
Since we now have default implementations for init_time and init_irq, the init_machine callback is the only one that is not yet optional, but since simple DT based platforms all have the same of_platform_populate function call in there, we can consolidate them as well, and then actually boot with a completely empty machine_desc. Unofortunately we cannot just default to an empty init_machine: We cannot call of_platform_populate before init_machine because that does not work in case of auxdata, and we cannot call it after init_machine either because the machine might need to run code after adding the devices. To take the final step, this adds support for booting without defining any machine_desc whatsoever. For the case that CONFIG_MULTIPLATFORM is enabled, it adds a global machine descriptor that never matches any machine but is used as a fallback if nothing else matches. We assume that without CONFIG_MULTIPLATFORM, we only want to boot on the systems that the kernel is built for, so we still retain the build-time warning for missing machine descriptors and the run-time warning when the platform does not match in that case. In the case that we run on a multiplatform kernel and the machine provides a fully populated device tree, we attempt to keep booting, hoping that no machine specific callbacks are necessary. Finally, this also removes the misguided "select ARCH_VEXPRESS" that was only added to avoid a build error for allnoconfig kernels. Signed-off-by: NArnd Bergmann <arnd@arndb.de> Acked-by: NNicolas Pitre <nico@linaro.org> Acked-by: NOlof Johansson <olof@lixom.net> Cc: "Russell King - ARM Linux" <linux@arm.linux.org.uk> Cc: Rob Herring <robherring2@gmail.com>
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