• Arnd Bergmann's avatar
    ARM: default machine descriptor for multiplatform · 883a106b
    Arnd Bergmann authored
    
    
    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: default avatarArnd Bergmann <arnd@arndb.de>
    Acked-by: default avatarNicolas Pitre <nico@linaro.org>
    Acked-by: default avatarOlof Johansson <olof@lixom.net>
    Cc: "Russell King - ARM Linux" <linux@arm.linux.org.uk>
    Cc: Rob Herring <robherring2@gmail.com>
    883a106b