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    SubjectRe: [PATCH v3 1/3] Documentation: arm: add UEFI support documentation
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    On Mon, 2 Dec 2013 13:51:22 -0600, Matt Sealey <neko@bakuhatsu.net> wrote:
    > > +UEFI kernel support on ARM
    > > +==========================
    > > +UEFI kernel support on the ARM architectures (arm and arm64) is only available
    > > +when boot is performed through the stub.
    > > +
    > > +The stub populates the FDT /chosen node with (and the kernel scans for) the
    > > +following parameters:
    > > +________________________________________________________________________________
    > > +Name | Size | Description
    > > +================================================================================
    > > +linux,uefi-system-table | 64-bit | Physical address of the UEFI System Table.
    > > +--------------------------------------------------------------------------------
    > > +linux,uefi-mmap-start | 64-bit | Physical address of the UEFI memory map,
    > > + | | populated by the UEFI GetMemoryMap() call.
    > > +--------------------------------------------------------------------------------
    > > +linux,uefi-mmap-size | 32-bit | Size in bytes of the UEFI memory map
    > > + | | pointed to in previous entry.
    > > +--------------------------------------------------------------------------------
    > > +linux,uefi-mmap-desc-size | 32-bit | Size in bytes of each entry in the UEFI
    > > + | | memory map.
    > > +--------------------------------------------------------------------------------
    > > +linux,uefi-mmap-desc-ver | 32-bit | Version of the mmap descriptor format.
    > > +--------------------------------------------------------------------------------
    > > +linux,uefi-stub-kern-ver | string | Copy of linux_banner from build.
    > > +--------------------------------------------------------------------------------
    >
    > This flies in the face of actually using #address-cells and
    > #size-cells to define how big addresses and sizes are. You're limited
    > here by the root node definitions... that's the spec.
    >
    > Here's where I think this whole thing falls down as being the weirdest
    > possible implementation of this. It defies logic to put this
    > information in the device tree /chosen node while also attempting to
    > boot the kernel using an EFI stub; the stub is going to have this
    > information because it is going to have the pointer to the system
    > System Table (since it was called by StartImage()). Why not stash the
    > System Table pointer somewhere safe in the stub?

    Everything here is about getting from the stub to the kernel. We have a
    boot interface for the kernel proper. It works, and this patch set works
    with it. Also, this is effectively a kernel-internal interface between
    the stub and the kernel so there aren't any ABI issues that we need to
    deail with.

    Go ahead and propose patches for a better interface, but in the mean
    time I see no reason not to merge this series.

    g.


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