Re: [Xen-devel] [PATCH] arm64/xen: Add missing #address-cells and #size-cells properties

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Thu, Nov 30, 2017 at 01:22:37PM +0000, Julien Grall wrote:
> Hi Daniel,
>
> On 30/11/17 13:06, Daniel Kiper wrote:
> >On Wed, Nov 29, 2017 at 05:08:12PM +0000, Julien Grall wrote:
> >>The properties #address-cells and #size-cells are used to know the
> >>number of cells for ranges provided by "regs". If they don't exist, the
> >>value are resp. 2 and 1.
> >>
> >>Currently, when multiboot nodes are created it is assumed that 
> >>#address-cells
> >
> >IIRC ARM boot protocol is not related to Multiboot protocol in any way.
> >So, calling it in that way is very confusing. Could you invent a better
> >not confusion name. Or at least provide a spec. I am happy to see it
> >in GRUB2 tree.
>
> That's the name of the node see the MODULE_CUSTOM_COMPATIBLE in the
> code... But this it not the Linux Arm boot protocol, it is an
> extension currently only used by Xen. See [1].

Oh, boy! It is unfortunate. Sadly it looks that we have to live with
this right now... Too late for change... I would just add the comment
to this file that this is not related to the Multiboot protocol family
in any way.

> >>and #size-cells are exactly 2. However, they are never set by GRUB and
> >>will result to later failure when the device-tree is generated by GRUB
> >>or contain different values.
> >>
> >>To prevent this failure, create the both properties in the chosen nodes.
> >>
> >>Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> >>---
> >>  grub-core/loader/arm64/xen_boot.c | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >>diff --git a/grub-core/loader/arm64/xen_boot.c 
> >>b/grub-core/loader/arm64/xen_boot.c
> >>index c95d6c5a8..6780b1f0c 100644
> >>--- a/grub-core/loader/arm64/xen_boot.c
> >>+++ b/grub-core/loader/arm64/xen_boot.c
> >>@@ -115,6 +115,17 @@ prepare_xen_hypervisor_params (void *xen_boot_fdt)
> >>    if (chosen_node < 1)
> >>      return grub_error (GRUB_ERR_IO, "failed to get chosen node in FDT");
> >>
> >>+  /*
> >>+   * The address and size are always written using 64-bits value. Set
> >
> >Here you say "64-bits value"...
> >
> >>+   * #address-cells and #size-cells accordingly.
> >>+   */
> >>+  retval = grub_fdt_set_prop32 (xen_boot_fdt, chosen_node, 
> >>"#address-cells", 2);
> >
> >...and then call grub_fdt_set_prop32(). I am confused...
>
> #address-cells and #size-cells are property to know the number of
> cells per address/size.
>
> The address and size are 64-bit (i.e 2 cells) as you can see the
> call to grub_fdt_set_reg64 in the prepare_xen_module_params.

Understood! I will apply this patch next week.

Daniel

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