[PATCH] [POWERPC] Improved documentation of device tree 'ranges'.

[Grant Likely]

On 12/3/07, Stephen Neuendorffer <stephen.neuendorffer at xilinx.com> wrote:
> I was misled by the prior language.  I've attempted to clarify how
> 'ranges' are used, in particular, how to get a 1:1 mapping.
>
> Signed-off-by: Stephen Neuendorffer <stephen.neuendorffer at xilinx.com>

Acked-by: Grant Likely <grant.likely at secretlab.ca>

> ---
>  Documentation/powerpc/booting-without-of.txt |   11 +++++++----
>  1 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
> index e9a3cb1..aad8bf5 100644
> --- a/Documentation/powerpc/booting-without-of.txt
> +++ b/Documentation/powerpc/booting-without-of.txt
> @@ -711,13 +711,14 @@ define a bus type with a more complex address format, including things
>  like address space bits, you'll have to add a bus translator to the
>  prom_parse.c file of the recent kernels for your bus type.
>
> -The "reg" property only defines addresses and sizes (if #size-cells
> -is non-0) within a given bus. In order to translate addresses upward
> +The "reg" property only defines addresses and sizes (if #size-cells is
> +non-0) within a given bus. In order to translate addresses upward
>  (that is into parent bus addresses, and possibly into CPU physical
>  addresses), all busses must contain a "ranges" property. If the
>  "ranges" property is missing at a given level, it's assumed that
> -translation isn't possible. The format of the "ranges" property for a
> -bus is a list of:
> +translation isn't possible, i.e., the registers are not visible on the
> +parent bus.  The format of the "ranges" property for a bus is a list
> +of:
>
>         bus address, parent bus address, size
>
> @@ -735,6 +736,8 @@ fit in a single 32-bit word.   New 32-bit powerpc boards should use a
>  1/1 format, unless the processor supports physical addresses greater
>  than 32-bits, in which case a 2/1 format is recommended.
>
> +Alternatively, the "ranges" property may be empty, indicating that the
> +registers are visible on the parent bus, with 1:1 address translation.
>
>  2) Note about "compatible" properties
>  -------------------------------------
> --
> 1.5.3.4
>
>
>
>


-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely at secretlab.ca
(403) 399-0195