[Power.org:parch] devicetree: Musings on reserved regions

[Yoder Stuart-B08248]

> -----Original Message-----
> From: glikely at secretlab.ca [mailto:glikely at secretlab.ca] On Behalf Of Grant
> Likely
> Sent: Monday, February 07, 2011 3:45 PM
> To: Benjamin Herrenschmidt
> Cc: parch at power.org; devicetree-discuss; David Gibson; Yoder Stuart-B08248;
> McClintock Matthew-B29882; Wood Scott-B07421
> Subject: Re: [Power.org:parch] devicetree: Musings on reserved regions
> 
> On Mon, Feb 7, 2011 at 2:39 PM, Benjamin Herrenschmidt
> <benh at kernel.crashing.org> wrote:
> >
> >> In addition to the reserved regions block in the header, define a set
> >> of properties in the memory node that specify the reserved regions
> >> with the name reflecting the usage.
> >> For example:
> >>
> >>       memory at 0 {
> >>               device_type = "memory";
> >>               reg = <0 0x40000000>;
> >>               reserved-ramdisk = <0xc00000 0x200000>; /* 2MB ramdisk
> >> */
> >>               reserved-dtb = <0xbf0000 0x1000>; /* devicetree */
> >>               reserved-fb0 = 0x1000000 0x400000>; /* framebuffer */
> >>       };
> >>
> >> Each reserved property would start with "reserved-" followed by a
> >> name.  reserved-ramdisk and reserved-dtb would be reserved for
> >> ramdisk and dtb images respectively.  Other names could also be
> >> defined; for example, reserved-openfirmware.
> >
> > I very much dislike the list of properties with magic names. I'd
> > rather have a pair of properties containing lists (reserved-names and
> > reserved-ranges).
> 
> Heh, I have very much the opposite opinion.  I'd rather have property names
> that match the usage than have the names and values split into two
> properties.  To me, keeping them together is more tasteful.  Queue the
> debate...  :-)

Could we not do both? Use an enum to identify the region type:

    reserved = <0x1 0xc00000 0x200000>; /* 2MB ramdisk
    reserved = <0x2 0xbf0000 0x1000>; /* devicetree */
    reserved = <0x3 0x1000000 0x400000>; /* framebuffer */

Stuart