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

[Grant Likely]

On Mon, Feb 7, 2011 at 2:53 PM, Yoder Stuart-B08248
<B08248 at freescale.com> wrote:
>
>
>> -----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 */

I really dislike enums for this sort of thing.  I'd rather have a
string encoded somewhere, even if it is in a different property.

g.