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

[Jimi Xenidis]

On Feb 7, 2011, at 3:56 PM, Grant Likely wrote:
> 
> 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.

ack
-JX

> 
> g.