Re: [PATCH v3 2/4] docs, xen/arm: Introduce static heap memory

[Michal Orzel <michal.orzel@xxxxxxx>]

On 07/09/2022 14:32, Julien Grall wrote:
> [CAUTION: External Email]
> 
> On 07/09/2022 13:12, Michal Orzel wrote:
>> Hi Julien,
> 
> Hi Michal,
> 
>> On 07/09/2022 13:36, Julien Grall wrote:
>>>
>>> Hi Henry,
>>>
>>> While reviewing the binding sent by Penny I noticed some inconsistency
>>> with the one you introduced. See below.
>>>
>>> On 07/09/2022 09:36, Henry Wang wrote:
>>>> +- xen,static-heap
>>>> +
>>>> +    Property under the top-level "chosen" node. It specifies the address
>>>> +    and size of Xen static heap memory. Note that at least a 64KB
>>>> +    alignment is required.
>>>> +
>>>> +- #xen,static-heap-address-cells and #xen,static-heap-size-cells
>>>> +
>>>> +    Specify the number of cells used for the address and size of the
>>>> +    "xen,static-heap" property under "chosen".
>>>> +
>>>> +Below is an example on how to specify the static heap in device tree:
>>>> +
>>>> +    / {
>>>> +        chosen {
>>>> +            #xen,static-heap-address-cells = <0x2>;
>>>> +            #xen,static-heap-size-cells = <0x2>;
>>>
>>> Your binding, is introduce #xen,static-heap-{address, size}-cells
>>> whereas Penny's one is using #{address, size}-cells even if the property
>>> is not "reg".
>>>
>>> I would like some consistency in the way we define bindings. Looking at
>>> the tree, we already seem to have introduced
>>> #xen-static-mem-address-cells. So maybe we should follow your approach?
>>>
>>> That said, I am wondering whether we should just use one set of property
>>> name.
>>>
>>> I am open to suggestion here. My only request is we are consistent (i.e.
>>> this doesn't depend on who wrote the bindings).
>>>
>> In my opinion we should follow the device tree specification which states
>> that the #address-cells and #size-cells correspond to the reg property.
> 
> Hmmm.... Looking at [1], the two properties are not exclusive to 'reg'
> Furthermore, I am not aware of any restriction for us to re-use them. Do
> you have a pointer?

As we are discussing re-usage of #address-cells and #size-cells for custom 
properties that are not "reg",
I took this info from the latest device tree specs found under 
https://www.devicetree.org/specifications/:
"The #address-cells property defines the number of <u32> cells used to encode 
the address field in a child node's reg property"
and
"The #size-cells property defines the number of <u32> cells used to encode the 
size field in a child node’s reg property"

> 
> Cheers,
> 
> [1] 
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Felinux.org%2FDevice_Tree_Mysteries%23.23xxx-cells_property_name&amp;data=05%7C01%7Cmichal.orzel%40amd.com%7C40290431f16748808b6308da90ccfc53%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637981507324472512%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=okN60ULg2Dx3cnlA5vPLMR%2F8QAKnbGmBpz7goXb5usw%3D&amp;reserved=0
> 
>>
>> ~Michal
> 
> --
> Julien Grall
> 

~Michal