Subject: Re: [PATCH V4 6/6] dt-bindings: xen: Clarify "reg" purpose
To:     Julien Grall <julien@xen.org>
Cc:     xen-devel@lists.xenproject.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Stefano Stabellini <sstabellini@kernel.org>
References: <1639080336-26573-1-git-send-email-olekstysh@gmail.com>
 <1639080336-26573-7-git-send-email-olekstysh@gmail.com>
 <669d3f56-13b8-f159-2053-b39f1ba4222f@xen.org>
From:   Oleksandr <olekstysh@gmail.com>
Message-ID: <35ee3534-9e24-5a11-0bf1-a5dd0b640186@gmail.com>
Date:   Fri, 10 Dec 2021 11:33:12 +0200
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On 10.12.21 11:09, Julien Grall wrote:
> Hi Oleksandr,


Hi Julien


>
> On 09/12/2021 20:05, Oleksandr Tyshchenko wrote:
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> Xen on Arm has gained new support recently to calculate and report
>> extended regions (unused address space) safe to use for external
>> mappings. These regions are reported via "reg" property under
>> "hypervisor" node in the guest device-tree. As region 0 is reserved
>> for grant table space (always present), the indexes for extended
>> regions are 1...N.
>>
>> No device-tree bindings update is needed (except clarifying the text)
>> as guest infers the presence of extended regions from the number
>> of regions in "reg" property.
>>
>> While at it, remove the following sentence:
>> "This property is unnecessary when booting Dom0 using ACPI."
>> for "reg" and "interrupts" properties as the initialization is not
>> done via device-tree "hypervisor" node in that case anyway.
> You sent a similar patch for Xen and have already commented there [1] 
> . In short, the OS will be using the node to discover whether it is 
> running on Xen for both ACPI and DT. The hypervisor node also contain 
> the UEFI information for dom0.

I agree with your comments. The sentence should remain in this case. 
Thank you for pointing this out.


>
>
> Cheers,
>
> [1] 
> https://lore.kernel.org/xen-devel/9602b019-6c20-cdc7-23f3-9e4f8fd720f6@xen.org/T/#t
>
-- 
Regards,

Oleksandr Tyshchenko