# Re: \[PATCH v2 03/11\] arm64: gunyah: Add Gunyah hypercalls ABI

- From: Elliot Berman \<hidden\>
- Date: 2022-08-03 21:15:35 
- List: linux-devicetree
- Page: https://ratatoskr.run/linux-devicetree/2022/08/8208359
- Thread: https://ratatoskr.run/linux-arm-kernel/2022/08/8208280/t.md

```text
Hi Dmitry,

On 8/2/2022 6:34 AM, Dmitry Baryshkov wrote:
> On 02/08/2022 00:12, Elliot Berman wrote:
>> Add initial support to perform Gunyah hypercalls. The arm64 ABI for
>> Gunyah hypercalls generally follows the SMC Calling Convention.
>
> Seeing a c&p (or c&rework) from arm-smccc.h, could you please describe:
>
> 1) Why can't you use the existing arm_smccc_1_1_hvc()? I checked, you don't seem to be getting more than 4 values back.
>

The Gunyah APIs can return up to 8 values. As you observed though, these initial patches are only using the first 4 values back. I'd like to use the larger v1.2 so I don't need to update later.

> 2) If #1 is not possible, why can't you add necessary glue code to the arm-smccc.h (as your code to support nargs/multiple return values is generic enough) and use corresponding macro in asm/gunyah.h ?
>

I think the code here may be considered Gunyah-specific as I am limiting to 8 arguments and return values. If I add to arm-smccc.h, I would need to expand out to x17. Does it make sense to add another SMCCC 1.2 interface to arm-smccc.h?
```