# Re: \[PATCH v2 00/11\] Drivers for gunyah hypervisor

- From: Jassi Brar \<jassisinghbrar@gmail.com\>
- Date: 2022-08-10 04:13:48 
- List: linux-devicetree
- Page: https://ratatoskr.run/linux-devicetree/2022/08/8208543
- Thread: https://ratatoskr.run/linux-arm-kernel/2022/08/8208280/t.md

```text
On Tue, Aug 9, 2022 at 7:07 PM Elliot Berman [ref] wrote:
>
> On 8/9/2022 6:13 AM, Robin Murphy wrote:
> > [drive-by observation since one thing caught my interest...] >
>
> Appreciate all the comments.
>
> Jassi,
>
> I understood you have talked with some of our folks (Trilok and Carl) a
> few years ago about using the mailbox APIs. We were steered away from
> using mailboxes then. Is that still the recommendation today?
>
Neither I nor Google remember any such conversation.

Doorbell had always been supported by the api. It was the
doorbell-mode of _mhu_ controller that had some contention.

I haven't read the complete history of Gunyah yet, but from a quick
look it uses the hvc/smc instruction as the "physical link" between
entities (?).    zynqmp-ipi-mailbox.c is one driver that uses smc in
such a manner. And I know there are some platforms that don't call
hvc/smc under mailbox api and I don't blame them.

Let me educate myself with the background and get back.... unless you
want to summarize a usecase that you doubt is supported.

Thanks.
```