Re: [PATCH v2] ArmPkg/ArmScmiDxe: Add clock enable function

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Thu, 6 Dec 2018 at 18:02, Jeff Brasen <jbrasen@nvidia.com> wrote:
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> -----Original Message-----
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Sent: Thursday, December 6, 2018 9:54 AM
> To: Jeff Brasen <jbrasen@nvidia.com>
> Cc: edk2-devel@lists.01.org; Leif Lindholm <leif.lindholm@linaro.org>; Girish Pathak <girish.pathak@arm.com>
> Subject: Re: [PATCH v2] ArmPkg/ArmScmiDxe: Add clock enable function
>
> On Thu, 6 Dec 2018 at 01:37, Jeff Brasen <jbrasen@nvidia.com> wrote:
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> > Leif/Ard,
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> >
> >   Any comments on this v2 patch for this?
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> >
>
> Hi Jeff,
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> I'm not sure what level of bikeshedding is justified when it comes to a driver such as this one, which is very recent, and mostly for platform internal use. However, I will note that the current versioning approach permits a *client* of the old SCMI_CLOCK_PROTOCOL to be built that invokes ->Enable(), which is not defined for it. This somewhat defeats the purpose of the versioning, since the whole point is to avoid invoking ->Enable() on older implementations of the protocol.
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> I'd be fine with just modifying the protocol, but if we decide we need versioning, we should not modify the public interface of the old one.
> How the driver reuses one implementation to back the other is another matter, of course.
> [JMB] I can either just change without versioning (that was my original approach but I also changed the guid which would primarily catch new clients running on old platforms from calling an undefined function), I am fine with either that (with maybe a switch back to original guid if we are not concerned about that issue) or a future update that creates a full v2 version of the protocol in the header.
>

Maybe Leif disagrees, but I am not too concerned about just changing
it. This is not a protocol that 3rd party drivers would invoke, right?