Re: [PATCH] rtc: efi: restore alarm support with runtime capability probe

[Ard Biesheuvel]

Hello Johnny,

On Fri, 28 Aug 2026, at 05:15, Johnny.Fan wrote:
> From: "Johnny.Fan" <Johnny.Fan@xxxxxxxxxxx>
>
> Restore the EFI RTC alarm functionality (read_alarm/set_alarm and
> procfs output) that was removed by commit 18a3510bc87d ("rtc: efi:
> Remove wakeup functionality").
>
> The removal was motivated by the observation that many EFI platforms
> lack RTC wakeup support while also omitting the RT_PROP table, causing
> the wakeup capability to be incorrectly advertised.  While that is
> true, removing the feature entirely also breaks platforms where the
> wakeup runtime service actually works.
>
> On CIX SoCs with an I2C-connected RTC, the firmware owns the RTC and
> exposes it via EFI runtime services.  Using the native I2C RTC driver
> under Linux breaks Windows, which relies on EFI runtime services to
> access the RTC.  rtc-efi is therefore the only viable option for
> shared RTC access across operating systems, and it needs working
> alarm/wakeup support.
>

Why does it need working alarm/wakeup support?

I'm not saying we shouldn't bring it back, but this deserves a bit of
motivation, no?