Re: [RFC PATCH 1/3] efi-rtc: Remove wakeup functionality

From: Demi Marie Obenour <demiobenour@gmail.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Juergen Gross <jgross@suse.com>,
	linux-rtc@vger.kernel.org,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Ard Biesheuvel <ardb+git@google.com>,
	linux-efi@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, Bibo Mao <maobibo@loongson.cn>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
	Heinrich Schuchardt <heinrich.schuchardt@canonical.com>,
	loongarch@lists.linux.dev, xen-devel@lists.xenproject.org,
	Feng Tang <feng.tang@linux.alibaba.com>,
	linux-riscv@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 1/3] efi-rtc: Remove wakeup functionality
Date: Mon, 14 Jul 2025 02:22:43 -0400	[thread overview]
Message-ID: <f538a1b9-6a7c-474f-af2a-d87c35b82fc5@gmail.com> (raw)
In-Reply-To: <CAMj1kXETDd+19i+awMx1v1sE4RXhF-r2a-mTa3rWfus5s4HMmw@mail.gmail.com>

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On 7/14/25 02:19, Ard Biesheuvel wrote:
> On Mon, 14 Jul 2025 at 16:13, Demi Marie Obenour <demiobenour@gmail.com> wrote:
>>
>> On 7/14/25 02:08, Ard Biesheuvel wrote:
>>> From: Ard Biesheuvel <ardb@kernel.org>
>>>
>>> The EFI rtc driver is used by non-x86 architectures only, and exposes
>>> the get/set wakeup time functionality provided by the underlying
>>> platform. This is usually broken on most platforms, and not widely used
>>> to begin with [if at all], so let's just remove it.
>> systemd uses the underlying functionality: a timer can wake the system up.
>> I have no idea if that is implemented in terms of this function, though.
> 
> To be clear, you are referring to wake from poweroff at some date/time
> in the future, right?

Yes.

> This change does not remove this functionality from the RTC subsystem,
> it just ceases to expose it on non-x86 EFI platforms that claim to
> support it.

Do these platforms generally expose the functionality in a different way?
If not, systemd should probably document that the functionality is
non-portable if it doesn't do that already.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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