linux-kernel - Re: [GIT PULL] ACPI updates for v5.14-rc1

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Date:   Wed, 30 Jun 2021 19:19:05 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] ACPI updates for v5.14-rc1

On Wed, Jun 30, 2021 at 12:47 PM Borislav Petkov <bp@...en8.de> wrote:
>
> On Tue, Jun 29, 2021 at 09:01:10PM +0200, Rafael J. Wysocki wrote:
> > Erik Kaneda (6):
> >       ACPICA: Fix memory leak caused by _CID repair function
> >       ACPICA: iASL: add disassembler support for PRMT
> >       ACPICA: Add support for PlatformRtMechanism OperationRegion handler
> >       ACPICA: Add PRMT module header to facilitate parsing
> >       ACPI: PRM: implement OperationRegion handler for the
> > PlatformRtMechanism subtype
>
> $ git checkout master
> $ git pull
> $ make oldconfig
>
> Platform Runtime Mechanism Support (ACPI_PRMT) [Y/n/?] (NEW) ?
>
> There is no help available for this option.
> Symbol: ACPI_PRMT [=y]
> Type  : bool
> Defined at drivers/acpi/Kconfig:547
>   Prompt: Platform Runtime Mechanism Support
>   Depends on: EFI [=y] && X86_64 [=y]
>   Location:
>     -> Power management and ACPI options
>
>
>
> Platform Runtime Mechanism Support (ACPI_PRMT) [Y/n/?] (NEW)
>
> I don't know what that means, there's no help, no nothing. And it is
> default y for no apparent reason.
>
> /me looks at the commit message:
>
>     Platform Runtime Mechanism (PRM) is a firmware interface that exposes
>     a set of binary executables that can either be called from the AML
>     interpreter or device drivers by bypassing the AML interpreter.
>     This change implements the AML interpreter path.
>
> I'm still unclear whether I need it or not.

That's a fair point.

> Guys, you need to think about your users and to write help text which is
> *actually* usable for people who do not deal with ACPI firmware gunk.

We will.

What about the following help text (white space damage by gmail)?

---
 drivers/acpi/Kconfig |   10 ++++++++++
 1 file changed, 10 insertions(+)

Index: linux-pm/drivers/acpi/Kconfig
===================================================================
--- linux-pm.orig/drivers/acpi/Kconfig
+++ linux-pm/drivers/acpi/Kconfig
@@ -548,3 +548,13 @@ config ACPI_PRMT
     bool "Platform Runtime Mechanism Support"
     depends on EFI && X86_64
     default y
+    help
+      Platform Runtime Mechanism (PRM) is a firmware interface exposing a
+      set of binary executables that can be called from the AML interpreter
+      or directly from device drivers.
+
+      Say Y to enable the AML interpreter to execute the PRM code.
+
+      While this feature is optional in principle, leaving it out may
+      substantially increase computational overhead related to the
+      initialization of some server systems.