Date:   Sun, 28 Nov 2021 01:43:22 +0100
From:   =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= <mirq-linux@rere.qmqm.pl>
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Greg Ungerer <gerg@linux-m68k.org>,
        Joshua Thompson <funaho@jurai.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Sebastian Reichel <sre@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Greentime Hu <green.hu@gmail.com>,
        Vincent Chen <deanbo422@gmail.com>,
        "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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        Albert Ou <aou@eecs.berkeley.edu>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
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        Lee Jones <lee.jones@linaro.org>,
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        Guenter Roeck <linux@roeck-us.net>,
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        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
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        "K . C . Kuen-Chern Lin" <kclin@andestech.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
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        linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org,
        xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org,
        linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org
Subject: Re: [PATCH v4 08/25] kernel: Add combined power-off+restart handler
 call chain API
Message-ID: <YaLQqks8cB0vWp6Q@qmqm.qmqm.pl>
References: <20211126180101.27818-1-digetx@gmail.com>
 <20211126180101.27818-9-digetx@gmail.com>
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On Fri, Nov 26, 2021 at 09:00:44PM +0300, Dmitry Osipenko wrote:
> SoC platforms often have multiple ways of how to perform system's
> power-off and restart operations. Meanwhile today's kernel is limited to
> a single option. Add combined power-off+restart handler call chain API,
> which is inspired by the restart API. The new API provides both power-off
> and restart functionality.
> 
> The old pm_power_off method will be kept around till all users are
> converted to the new API.
> 
> Current restart API will be replaced by the new unified API since
> new API is its superset. The restart functionality of the sys-off handler
> API is built upon the existing restart-notifier APIs.
> 
> In order to ease conversion to the new API, convenient helpers are added
> for the common use-cases. They will reduce amount of boilerplate code and
> remove global variables. These helpers preserve old behaviour for cases
> where only one power-off handler is expected, this is what all existing
> drivers want, and thus, they could be easily converted to the new API.
> Users of the new API should explicitly enable power-off chaining by
> setting corresponding flag of the power_handler structure.
[...]

Hi,

A general question: do we really need three distinct chains for this?
Can't there be only one that chain of callbacks that get a stage
(RESTART_PREPARE, RESTART, POWER_OFF_PREPARE, POWER_OFF) and can ignore
them at will? Calling through POWER_OFF_PREPARE would also return
whether that POWER_OFF is possible (for kernel_can_power_off()).

I would also split this patch into preparation cleanups (like wrapping
pm_power_off call with a function) and adding the notifier-based
implementation.

Best Regards
Micha??Miros?aw