linux-kernel - Re: [PATCH v7 04/20] kernel: Add combined power-off+restart handler call chain API

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Date:   Fri, 6 May 2022 18:28:49 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Joshua Thompson <funaho@...ai.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sebastian Reichel <sre@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
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Subject: Re: [PATCH v7 04/20] kernel: Add combined power-off+restart handler
 call chain API

On 4/20/22 21:47, Rafael J. Wysocki wrote:
>>>> +       spin_unlock(&platform_power_off_lock);
>>>> +
>>>> +       if (ret)
>>>> +               return ret;
>>>> +
>>>> +       ret = register_power_off_handler(&priv->power_off_nb);
>>>> +       if (ret)
>>>> +               priv->platform_power_off_cb = NULL;
>>>> +
>>>> +       return ret;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(register_platform_power_off);
>>>> +
>>>> +/**
>>>> + *     unregister_platform_power_off - Unregister platform-level power-off callback
>>>> + *     @power_off: Power-off callback
>>>> + *
>>>> + *     Unregisters previously registered platform power-off callback.
>>>> + *
>>>> + *     Returns zero on success, or error code on failure.
>>>> + */
>>>> +int unregister_platform_power_off(void (*power_off)(void))
>>>> +{
>>>> +       struct sys_off_handler_private_data *priv;
>>>> +       int ret;
>>>> +
>>>> +       priv = sys_off_handler_private_data(&platform_power_off_handler);
>>>> +
>>>> +       if (priv->platform_power_off_cb != power_off)
>>>> +               return -EINVAL;
>>>> +
>>>> +       ret = unregister_power_off_handler(&priv->power_off_nb);
>>>> +       priv->platform_power_off_cb = NULL;
>>>> +
>>>> +       return ret;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(unregister_platform_power_off);
>>>> +
>>>> +/**
>>>> + *     do_kernel_power_off - Execute kernel power-off handler call chain
>>>> + *
>>>> + *     Calls functions registered with register_power_off_handler.
>>>> + *
>>>> + *     Expected to be called as last step of the power-off sequence.
>>>> + *
>>>> + *     Powers off the system immediately if a power-off handler function has
>>>> + *     been registered. Otherwise does nothing.
>>>> + */
>>>> +void do_kernel_power_off(void)
>>>> +{
>>>> +       /* legacy pm_power_off() is unchained and has highest priority */
>>>> +       if (pm_power_off && pm_power_off != dummy_pm_power_off)
>>>> +               return pm_power_off();
>>>> +
>>>> +       blocking_notifier_call_chain(&power_off_handler_list, POWEROFF_NORMAL,
>>>> +                                    NULL);
>>>> +}
>>>> +
>>>> +static void do_kernel_power_off_prepare(void)
>>>> +{
>>>> +       /* legacy pm_power_off_prepare() is unchained and has highest priority */
>>>> +       if (pm_power_off_prepare)
>>>> +               return pm_power_off_prepare();
>>>> +
>>>> +       blocking_notifier_call_chain(&power_off_handler_list, POWEROFF_PREPARE,
>>>> +                                    NULL);
>>>> +}
>>>> +
>>>>  /**
>>>>   *     kernel_power_off - power_off the system
>>>>   *
>>>> @@ -304,8 +893,7 @@ EXPORT_SYMBOL_GPL(kernel_halt);
>>>>  void kernel_power_off(void)
>>>>  {
>>>>         kernel_shutdown_prepare(SYSTEM_POWER_OFF);
>>>> -       if (pm_power_off_prepare)
>>>> -               pm_power_off_prepare();
>>>> +       do_kernel_power_off_prepare();
>>>>         migrate_to_reboot_cpu();
>>>>         syscore_shutdown();
>>>>         pr_emerg("Power down\n");
>>>> @@ -314,6 +902,16 @@ void kernel_power_off(void)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(kernel_power_off);
>>>>
>>>> +bool kernel_can_power_off(void)
>>>> +{
>>>> +       if (!pm_power_off &&
>>>> +           blocking_notifier_call_chain_is_empty(&power_off_handler_list))
>>>> +               return false;
>>>> +
>>>> +       return true;
>>> return pm_power_off ||
>>> blocking_notifier_call_chain_is_empty(&power_off_handler_list);
>> Thank you for the thorough review!
> You're very welcome!

Thanks again for taking a look at the patches. I don't have strong
preferences about the names and etc, so I'll update it all in v8 like
you suggested.

-- 
Best regards,
Dmitry