Re: [PATCH v7 04/20] kernel: Add combined power-off+restart handler call chain API
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- To: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
- Subject: Re: [PATCH v7 04/20] kernel: Add combined power-off+restart handler call chain API
- From: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
- Date: Fri, 6 May 2022 17:10:24 +0300
- Cc: Thierry Reding <thierry.reding@xxxxxxxxx>, Jonathan Hunter <jonathanh@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>, Greg Ungerer <gerg@xxxxxxxxxxxxxx>, Joshua Thompson <funaho@xxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, Sebastian Reichel <sre@xxxxxxxxxx>, Linus Walleij <linus.walleij@xxxxxxxxxx>, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>, Greentime Hu <green.hu@xxxxxxxxx>, Vincent Chen <deanbo422@xxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Yoshinori Sato <ysato@xxxxxxxxxxxxx>, Rich Felker <dalias@xxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>, Santosh Shilimkar <ssantosh@xxxxxxxxxx>, Krzysztof Kozlowski <krzk@xxxxxxxxxx>, Liam Girdwood <lgirdwood@xxxxxxxxx>, Mark Brown <broonie@xxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, Lee Jones <lee.jones@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Guenter Roeck <linux@xxxxxxxxxxxx>, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>, Ulf Hansson <ulf.hansson@xxxxxxxxxx>, Michał Mirosław <mirq-linux@xxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, linux-csky@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-m68k@xxxxxxxxxxxxxxx, "open list:BROADCOM NVRAM DRIVER" <linux-mips@xxxxxxxxxxxxxxx>, linux-parisc@xxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, Linux-sh list <linux-sh@xxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, ACPI Devel Maling List <linux-acpi@xxxxxxxxxxxxxxx>, Linux PM <linux-pm@xxxxxxxxxxxxxxx>, linux-tegra <linux-tegra@xxxxxxxxxxxxxxx>
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- References: <20220411233832.391817-1-dmitry.osipenko@collabora.com> <20220411233832.391817-5-dmitry.osipenko@collabora.com> <CAJZ5v0gnTSoeNP+QXwrZ45FQY4howVkJMuCjM=j+_-2BngJdQg@mail.gmail.com> <990621e7-9f8a-8b4a-02ec-fd6c1e1f48ff@collabora.com> <CAJZ5v0jxXtwot0qpib4UG8Tz8Hd1dEbgo58tEdPFboU8xwKHNw@mail.gmail.com>
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On 4/20/22 21:47, Rafael J. Wysocki wrote:
>>>> + POWEROFF_PREPARE,
>>>> +};
>>>> +
>>>> +/**
>>>> + * struct power_off_data - Power-off callback argument
>>>> + *
>>>> + * @cb_data: Callback data.
>>>> + */
>>>> +struct power_off_data {
>>>> + void *cb_data;
>>>> +};
>>>> +
>>>> +/**
>>>> + * struct power_off_prep_data - Power-off preparation callback argument
>>>> + *
>>>> + * @cb_data: Callback data.
>>>> + */
>>>> +struct power_off_prep_data {
>>>> + void *cb_data;
>>>> +};
>>> Why does this need to be a separate data type?
>> To allow us extend the "struct power_off_prep_data" with more parameters
>> later on without a need to update each driver with the new arguments.
> I'm not really sure what you mean here. Can you give an example?
>
The restart callbacks use more than the cb_data and we have:
struct restart_data {
void *cb_data;
const char *cmd;
bool stop_chain;
enum reboot_mode mode;
};
If we'll ever need to extended struct power_off_data similarly to the
restart_data, then we will need to update all the power-off callbacks
instead of adding a new field to the power_off_data.
Hence, for example, if you'll want to extend power_off_data with "enum
poweroff_mode mode", then for each driver you'll need to do this change:
-power_off(void *cb_data)
+power_off(void *cb_data, enum poweroff_mode mode)
and you won't need to do that using struct power_off_data.
Why do we need this? Because I saw in the past people changing kernel
APIs that way when they wanted to add new arguments and then needed to
update every call site around the kernel.
--
Best regards,
Dmitry
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