Re: [PATCH v1 0/6] Introduce power off call chain API

From: Dmitry Osipenko <digetx@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Lee Jones <lee.jones@linaro.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Mark Brown <broonie@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Russell King <linux@armlinux.org.uk>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-tegra <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH v1 0/6] Introduce power off call chain API
Date: Thu, 7 Oct 2021 13:11:19 +0300	[thread overview]
Message-ID: <54c7b83e-22ae-2521-1f44-ec9b2e21464e@gmail.com> (raw)
In-Reply-To: <YV65qsQPtQfWvE9W@smile.fi.intel.com>

07.10.2021 12:11, Andy Shevchenko пишет:
> On Thu, Oct 07, 2021 at 11:52:46AM +0300, Dmitry Osipenko wrote:
>> 07.10.2021 10:18, Andy Shevchenko пишет:
>>> On Thu, Oct 7, 2021 at 9:05 AM Dmitry Osipenko <digetx@gmail.com> wrote:
> 
> ...
> 
>>>> This
>>>> is a somewhat simplified version which doesn't try to convert whole kernel
>>>> to the new API at once, but solves immediate practical problem that we
>>>
>>> problems
>>>
>>>> have on Nexus 7 Android tablet where device needs to chain power off
>>>
>>> tablets where the device
>>
>> Thank you for the corrections, so far there is one problem and one tablet :)
> 
> Then use "the Nexus 7 Android tablet" :-)
> 
>>> Immediate question here is how do you see the plan of spreading this.
>>> I.o.w. can you put an explanation that you have checked, let's say
>>>> 80% current users, and they may be converted like [example
>>> placeholder] without any special tricks?
>>
>> The rough plan is:
>>
>> 1. Add new API.
>> 2. Convert drivers to the new API per subsystem.
> 
> I would suggest to show that you are actually into it by converting a couple of
> the subsystems for the starter.

Noted

>> 3. Expose do_kernel_restart().
>> 4. Replace pm_power_off() with do_kernel_poweroff() per arch/, making
>> power off similar to the restart that uses do_kernel_restart().
>> 5. Remove do_kernel_restart() from kernel/reboot.c
>>
>> Majority of pm_power_off() users shouldn't need the chaining and
>> pm_power_off() doesn't conflict with the new API, so there is no need to
>> rush the conversion.
>>
>> The single-link chain users could be converted to the new API directly,
>> this will remove some global variables. But at first should be better to
>> gain more users who actually need the chained power off since they may
>> have very specific requirements not covered by the current variant of
>> the API and will be easier to evolve API with less users.
> 
> All above in one or another form should be in cover letter.

Alright, apparently I overestimated a tad awareness about the current
status. I'll extend the cover letter next time, thanks.