linux-kernel - Re: [PATCH v5 RESEND 1/6] platform: x86-android-tablets: other: Add swnode for Xiaomi pad2 indicator LED

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Date: Wed, 27 Mar 2024 13:21:48 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Kate Hsuan <hpa@...hat.com>, Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>, 
	linux-leds@...r.kernel.org, platform-driver-x86@...r.kernel.org, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	André Apitzsch <git@...tzsch.eu>, 
	linux-kernel@...r.kernel.org, Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v5 RESEND 1/6] platform: x86-android-tablets: other: Add
 swnode for Xiaomi pad2 indicator LED

On Wed, Mar 27, 2024 at 1:18 PM Hans de Goede <hdegoede@...hat.com> wrote:
> On 3/27/24 12:05 PM, Andy Shevchenko wrote:
> > On Wed, Mar 27, 2024 at 9:58 AM Kate Hsuan <hpa@...hat.com> wrote:
> >> On Mon, Mar 25, 2024 at 3:30 AM Andy Shevchenko
> >> <andy.shevchenko@...il.com> wrote:
> >>> On Sun, Mar 24, 2024 at 5:02 PM Kate Hsuan <hpa@...hat.com> wrote:

..

> >>>> +static int __init xiaomi_mipad2_init(void)
> >>>> +{
> >>>> +       return software_node_register_node_group(ktd2026_node_group);
> >>>> +}
> >>>> +
> >>>> +static void xiaomi_mipad2_exit(void)
> >>>
> >>> __exit ?
> >> No need.
> >> x86-andriod-tablet is based on platform_driver and platform_device so
> >> it doesn't need __exit.
> >>
> >> I put __exit and the compiler complained about the warning.
> >> ===
> >> WARNING: modpost:
> >> drivers/platform/x86/x86-android-tablets/x86-android-tablets: section
> >> mismatch in reference: xiaomi_mipad2_info+0x50 (section: .init.rodata)
> >> -> xiaomi_mipad2_exit (section: .exit.text)
> >> ===
> >
> > This is interesting. Why then do we call them symmetrically?
> >
> > Hans, do we need to have anything here been amended?
>
> No this is all as expected.
>
> The platform driver's probe() function can be __init because
> the platform device is registered with the special:
> platform_create_bundle() function which takes a probe() function
> and the actual "struct platform_driver" does not have .probe
> set at all.
>
> Since we need to do manual cleanup on remove() however we need
> a remove() callback and that does sit in the struct platform_driver
> and since remove() can normally also be called on manual unbind
> of the driver through sysfs it cannot be in the __exit section.
>
> I say normally because IIRC platform_create_bundle() disables
> manual unbinding but the section checking code does not know this,
> all it sees is that the "struct platform_driver" is not __exit
> and that it references the remove() callback and therefor the
> remove() callback itself cannot be __exit.

Thank you for the detailed explanation!

-- 
With Best Regards,
Andy Shevchenko