linux-kernel - Re: [PATCH 09/13] cpufreq: acpi-cpufreq: Remove unused ID structs

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Date:   Wed, 15 Jul 2020 08:57:18 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Andy Grover <andrew.grover@...el.com>,
        Paul Diefenbaugh <paul.s.diefenbaugh@...el.com>,
        Dominik Brodowski <linux@...do.de>,
        Denis Sadykov <denis.m.sadykov@...el.com>
Subject: Re: [PATCH 09/13] cpufreq: acpi-cpufreq: Remove unused ID structs

On 15-07-20, 08:54, Viresh Kumar wrote:
> On 14-07-20, 22:03, Lee Jones wrote:
> > On Tue, 14 Jul 2020, Rafael J. Wysocki wrote:
> > 
> > > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@...aro.org> wrote:
> > > >
> > > > Can't see them being used anywhere and the compiler doesn't complain
> > > > that they're missing, so ...
> > > 
> > > Aren't they needed for automatic module loading in certain configurations?
> > 
> > Any idea how that works, or where the code is for that?
> 
> The MODULE_DEVICE_TABLE() thingy creates a map of vendor-id,
> product-id that the kernel keeps after boot (and so there is no static
> reference of it for the compiler), later when a device is hotplugged
> into the kernel it refers to the map to find the related driver for it
> and loads it if it isn't already loaded.
> 
> This has some of it, search for MODULE_DEVICE_TABLE() in it.
> Documentation/driver-api/usb/hotplug.rst

And you just need to add __maybe_unused to them to suppress the
warning.

-- 
viresh