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

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Date:   Wed, 15 Jul 2020 08:54:42 +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 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

-- 
viresh