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

On Wed, Jul 15, 2020 at 1:34 PM Lee Jones [off-list ref] wrote:

On Wed, 15 Jul 2020, Rafael J. Wysocki wrote:

quoted

On Wed, Jul 15, 2020 at 5:27 AM Viresh Kumar [off-list ref] wrote:

quoted

On 15-07-20, 08:54, Viresh Kumar wrote:

quoted

On 14-07-20, 22:03, Lee Jones wrote:

quoted

On Tue, 14 Jul 2020, Rafael J. Wysocki wrote:

quoted

On Tue, Jul 14, 2020 at 4:51 PM Lee Jones [off-list ref] wrote:

quoted

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.

Wouldn't that cause the compiler to optimize them away if it doesn't
see any users?

It looks like they're only unused when !MODULE,

OK

in which case optimising them away would be the correct thing to do, no?

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