Re: [RFC PATCH 6/9] memory: apple: Add apple-mcc driver to manage MCC perf in Apple SoCs

[Krzysztof Kozlowski]

On 14/10/2021 09:52, Hector Martin wrote:
> On 14/10/2021 16.36, Krzysztof Kozlowski wrote:

(...)

> 
>>> Ah, I didn't realize that was a valid option for MODULE_LICENSE. I guess
>>> anything containing "GPL" works with EXPORT_SYMBOL_GPL?
>>
>> I don't think exporting symbols is related to how you license your code.
> 
> It is; only modules with a GPL-compatible MODULE_LICENSE get to use 
> symbols exported via EXPORT_SYMBOL_GPL.

Although there might be such correlation but it's not a rule. You can
have a GPL module exporting symbols without GPL requirement
(EXPORT_SYMBOLS). You can have a GPL+MIT module exporting symbols as
GPL. Obviously you cannot have a non-GPL module, as we do not accept
these and there is no such choice.

So answering your question that "GPL" works with EXPORT_SYMBOL_GPL -
everything is GPL but it works with both EXPORT_SYMBOL and
EXPORT_SYMBOL_GPL.

> 
> See kernel/module.c for the symbol lookup logic and 
> include/linux/license.h for the logic to check the string (seems like 
> "Dual MIT/GPL" is explicitly whitelisted there).

Not related to export symbol. It is used for determining the tainted
kernel via other licenses.

> 
> Of course, this is a futile effort, as ~every time I see a proprietary 
> module in some embedded device, it either falsely declares itself to be 
> GPL, or they have a shim module that re-exports GPL symbols as non-GPL.
> 

This is being removed soon (or already).


Best regards,
Krzysztof