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SubjectRe: [PATCH 2/8] x86/platform/uv: Return UV Hubless System Type
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On 9/3/2019 8:41 AM, Christoph Hellwig wrote:
> On Tue, Sep 03, 2019 at 07:12:28AM -0700, Mike Travis wrote:
>>>> +#define is_uv_hubless _is_uv_hubless
>>>
>>> Why the weird macro indirection?
>>>
>>>> -static inline int is_uv_hubless(void) { return 0; }
>>>> +static inline int _is_uv_hubless(int uv) { return 0; }
>>>> +#define is_uv_hubless _is_uv_hubless
>>>
>>> And here again.
>>>
>>
>> Sorry, I should have explained this better. The problem arises because
>> we have a number of UV specific kernel modules that support multiple
>> distributions. And with back porting to earlier distros we cannot
>> rely on the KERNEL_VERSION macro to define whether the source is being
>> built for an earlier kernel. So this allows an ifdef on the function
>> name to discover if the kernel is before or after these changes.
>
> And none of these matter for upstream. We'd rather not make the code
> more convouluted than required. If you actually really cared about these
> modules you would simply submit them upstream.
>

That is always being considered for everything we include into the
community kernel source. The problem is a couple of the kernel modules
(hwperf being the prime example) is much more tied to hardware and
BIOS/FW updates so has to be updated much more often than the current
submittal/acceptance process allows. We do opensource these modules but
they are built from single source directories and have to be released as
a module into a package that can be installed on different distros.
There is not a source version for each kernel version.

I have seen this method (declare the function with a leading underscore
and a #define for the function reference) which is why I'm assuming it's
a standard kernel practice? (I'll find some examples if necessary?)

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