linux-kernel - Re: [PATCH v25 01/10] drivers/base: refactor cpu.c to use .is

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Date:   Fri, 21 Jul 2023 11:32:14 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, david@...hat.com, osalvador@...e.de,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
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        boris.ostrovsky@...cle.com
Subject: Re: [PATCH v25 01/10] drivers/base: refactor cpu.c to use
 .is_visible()



On 7/3/23 11:53, Eric DeVolder wrote:
> 
> 
> On 7/3/23 08:05, Greg KH wrote:
>> On Thu, Jun 29, 2023 at 03:21:10PM -0400, Eric DeVolder wrote:
>>>   - the function body of the callback functions are now wrapped with
>>>     IS_ENABLED(); as the callback function must exist now that the
>>>     attribute is always compiled-in (though not necessarily visible).
>>
>> Why do you need to do this last thing?  Is it a code savings goal?  Or
>> something else?  The file will not be present in the system if the
>> option is not enabled, so it should be safe to not do this unless you
>> feel it's necessary for some reason?
> 
> To accommodate the request, all DEVICE_ATTR() must be unconditionally present in this file. The 
> DEVICE_ATTR() requires the .show() callback. As the callback is referenced from a data structure, 
> the callback has to be present for link. All the callbacks for these attributes are in this file.
> 
> I have two basic choices for gutting the function body if the config feature is not enabled. I can 
> either use #ifdef or IS_ENABLED(). Thomas has made it clear I need to use IS_ENABLED(). I can 
> certainly use #ifdef (which is what I did in v24).
> 
>>
>> Not doing this would make the diff easier to read :)
> 
> I agree this is messy. I'm not really sure what this request/effort achieves as these attributes are 
> not strongly related (unlike cacheinfo) and the way the file was before results in less code.
> 
> At any rate, please indicate if you'd rather I use #ifdef.
> Thanks for your time!
> eric
> 
>>
>> thanks,
>>
>> greg k-h

Hi Greg,
I was wondering if you might weigh-in so that I can proceed.

I think there are three options on the table:
- use #ifdef to comment out these function bodies, which keeps the diff much more readable
- use IS_ENABLED() as Thomas has requested I do, but makes the diff more difficult to read
- remove this refactor altogether, perhaps post-poning until after this crash hotplug series merges, 
as this refactor is largely unrelated to crash hotplug.

Thank you for your time on this topic!
eric