linux-kernel - Re: [PATCH v4 3/3] powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior

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Message-ID: <552CCB77.1000307@linux.vnet.ibm.com>
Date:	Tue, 14 Apr 2015 13:40:31 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>
CC:	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v4 3/3] powerpc/powernv: Introduce sysfs control for fastsleep
 workaround behavior


>>
>> By default, fastsleep_workaround_state = dynamic. In this case, workaround
>> is applied/undone everytime the core enters/exits fastsleep.
>>
>> fastsleep_workaround_state = applyonce. In this case the workaround is
>> applied once on all the cores and never undone. This can be triggered by
>> echo applyonce > /sys/devices/system/cpu/fastsleep_workaround_state
> 
> I was wondering if we really need such an elaborate design for this
> sysfs file. Why not a sysfs file called fastsleep_workaround_apply_once,
> which is set to '0' by default and the only value that it can take is
> '1' ? The name easily implies that the workaround is applied only once
> if it is set. I can see that this can cut down a good chunk of code from
> this patch. I just didn't find too much value in having so much code for
> a simple 'on' knob.

I was considering something similar too. But then moved to this format
as I thought this was unambiguous. Also moving to a binary attribute
will reduces code only in show_fastsleep_workaround_state which I don't
feel is much.
That said, if you feel strongly about it, I can change it to the format
you suggested.

Thanks,
Shreyas

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