Re: [PATCH 6/6] MIPS: Expose current_cpu_data.options through debugfs

[Florian Fainelli <f.fainelli@gmail.com>]

On 10/02/16 02:46, Ralf Baechle wrote:
> On Tue, Feb 09, 2016 at 12:55:54PM -0800, Florian Fainelli wrote:
> 
>> Debugging a missing features in cpu-features-override.h, or a runtime feature
>> set/clear in the vendor specific cpu_probe() function can be a little tedious,
>> ease that by providing a debugfs entry representing the
>> current_cpu_data.options bitmask.
> 
> Hm..  Bits in the options bitmaps are not an ABI, they come and sometimes
> they go as well and manual decoding can be tedious to humans.  so I'm
> wondering if something in /sys/devices/system/cpu would be more suitable.

Not sure, you need this while bringing up systems and/or debugging why a
kernel does not have this or that enabled as you think it should,
outside of that, not so much probably?. More standard interfaces like
/proc/cpuinfo should be used, but that does not give you the full picture.

> It'd depend on just sysfs, not debugfs which is disabled in production
> kernels.
> 
> Thoughts?

I suppose this is fine, in that case, we would probably want to go with
a text-based approach to make the interface more stable.

NB: I also have a patch that adds cache info reporting to MIPS, since it
seems useful for people dealing with user-space cache flushes (graphics,
JIT, etc.), Russell King rejected adding that for ARM, but ARM64 and x86
have it (arch/arm64/kernel/cacheinfo.c) would you oppose to having that
for MIPS?
-- 
Florian