Re: [PATCH] MIPS: Make CP0 config registers readable via sysfs.

[David Daney <ddaney.cavm@gmail.com>]

On 12/12/2012 10:49 AM, Lars-Peter Clausen wrote:
> On 12/12/2012 05:44 PM, Hill, Steven wrote:
>> Lars,
>>
>> This patch was requested by our DSP/Codec group to help with selecting the best user-space codecs at runtime. Simply reading /proc/cpuinfo was insufficient. I posted this patch more for feedback and interest with minimal expectations that it would make it upstream. This patch will always be in our supported branches, but I will defer to everyone else on its worth for upstream.
>>
>> -Steve
>
> Well if it is something that is useful it makes sense to upstream it,
> especially if you are developing applications. Many people before you have
> learned the hard way that stashing stuff away in their private branches was not
> the best idea. If you are smart you are going to avoid that.
>
> It may not be the best solution though to just dump all the cp register to
> userspace. As Florian suggested there might be a smarter way to solve this.


If you want to have glibc's ld.so automatically select optimal libraries 
for a given platform, then the elf_platform is the way to do it.

However I don't think this is necessarily the case here.  elf_platform 
cannot easily handle a bunch of orthogonal capabilities.  So I am in 
favor of the principle of this patch.

There should be a per CPU file (probably in 
/sys/devices/system/cpu/cpuXX) with the CP0_Config values.

One question I have is:  Should it be a single file with one row for 
each implemented Config register, or one file per register?

David Daney