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

To: Lars-Peter Clausen <lars@metafoo.de>, "Hill, Steven" <sjhill@mips.com>, Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH] MIPS: Make CP0 config registers readable via sysfs.
From: David Daney <ddaney.cavm@gmail.com>
Date: Wed, 12 Dec 2012 11:08:52 -0800
Cc: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>
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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

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