linux-kernel - Re: [RFC][PATCH] perf: sysfs type id

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Message-ID: <20101109221338.GA19947@suse.de>
Date:	Tue, 9 Nov 2010 14:13:38 -0800
From:	Greg KH <gregkh@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Lin Ming <ming.m.lin@...el.com>,
	Stephane Eranian <eranian@...gle.com>,
	"robert.richter" <robert.richter@....com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	fweisbec <fweisbec@...il.com>, paulus <paulus@...ba.org>,
	Kay Sievers <kay.sievers@...y.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC][PATCH] perf: sysfs type id

On Tue, Nov 09, 2010 at 10:45:19PM +0100, Peter Zijlstra wrote:
> The below is a RFC patch adding dynamic type ids to perf.
> 
> We need to represent PMUs in sysfs because we want to allow multiple
> (loadable) PMUs and need a way to identify them.
> 
> This patch creates a new device class "pmu" and adds a single attribute
> "type" to it. This device attribute will expose the dynamic type id as
> required by perf_event_attr::type.
> 
> The sysfs layout looks like:
> 
> [root@...tmere ~]# cd /sys/class/pmu/

You missed the embedded track at Plumbers where we talked about never
adding another class to the kernel.  Please use bus_id instead for this.

> [root@...tmere pmu]# ls -la
> total 0
> drwxr-xr-x  2 root root 0 2010-11-09 22:22 .
> drwxr-xr-x 47 root root 0 2010-11-09 22:22 ..
> lrwxrwxrwx  1 root root 0 2010-11-09 22:22 breakpoint -> ../../devices/virtual/pmu/breakpoint
> lrwxrwxrwx  1 root root 0 2010-11-09 22:22 cpu -> ../../devices/virtual/pmu/cpu
> lrwxrwxrwx  1 root root 0 2010-11-09 22:22 frob -> ../../devices/virtual/pmu/frob
> lrwxrwxrwx  1 root root 0 2010-11-09 22:22 software -> ../../devices/virtual/pmu/software
> lrwxrwxrwx  1 root root 0 2010-11-09 22:22 tracepoint -> ../../devices/virtual/pmu/tracepoint
> [root@...tmere pmu]# cd frob/
> [root@...tmere frob]# ls -la
> total 0
> drwxr-xr-x 3 root root    0 2010-11-09 22:22 .
> drwxr-xr-x 7 root root    0 2010-11-09 22:22 ..
> drwxr-xr-x 2 root root    0 2010-11-09 22:23 power
> lrwxrwxrwx 1 root root    0 2010-11-09 22:23 subsystem -> ../../../../class/pmu
> -r--r--r-- 1 root root 4096 2010-11-09 22:23 type
> -rw-r--r-- 1 root root 4096 2010-11-09 22:22 uevent
> [root@...tmere frob]# cat type 
> 6
> 
> Not at all sure what all those power bits mean, Greg?

All devices get a "default" power directory by the core, not much you
can do about it.

thanks,

greg k-h
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