linux-kernel - Re: [PATCH 4/8] Thermal: Add Thermal

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Date:	Thu, 20 Dec 2012 09:51:16 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	"R, Durgadoss" <durgadoss.r@...el.com>
Cc:	"Zhang, Rui" <rui.zhang@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hongbo.zhang@...aro.org" <hongbo.zhang@...aro.org>,
	"wni@...dia.com" <wni@...dia.com>
Subject: Re: [PATCH 4/8] Thermal: Add Thermal_trip sysfs node

On Thu, Dec 20, 2012 at 04:58:32PM +0000, R, Durgadoss wrote:
> > -----Original Message-----
> > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > Sent: Thursday, December 20, 2012 10:09 PM
> > To: R, Durgadoss
> > Cc: Zhang, Rui; linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org;
> > hongbo.zhang@...aro.org; wni@...dia.com
> > Subject: Re: [PATCH 4/8] Thermal: Add Thermal_trip sysfs node
> > 
> > On Thu, Dec 20, 2012 at 04:25:32PM +0000, R, Durgadoss wrote:
> > >
> > > > -----Original Message-----
> > > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > > Sent: Thursday, December 20, 2012 9:42 PM
> > > > To: R, Durgadoss
> > > > Cc: Zhang, Rui; linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > > hongbo.zhang@...aro.org; wni@...dia.com
> > > > Subject: Re: [PATCH 4/8] Thermal: Add Thermal_trip sysfs node
> > > >
> > > > On Thu, Dec 20, 2012 at 07:52:03AM +0000, R, Durgadoss wrote:
> > > > > > On Tue, Dec 18, 2012 at 02:59:33PM +0530, Durgadoss R wrote:
> > > > > > > This patch adds a thermal_trip directory under
> > > > > > > /sys/class/thermal/zoneX. This directory contains
> > > > > > > the trip point values for sensors bound to this
> > > > > > > zone.
> > > > > >
> > > > > > Eeek, you just broke userspace tools that now can no longer see
> > these
> > > > > > entries :(
> > > > > >
> > > > > > Why do you need to create a subdirectory?  As you found out, doing
> > so
> > > > > > isn't the easiest, right?  That is on purpose.
> > > > >
> > > > > Yes, I observed the complexity.
> > > > >
> > > > > >
> > > > > > I really wouldn't recommend doing this at all, please stick within the
> > > > > > 'struct device' framework here, don't create new kobjects and hang
> > sysfs
> > > > > > files off of them.
> > > > >
> > > > > But, we cannot put all _trip directly under ZoneX directory.
> > > >
> > > > Why not?  What is preventing this?
> > > >
> > > > > We can remove the thermal_trip directory, and put sensorY_trip under
> > > > > /sys/class/thermal/zoneX/.  But this sensorY_trip needs to be a
> > > > > directory which has four sysfs nodes named, active, passive, crit,
> > > > > hot.
> > > > >
> > > > > Rui, What do you think about this ?
> > > > >
> > > > > The only other way I see, is directly put
> > > > sensorY_trip_[active/passive/hot/crit]
> > > > > which will create way too many nodes, under
> > /sys/class/thermal/zoneX/.
> > > >
> > > > What is "too many"?  20000?  50000?  How many are we talking about
> > here?
> > >
> > > Not in 1000's though..
> > >
> > > > What is the limiting factor that is preventing this from all going into
> > > > one directory?
> > >
> > > We support a MAX of 12 sensors per zone today, which will lead to
> > > 12 * 4, 48 nodes under this directory named
> > > sensorY_trip_[active/passive/hot/crit], besides the other nodes.
> > 
> > That's fine, we can easily support that many files, have you tried this
> > already?
> 
> Yes, in fact, this is sort of what was the old implementation..
> although with different sysfs nodes.

What "old" implementation, one that is in-kernel?  Are you changing the
user interface here?

thanks,

greg k-h
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