linux-kernel - Re: Strange location and name for platform devices when device-tree is used.

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Date:	Fri, 01 Nov 2013 15:22:24 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	NeilBrown <neilb@...e.de>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	devicetree@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: Strange location and name for platform  devices when
 device-tree is used.

On Fri, 2013-11-01 at 14:59 +1100, NeilBrown wrote:
> and I wonder how relevant it still is in this context.  As platform devices
> are all in the root of the device-tree and hence are siblings, they must have
> unique names in the device-tree and  so the platform devices created from
> them will also have unique names -- won't they?

I agree about /sys/devices -> /sys/devices/platform, that makes more
sense

The problem with names is that we don't *know* that your devices are
at the root and unique. They don't have to be. I have platforms that
have several "chips" each containing all the same devices. They need to
be de-duped.

Maybe the right approach is to build the de-duplication in sysfs
itself ?

Cheers,
Ben.

> Any help understanding and/or fixing this discrepancy greatly appreciated.
> 
> The change of name is particularly annoying to me because one of my platform
> devices is a pwm_bl.c backlight.  With a boardfile I
> get /sys/class/pwm_backlight.  With devicetree the best I can get
> is /sys/class/pwm_backlight.23 (or similar).  It would be really nice to have
> a more stable and sensible name here.


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