linux-kernel - Re: [PATCH] sysfs, device-tree: aid for debugging device tree boot problems

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Date:	Wed, 23 Apr 2014 15:48:15 -0700
From:	Frank Rowand <frowand.list@...il.com>
To:	Grant Likely <grant.likely@...aro.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh+dt@...nel.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH] sysfs, device-tree: aid for debugging device tree boot
 problems

On 4/23/2014 4:54 AM, Grant Likely wrote:
> On Tue, 22 Apr 2014 20:20:44 -0700, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
>> On Tue, Apr 22, 2014 at 06:25:25PM -0700, Frank Rowand wrote:
>>> Create some infrastructure to aid trouble shooting device tree related
>>> boot issues.
>>>
>>> Add a %driver_name file to each device tree node sysfs directory which has had
>>> a driver bound to it.  This allows detecting device tree nodes which failed
>>> to be bound to any driver.
>>
>> Why is this needed, shouldn't there already be a "driver" symlink in
>> sysfs for these devices when a driver binds to them?  The rest of the
>> driver model works that way, why is of devices any different?
>>
> 
> Because it hasn't been added yet! I only just committed the change to
> convert device_nodes into kobjects in v3.14. The next step is to add
> driver symlinks.

No need to add a "driver" symlink.  The device directories in sysfs already
have a driver symlink.

> 
> That said, the devicetree node is already exposed in the uevent for a
> device. It should already be possible to find all device tree nodes that
> don't have a device, or devices without a driver:
> 
> To get a list of all nodes:
> 
> find /proc/device-tree/ -type d | sed -e 's/\/proc\/device-tree//'
> 
> or a little more nuanced, only choosing nodes with a compatible property:
> 
> for k in `find /proc/device-tree/ -name compatible`; do
> 	echo $(dirname $k) | sed -e 's/\/proc\/device-tree//'
> done | sort
> 
> It can get even more refined than that if need be.
> 
> To get a list of all nodes with a device that has been created:
> 
> for k in `find devices -name uevent`; do
> 	grep '^OF_FULLNAME' $k | sed -e 's/OF_FULLNAME=//'
> done | sort

< snip >

Thanks Grant!  I did not realize that uevent contained that
information.

-Frank

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