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

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Date:	Tue, 22 Apr 2014 20:20:44 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Frank Rowand <frowand.list@...il.com>
Cc:	Grant Likely <grant.likely@...aro.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 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?

> Examples of using the %driver_name file (note that /proc/device-tree is a
> link to the base of the device tree sysfs tree):
> 
> 
>   1) To find list of device tree nodes with no driver:
> 
>   # A few false positives may be reported.  For example,
>   #   node_full_path of "." is the board.
>   #
>   # output is: node_full_path compatible_string
>   #
>   cd /proc/device-tree
>   for k in `find . -type d`; do
>      if [[ -f ${k}/compatible && ! -f ${k}/%driver_name ]] ; then
>         if [[ "`cat ${k}/compatible`" != "simple-bus" ]] ; then
>            echo `echo ${k} | sed -e 's|./||'` `cat ${k}/compatible`
>         fi
>      fi
>   done | sort
> 
> 
>   2) To find list of device tree nodes with a bound driver:
> 
>   # output is:  node_full_path driver_name
>   #
>   cd /proc/device-tree
>   for k in `find . -name %driver_name` ; do
>      echo `echo ${k} | sed -e 's|./||' -e 's|/%driver_name$||'` `cat ${k}`
>   done | sort
> 
> 
>   3) To find list of device tree nodes with a bound driver:
> 
>   # output is:  driver_name node_full_path
>   #
>   cd /proc/device-tree
>   for k in `find . -name %driver_name` ; do
>      echo `cat ${k}` `echo ${k} | sed -e 's|./||' -e 's|/%driver_name$||'`
>   done | sort

If we take this patch, these examples should be somewhere in the
documentation to make it easy for others.

> Signed-off-by: Frank Rowand <frank.rowand@...ymobile.com>

Minor nit, your From: line doesn't match this signed-off-by: so
something has to change (or add a new From: line, like SubmittingPatches
decribes how to do.)

thanks,

greg k-h
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