On 4/22/2014 8:20 PM, Greg Kroah-Hartman 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?
Yes, the devices do have a "driver" symlink in sysfs.
The problem I had was that I could not deterministically determine the
device name in /sysfs that was associated with a device tree node that
the device was created for. And I couldn't find a link from the device
tree entries to the device tree node.
Grant's reply to your email provided the solution to my problem; the
device uevents file contains the full device tree path of the associated
device tree node.
Grant's reply removes the need for my patch.
>
>> 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.
That is a good idea. I'll package up the equivalent shell code from
Grant's email. Any suggestions on location?
scripts/debug/devicetree/
scripts/devicetree/debug/
Documentation/devicetree/scripts/
If there is no good location in the kernel tree, then I will put them
either on the devicetree wiki, or the devicetree section of the
elinux wiki.
>
>> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>
>
> 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.)
Oops, thanks for pointing that out.
>
> thanks,
>
> greg k-h
-Frank
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