sysfs, device-tree: aid for debugging device tree boot problems

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.

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

Signed-off-by Frank Rowand <[email protected]>

Quoted 3 lines · Frank Rowand

Create some infrastructure to aid trouble shooting device tree related boot issues.

Quoted 3 lines

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?

Quoted 31 lines

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

Quoted 8 lines

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.

Quoted 1 line

Signed-off-by Frank Rowand <frank.rowand-/[email protected]>

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

Quoted 8 lines · Greg Kroah-Hartman

Quoted 6 lines · Frank Rowand

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.

Quoted 4 lines

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.

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

Quoted 14 lines · Grant Likely

Quoted 12 lines · Greg Kroah-Hartman

Quoted 6 lines · Frank Rowand

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?

Quoted 3 lines

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.

Quoted 6 lines · Frank Rowand

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?

Quoted 32 lines

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

Quoted 8 lines

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.

Quoted 2 lines

Signed-off-by Frank Rowand <frank.rowand-/[email protected]>

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

Quoted 11 lines

Quoted 8 lines

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/