Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

Hi Michael,

In Rob's reply to you email, he said:

   I'd like to move towards dropping 'linux,phandle' including changing 
   dtc to stop generating both properties by default. Perhaps we should 
   just be more explicit that we are doing that. Stop exposing it first and 
   then change how phandles are stored/managed a cycle later. Then we can 
   easily revert it if needed.

My current plan is to follow that suggestion.  So fixing my patches that
started this thread will wait for a later cycle.  But I would like to
try to address the issues with property "ibm,phandle" that you raised
below _before_ fixing my patches.  Those fixes should help me understand
"ibm,phandle" better, and hopefully when I update my patches I will not
cause further "ibm,phandle" issues.

More comments from me, embedded below.


On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.

This is where I get lost, and need your help and expertise.

If I do the naive search:

   git grep '"ibm,phandle"'


I find it used in three files.

(1) drivers/of/fdt.c, which is part of what my patches modified.

(2) drivers/misc/cxl/of.c reads (and optionally reports the value of)
"ibm,phandle", but does not use the value for anything else.

(3) drivers/of/dynamic.c gets and uses the value of "ibm,phandle"
only if properties "phandle" and "linux,phandle" do not exist.
If either of those two properties exist, their value is used
preferentially to the value of "ibm,phandle".  So in this case
it seems that folding the value of "ibm,phandle" into "phandle"
would work properly.

Is the "ibm,phandle" property used elsewhere in a way that my
naive search missed it?  Should it be used in a place that is
not using it?


> So sorry that's a big mess, but we can't just rip out those properties.

You provide some useful references and information above, but I do not
understand what I am reading.  :-)


> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?

This sounds reasonable.  Since userspace is using the "ibm,phandle"
property we need to continue to expose that property to userspace.

If userspace needs to differentiate between "phandle" and "ibm,phandle"
then we will need to keep "ibm,phandle" for as long as userspace needs
it.  Otherwise, there is a possibility that we could update userspace,
wait a long time, then remove "ibm,phandle".


> The other thing 

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

Hi Michael,

In Rob's reply to you email, he said:

   I'd like to move towards dropping 'linux,phandle' including changing 
   dtc to stop generating both properties by default. Perhaps we should 
   just be more explicit that we are doing that. Stop exposing it first and 
   then change how phandles are stored/managed a cycle later. Then we can 
   easily revert it if needed.

My current plan is to follow that suggestion.  So fixing my patches that
started this thread will wait for a later cycle.  But I would like to
try to address the issues with property "ibm,phandle" that you raised
below _before_ fixing my patches.  Those fixes should help me understand
"ibm,phandle" better, and hopefully when I update my patches I will not
cause further "ibm,phandle" issues.

More comments from me, embedded below.


On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.

This is where I get lost, and need your help and expertise.

If I do the naive search:

   git grep '"ibm,phandle"'


I find it used in three files.

(1) drivers/of/fdt.c, which is part of what my patches modified.

(2) drivers/misc/cxl/of.c reads (and optionally reports the value of)
"ibm,phandle", but does not use the value for anything else.

(3) drivers/of/dynamic.c gets and uses the value of "ibm,phandle"
only if properties "phandle" and "linux,phandle" do not exist.
If either of those two properties exist, their value is used
preferentially to the value of "ibm,phandle".  So in this case
it seems that folding the value of "ibm,phandle" into "phandle"
would work properly.

Is the "ibm,phandle" property used elsewhere in a way that my
naive search missed it?  Should it be used in a place that is
not using it?


> So sorry that's a big mess, but we can't just rip out those properties.

You provide some useful references and information above, but I do not
understand what I am reading.  :-)


> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?

This sounds reasonable.  Since userspace is using the "ibm,phandle"
property we need to continue to expose that property to userspace.

If userspace needs to differentiate between "phandle" and "ibm,phandle"
then we will need to keep "ibm,phandle" for as long as userspace needs
it.  Otherwise, there is a possibility that we could update userspace,
wait a long time, then remove "ibm,phandle".


> The other thing that worries me is that 

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Rob Herring]

On Wed, Jun 21, 2017 at 02:57:35PM +1000, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
> > From: Frank Rowand 
> >
> > Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
> > the internal device tree.  The phandle will still be in the struct
> > device_node phandle field and will still be displayed as if it is
> > a property in /proc/device_tree.
> >
> > This is to resolve the issue found by Stephen Boyd [1] when he changed
> > the type of struct property.value from void * to const void *.  As
> > a result of the type change, the overlay code had compile errors
> > where the resolver updates phandle values.
> >
> >   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
> >
> > - Add sysfs infrastructure to report np->phandle, as if it was a property.
> > - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
> >   in the expanded device tree.
> > - Remove phandle properties in of_attach_node(), for nodes dynamically
> >   attached to the live tree.  Add the phandle sysfs entry for these nodes.
> > - When creating an overlay changeset, duplicate the node phandle in
> >   __of_node_dup().
> > - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
> >   properties in several locations.
> > - A side effect of these changes is that the obsolete "linux,phandle" and
> >   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
> >   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.
> 
> So sorry that's a big mess, but we can't just rip out those properties.
> 
> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?
> 
> 
> The other thing that worries me is that by renaming (effectively)
> "linux,phandle" to "phandle", we lose the ability to accurately
> regenerate the device tree from /proc/device-tree. In theory it
> shouldn't matter, but I worry that in practice something will break.

The only scenario I can come up with is booting a kernel with this 
change and kexec'ing to a kernel older than 2010 (when ePAPR phandle was 
added). Some how I doubt that would work without this change.

> What if we just kept a single bit flag somewhere indicating if the name of
> the phandle property we found was "phandle" or "linux,phandle", and
> create the sysfs phandle using that name?

I'd like to move towards dropping 'linux,phandle' including changing 
dtc to stop generating both properties by default. Perhaps we should 
just be more explicit that we are doing that. Stop exposing it first and 
then change how phandles are stored/managed a cycle later. Then we can 
easily revert it if needed.

Rob

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Rob Herring]

On Wed, Jun 21, 2017 at 02:57:35PM +1000, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
> > From: Frank Rowand 
> >
> > Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
> > the internal device tree.  The phandle will still be in the struct
> > device_node phandle field and will still be displayed as if it is
> > a property in /proc/device_tree.
> >
> > This is to resolve the issue found by Stephen Boyd [1] when he changed
> > the type of struct property.value from void * to const void *.  As
> > a result of the type change, the overlay code had compile errors
> > where the resolver updates phandle values.
> >
> >   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
> >
> > - Add sysfs infrastructure to report np->phandle, as if it was a property.
> > - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
> >   in the expanded device tree.
> > - Remove phandle properties in of_attach_node(), for nodes dynamically
> >   attached to the live tree.  Add the phandle sysfs entry for these nodes.
> > - When creating an overlay changeset, duplicate the node phandle in
> >   __of_node_dup().
> > - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
> >   properties in several locations.
> > - A side effect of these changes is that the obsolete "linux,phandle" and
> >   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
> >   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.
> 
> So sorry that's a big mess, but we can't just rip out those properties.
> 
> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?
> 
> 
> The other thing that worries me is that by renaming (effectively)
> "linux,phandle" to "phandle", we lose the ability to accurately
> regenerate the device tree from /proc/device-tree. In theory it
> shouldn't matter, but I worry that in practice something will break.

The only scenario I can come up with is booting a kernel with this 
change and kexec'ing to a kernel older than 2010 (when ePAPR phandle was 
added). Some how I doubt that would work without this change.

> What if we just kept a single bit flag somewhere indicating if the name of
> the phandle property we found was "phandle" or "linux,phandle", and
> create the sysfs phandle using that name?

I'd like to move towards dropping 'linux,phandle' including changing 
dtc to stop generating both properties by default. Perhaps we should 
just be more explicit that we are doing that. Stop exposing it first and 
then change how phandles are stored/managed a cycle later. Then we can 
easily revert it if needed.

Rob

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

adding Ben and Paul.

Hi Michael,

On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:

This is the LoPAPR, section 2.1.4, R1-2.1.4-3

   https://members.openpowerfoundation.org/document/dl/469


>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.

My interpretation of the LoPAPR R1-2.1.4-1 and R1-2.1.4-2 is that the
ibm-phandle property it the node's phandle value that other nodes may
refer to.  Thus this is the value that should be placed in np->phandle,
which is the value that will be used to find a node based on its
phandle value.  Which is the way the drivers/of/fdt.c currently works:

/* We accept flattened tree phandles either in
 * ePAPR-style "phandle" properties, or the
 * legacy "linux,phandle" properties.  If both
 * appear and have different values, things
 * will get weird. Don't do that.
 */
if (!strcmp(pname, "phandle") ||
!strcmp(pname, "linux,phandle")) {
if (!np->phandle)
np->phandle = be32_to_cpup(val);
}

/* And we process the "ibm,phandle" property
 * used in pSeries dynamic device tree
 * stuff
 */
if (!strcmp(pname, "ibm,phandle"))
np->phandle = be32_to_cpup(val);

My interpratation of R1-2.1.4-1 through R1-2.1.4-3 is that the
"ibm,phandle" property is relevant to the contents of the Linux
kernel device tree and that the "phandle returned by a client
interface service" is not relevant to the Linux kernel device
tree.  I would not expect the powerpc code to expose the
device tree code to a "phandle returned by a client
interface service".  Is that correct?

The current code which chooses which value potentially ends up in
np->phandle seems to involve a little bit of cargo cult coding.
This code has been adapted and combined from several locations,
see commits:

   dfbd4c6eff35f1b1065cca046003cc9d7ff27222

then earlier:

   04b954a673dd02f585a2769c4945a43880faa989
   6016a363f6b56b46b24655bcfc0499b715851cf3
   e6a6928c3ea1d0195ed75a091e345696b916c09b
   bbd33931a08362f78266a4016211a35947b91041

I would like for the code that sets the value of np->phandle
to simply say:

   if name is "phandle", "linux,phandle", or "ibm,phandle" then
  np->phandle = the value

Does anyone know if the additional logic in the current code is

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

adding Ben and Paul.

Hi Michael,

On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:

This is the LoPAPR, section 2.1.4, R1-2.1.4-3

   https://members.openpowerfoundation.org/document/dl/469


>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.

My interpretation of the LoPAPR R1-2.1.4-1 and R1-2.1.4-2 is that the
ibm-phandle property it the node's phandle value that other nodes may
refer to.  Thus this is the value that should be placed in np->phandle,
which is the value that will be used to find a node based on its
phandle value.  Which is the way the drivers/of/fdt.c currently works:

/* We accept flattened tree phandles either in
 * ePAPR-style "phandle" properties, or the
 * legacy "linux,phandle" properties.  If both
 * appear and have different values, things
 * will get weird. Don't do that.
 */
if (!strcmp(pname, "phandle") ||
!strcmp(pname, "linux,phandle")) {
if (!np->phandle)
np->phandle = be32_to_cpup(val);
}

/* And we process the "ibm,phandle" property
 * used in pSeries dynamic device tree
 * stuff
 */
if (!strcmp(pname, "ibm,phandle"))
np->phandle = be32_to_cpup(val);

My interpratation of R1-2.1.4-1 through R1-2.1.4-3 is that the
"ibm,phandle" property is relevant to the contents of the Linux
kernel device tree and that the "phandle returned by a client
interface service" is not relevant to the Linux kernel device
tree.  I would not expect the powerpc code to expose the
device tree code to a "phandle returned by a client
interface service".  Is that correct?

The current code which chooses which value potentially ends up in
np->phandle seems to involve a little bit of cargo cult coding.
This code has been adapted and combined from several locations,
see commits:

   dfbd4c6eff35f1b1065cca046003cc9d7ff27222

then earlier:

   04b954a673dd02f585a2769c4945a43880faa989
   6016a363f6b56b46b24655bcfc0499b715851cf3
   e6a6928c3ea1d0195ed75a091e345696b916c09b
   bbd33931a08362f78266a4016211a35947b91041

I would like for the code that sets the value of np->phandle
to simply say:

   if name is "phandle", "linux,phandle", or "ibm,phandle" then
  np->phandle = the value

Does anyone know if the additional logic in the current code is
needed?

Beyond the 

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

On 06/20/17 23:18, Frank Rowand wrote:
> Hi Rob,
> 
> Michael has an issue that means this patch series is not OK in the
> current form.  I will work on a v7 to see if I can resolve the
> issue.
> 
> -Frank

< snip >

Hi Rob,

The issue is in patch 1.  Patches 2 - 4 are small independent patches
that are not dependent on patch 1, so I just sent them as individual
patches.  Version 7 of this series will be just patch 1.

-Frank

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

On 06/20/17 23:18, Frank Rowand wrote:
> Hi Rob,
> 
> Michael has an issue that means this patch series is not OK in the
> current form.  I will work on a v7 to see if I can resolve the
> issue.
> 
> -Frank

< snip >

Hi Rob,

The issue is in patch 1.  Patches 2 - 4 are small independent patches
that are not dependent on patch 1, so I just sent them as individual
patches.  Version 7 of this series will be just patch 1.

-Frank

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

Hi Rob,

Michael has an issue that means this patch series is not OK in the
current form.  I will work on a v7 to see if I can resolve the
issue.

-Frank


On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.
> 
> So sorry that's a big mess, but we can't just rip out those properties.
> 
> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?
> 
> 
> The other thing that worries me is that by renaming (effectively)
> "linux,phandle" to "phandle", we lose the ability to accurately
> regenerate the device tree from /proc/device-tree. In theory it
> shouldn't matter, but I worry that in practice something will break.
> 
> What if we just kept a single bit flag somewhere indicating if the name of
> the phandle property we found was "phandle" or "linux,phandle", and
> create the sysfs phandle using that name?
> 
> cheers
> 

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Frank Rowand]

Hi Rob,

Michael has an issue that means this patch series is not OK in the
current form.  I will work on a v7 to see if I can resolve the
issue.

-Frank


On 06/20/17 21:57, Michael Ellerman wrote:
> Hi Frank,
> 
> frowand.l...@gmail.com writes:
>> From: Frank Rowand 
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field and will still be displayed as if it is
>> a property in /proc/device_tree.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
> 
> Sorry but I don't think that can work for us.
> 
> Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
> "ibm,phandle", and it's not the same thing as "phandle" /
> "linux,phandle".
> 
> I don't know the code well myself, but the spec (PAPR) says:
> 
>   Note: If the “ibm,phandle” property exists, there are two “phandle”
>   namespaces which must be kept separate. One is that actually used by
>   the OF client interface, the other is properties in the device tree
>   making reference to device tree nodes. These requirements are written
>   to maintain backward compatibility with older FW versions predating
>   these requirements; if the “ibm,phandle” property is not present, the
>   OS may assume that any device tree properties which refer to this node
>   will have a phandle value matching that returned by client interface
>   services.
> 
> I have systems here that still use "ibm,phandle". I also see at least
> some of the userspace code that looks for "ibm,phandle", and nothing
> else.
> 
> The note above actually implies that the current Linux code is wrong,
> when it uses "ibm,phandle" as the value of np->phandle.
> 
> So sorry that's a big mess, but we can't just rip out those properties.
> 
> I think the minimal change would be to treat "ibm,phandle" like a normal
> property, I think that would allow our tools to keep working?
> 
> 
> The other thing that worries me is that by renaming (effectively)
> "linux,phandle" to "phandle", we lose the ability to accurately
> regenerate the device tree from /proc/device-tree. In theory it
> shouldn't matter, but I worry that in practice something will break.
> 
> What if we just kept a single bit flag somewhere indicating if the name of
> the phandle property we found was "phandle" or "linux,phandle", and
> create the sysfs phandle using that name?
> 
> cheers
> 

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Michael Ellerman]

Hi Frank,

frowand.l...@gmail.com writes:
> From: Frank Rowand 
>
> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
> the internal device tree.  The phandle will still be in the struct
> device_node phandle field and will still be displayed as if it is
> a property in /proc/device_tree.
>
> This is to resolve the issue found by Stephen Boyd [1] when he changed
> the type of struct property.value from void * to const void *.  As
> a result of the type change, the overlay code had compile errors
> where the resolver updates phandle values.
>
>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>
> - Add sysfs infrastructure to report np->phandle, as if it was a property.
> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>   in the expanded device tree.
> - Remove phandle properties in of_attach_node(), for nodes dynamically
>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
> - When creating an overlay changeset, duplicate the node phandle in
>   __of_node_dup().
> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>   properties in several locations.
> - A side effect of these changes is that the obsolete "linux,phandle" and
>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>   will appear as "phandle").

Sorry but I don't think that can work for us.

Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
"ibm,phandle", and it's not the same thing as "phandle" /
"linux,phandle".

I don't know the code well myself, but the spec (PAPR) says:

  Note: If the “ibm,phandle” property exists, there are two “phandle”
  namespaces which must be kept separate. One is that actually used by
  the OF client interface, the other is properties in the device tree
  making reference to device tree nodes. These requirements are written
  to maintain backward compatibility with older FW versions predating
  these requirements; if the “ibm,phandle” property is not present, the
  OS may assume that any device tree properties which refer to this node
  will have a phandle value matching that returned by client interface
  services.

I have systems here that still use "ibm,phandle". I also see at least
some of the userspace code that looks for "ibm,phandle", and nothing
else.

The note above actually implies that the current Linux code is wrong,
when it uses "ibm,phandle" as the value of np->phandle.

So sorry that's a big mess, but we can't just rip out those properties.

I think the minimal change would be to treat "ibm,phandle" like a normal
property, I think that would allow our tools to keep working?


The other thing that worries me is that by renaming (effectively)
"linux,phandle" to "phandle", we lose the ability to accurately
regenerate the device tree from /proc/device-tree. In theory it
shouldn't matter, but I worry that in practice something will break.

What if we just kept a single bit flag somewhere indicating if the name of
the phandle property we found was "phandle" or "linux,phandle", and
create the sysfs phandle using that name?

cheers

Re: [PATCH v6 1/4] of: remove *phandle properties from expanded device tree

[Michael Ellerman]

Hi Frank,

frowand.l...@gmail.com writes:
> From: Frank Rowand 
>
> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
> the internal device tree.  The phandle will still be in the struct
> device_node phandle field and will still be displayed as if it is
> a property in /proc/device_tree.
>
> This is to resolve the issue found by Stephen Boyd [1] when he changed
> the type of struct property.value from void * to const void *.  As
> a result of the type change, the overlay code had compile errors
> where the resolver updates phandle values.
>
>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>
> - Add sysfs infrastructure to report np->phandle, as if it was a property.
> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>   in the expanded device tree.
> - Remove phandle properties in of_attach_node(), for nodes dynamically
>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
> - When creating an overlay changeset, duplicate the node phandle in
>   __of_node_dup().
> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>   properties in several locations.
> - A side effect of these changes is that the obsolete "linux,phandle" and
>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>   will appear as "phandle").

Sorry but I don't think that can work for us.

Our DLPAR (ie. CPU/memory/device hotplug) stuff on PowerVM uses
"ibm,phandle", and it's not the same thing as "phandle" /
"linux,phandle".

I don't know the code well myself, but the spec (PAPR) says:

  Note: If the “ibm,phandle” property exists, there are two “phandle”
  namespaces which must be kept separate. One is that actually used by
  the OF client interface, the other is properties in the device tree
  making reference to device tree nodes. These requirements are written
  to maintain backward compatibility with older FW versions predating
  these requirements; if the “ibm,phandle” property is not present, the
  OS may assume that any device tree properties which refer to this node
  will have a phandle value matching that returned by client interface
  services.

I have systems here that still use "ibm,phandle". I also see at least
some of the userspace code that looks for "ibm,phandle", and nothing
else.

The note above actually implies that the current Linux code is wrong,
when it uses "ibm,phandle" as the value of np->phandle.

So sorry that's a big mess, but we can't just rip out those properties.

I think the minimal change would be to treat "ibm,phandle" like a normal
property, I think that would allow our tools to keep working?


The other thing that worries me is that by renaming (effectively)
"linux,phandle" to "phandle", we lose the ability to accurately
regenerate the device tree from /proc/device-tree. In theory it
shouldn't matter, but I worry that in practice something will break.

What if we just kept a single bit flag somewhere indicating if the name of
the phandle property we found was "phandle" or "linux,phandle", and
create the sysfs phandle using that name?

cheers