[RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[Srinivas KANDAGATLA]

From: Srinivas Kandagatla <srinivas.kandagatla-qxv4g6HH51o@public.gmane.org>

As part of of_platform_populate call, the existing code iterates each
child node and then creates a platform device for each child, however
there is bug in the code which does not check the match table before
creating the platform device. This might result creating two platfrom
devices and also invoking driver probe twice, which is incorrect.

This patch moves a existing of_match_node check to start of the function
to fix the bug, doing this way will return immediately without creating
any datastructures if the child does not match the supplied match-table.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla-qxv4g6HH51o@public.gmane.org>
---
 drivers/of/platform.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index b80891b..1aaa560 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -367,6 +367,9 @@ static int of_platform_bus_create(struct device_node *bus,
 		return 0;
 	}
 
+	if (!of_match_node(matches, bus))
+		return 0;
+
 	auxdata = of_dev_lookup(lookup, bus);
 	if (auxdata) {
 		bus_id = auxdata->name;
@@ -379,7 +382,7 @@ static int of_platform_bus_create(struct device_node *bus,
 	}
 
 	dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
-	if (!dev || !of_match_node(matches, bus))
+	if (!dev)
 		return 0;
 
 	for_each_child_of_node(bus, child) {
-- 
1.7.0.4

Re: [RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[Rob Herring]

Adding lkml. DT patches should go to both lists.

On 10/23/2012 05:30 AM, Srinivas KANDAGATLA wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@st.com>
> 
> As part of of_platform_populate call, the existing code iterates each
> child node and then creates a platform device for each child, however
> there is bug in the code which does not check the match table before
> creating the platform device. This might result creating two platfrom
> devices and also invoking driver probe twice, which is incorrect.
> 
> This patch moves a existing of_match_node check to start of the function
> to fix the bug, doing this way will return immediately without creating
> any datastructures if the child does not match the supplied match-table.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
> ---
>  drivers/of/platform.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index b80891b..1aaa560 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -367,6 +367,9 @@ static int of_platform_bus_create(struct device_node *bus,
>  		return 0;
>  	}
>  
> +	if (!of_match_node(matches, bus))
> +		return 0;
> +

This is not right. This function is recursive and this change would
break that. Perhaps we could only call of_platform_device_create_pdata
if !of_match_node instead, but I'm not completely sure that would be the
right thing to do. There's also some historical things we have to
support which is why we have of_platform_populate and of_platform_bus_probe.

Rob

>  	auxdata = of_dev_lookup(lookup, bus);
>  	if (auxdata) {
>  		bus_id = auxdata->name;
> @@ -379,7 +382,7 @@ static int of_platform_bus_create(struct device_node *bus,
>  	}
>  
>  	dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
> -	if (!dev || !of_match_node(matches, bus))
> +	if (!dev)
>  		return 0;
>  
>  	for_each_child_of_node(bus, child) {
> 

Re: [RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[Srinivas KANDAGATLA]

On 23/10/12 14:15, Rob Herring wrote:
> Adding lkml. DT patches should go to both lists.
>
> On 10/23/2012 05:30 AM, Srinivas KANDAGATLA wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@st.com>
>>
>> As part of of_platform_populate call, the existing code iterates each
>> child node and then creates a platform device for each child, however
>> there is bug in the code which does not check the match table before
>> creating the platform device. This might result creating two platfrom
>> devices and also invoking driver probe twice, which is incorrect.
>>
>> This patch moves a existing of_match_node check to start of the function
>> to fix the bug, doing this way will return immediately without creating
>> any datastructures if the child does not match the supplied match-table.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
>> ---
>>  drivers/of/platform.c |    5 ++++-
>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> index b80891b..1aaa560 100644
>> --- a/drivers/of/platform.c
>> +++ b/drivers/of/platform.c
>> @@ -367,6 +367,9 @@ static int of_platform_bus_create(struct device_node *bus,
>>  		return 0;
>>  	}
>>  
>> +	if (!of_match_node(matches, bus))
>> +		return 0;
>> +
> This is not right. This function is recursive and this change would
> break that. 
You are correct, this change might break the functionality.
> Perhaps we could only call of_platform_device_create_pdata
> if !of_match_node instead, but I'm not completely sure that would be the
> right thing to do. 
I did try to do the same thing in the patch.
May be I should have moved check just before calling
of_platform_device_create_pdata?
> There's also some historical things we have to
> support which is why we have of_platform_populate and of_platform_bus_probe.
Am just trying to understand the difference between of_platform_populate
and of_platform_bus_probe.
Looking at the function documentation, which states
of_platform_bus_probe will only create children of the root which are
selected by the @matches argument.

of_platform_populate walks the device tree and creates devices from
nodes.  It differs in that it follows the modern convention of requiring
all device nodes to have a 'compatible' property, and it is suitable for
creating devices which are children of the root node.

Lets say If we call of_platform_populate(NULL, match_table, NULL, NULL)
on a device trees like the below with
struct of_device_id match_table[] = {
    { .compatible = "simple-bus", }
    {}
};

parent@0{
    compatible    = "xxx,parent1", "simple-bus";
    ...
    child@0 {
        compatible    = "xxx,child0", "simple-bus";
        ...
    };
    child@1 {
        compatible    = "xxx,child1";
        ...
    };
    child@2 {
        compatible    = "xxx,child2", "simple-bus";
        ...
    };
};

of_platform_bus_probewould create platform-devices for parent@0,
child@0and child@2
where as
of_platform_populate would create platform-devices for parent@0,
child@0, child@1 and child@2 nodes.

So the question is
why do we need to have @matches argument to of_platform_populate in the
first place, if it creates all the devices by walking the dt nodes?

It is bit confusion, As some platforms use of_platform_populate(NULL,
of_default_bus_match_table, NULL, NULL) assuming that only matching
nodes will end up having platform device.
Also
some platforms use of_platform_bus_probe(NULL, match_table, NULL), 
where match table is of_default_bus_match_table.

IMO, we could do two things to avoid this confusion in future.

1. Remove matches from of_platform_populate
2. add Lookup argument to of_platform_bus_probe

What do you think?

--srini




>
> Rob
>
>>  	auxdata = of_dev_lookup(lookup, bus);
>>  	if (auxdata) {
>>  		bus_id = auxdata->name;
>> @@ -379,7 +382,7 @@ static int of_platform_bus_create(struct device_node *bus,
>>  	}
>>  
>>  	dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
>> -	if (!dev || !of_match_node(matches, bus))
>> +	if (!dev)
>>  		return 0;
>>  
>>  	for_each_child_of_node(bus, child) {
>>
>
>

Re: [RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[Srinivas KANDAGATLA]

On 23/10/12 14:15, Rob Herring wrote:
re-sending my reply again, as it did not appear in my inbox from dt
mailing list.
> Adding lkml. DT patches should go to both lists.
>
> On 10/23/2012 05:30 AM, Srinivas KANDAGATLA wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla-qxv4g6HH51o@public.gmane.org>
>>
>> As part of of_platform_populate call, the existing code iterates each
>> child node and then creates a platform device for each child, however
>> there is bug in the code which does not check the match table before
>> creating the platform device. This might result creating two platfrom
>> devices and also invoking driver probe twice, which is incorrect.
>>
>> This patch moves a existing of_match_node check to start of the function
>> to fix the bug, doing this way will return immediately without creating
>> any datastructures if the child does not match the supplied match-table.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla-qxv4g6HH51o@public.gmane.org>
>> ---
>>  drivers/of/platform.c |    5 ++++-
>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> index b80891b..1aaa560 100644
>> --- a/drivers/of/platform.c
>> +++ b/drivers/of/platform.c
>> @@ -367,6 +367,9 @@ static int of_platform_bus_create(struct device_node *bus,
>>  		return 0;
>>  	}
>>  
>> +	if (!of_match_node(matches, bus))
>> +		return 0;
>> +
> This is not right. This function is recursive and this change would
> break that.

You are correct, this change might break the functionality.


>  Perhaps we could only call of_platform_device_create_pdata
> if !of_match_node instead, but I'm not completely sure that would be the
> right thing to do.

I did try to do the same thing in the patch.
May be I should have moved check just before calling
of_platform_device_create_pdata?

>  There's also some historical things we have to
> support which is why we have of_platform_populate and of_platform_bus_probe.

m just trying to understand the difference between of_platform_populate
and of_platform_bus_probe.
Looking at the function documentation, which states
of_platform_bus_probe will only create children of the root which are
selected by the @matches argument.

of_platform_populate walks the device tree and creates devices from
nodes.  It differs in that it follows the modern convention of requiring
all device nodes to have a 'compatible' property, and it is suitable for
creating devices which are children of the root node.

Lets say If we call of_platform_populate(NULL, match_table, NULL, NULL)
on a device trees like the below with
struct of_device_id match_table[] = {
    { .compatible = "simple-bus", }
    {}
};

parent@0{
    compatible    = "xxx,parent1", "simple-bus";
    ...
    child@0 {
        compatible    = "xxx,child0", "simple-bus";
        ...
    };
    child@1 {
        compatible    = "xxx,child1";
        ...
    };
    child@2 {
        compatible    = "xxx,child2", "simple-bus";
        ...
    };
};

of_platform_bus_probe would create platform-devices for parent@0,
child@0and child@2
where as
of_platform_populate would create platform-devices for parent@0,
child@0, child@1 and child@2 nodes.

So the question is
why do we need to have @matches argument to of_platform_populate in the
first place, if it creates all the devices by walking the dt nodes?

It is bit confusing, As some platforms use of_platform_populate(NULL,
of_default_bus_match_table, NULL, NULL) assuming that only matching
nodes will end up having platform device.
Also
some platforms use of_platform_bus_probe(NULL, match_table, NULL), 
where match table is of_default_bus_match_table.

Am not 100% sure what is the right solution, but I think lot of platforms would want behavior like of_platform_bus_probe which takes lookups aswell.

IMO, we could do two things to avoid this confusion in future and achieve the expected behaviour.

1. Remove matches from of_platform_populate
2. add Lookup argument to of_platform_bus_probe

??

--srini

> Rob
>
>>  	auxdata = of_dev_lookup(lookup, bus);
>>  	if (auxdata) {
>>  		bus_id = auxdata->name;
>> @@ -379,7 +382,7 @@ static int of_platform_bus_create(struct device_node *bus,
>>  	}
>>  
>>  	dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
>> -	if (!dev || !of_match_node(matches, bus))
>> +	if (!dev)
>>  		return 0;
>>  
>>  	for_each_child_of_node(bus, child) {
>>
>
>

Re: [RFC PATCH 3.7.0-rc2] dt: match id-table before creating platform device

[Grant Likely]

On Fri, 26 Oct 2012 08:12:38 +0100, Srinivas KANDAGATLA <srinivas.kandagatla@st.com> wrote:
> On 23/10/12 14:15, Rob Herring wrote:
> re-sending my reply again, as it did not appear in my inbox from dt
> mailing list.
> > Adding lkml. DT patches should go to both lists.
> >
> > On 10/23/2012 05:30 AM, Srinivas KANDAGATLA wrote:
> >> From: Srinivas Kandagatla <srinivas.kandagatla@st.com>
> >>
> >> As part of of_platform_populate call, the existing code iterates each
> >> child node and then creates a platform device for each child, however
> >> there is bug in the code which does not check the match table before
> >> creating the platform device. This might result creating two platfrom
> >> devices and also invoking driver probe twice, which is incorrect.
> >>
> >> This patch moves a existing of_match_node check to start of the function
> >> to fix the bug, doing this way will return immediately without creating
> >> any datastructures if the child does not match the supplied match-table.
> >>
> >> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
> >> ---
> >>  drivers/of/platform.c |    5 ++++-
> >>  1 files changed, 4 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> >> index b80891b..1aaa560 100644
> >> --- a/drivers/of/platform.c
> >> +++ b/drivers/of/platform.c
> >> @@ -367,6 +367,9 @@ static int of_platform_bus_create(struct device_node *bus,
> >>  		return 0;
> >>  	}
> >>  
> >> +	if (!of_match_node(matches, bus))
> >> +		return 0;
> >> +
> > This is not right. This function is recursive and this change would
> > break that.
> 
> You are correct, this change might break the functionality.
> 
> 
> >  Perhaps we could only call of_platform_device_create_pdata
> > if !of_match_node instead, but I'm not completely sure that would be the
> > right thing to do.
> 
> I did try to do the same thing in the patch.
> May be I should have moved check just before calling
> of_platform_device_create_pdata?

No, the current code is correct. The purpose of the match table passed
to of_platform_populate is to figure out which nodes are bus nodes that
need to be recursed into.

However, *every single* child node of the root when
of_platform_populate() is called will be used to create a
platform_device. This is by design.

So, if somewhere is calling of_platform_populate() with the expectation
that it will only create devices for a subset of the nodes, then that
code is working on an incorrect assumption.

> 
> >  There's also some historical things we have to
> > support which is why we have of_platform_populate and of_platform_bus_probe.
> 
> m just trying to understand the difference between of_platform_populate
> and of_platform_bus_probe.
> Looking at the function documentation, which states
> of_platform_bus_probe will only create children of the root which are
> selected by the @matches argument.
> 
> of_platform_populate walks the device tree and creates devices from
> nodes.  It differs in that it follows the modern convention of requiring
> all device nodes to have a 'compatible' property, and it is suitable for
> creating devices which are children of the root node.
> 
> Lets say If we call of_platform_populate(NULL, match_table, NULL, NULL)
> on a device trees like the below with
> struct of_device_id match_table[] = {
>     { .compatible = "simple-bus", }
>     {}
> };
> 
> parent@0{
>     compatible    = "xxx,parent1", "simple-bus";
>     ...
>     child@0 {
>         compatible    = "xxx,child0", "simple-bus";
>         ...
>     };
>     child@1 {
>         compatible    = "xxx,child1";
>         ...
>     };
>     child@2 {
>         compatible    = "xxx,child2", "simple-bus";
>         ...
>     };
> };
> 
> of_platform_bus_probe would create platform-devices for parent@0,
> child@0and child@2
> where as
> of_platform_populate would create platform-devices for parent@0,
> child@0, child@1 and child@2 nodes.
> 
> So the question is
> why do we need to have @matches argument to of_platform_populate in the
> first place, if it creates all the devices by walking the dt nodes?

of_platform_populate will create devices for all the children of
child@0 and child@2 also. The intent is for generic board support to
call of_platform_populate() on the root of the tree and have all the
nodes with compatible properties *and all the children of simple memory
mapped busses* created into devices. This is normally what we want;
particularly for new board support.

> 
> It is bit confusing, As some platforms use of_platform_populate(NULL,
> of_default_bus_match_table, NULL, NULL) assuming that only matching
> nodes will end up having platform device.
> Also
> some platforms use of_platform_bus_probe(NULL, match_table, NULL), 
> where match table is of_default_bus_match_table.

of_platform_bus_probe() is old code used by most of the powerpc
platforms. Don't use it for new board support.

g.