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 <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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) {
>>
>
>
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