On Oct 24, 2013, at 4:21 AM, Hiroshi Doyu wrote:
> Hi Grant,
>
> Grant Likely <grant.likely@xxxxxxxxxx> wrote @ Thu, 24 Oct 2013 10:55:31 +0200:
> ....
>>> diff --git a/include/linux/of.h b/include/linux/of.h
>>> index f95aee3..638a88a 100644
>>> --- a/include/linux/of.h
>>> +++ b/include/linux/of.h
>>> @@ -60,6 +60,7 @@ struct device_node {
>>> struct kref kref;
>>> unsigned long _flags;
>>> void *data;
>>> + struct device *dev; /* Set only after populated */
>>
>> Is this being used merely to indicate that a device has been processed
>> by of_platform_device_create()? Or do you intend to dereference this
>> pointer? I've avoided putting the struct device in to the device_node
>> structure up to this point simply becuase there aren't any good clues
>> for what /kind/ of device it actually points to. I worry that bad
>> assumptions will get made when other subsystems try to use the
>> same pointer. ie. if one subsystem creates its own device and sets this
>> pointer, and then of_platform_device_create() comes along behind, sees
>> that it is already created, and then returns a platform_device pointer
>> *for something that isn't a struct platform_device*. This is very bad.
>>
>> Instead of using a pointer to the struct device, would a flag be
>> sufficient for your purposes? Would it be fine to return NULL if the
>> device has already been created?
>
> Yes, a flag would be enough for this purpose.
>
> This patch is a part of HACK to control device instanciation order. We
> have an IOMMU device(platform) which needs to be instanciated earlier
> than other (platform)devices so that IOMMU driver would configure them
> as IOMMU'able device.
>
> Is there any better way to control device instanciation order from DT?
I was also thinking being able to call of_platform_populate multiple times and have explicit lists to control device init order might be a workable solution. So might be worth continuing down this path to make device nodes that have already be created.
- k
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