[RFC] early init and DT platform devices allocation/registration

[Grant Likely]

On Wed, Jun 26, 2013 at 11:31 AM, Thierry Reding
<thierry.reding at gmail.com> wrote:
> On Wed, Jun 26, 2013 at 11:03:20AM +0100, Grant Likely wrote:
>> On Wed, Jun 26, 2013 at 7:00 AM, Hiroshi Doyu <hdoyu at nvidia.com> wrote:
>> > Grant Likely <grant.likely at secretlab.ca> wrote @ Tue, 25 Jun 2013 19:52:33 +0200:
>> >
>> >> > Here's my workaround. I need to call of_detach_node() with OF_DYNAMIC
>> >> > to avoid duplicated device registration.
>> >>
>> >> Gah! my eyes!
>> >>
>> >> Don't do that. It is incredibly problematic. Look at inhibiting
>> >> duplicate device creation instead.
>> >
>> > I may not follow this thread correctly, but could anyone point out the
>> > above "inhibiting duplicate device creation" if there's already such
>> > solution?
>>
>> No, the solution doesn't exist yet, but it wouldn't be hard to
>> implement. What you need to do is to add a struct device pointer to
>> struct device_node, and set the pointer to the struct device when
>> of_platform_device_create creates a device. (it would also need to be
>> set for early_platform_device creation, but that's not something that
>> should affect you). You would also add a check to
>> of_platform_device_create to check if the device pointer is already
>> set. If it is, then skip creation of the device.
>
> One problem with this method is that every driver that needs or wants
> the device early has to do it explicitly, but I guess we can't have it
> all.

The other option is to modify of_device_add() to allow it to be called
before the platform bus is set up, and then to 'fixup' the
registrations at initcall time. That would mean of_platform_populate
can be called really early and it would solve the problem of
preserving the device hierarchy.

g.