Messages in this thread | | | Date | Thu, 22 Dec 2011 14:45:01 -0600 | From | Rob Herring <> | Subject | Re: Driver core support for early platform devices |
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On 12/22/2011 11:55 AM, Moffett, Kyle D wrote: > On Dec 22, 2011, at 12:45, Greg KH wrote: >> On Thu, Dec 22, 2011 at 11:15:06AM -0600, Moffett, Kyle D wrote: >>> Hi, >>> >>> I'm tinkering with some improvements to the way that OpenPIC/MPIC are >>> detected and loaded on PowerPC platforms, and it seems like I am trying >>> to use the driver model before it is fully initialized. >>> >>> In particular, it seems like it should be possible to simply declare an >>> OpenPIC in the device-tree and have it automatically bound to a platform >>> driver declaring the right OpenFirmware match strings. >>> >>> Unfortunately, it needs to be bound by init_IRQ() time, while the driver >>> model does not get initialized until much later (after the scheduler is >>> up and running). >>> >>> As far as I can tell, there seem to be 2 possible approaches to making >>> that possible: >>> >>> (1) Split the driver-model initialization into "early" and "late" phases >>> so that drivers can be registered and devices probed very early on >>> and then replay the necessary scheduler-dependent things after the >>> system is mostly started up (IE: devtmpfs, etc). >> >> We already have that today with the "early_platform*" functions, right? >> Will those work for you, or do you need this for a bus you are creating >> and not using the platform bus? > > Well, I can't figure out how "early_platform" is actually supposed to > integrate with the platform bus itself. It seems designed mostly for > drivers like "earlyprintk" et. al. for which loading is controlled by > a kernel parameter. > > Specifically, I don't see any "early_platform" logic to match devices in > the OF device-tree based on the driver "of_match" parameters, just based > on text strings in early_param(). > > Furthermore, if I register an "early_platform" device, it seems to get > unregistered when the normal driver model is brought up, instead of > being sucked in and promoted to a normal platform_device. That code is > pretty poorly documented and only used in a couple places right now, > though, so it's possible I am misreading it. > > Cheers, > Kyle Moffett
There was a proposal for DT support of early platform devices here:
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-June/054529.html
Rob
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