On Thu, Jan 02, 2014 at 09:27:58PM +0000, Russell King wrote:
Subsystems such as ALSA, DRM and others require a single card-level device structure to represent a subsystem. However, firmware tends to describe the individual devices and the connections between them.
Therefore, we need a way to gather up the individual component devices together, and indicate when we have all the component devices.
We do this in DT by providing a "superdevice" node which specifies the components, eg:
imx-drm { compatible = "fsl,drm"; crtcs = <&ipu1>; connectors = <&hdmi>; };
The superdevice is declared into the component support, along with the subcomponents. The superdevice receives callbacks to locate the subcomponents, and identify when all components are present. At this point, we bind the superdevice, which causes the appropriate subsystem to be initialised in the conventional way.
When any of the components or superdevice are removed from the system, we unbind the superdevice, thereby taking the subsystem down.
This sounds a lot like the "containers" code that Rafael just submitted and I acked for 3.14. Look at the lkml post: Subject: [PATCH 2/2] ACPI / hotplug / driver core: Handle containers in a special way Message-ID: 1991202.gilW172FBV@vostro.rjw.lan
And see if that could possibly be used instead?
thanks,
greg k-h