> -----Original Message----- > From: > [email protected] > [mailto:devicetree-discuss-bounces+leoli=freescale....@ozlabs. > org] On Behalf Of David Gibson > Sent: Tuesday, January 06, 2009 9:43 AM > To: Wood Scott-B07421 > Cc: [email protected]; Li Yang-R58472; > [email protected] > Subject: Re: The usage of compatible 'simple-bus' > > On Mon, Jan 05, 2009 at 01:20:53PM -0600, Scott Wood wrote: > > On Mon, Jan 05, 2009 at 06:27:39PM +0800, Li Yang wrote: > > > I got an assumption from the existing device trees that having > > > 'simple-bus' in the compatible property of a node means that all > > > child nodes should be added as of_platform_device in platform > > > initialization phase. No matter it represents a bus in > common sense > > > or not. Is this truly the case? > > > > Yes, simple-bus indicates that the children can be driven > standalone > > from any knowledge of the parent bus. > > Erm, well, sort of. Strictly it indicates that the only way > to locate the child devices of this bus is by using the > address information in the device tree - there's no way to > dynamically probe the bus.
So if I understand correctly, "simple-bus" is intended to be used for true buses. > > The fact that this causes of_platform_devices to be > instantiated is a Linux implementation specific detail (and > one we might change in future). Here we have a common case for SoC that part of a device has its separate driver besides the driver for the main feature of the whole device. The resources used by the sub-device is usually part of the resources of the parent device. So it makes sense to put the node of sub-device beneathe the node of main device. Shall we have a convention to mark such devices in device tree so that the sub-device can be scanned and probed as a standalone of_platform_device? If "simple-bus" may cause confusion to do this job as it's not a bus actually, I propose to use "has-subdevice". - Leo _______________________________________________ devicetree-discuss mailing list [email protected] https://ozlabs.org/mailman/listinfo/devicetree-discuss
