On Tue, Aug 03, 2010 at 05:02:29PM -0700, Patrick Pannuto wrote: > On 08/03/2010 04:56 PM, Greg KH wrote: > > On Tue, Aug 03, 2010 at 04:35:06PM -0700, Patrick Pannuto wrote: > >> Inspiration for this comes from: > >> http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg31161.html > >> > >> INTRO > >> > >> As SOCs become more popular, the desire to quickly define a simple, > >> but functional, bus type with only a few unique properties becomes > >> desirable. As they become more complicated, the ability to nest these > >> simple busses and otherwise orchestrate them to match the actual > >> topology also becomes desirable. > >> > >> EXAMPLE USAGE > >> > >> /arch/ARCH/MY_ARCH/my_bus.c: > >> > >> #include <linux/device.h> > >> #include <linux/platform_device.h> > >> > >> struct bus_type my_bus_type = { > >> .name = "mybus", > >> }; > >> EXPORT_SYMBOL_GPL(my_bus_type); For your question below, this could be in write-only memory. Well, I guess it never is as we modify things in the bus structure, so nevermind about that, false alarm. > >> > >> struct platform_device sub_bus1 = { > >> .name = "sub_bus1", > >> .id = -1, > >> .dev.bus = &my_bus_type, > >> } > >> EXPORT_SYMBOL_GPL(sub_bus1); > > > > You really want a bus hanging off of a bus? Normally you need a device > > to do that, which is what I think you have here, but the naming is a bit > > odd to me. > > > > What would you do with this "sub bus"? It's just a device, but you are > > wanting it to be around for something. > > > > It's for power management stuff, basically, there are actual physical buses > involved that can be completely powered off IFF all of their devices are > not in use. Plus it actually matches bus topology this way. Then create a real bus hanging off of a device, not another device that "acts" like a bus here, right? Or am I missing the point? > >> +void platform_bus_type_init(struct bus_type *bus) > >> +{ > >> + if (!bus->dev_attrs) > >> + bus->dev_attrs = platform_bus_type.dev_attrs; > >> + if (!bus->match) > >> + bus->match = platform_bus_type.match; > >> + if (!bus->uevent) > >> + bus->uevent = platform_bus_type.uevent; > >> + if (!bus->pm) > >> + bus->pm = platform_bus_type.pm; > > > > Watch out for things in "write only" memory here. That could cause > > problems. > > Pardon my ignorance (I'm quite new to kernel work), what do you mean > here? What memory could be "write only"? See above. I was thinking that struct bus would be a constant or something. Sorry. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
