[RFC PATCH] Documentation: devicetree: add description for generic bus properties

[Will Deacon]

On Fri, Nov 29, 2013 at 05:37:01PM +0000, Greg KH wrote:
> On Fri, Nov 29, 2013 at 11:44:53AM +0000, Will Deacon wrote:
> > On Thu, Nov 28, 2013 at 09:25:28PM +0000, Greg KH wrote:
> > > On Thu, Nov 28, 2013 at 07:39:17PM +0000, Dave Martin wrote:
> > > > On Thu, Nov 28, 2013 at 11:13:31AM -0800, Greg KH wrote:
> > > > > Yes it is, you all are the ones tasked with implementing the crazy crap
> > > > > the hardware people have created, best of luck with that :)
> > > > 
> > > > Agreed.  The first assumption should be that we can fit in with the
> > > > existing device model -- we should only reconsider if we find that
> > > > to be impossible.
> > > 
> > > Let me know if you think it is somehow impossible, but you all should
> > > really push back on the insane hardware designers that are forcing you
> > > all to do this work.  I find it "interesting" how this all becomes your
> > > workload for their crazy ideas.
> > 
> > Oh, I don't think we're claiming anything is impossible here :) It's more
> > that we will probably want to make some changes to the device model to allow,
> > for example, a device to be associated with multiple buses of potentially
> > different types.
> 
> Why would you want that?  What good would that help with?

It would help with devices which have their slave interface on one bus, but
master to another.

We need a way to configure the master side of things (IOMMU, coherency, MSI
routing, etc) on one bus and configure the slave side (device probing, power
management, clocks, etc) on another.

> > Step one is to get the DT binding sorted, then we can try and get Linux to
> > make use of it. This goes hand-in-hand with the IOMMU discussion going on
> > here:
> > 
> >   http://lists.infradead.org/pipermail/linux-arm-kernel/2013-November/210401.html
> > 
> > which is one of the issues that is hitting us right now.
> 
> Interesting how people seem to not know how to cc: the needed
> maintainers when they touch core code :(

To be fair, I don't think that code was intended to be merged, and ended up
sparking a discussion about what we need in the DT to represent these
topologies. DT people were on CC iirc.

Will