Subject: Re: Could the DTS experts look at this?
Date: Tuesday 12th February 2008 23:17:02 UTC (over 8 years ago)
On Tue, Feb 12, 2008 at 12:51:06PM -0600, Scott Wood wrote: > On Tue, Feb 12, 2008 at 11:36:33AM +1100, David Gibson wrote: > > On Tue, Feb 12, 2008 at 01:21:44AM +0100, Arnd Bergmann wrote: > > > On Tuesday 12 February 2008, David Gibson wrote: > > > > Or to expand. It's relatively easy now to just include multiple nodes > > > > in the tree and either delete or nop some of them out conditionally > > > > using libfdt. But the conditional logic should be in the manipulating > > > > agent (u-boot or bootwrapper or whatever), there's no way we're going > > > > to require a conditional expression parser to interpret the device > > > > tree blob itself. > > > > > > How about making the logic to nop out nodes a little more generic > > > without changes to the binary format? > > > E.g. you could have a "linux,conditional-node" property in the device > > > tree whose value is compared to a HW configuration specific string. > > > In Sean's example, you can have linux,conditional-node="Rev.A" in > > > some nodes and linux,conditional-node="Rev.B" in others, then > > > knock out all devices that have a non-matching linux,conditional-node > > > property, and finally remove the properties themselves before starting > > > the kernel. > > > > Well, that's basically a u-boot issue. If they want to do their input > > trees that way, and have helper functions that deal with it... > > The actual mechanism that we originially discussed, which Timur later > morphed into conditions-on-nodes, was to have a separate hwoptions node, > under which would be described various hwoptions (jumpers and such) whose > state could be either detected by u-boot or set by environment variable. > Each hwoption setting would contain a device tree fragment to be merged into > the main device tree. I'm not sure I'm entirely happy about storing the fragments under a special node - but certainly u-boot could do that if it wants. What would certainly be ok is to store various fragments as separate blobs and fold them together as necessary. Which reminds me, I meant to implement a "graft" function in libfdt. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson