On 11/12/2012 05:50 AM, Pantelis Antoniou wrote: > Hi Rob. > > On Nov 11, 2012, at 10:47 PM, Rob Landley wrote: > >> On 11/09/2012 10:28:59 AM, Grant Likely wrote: >>> On Tue, Nov 6, 2012 at 10:37 PM, Stephen Warren <swar...@wwwdotorg.org> >>> wrote: >>>> On 11/05/2012 01:40 PM, Grant Likely wrote: >>> I'm not actually opposed to it, but it needs to be done in an elegant >>> way. The DT data model already imposes more of a conceptual learning >>> curve than I wish it did and I don't want to make that worse with a >>> versioning model that is difficult to get ones head around. >> >> Speaking of which... >> >> I want to poke at board emulation in qemu, from scratch. Specifically, I >> want to start with an unpopulated board (just the processor), add a block of >> physical memory and a serial device, and boot an initramfs in there with >> stdin/stdout. Then I want to incrementally add an RTC, network card, and >> three block devices. >> >> I'd like to define this board by giving qemu and the kernel the same device >> tree they can parse, and I'd like to _build_ this device tree so I >> understand what's in it. I'd like to repeat this exercize for arm, mips, >> ppc, x86, x86-64, sparc, sh4, and maybe other boards. >> >> And I'd like to write up an article on doing it as a learning exercise. >> >> Last time I checked, doing this wasn't possible. (qemu couldn't define a >> board by parsing a device tree, the kernel used the device tree as a >> guideline but it only really read data the drivers you linked in were >> expecting, the only documentation about what any of the nodes were was was >> read the other device trees as examples or read the source code of the >> drivers looking for data in the tree...) >> >> Is it a more realistic project now? If so, where would I start? (Once upon a >> time I read the booting-without-of document, back when it lived in the ppc >> directory. It didn't really say what should go in any of the nodes.) >> >> Rob > > It should be possible when the stuff we're talking about is ready. > > I don't know what you'll find is broken during the exercise, but I guess > your article is going to be entertaining at least :)
To be honest, I think Rob's proposal should be possible irrespective of this conversation; if he wants to simply define the HW structure once before running qemu, then none of this overlay discussion is relevant. Perhaps the missing piece is the Documentation/devicetree/bindings/ directory? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
