[Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?]
From: dwmw2@infradead.org (David Woodhouse)
Date: 2013-07-26 09:42:45
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On Fri, 2013-07-26 at 10:01 +0200, Richard Cochran wrote:
On Thu, Jul 25, 2013 at 03:37:53PM -0600, Jason Gunthorpe wrote:quoted
We use DT has a kernel configuration input. Our environment is designed to guarantee 100% that the kernel and DT match exactly. DT very deliberately isn't an ABI boundary in our systems.Think about what you just said. The DT describes the *hardware* not the kernel. Why should you ever need to update your DT at all?
Well, the nodes which describe hardware devices, according to the bindings which form an ABI contract between DT and drivers, should not normally change. Although they *can* change, if for example you change the MAC address and that's stored there. Or you change the PHY you want it to use. Or something like that. The *ABI* doesn't change, but the data you express *using* that ABI can change. That's kind of the point. And the nodes in /chosen aren't describing hardware at all. Those are *absolutely* expected to be configuration things. It's quite normal for those to vary from one boot to the next, if your bootloader is sophisticated enough to do that. And if Jason wants to hard-code that kind of configuration data into his device-tree and ship it as part of the overall system image that gets installed, I see no particular problem with that. -- David Woodhouse Open Source Technology Centre David.Woodhouse at intel.com Intel Corporation -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 5745 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20130726/b2ffc9da/attachment.bin>