Messages in this thread | | | Date | Thu, 28 May 2009 01:48:01 +0200 | From | Robert Schwebel <> | Subject | Re: [RFC] [PATCH] Device Tree on ARM platform |
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On Wed, May 27, 2009 at 02:35:11PM -0600, Grant Likely wrote: > > Unfortunately, it is an incomplete data structure regarding to what > > the kernel needs. > > I don't follow your argument. It's a data structure that uniquely > describes your hardware in a way which encourages the most code reuse > possible; but is still independent of kernel internal implementation. > ie. a FDT blob should be usable not just by Linux, but also by BSD or > any of the other OS options. It is not an attempt to eliminate > platform specific code; just to reduce it as much as possible. Weird, > harry, non-standard stuff probably still needs board specific code to > handle.
The oftree by design wants to be a complete hardware description. As you mention above, there are cases where you *nevertheless* need ad-hoc information about things *not* encoded into the device tree.
This renders the whole concept ad absurdum. You need a machine number again - and if you need that: why not stay with the ARM model, define everything with platform data and avoid the whole thing?
Regarding the multi OS argument: I consider it impossible that people agree on all micro details of a hardware decision. Will it really be possible to get a common agreement about let's say Russell's SMSC example between all these people? Remember: if we forget (or don't agree on) one single aspect which a driver developer *needs*, he will have to work around it -> machine number land.
My impression is that oftree only works in a perfect world. But we don't have one, so the fundamental design decision is broken.
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