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SubjectRe: [GIT PULL 0/3] ARM: SoC: Second round of changes for v3.12
On Mon, 2013-09-09 at 16:49 -0700, Linus Torvalds wrote:
> Ok. I still really despise the absolute incredible sh*t that is
> non-discoverable buses, and I hope that ARM SoC hardware designers all
> die in some incredibly painful accident. DT only does so much.

Setting aside the inevitable whining from the emotionally-incontinent
contingent that the above way of saying it will provoke, I'm not quite
sure why you still haven't got over the fact that we have
non-discoverable buses.

In cost-sensitive products (and what *isn't* cost-sensitive these days),
you really don't want to have to put an extra EEPROM on the board
somewhere, just to describe what devices you've hung off which
chip-select today. Storing that in the main flash is just *going* to
happen, however much we'd like to think that devices should identify
themselves cleanly and autonomously.

And it isn't even something that a simple number like a PCI ID could
manage. Peripherals are synthesisable components which vary *wildly*,
with what are essentially #ifdefs in the VHDL. So a given controller
could be seen with different FIFO depths, different numbers of queues,
all kinds of variations. To cover the various permutations, you'd have
to assign an *insane* number of PCI IDs. And then there's the various
ways that you can connect blocks *together*...

That's why we end up with the device-tree model which gives us a rich
way to describe *this* instance of the hardware. If it wasn't
device-tree, it'd have to be something *else*.

From a software point of view it *isn't* nice, I agree. But you might as
well be railing against the sunset, as far as I can tell.

Not that any of this excuses crappy merges with lots of conflicts; but
those don't seem to be an inexorable result of non-discoverable buses.


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