Unifying cape overlays into boot .dtb for BeagleBoard.org boards

Hi Russell,

On Jun 17, 2014, at 8:05 PM, Russell King - ARM Linux wrote:

On Tue, Jun 17, 2014 at 07:59:21PM +0300, Pantelis Antoniou wrote:

quoted

That case might already work on FPGA people's trees. I know Altera for sure
uses overlays, and some xilinx guys popped up on past discussions.
Their vendor trees probably use an older revision of the patches.

BTW, there is nothing special about DRM/v4l2 that can't be handled by
a generic DT mechanism. What makes this such a big problem?

Really?

DRM is not hotpluggable in any shape or form, and David Airlie has
indicated that he does strongly opposes moving it in that direction.

DRM follows the "card" model, where, at probe time, the hardware is
known and never changes until the "card" is torn down.  No new
connectors can be added once the "card" is initialised, and no
connectors can be removed.  Any changes must be done by tearing down
the entire card and reconstructing it (if reconstructing it with a
reduced set of hardware is appropriate.)

That is a limitation of the current DRM implementation.

I seems to be this is born out of some kind of misunderstanding about how
DT can (and does) support dynamic changes.

I admit that I haven't done much work on DRM (besides some tinkering with
Rob Clark's ti_lcdc DRM driver), but knowing what DT does have a dynamic
change notifier support, perhaps it can be made to work.

As I said, the next thing coming is transactional DT support, perhaps you
can share the DT fragment describing your use-case (before/after) and 
I'll try to accommodate in the next patch series.

Regards

-- Pantelis

-- 
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