[PATCH v4 0/5] simplefb: add clock handling code

On Wednesday, November 12, 2014, Geert Uytterhoeven
[off-list ref] wrote:

Hi Grant,

On Tue, Nov 11, 2014 at 10:49 PM, Grant Likely [off-list ref] wrote:

quoted

However, I am concerned about handover. I've lost track over the entire
thread on whether the handover mechanism has been resolved, and I would
really like to have a proposed solution to this documented in the
binding. The fact that there is nothing tying the simple framebuffer to
the actual hardware backing the framebuffer is concerning. It means the
kernel needs to guess which graphics device is associated with the
framebuffer.

We did discuss handover in D?sseldorf, and concluded that the simplefb's
regs property can be used for this.

While on a modern system with unified memory this association cannot be
derived in a generic way, a device-specific driver for the graphics hardware
can if the regs property of the simplefb node matches the address the CRTC
engine is configured for.

???

Right, I'm going to be blunt here: That's just dumb. All the
capability needed is there in the DT to associate a simple FB to a
display controller, and the solution chosen is to use a heuristic?

The association needs to be explicit. I strongly prefer putting the
simple FB directly into the display controller node, but I would
consider phandle linkage also.

g.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds