Mode validation outside of connector or encoder (i.e. at CRTC or drm_driver level)

[Matt Sealey]

Quick question; if I want to validate a mode given to me by a
connector/encoder as workable or not before I am going through the
code to actually set that mode, how would I do this?

I expected to see a mode_valid callback in crtc or somewhere similar.
What I've got right now is a drm connector and encoder, which are
describing a silicon image hdmi transmitter,
and an embedded crtc connected to it. While the transmitter is fairly
capable the crtc in the SoC is not (it has a maximum pixel clock
limitation of 133MHz which means I have to
kill off modes above that like 1080p at 60. There are other things I may
need to limit too).

How do I coordinate such things from the drm_driver or crtc level up
to the connector/encoder without making the connector/encoder
intimately knowledgeable about the underlying
crtc? Currently my only resort is to put the limits in platform data
for the connector/encoder and use the mode_valid I already have to
parse and discard modes which are plainly not
going to be able to be clocked.

-- 
Matt Sealey <matt at genesi-usa.com>
Product Development Analyst, Genesi USA, Inc.