[Intel-gfx] [PATCH 0/5] drm/i915 Avoid long delays when reading EDID on eDP

[Egbert Eich]

Daniel Vetter writes:

 > Imo this approach with overwrite all the entry points won't scale since
 > besides i2c and dpcd there will be more sooner or later (oui, dp mst, some
 > debugfs userspace dp aux tools, ...).
 > 
 > I think what we need is the same as in the i2c layer has with the
 > xfer_pre/post functions. To make this as painless as possible we should
 > probably refcount that in the dp helper, protected by aux->hw_mutex. That
 > way normal dp reads could just do the xfer_pre/post around the call to
 > aux->transfer while i2c could do it around the entire i2c transaction.

I agree with your idea of having xfer_pre/post functions. 
I'm not sure though if I understand your idea about reference counters:
are you trying to protect from xfer_pre/post being called at different
levels here? 
With my proposal entire transactions (I2C) are serialized thru the pps_mutex 
lock. This is a side effect that's probably unwanted. Is this what you are
trying to avoid by using ref counters?

Cheers,
	Egbert.