DRM encoder/bridge architecture questions

Sean Cross xobs at kosagi.com
Mon Aug 18 01:29:24 PDT 2014


We've got an IT6251 LVDS -> eDP bridge chip we're hanging off of a
dual-lane LVDS port on an i.MX6.  We have a driver we're using
internally that's little more than a series of register pokes to boot
the chip, but I'd like to clean it up for submission.

What kind of device is this?  It's externally connected to the main SoC
via LVDS and I2C.  It's conceptually hanging off of the ldb "LVDS
Display Bridge" encoder, which means it's an encoder attached to an
encoder.  Is that allowed in the DRM model?

With the current driver, I have it just sitting in drivers/gpu/drm/i2c/,
and it's not "attached" to anything.  The encoder chip automatically
figures out display timings and the like.  Where should the file
actually go?

Finally, how would the driver get attached to the system?  I see there's
an Exynos bridge device that appears to go the other way, but it's
explicitly loaded by the Exynos display adapter.  Since most devices
will have an LVDS panel attached directly to the LDB port, it seems
silly to have it explicitly look for an additional bridge device to plug
in as this is a special case.  Is there any way I could pass the it6251
a handle to the ldb in device tree and have it hang itselff of the end
that way?


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