[pvrusb2] I got 24xxx IR working(!)

[Mike Isely]

29xxx devices have a dedicated chip for IR reception.  This device is 
accessible via I2C so the pvrusb2 driver doesn't need to do anything 
special to support it.  Instead the appropriate lirc I2C chip-level driver 
just "sees" it and uses it.  (Or ir-kbd-i2c.ko can be loaded which will do 
the same thing.)

The problem with 24xxx devices is that the IR receiver chip has been 
removed.  In its place is (apparently) some glue logic and additional 
firmware in the FX2 microcontroller.  So IR access on 24xxx devices 
doesn't happen over I2C any more, and the protocol to get at the IR data 
is now made specific to the PVR USB2 device itself.  This in theory 
requires additional logic in the pvrusb2 driver to issue the appropriate 
commands and whatever else is needed to support a /dev/input style of IR 
reception.  Doing this lirc style just isn't going to work.

Well in a fit of insanity I came up with a clever idea.

The pvrusb2 driver already has a I2C "filter" mechanism whereby it can 
take special actions based on the I2C address being accessed from the 
outside.  This was implemented last Spring in order to get 24xxx devices 
to work at all.  Filters are already in place for wm8775 to simulate 
auto-detection correctly and cx25840 to keep msp3400 from messing it up 
because the real cx25840 module can detect and configure it.

So I added another filter.  It is only inserted for 24xxx devices and 
answers at the I2C address for where the IR receiver chip would otherwise 
respond for 29xxx devices.  The filter checks that the expected type of 
access is being attempted and then "responds" by merely issuing an IR 
receive command to the FX2.  It takes that result and then munges it into 
the form normally expected from the 29xxx's I2C IR receiver.  The net 
effect of this is that once again outside logic "sees" an IR receiver chip 
when in fact the pvrusb2 driver is emulating it with an FX2 commmand.  So 
now lirc and ir-kbd-i2c.ko should both work again, unmodified, with 24xxx 
hardware.

I've just tested this new filter against ir-kbd-i2c and it works 
perfectly!  I'm going to test it next against lirc, and if that works 
there will be a new pvrusb2 driver snapshot released.

  -Mike


-- 
                        |         Mike Isely          |     PGP fingerprint
     Spammers Die!!     |                             | 03 54 43 4D 75 E5 CC 92
                        |   isely @ pobox (dot) com   | 71 16 01 E2 B5 F5 C1 E8
                        |                             |