So I augmented the subcpu.c file as more stuff made sense (my friend kinda got infected with my excitement too, and he helped figure out the sequence numbers).
Here's a sample interaction, me pressing every single button and then briefly tapping the screen (all numbers are in hex):
Code:
# ./subcpu
MSG: KEY: 17 (Page left ), EVENT: key down (2b)
MSG: KEY: 17 (Page left ), EVENT: key up (2d)
MSG: KEY: 0b (Page right ), EVENT: key down (2b)
MSG: KEY: 0b (Page right ), EVENT: key up (2d)
MSG: KEY: 0c (Home ), EVENT: key down (2b)
MSG: KEY: 0c (Home ), EVENT: key up (2d)
MSG: KEY: 03 (Zoom ), EVENT: key down (2b)
MSG: KEY: 03 (Zoom ), EVENT: key up (2d)
MSG: KEY: 02 (Options ), EVENT: key down (2b)
MSG: KEY: 02 (Options ), EVENT: key up (2d)
MSG: KEY: 00 (Volume down ), EVENT: key down (2b)
MSG: KEY: 00 (Volume down ), EVENT: key up (2d)
MSG: KEY: 01 (Volume up ), EVENT: key down (2b)
MSG: KEY: 01 (Volume up ), EVENT: key up (2d)
MSG: TOUCH: SEQ: 09 X: 686 Y: 3e8
MSG: TOUCH: SEQ: 09 X: 24c Y: a90 (pressure)
MSG: TOUCH: SEQ: 0a X: 6b2 Y: 3f6
MSG: TOUCH: SEQ: 0a X: 266 Y: a85 (pressure)
MSG: TOUCH: SEQ: 0b X: 6d7 Y: 403
MSG: TOUCH: SEQ: 0b X: 25d Y: abb (pressure)
MSG: TOUCH: pen lift
ACK
Notice that the touchscreen sends two messages with the same sequence number for every time it polls the surface. First, it sends the raw x and y. Then it sends the pressure x and y. Note that I have no idea what this pressure is, as two numbers for pressure make no sense to me. Also, sony's own diagnostic test screen has two numbers for pressure which don't make sense either, so maybe they're just irrelevant numbers.
The pen lift message comes just once with its own sequence number.