Why don't you use a I2C expander PCF 8574 from Philips.
It s great solution. You have a port 8 bit so Keyboard can use 16 keys. You can conect expander do uPC by tree wires SDA i SCL and INT1 line. So expander can interrupt main process in uPC and please about read a byte. It's buffered and You can use standard I2C procedures to read keyboard or You have at one function "Keypressed" in a system :) (You don't need pull a port P1). This is little slow, but easy and uPC can make sth different.

Im going to publish a procedure to make my own keyboard on I2C.

Jdsoul.