to the screen on which they are being called. The driver cannot guess
this by itself but it is needed to implement, at least, the getwschar and
putwschar functions in the correct place. There are no functional changes
yet.
Tested on i386 (vga, vga_raster, machfb, vesafb), macppc and sparc64.
Suggested and reviewed by macallan@.
The HD44780 actually doesn't support 4 lines, but the 4 line displays
use two chips, one for the top two lines and one for the bottom
two lines. The chips share the databus, register-select, and write
signals but have separate enable signals.
o add sc_writereg and sc_readreg functions that get passed the hd44780_chip
struct and RS (register-select) signal
o add sc_dev to struct hd44780_chip so upper level read/write routines can get
back to their parent softc
o change TIMEOUT_XXX to HD_TIMEOUT_XXX
o remove sc_rread and sc_rwrite in favor of new sc_writereg and sc_readreg
o add new flag HD_UP to sc_flags that is set once 4bit/8bit mode selection
has been finalized.
o remove sc_irwrite, MD readreg/writereg should check state of HD_UP instead
