staging: speakup: make input functionality swappable

This moves functions which take input from external synth, into struct
spk_io_ops. The calling code then uses serial implementation of those methods
through spk_io_ops. That way we can add a parallel TTY-based implementation and
simply replace serial with TTY. That is what the next patch in this series does.

speakup_decext.c has get_last_char function which reads the most recent
available character from the synth. This patch changes that by defining
read_buff_add callback method of spk_syth and letting that update the last_char
global character read from the synth. read_buff_add is called from ISR, so
there is a possibility for last_char to be stale. Therefore it is marked as
volatile. It also pulls a repeated get_index implementation into synth.c, to
be used as a utility function.

Signed-off-by: Okash Khawaja <[email protected]>
Reviewed-by: Samuel Thibault <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions