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 <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/staging/speakup/spk_types.h b/drivers/staging/speakup/spk_types.h
index c156975392c8..ad7b9480a37f 100644
--- a/drivers/staging/speakup/spk_types.h
+++ b/drivers/staging/speakup/spk_types.h
@@ -152,6 +152,8 @@ struct spk_io_ops {
 	int (*synth_out)(struct spk_synth *synth, const char ch);
 	void (*send_xchar)(char ch);
 	void (*tiocmset)(unsigned int set, unsigned int clear);
+	unsigned char (*synth_in)(void);
+	unsigned char (*synth_in_nowait)(void);
 };
 
 struct spk_synth {
@@ -182,7 +184,7 @@ struct spk_synth {
 	int (*is_alive)(struct spk_synth *synth);
 	int (*synth_adjust)(struct st_var_header *var);
 	void (*read_buff_add)(u_char);
-	unsigned char (*get_index)(void);
+	unsigned char (*get_index)(struct spk_synth *synth);
 	struct synth_indexing indexing;
 	int alive;
 	struct attribute_group attributes;