[PATCH v3 4/6] vt/vt: Add SRG mouse reporting protocol

[Tammo Block <tammo.block@gmail.com>]

The SRG protocol indicates a button release by appending a "m" to the
report. In this case the button number is not 3 (RELEASEEVENT) but
the number of the button that was released. As release events are only
reported for the first three buttons (LOWBUTTON_MASK), we need to store
the number on click events because it is not sent to us from userspace.

We also need to check for the case where no button state change occurred
at all (bit 6 set), in this case a value of 3 is OK even in SRG.

Signed-off-by: Tammo Block <tammo.block@gmail.com>
---
 drivers/tty/vt/vt.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3699e488ef19..766983a848bb 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1838,13 +1838,32 @@ static inline void respond_ID(struct tty_struct *tty)
 	respond_string(vt102_id, strlen(vt102_id), tty->port);
 }
 
+#define ANYBUTTON_MASK	0xc3
+#define LOWBUTTON_MASK	0x03
+#define RELEASEEVENT	0x03
+
 void mouse_report(struct tty_struct *tty, int butt, int mrx, int mry)
 {
-	char buf[8];
+	static char last_btn = RELEASEEVENT;
+	char buf[20];
+	bool rel;
 	int len;
 
-	len = sprintf(buf, "\033[M%c%c%c", (char)(' ' + butt),
-			(char)('!' + mrx), (char)('!' + mry));
+	switch (vc_cons[fg_console].d->vc_protocol_mouse) {
+	case VC_PMOUSE_SRG:
+		rel = (butt & ANYBUTTON_MASK) == RELEASEEVENT;
+		if ((butt & ANYBUTTON_MASK) < RELEASEEVENT)
+			last_btn = butt & LOWBUTTON_MASK;
+		if ((butt & TIOCL_SELBUTTONMASK) == RELEASEEVENT)
+			butt = (butt & ~LOWBUTTON_MASK) | last_btn;
+		len = sprintf(buf, "\033[<%d;%d;%d%c", butt,
+				mrx + 1, mry + 1, rel ? 'm' : 'M');
+		break;
+	default:
+		len = sprintf(buf, "\033[M%c%c%c", (char)(' ' + butt),
+				(char)('!' + mrx), (char)('!' + mry));
+		break;
+	}
 	respond_string(buf, len, tty->port);
 }
 
-- 
2.27.0