linux-kernel - [PATCH v1 4/6] vt/vt: Add SRG mouse reporting protocol

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Date:   Tue, 30 Jun 2020 09:11:28 +0200
From:   Tammo Block <tammo.block@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Subject: [PATCH v1 4/6] vt/vt: Add SRG mouse reporting protocol

The SRG protocol indicates a button release by appending a "m" to the
report. In this case the button number is not 3 ("release state") but
the number of the button that was released. As release event are only
reported for the first three buttons, 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.

Bitmasks for your convenience:
195 - All bits related to any button number
227 - All bits related to button number and "state not changed" bit
252 - All, except low button numbers (left, middle, right button)

Signed-off-by: Tammo Block <tammo.block@...il.com>
---
 drivers/tty/vt/vt.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index e2324d8e4e74..36520f7f0315 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -183,6 +183,9 @@ core_param(consoleblank, blankinterval, int, 0444);
 static DECLARE_WORK(console_work, console_callback);
 static DECLARE_WORK(con_driver_unregister_work, con_driver_unregister_callback);
 
+/* remember mouse state */
+unsigned char last_button_pressed = 3;
+
 /*
  * fg_console is the current virtual console,
  * last_console is the last used one,
@@ -1840,11 +1843,21 @@ static inline void respond_ID(struct tty_struct *tty)
 
 void mouse_report(struct tty_struct *tty, int butt, int mrx, int mry)
 {
-	char buf[8];
+	char buf[20];
+	bool rel;
 	int len;
 
-	len = sprintf(buf, "\033[M%c%c%c", (char)(' ' + butt),
-			(char)('!' + mrx), (char)('!' + mry));
+	if (vc_cons[fg_console].d->vc_protocol_mouse == 1) {	/* SRG*/
+		/* For SRG release events, we send the last clicked button < 3 */
+		rel = ((butt & 195) == 3);
+		if ((butt & 195) < 3)
+			last_button_pressed = butt & 3;
+		if ((butt & 227) == 3)
+			butt = (butt & 252) | last_button_pressed;
+		len = sprintf(buf, "\033[<%d;%d;%d%c", butt, mrx + 1, mry + 1, rel ? 'm' : 'M');
+	} else							/* X10 */
+		len = sprintf(buf, "\033[M%c%c%c", (char)(' ' + butt),
+				(char)('!' + mrx), (char)('!' + mry));
 	respond_string(buf, len, tty->port);
 }
 
-- 
2.27.0