linux-kernel - [RFC 2/2] input: evdev: Add EVIOC mechanism to extract the MT slot state

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Date:	Thu, 27 Jan 2011 11:35:47 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...c.fr>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Ping Cheng <pingc@...om.com>,
	Benjamin Tissoires <benjamin.tissoires@...c.fr>,
	Jiri Kosina <jkosina@...e.cz>,
	Chris Bagwell <chris@...bagwell.com>,
	Rafi Rubin <rafi@...s.upenn.edu>,
	Stephane Chatty <chatty@...-enac.fr>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC 2/2] input: evdev: Add EVIOC mechanism to extract the MT slot state

This patch adds the ability to extract the MT slot state sequentially
via EVIOCGABS. The slot parameter is first selected by calling
EVIOCSABS with ABS_MT_SLOT as argument, followed by a set of EVIOCGABS
calls. The slot selection is local to the evdev client handler, and
does not affect the actual input state.

Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...c.fr>
---
 drivers/input/evdev.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index c8471a2..a689079 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -23,6 +23,7 @@
 #include <linux/input.h>
 #include <linux/major.h>
 #include <linux/device.h>
+#include <linux/input/mt.h>
 #include "input-compat.h"
 
 struct evdev {
@@ -45,6 +46,7 @@ struct evdev_client {
 	struct fasync_struct *fasync;
 	struct evdev *evdev;
 	struct list_head node;
+	int slot; /* used to extract MT events via EVIOC */
 	int bufsize;
 	struct input_event buffer[];
 };
@@ -741,7 +743,7 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
 				return -EINVAL;
 
 			t = _IOC_NR(cmd) & ABS_MAX;
-			abs = dev->absinfo[t];
+			abs = input_mt_get_absinfo(dev, t, client->slot);
 
 			if (copy_to_user(p, &abs, min_t(size_t,
 					size, sizeof(struct input_absinfo))))
@@ -767,9 +769,10 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
 			if (size < sizeof(struct input_absinfo))
 				abs.resolution = 0;
 
-			/* We can't change number of reserved MT slots */
-			if (t == ABS_MT_SLOT)
-				return -EINVAL;
+			if (t == ABS_MT_SLOT) {
+				client->slot = abs.value;
+				return 0;
+			}
 
 			/*
 			 * Take event lock to ensure that we are not
-- 
1.7.3.4

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