[SRU][Trusty][LTS-Utopic] HID: wacom - make sure touch_input is valid before using it

[Luis Henriques]

From: Ping Cheng <pinglinux at gmail.com>

touch_input is stored in wacom_shared for pen data to report touch
switch status. It is possible, although we didn't see it happen on
Linux yet, that pen data is procesed before touch interface is
fully probed.

As a by-product of this patch, it fixes the FreeBSD issue reported
by Denis Akiyakov http://www.spinics.net/lists/linux-input/msg33971.html

Reviewed-by: Hans Petter Selasky <hps at selasky.org>
Tested-by: Denis Akiyakov <d.akiyakov at gmail.com>
Signed-off-by: Ping Cheng <pingc at wacom.com>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
BugLink: https://bugs.launchpad.net/bugs/1310800
(backported from commit 44b9683853c7b47d039366d7d2fd0d5380aba276)
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/input/tablet/wacom_wac.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/input/tablet/wacom_wac.c b/drivers/input/tablet/wacom_wac.c
index 05f371df6c40..996cf28b0781 100644
--- a/drivers/input/tablet/wacom_wac.c
+++ b/drivers/input/tablet/wacom_wac.c
@@ -1284,7 +1284,9 @@ static int wacom_bpt_pen(struct wacom_wac *wacom)
 	    return 0;
 
 	if (data[0] == WACOM_REPORT_USB) {
-		if (features->type == INTUOSHT && features->touch_max) {
+		if (features->type == INTUOSHT &&
+		    wacom->shared->touch_input &&
+		    features->touch_max) {
 			input_report_switch(wacom->shared->touch_input,
 					    SW_MUTE_DEVICE, data[8] & 0x40);
 			input_sync(wacom->shared->touch_input);
@@ -1377,7 +1379,8 @@ static int wacom_wireless_irq(struct wacom_wac *wacom, size_t len)
 		int pid, battery;
 
 		if ((wacom->shared->type == INTUOSHT) &&
-				wacom->shared->touch_max) {
+		    wacom->shared->touch_input &&
+		    wacom->shared->touch_max) {
 			input_report_switch(wacom->shared->touch_input,
 					SW_MUTE_DEVICE, data[5] & 0x40);
 			input_sync(wacom->shared->touch_input);