On Tue, 25 Apr 2017, Jason Gerecke wrote:

The following Smatch complaint was generated in response to commit
2a6cdbd ("HID: wacom: Introduce new 'touch_input' device"):

    drivers/hid/wacom_wac.c:1586 wacom_tpc_irq()
             error: we previously assumed 'wacom->touch_input' could be null (see line 1577)

The 'touch_input' and 'pen_input' variables point to the 'struct input_dev'
used for relaying touch and pen events to userspace, respectively. If a
device does not have a touch interface or pen interface, the associated
input variable is NULL. The 'wacom_tpc_irq()' function is responsible for
forwarding input reports to a more-specific IRQ handler function. An
unknown report could theoretically be mistaken as e.g. a touch report
on a device which does not have a touch interface. This can be prevented
by only calling the pen/touch functions are called when the pen/touch
pointers are valid.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>

Applied to for-4.12/upstream-fixes branch with these tags:

    Fixes: 2a6cdbd ("HID: wacom: Introduce new 'touch_input' device")
    Signed-off-by: Jason Gerecke [off-list ref]
    Reviewed-by: Ping Cheng [off-list ref]
    Cc: stable@vger.kernel.org

-- 
Jiri Kosina
SUSE Labs