HID: hidraw: Fix returning EPOLLOUT from hidraw_poll

BugLink: https://bugs.launchpad.net/bugs/1860681

[ Upstream commit 9f3b61dc ]

When polling a connected /dev/hidrawX device, it is useful to get the
EPOLLOUT when writing is possible. Since writing is possible as soon as
the device is connected, always return it.

Right now EPOLLOUT is only returned when there are also input reports
are available. This works if devices start sending reports when
connected, but some HID devices might need an output report first before
sending any input reports. This change will allow using EPOLLOUT here as
well.

Fixes: 378b8037 ("hidraw: Return EPOLLOUT from hidraw_poll")
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/hid/hidraw.c

@@ -265,10 +265,10 @@ static unsigned int hidraw_poll(struct file *file, poll_table *wait)
 
 	poll_wait(file, &list->hidraw->wait, wait);
 	if (list->head != list->tail)
-		return POLLIN | POLLRDNORM | POLLOUT;
+		return POLLIN | POLLRDNORM;
 	if (!list->hidraw->exist)
 		return POLLERR | POLLHUP;
-	return 0;
+	return POLLOUT | POLLWRNORM;
 }
 
 static int hidraw_open(struct inode *inode, struct file *file)