linux-kernel - [PATCH 4.14 01/71] hidraw: Return EPOLLOUT from hidraw

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Date:   Fri, 17 Jan 2020 00:17:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Fabian Henneke <fabian.henneke@...il.com>,
        Jiri Kosina <jkosina@...e.cz>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 01/71] hidraw: Return EPOLLOUT from hidraw_poll

From: Fabian Henneke <fabian.henneke@...il.com>

[ Upstream commit 378b80370aa1fe50f9c48a3ac8af3e416e73b89f ]

Always return EPOLLOUT from hidraw_poll when a device is connected.
This is safe since writes are always possible (but will always block).

hidraw does not support non-blocking writes and instead always calls
blocking backend functions on write requests. Hence, so far, a call to
poll never returned EPOLLOUT, which confuses tools like socat.

Signed-off-by: Fabian Henneke <fabian.henneke@...il.com>
In-reply-to: <CA+hv5qkyis03CgYTWeWX9cr0my-d2Oe+aZo+mjmWRXgjrGqyrw@...l.gmail.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hid/hidraw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 5652bd0ffb4d..1ac82e194818 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -260,7 +260,7 @@ 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;
+		return POLLIN | POLLRDNORM | POLLOUT;
 	if (!list->hidraw->exist)
 		return POLLERR | POLLHUP;
 	return 0;
-- 
2.20.1