linux-kernel - [PATCH 2/8] serdev: fix receive_buf return value when no callback

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Message-Id: <20171103143059.20749-3-johan@kernel.org>
Date:   Fri,  3 Nov 2017 15:30:53 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH 2/8] serdev: fix receive_buf return value when no callback

The receive_buf callback is supposed to return the number of bytes
processed and should specifically not return a negative errno.

Due to missing sanity checks in the serdev tty-port controller, a driver
not providing a receive_buf callback could cause the flush_to_ldisc()
worker to spin in a tight loop when the tty buffer pointers are
incremented with -EINVAL (-22).

The missing sanity checks have now been added to the tty-port
controller, but let's fix up the serdev-controller helper as well.

Signed-off-by: Johan Hovold <johan@...nel.org>
---
 include/linux/serdev.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index e69402d4a8ae..d609e6dc5bad 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -184,7 +184,7 @@ static inline int serdev_controller_receive_buf(struct serdev_controller *ctrl,
 	struct serdev_device *serdev = ctrl->serdev;

 	if (!serdev || !serdev->ops->receive_buf)
-		return -EINVAL;
+		return 0;

 	return serdev->ops->receive_buf(serdev, data, count);
 }
-- 
2.15.0