linux-kernel - [patch] staging: speakup: check for null before calling TTY's flush

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Date:   Wed, 31 May 2017 20:50:12 +0100
From:   Okash Khawaja <okash.khawaja@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Samuel Thibault <samuel.thibault@...-lyon.org>,
        linux-kernel@...r.kernel.org
Cc:     William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org
Subject: [patch] staging: speakup: check for null before calling TTY's
 flush_buffer

We should check the flush_buffer method of a tty for null before
invoking it. Some drivers such as usbserial don't implement
flush_buffer. This will be required for upcoming patches where we expand
spk_ttyio to support more than just ttyS*.

Signed-off-by: Okash Khawaja <okash.khawaja@...il.com>
Reviewed-by: Samuel Thibault <samuel.thibault@...-lyon.org>

---
 drivers/staging/speakup/spk_ttyio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -227,7 +227,8 @@ static unsigned char spk_ttyio_in_nowait
 
 static void spk_ttyio_flush_buffer(void)
 {
-	speakup_tty->ops->flush_buffer(speakup_tty);
+	if (speakup_tty->ops->flush_buffer)
+		speakup_tty->ops->flush_buffer(speakup_tty);
 }
 
 int spk_ttyio_synth_probe(struct spk_synth *synth)