caif: check write operations

write is optional for a tty device. Check that we have a write op rather
than calling NULL.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index 3502f607117f..c669ec37483b 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -312,6 +312,10 @@ static int ldisc_open(struct tty_struct *tty)
         char name[64];
         int result;
 
+        /* No write no play */
+        if (tty->ops->write == NULL)
+                return -EOPNOTSUPP;
+
         sprintf(name, "cf%s", tty->name);
         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
         ser = netdev_priv(dev);