[bug report] rpmsg: Handle invalid parameters in public API

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Bjorn Andersson,

The patch 93e9324431c9: "rpmsg: Handle invalid parameters in public
API" from Oct 18, 2016, leads to the following static checker warning:

	drivers/rpmsg/rpmsg_core.c:421 rpmsg_dev_probe()
	error: 'ept' dereferencing possible ERR_PTR()

drivers/rpmsg/rpmsg_core.c
    60   * Drivers should provide their @rpdev channel (so the new endpoint would belong
    61   * to the same remote processor their channel belongs to), an rx callback
    62   * function, an optional private data (which is provided back when the
    63   * rx callback is invoked), and an address they want to bind with the
    64   * callback. If @addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
    65   * dynamically assign them an available rpmsg address (drivers should have
    66   * a very good reason why not to always use RPMSG_ADDR_ANY here).
    67   *
    68   * Returns a pointer to the endpoint on success, or NULL on error.
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    69   */
    70  struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_device *rpdev,
    71                                          rpmsg_rx_cb_t cb, void *priv,
    72                                          struct rpmsg_channel_info chinfo)
    73  {
    74          if (WARN_ON(!rpdev))
    75                  return ERR_PTR(-EINVAL);

The callers aren't expecting error pointers.  I could filter out this
one because Smatch knows it's impossible for that caller because rpdev
isn't NULL, but I feel like this should really return NULL.

    76  
    77          return rpdev->ops->create_ept(rpdev, cb, priv, chinfo);
    78  }

regards,
dan carpenter