[PATCH] can: etas_es58x: do not send disable channel command if device is unplugged

[Vincent Mailhol]

When turning the network interface down, es58x_stop() is called and
will send a command to the ES58x device to disable the channel
c.f. es58x_ops::disable_channel().

However, if the device gets unplugged while the network interface is
still up, es58x_ops::disable_channel() will obviously fail to send the
URB command and the driver emits below error message:

  es58x_submit_urb: USB send urb failure: -ENODEV

Check the usb device state before sending the disable channel command
in order to silence above error message.

Update the documentation of es58x_stop() accordingly.

The check being added in es58x_stop() is:

  	if (es58x_dev->udev->state >= USB_STATE_UNAUTHENTICATED)

This is just the negation of the check done in usb_submit_urb()[1].

[1] usb_submit_urb(), verify usb device's state.
Link: https://elixir.bootlin.com/linux/v6.1/source/drivers/usb/core/urb.c#L384

Fixes: 8537257874e9 ("can: etas_es58x: add core support for ETAS ES58X CAN USB interfaces")
Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
As far as I know, there doesn't seem to be an helper function to check
udev->state values. If anyone is aware of such helper function, let me
know..
---
 drivers/net/can/usb/etas_es58x/es58x_core.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c b/drivers/net/can/usb/etas_es58x/es58x_core.c
index 3e87f4c1547c..916bd9e2e9ea 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_core.c
+++ b/drivers/net/can/usb/etas_es58x/es58x_core.c
@@ -1817,9 +1817,10 @@ static int es58x_open(struct net_device *netdev)
  * es58x_stop() - Disable the network device.
  * @netdev: CAN network device.
  *
- * Called when the network transitions to the down state. If all the
- * channels of the device are closed, free the URB resources which are
- * not needed anymore.
+ * Called when the network interface transitions to the down
+ * state. Send a disable command to the device if it is still
+ * connected. If all the channels of the device are closed, free the
+ * URB resources which are not needed anymore.
  *
  * Return: zero on success, errno when any error occurs.
  */
@@ -1830,9 +1831,12 @@ static int es58x_stop(struct net_device *netdev)
 	int ret;
 
 	netif_stop_queue(netdev);
-	ret = es58x_dev->ops->disable_channel(priv);
-	if (ret)
-		return ret;
+
+	if (es58x_dev->udev->state >= USB_STATE_UNAUTHENTICATED) {
+		ret = es58x_dev->ops->disable_channel(priv);
+		if (ret)
+			return ret;
+	}
 
 	priv->can.state = CAN_STATE_STOPPED;
 	es58x_can_reset_echo_fifo(netdev);
-- 
2.39.1