usb: gadget: f_ncm: remove timer_force_tx field

It is simply not needed.  This field is equivalent to skb being NULL.

Currently with the boolean set to true we call:
  ncm->netdev->netdev_ops->ndo_start_xmit(NULL, ncm->netdev);
which calls u_ether's:
  eth_start_xmit(NULL, ...)
which then calls:
  skb = dev->wrap(dev->port_usb, NULL);
which calls back into f_ncm's:
  ncm_wrap_ntb(..., NULL)

Cc: Brooke Basile <brookebasile@gmail.com>
Cc: "Bryan O'Donoghue" <bryan.odonoghue@linaro.org>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20210701114834.884597-1-zenczykowski@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index 8551272..afbe70b 100644 (file)
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -72,7 +72,6 @@ struct f_ncm {
        struct sk_buff                  *skb_tx_data;
        struct sk_buff                  *skb_tx_ndp;
        u16                             ndp_dgram_count;
-       bool                            timer_force_tx;
        struct hrtimer                  task_timer;
        bool                            timer_stopping;
 };
@@ -1126,8 +1125,11 @@ static struct sk_buff *ncm_wrap_ntb(struct gether *port,
                dev_consume_skb_any(skb);
                skb = NULL;
 
-       } else if (ncm->skb_tx_data && ncm->timer_force_tx) {
-               /* If the tx was requested because of a timeout then send */
+       } else if (ncm->skb_tx_data) {
+               /* If we get here ncm_wrap_ntb() was called with NULL skb,
+                * because eth_start_xmit() was called with NULL skb by
+                * ncm_tx_timeout() - hence, this is our signal to flush/send.
+                */
                skb2 = package_for_tx(ncm);
                if (!skb2)
                        goto err;
@@ -1158,8 +1160,6 @@ static enum hrtimer_restart ncm_tx_timeout(struct hrtimer *data)
 
        /* Only send if data is available. */
        if (!ncm->timer_stopping && ncm->skb_tx_data) {
-               ncm->timer_force_tx = true;
-
                /* XXX This allowance of a NULL skb argument to ndo_start_xmit
                 * XXX is not sane.  The gadget layer should be redesigned so
                 * XXX that the dev->wrap() invocations to build SKBs is transparent
@@ -1167,8 +1167,6 @@ static enum hrtimer_restart ncm_tx_timeout(struct hrtimer *data)
                 * XXX interface.
                 */
                ncm->netdev->netdev_ops->ndo_start_xmit(NULL, ncm->netdev);
-
-               ncm->timer_force_tx = false;
        }
        return HRTIMER_NORESTART;
 }