USBNET: centralize computing of max rx/tx qlen

This patch centralizes computing of max rx/tx qlen, because:

- RX_QLEN()/TX_QLEN() is called in hot path
- computing depends on device's usb speed, now we have ls/fs, hs, ss,
so more checks need to be involved
- in fact, max rx/tx qlen should not only depend on device USB
speed, but also depend on ethernet link speed, so we need to
consider that in future.
- if SG support is done, max tx qlen may need change too

Generally, hard_mtu and rx_urb_size are changed in bind(), reset()
and link_reset() callback, and change mtu network operation, this
patches introduces the API of usbnet_update_max_qlen(), and calls
it in above path.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index ad5d1e4384d..b96ad4f15b8 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -778,6 +778,9 @@ static int ax88178_change_mtu(struct net_device *net, int new_mtu)
 	dev->hard_mtu = net->mtu + net->hard_header_len;
 	ax88178_set_mfb(dev);
 
+	/* max qlen depend on hard_mtu and rx_urb_size */
+	usbnet_update_max_qlen(dev);
+
 	return 0;
 }