Hi Andrew,

Thanks for the review. You are right that this is not bonding-specific -
any caller of ndo_set_mac_address() (including netif_set_mac_address()
and "ip link set address") expects 0 on success and treats any non-zero
return value as failure.

I audited all drivers under drivers/net/usb/ that implement a custom
ndo_set_mac_address callback:

  aqc111.c        - BUG: returns usb_control_msg byte count (6) [this patch]
  ax88179_178a.c  - OK: returns 0 after ax_write_cmd()
  asix_common.c   - OK: returns 0 (async write to hardware)
  ch397.c         - OK: returns 0
  dm9601.c        - OK: returns 0 (async write)
  lan78xx.c       - OK: returns 0
  mcs7830.c       - OK: returns 0
  qmi_wwan.c      - OK: returns 0
  r8152.c/r8157.c - OK: returns 0 on success (via usb_autopm_get_interface)
  rtl8150.c       - OK: returns 0
  sr9700.c        - OK: returns 0 (async write)
  sr9800.c        - OK: returns 0 (async write)

Drivers that use eth_mac_addr as ndo_set_mac_address (smsc95xx,
smsc75xx, cdc_ncm, rndis, pegasus, usbnet default, etc.) always
return 0 from the netdev op.

As far as I can tell, aqc111 is the only driver that directly returns
the result of a USB control write without normalizing success to 0.

Please let me know if you would like any further changes to this patch.

Best regards,
Hanson Wang