The TXSCHED setting may be changed at runtime, via sysfs, for devices
using multiple H/W Tx queues. For single queue devices this config
option is disabled, as the TXSCHED setting is superfluous in those cases.
Please, no special driver specific sysfs knobs.
Extend ethtool as necessary for your needs, so that any driver can
provide this kind of configurability in a consistent way for users..