+- ``fw_variant`` [dont-care|full-feature|ultra-low-latency|
+ capture-packed-stream|dpdk] (default **dont-care**)
+
+ Choose the preferred firmware variant to use. In order for the selected
+ option to have an effect, the **sfboot** utility must be configured with the
+ **auto** firmware-variant option. The preferred firmware variant applies to
+ all ports on the NIC.
+ **dont-care** ensures that the driver can attach to an unprivileged function.
+ The datapath firmware type to use is controlled by the **sfboot**
+ utility.
+ **full-feature** chooses full featured firmware.
+ **ultra-low-latency** chooses firmware with fewer features but lower latency.
+ **capture-packed-stream** chooses firmware for SolarCapture packed stream
+ mode.
+ **dpdk** chooses DPDK firmware with equal stride super-buffer Rx mode
+ for higher Rx packet rate and packet marks support and firmware subvariant
+ without checksumming on transmit for higher Tx packet rate if
+ checksumming is not required.
+
+- ``rxd_wait_timeout_ns`` [long] (default **200 us**)
+
+ Adjust timeout in nanoseconds to head-of-line block to wait for
+ Rx descriptors.
+ The accepted range is 0 to 400 ms.
+ Flow control should be enabled to make it work.
+ The value of **0** disables it and packets are dropped immediately.
+ When a packet is dropped because of no Rx descriptors,
+ ``rx_nodesc_drop_cnt`` counter grows.
+ The feature is supported only by the DPDK firmware variant when equal
+ stride super-buffer Rx mode is used.
+