Hi,
I have question regarding ethtool_ops.set_coalesce parameters.
>From one side, documentation (include/uapi/linux/ethtool.h) states:
* Each pair of (usecs, max_frames) fields specifies that interrupts
* should be coalesced until
* (usecs > 0 && time_since_first_completion >= usecs) ||
* (max_frames > 0 && completed_frames >= max_frames)
*
* It is illegal to set both usecs and max_frames to zero as this
* would cause interrupts to never be generated. To disable
* coalescing, set usecs = 0 and max_frames = 1.
So, it suggests:
Drivers for hardware that does not support
counting completions should validate that max_frames == !rx_usecs.
Thus, I can conclude I should verify this for every pair.
Then, same documentation states following must not be 0:
- stats_block_coalesce_usecs
- rate_sample_interval
But, I see drivers either ignore unsupported values, or check that all of it are 0,
see for example in drivers/net/ethernet/amd/xgbe/xgbe-ethtool.c:
/* Check for not supported parameters */
if ((ec->rx_coalesce_usecs_irq) ||
(ec->rx_max_coalesced_frames_irq) ||
(ec->tx_coalesce_usecs_irq) ||
(ec->tx_max_coalesced_frames_irq) ||
(ec->stats_block_coalesce_usecs) ||
(ec->use_adaptive_rx_coalesce) ||
(ec->use_adaptive_tx_coalesce) ||
(ec->pkt_rate_low) ||
(ec->rx_coalesce_usecs_low) ||
(ec->rx_max_coalesced_frames_low) ||
(ec->tx_coalesce_usecs_low) ||
(ec->tx_max_coalesced_frames_low) ||
(ec->pkt_rate_high) ||
(ec->rx_coalesce_usecs_high) ||
(ec->rx_max_coalesced_frames_high) ||
(ec->tx_coalesce_usecs_high) ||
(ec->tx_max_coalesced_frames_high) ||
(ec->rate_sample_interval))
return -EOPNOTSUPP;
Bottom line, my question is: what is the right way to handle parameters in
ethtool_ops.set_coalesce?
Thanks, Vladimir