ethtool: Explicitly state the exit condition for interrupt coalescing
Also explicitly state how to disable interrupt coalescing.
Remove the now-redundant text from field descriptions.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 18059ca..42378b3 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -121,20 +121,18 @@
* struct ethtool_coalesce - coalescing parameters for IRQs and stats updates
* @cmd: ETHTOOL_{G,S}COALESCE
* @rx_coalesce_usecs: How many usecs to delay an RX interrupt after
- * a packet arrives. If 0, only @rx_max_coalesced_frames is used.
+ * a packet arrives.
* @rx_max_coalesced_frames: Maximum number of packets to receive
- * before an RX interrupt. If 0, only @rx_coalesce_usecs is used.
+ * before an RX interrupt.
* @rx_coalesce_usecs_irq: Same as @rx_coalesce_usecs, except that
* this value applies while an IRQ is being serviced by the host.
* @rx_max_coalesced_frames_irq: Same as @rx_max_coalesced_frames,
* except that this value applies while an IRQ is being serviced
* by the host.
* @tx_coalesce_usecs: How many usecs to delay a TX interrupt after
- * a packet is sent. If 0, only @tx_max_coalesced_frames
- * is used.
+ * a packet is sent.
* @tx_max_coalesced_frames: Maximum number of packets to be sent
- * before a TX interrupt. If 0, only @tx_coalesce_usecs is
- * used.
+ * before a TX interrupt.
* @tx_coalesce_usecs_irq: Same as @tx_coalesce_usecs, except that
* this value applies while an IRQ is being serviced by the host.
* @tx_max_coalesced_frames_irq: Same as @tx_max_coalesced_frames,
@@ -167,8 +165,13 @@
* @rate_sample_interval: How often to do adaptive coalescing packet rate
* sampling, measured in seconds. Must not be zero.
*
- * It is illegal to set both usecs and max frames to zero as this
- * would cause interrupts to never be generated.
+ * Each pair of (usecs, max_frames) fields specifies this exit
+ * condition for interrupt coalescing:
+ * (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.
*
* Adaptive RX/TX coalescing is an algorithm implemented by some
* drivers to improve latency under low packet rates and improve