[PATCH v2 net-next] doc: update driver TX algorithm in timestamping.txt
From: Jakub Kicinski <hidden>
Date: 2014-03-16 19:32:48
Subsystem:
documentation, networking [general], the rest · Maintainers:
Jonathan Corbet, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Since cd4d8fdad1f1 ("net: kernel panic in dev_hard_start_xmit:
remove faulty software TX time stamping") dev_hard_start_xmit()
will not provide software timestamps. It's a responsibility of
the drivers to call skb_tx_timestamp() at the right time.
Cc: linux-doc@vger.kernel.org
Signed-off-by: Jakub Kicinski <redacted>
---
v1 -> v2: fix commit message, thanks Sergei!
---
Documentation/networking/timestamping.txt | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 661d3c3..e0f259c 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt@@ -190,6 +190,9 @@ Time stamps for outgoing packets are to be generated as follows: and not free the skb. A driver not supporting hardware time stamping doesn't do that. A driver must never touch sk_buff::tstamp! It is used to store software generated time stamps by the network subsystem. +- Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware + as possible. skb_tx_timestamp() provides a software time stamp if requested + and hardware timestamping is not possible (SKBTX_IN_PROGRESS not set). - As soon as the driver has sent the packet and/or obtained a hardware time stamp for it, it passes the time stamp back by calling skb_hwtstamp_tx() with the original skb, the raw
@@ -200,6 +203,3 @@ Time stamps for outgoing packets are to be generated as follows: this would occur at a later time in the processing pipeline than other software time stamping and therefore could lead to unexpected deltas between time stamps. -- If the driver did not set the SKBTX_IN_PROGRESS flag (see above), then - dev_hard_start_xmit() checks whether software time stamping - is wanted as fallback and potentially generates the time stamp.
--
1.8.5.3