diff options
| author | Jakub Kicinski <kubakici@wp.pl> | 2014-03-16 20:32:48 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-03-18 15:16:48 -0400 |
| commit | 59cb89e6b763443c6360f634288c57668efeecc5 (patch) | |
| tree | b5843736143abae447d36597bd7b07046039d105 /Documentation/networking/timestamping.txt | |
| parent | 86a2b9cfccea1fb1fcb16a549ccddfe40be391d1 (diff) | |
| download | linux-59cb89e6b763443c6360f634288c57668efeecc5.tar.bz2 | |
doc: update driver TX algorithm in timestamping.txt
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 <kubakici@wp.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking/timestamping.txt')
| -rw-r--r-- | Documentation/networking/timestamping.txt | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index 048c92b487f6..bc3554124903 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -202,6 +202,9 @@ 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 @@ -212,6 +215,3 @@ 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. |