diff options
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: | |||
202 | and not free the skb. A driver not supporting hardware time stamping doesn't | 202 | and not free the skb. A driver not supporting hardware time stamping doesn't |
203 | do that. A driver must never touch sk_buff::tstamp! It is used to store | 203 | do that. A driver must never touch sk_buff::tstamp! It is used to store |
204 | software generated time stamps by the network subsystem. | 204 | software generated time stamps by the network subsystem. |
205 | - Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware | ||
206 | as possible. skb_tx_timestamp() provides a software time stamp if requested | ||
207 | and hardware timestamping is not possible (SKBTX_IN_PROGRESS not set). | ||
205 | - As soon as the driver has sent the packet and/or obtained a | 208 | - As soon as the driver has sent the packet and/or obtained a |
206 | hardware time stamp for it, it passes the time stamp back by | 209 | hardware time stamp for it, it passes the time stamp back by |
207 | calling skb_hwtstamp_tx() with the original skb, the raw | 210 | 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: | |||
212 | this would occur at a later time in the processing pipeline than other | 215 | this would occur at a later time in the processing pipeline than other |
213 | software time stamping and therefore could lead to unexpected deltas | 216 | software time stamping and therefore could lead to unexpected deltas |
214 | between time stamps. | 217 | between time stamps. |
215 | - If the driver did not set the SKBTX_IN_PROGRESS flag (see above), then | ||
216 | dev_hard_start_xmit() checks whether software time stamping | ||
217 | is wanted as fallback and potentially generates the time stamp. | ||