diff options
| author | David Woodhouse <David.Woodhouse@intel.com> | 2010-10-30 12:35:11 +0100 |
|---|---|---|
| committer | David Woodhouse <David.Woodhouse@intel.com> | 2010-10-30 12:35:11 +0100 |
| commit | 67577927e8d7a1f4b09b4992df640eadc6aacb36 (patch) | |
| tree | 2e9efe6b5745965faf0dcc084d4613d9356263f9 /Documentation/networking/timestamping.txt | |
| parent | 6fe4c590313133ebd5dadb769031489ff178ece1 (diff) | |
| parent | 51f00a471ce8f359627dd99aeac322947a0e491b (diff) | |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
Conflicts:
drivers/mtd/mtd_blkdevs.c
Merge Grant's device-tree bits so that we can apply the subsequent fixes.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'Documentation/networking/timestamping.txt')
| -rw-r--r-- | Documentation/networking/timestamping.txt | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index e8c8f4f06c6..98097d8cb91 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -172,15 +172,19 @@ struct skb_shared_hwtstamps { }; Time stamps for outgoing packets are to be generated as follows: -- In hard_start_xmit(), check if skb_tx(skb)->hardware is set no-zero. - If yes, then the driver is expected to do hardware time stamping. +- In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) + is set no-zero. If yes, then the driver is expected to do hardware time + stamping. - If this is possible for the skb and requested, then declare - that the driver is doing the time stamping by setting the field - skb_tx(skb)->in_progress non-zero. You might want to keep a pointer - to the associated skb for the next step 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. + that the driver is doing the time stamping by setting the flag + SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with + + skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS; + + You might want to keep a pointer to the associated skb for the next step + 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. - 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 @@ -191,6 +195,6 @@ 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 call set skb_tx(skb)->in_progress, then +- 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. |