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| author | Oliver Hartkopp <socketcan@hartkopp.net> | 2010-08-17 08:59:14 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-08-19 00:08:30 -0700 |
| commit | 2244d07bfa2097cb00600da91c715a8aa547917e (patch) | |
| tree | 44d67d9ffba3697fffeb05c13e88aa76ebc3fd4a /Documentation/networking/timestamping.txt | |
| parent | 4d5870ec103e6569851b9710f0093f072b08439a (diff) | |
| download | linux-2244d07bfa2097cb00600da91c715a8aa547917e.tar.gz linux-2244d07bfa2097cb00600da91c715a8aa547917e.tar.bz2 linux-2244d07bfa2097cb00600da91c715a8aa547917e.zip | |
net: simplify flags for tx timestamping
This patch removes the abstraction introduced by the union skb_shared_tx in
the shared skb data.
The access of the different union elements at several places led to some
confusion about accessing the shared tx_flags e.g. in skb_orphan_try().
http://marc.info/?l=linux-netdev&m=128084897415886&w=2
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 e8c8f4f06c67..98097d8cb910 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. |