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-rw-r--r--Documentation/networking/timestamping.txt9
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 98097d8..661d3c3 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
@@ -85,7 +85,7 @@ Filled in if SOF_TIMESTAMPING_SYS_HARDWARE is set. Requires support
by the network device and will be empty without that support.
-SIOCSHWTSTAMP:
+SIOCSHWTSTAMP, SIOCGHWTSTAMP:
Hardware time stamping must also be initialized for each device driver
that is expected to do hardware time stamping. The parameter is defined in
@@ -115,6 +115,10 @@ Only a processes with admin rights may change the configuration. User
space is responsible to ensure that multiple processes don't interfere
with each other and that the settings are reset.
+Any process can read the actual configuration by passing this
+structure to ioctl(SIOCGHWTSTAMP) in the same way. However, this has
+not been implemented in all drivers.
+
/* possible values for hwtstamp_config->tx_type */
enum {
/*
@@ -157,7 +161,8 @@ DEVICE IMPLEMENTATION
A driver which supports hardware time stamping must support the
SIOCSHWTSTAMP ioctl and update the supplied struct hwtstamp_config with
-the actual values as described in the section on SIOCSHWTSTAMP.
+the actual values as described in the section on SIOCSHWTSTAMP. It
+should also support SIOCGHWTSTAMP.
Time stamps for received packets must be stored in the skb. To get a pointer
to the shared time stamp structure of the skb call skb_hwtstamps(). Then
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