clarify behavior of get_ts_info and hwtstamp ioctl

This patch series attempts to clarify some expected behavior for drivers
when implementing SIOCSHWSTAMP and Ethtool's get_ts_info ioctl.

The SIOCSHWTSTAMP ioctl has several available filters for Rx timestamps
ranging from as specific as HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ_MESSAGE
up to as general as HWTSTAMP_FILTER_ALL. It is expressly allowed for a driver to timestamp more than the requested packets, as long as at least
the requested packets are timestamped. Many drivers do this by upscaling
from the more specific filters into the most generic supported filters.
In this case, some drivers also only report in the Ethtool ioctl those filters which are generic. Since the generic filters are more valuable to users of the Rx timestamps, and it is obvious that HWTSTAMP_FILTER_PTP_V2_EVENT will timestamp SYNC and DELAY_REQ messages,
this patch series clarifies that this behavior is ok. In addition, I provided patches to implement this behavior in get_ts_info for all drivers which currently upscale their hwtstamp ioctl return value.

I did not modify SIOCSHWTSTAMP semantics, and only modified ethtool output. In addition, I left alone drivers which do not actually upscale
their filters. In this way only the filters which are *not* upscaled are
reported in ethtool output.

The intention of this change is to report only the most useful filters to ethtool op output. It should not impact userspace as user applications most often check for the most general filters first and only try the very specific filters as a fallback. I tried to Cc the driver owners where I knew them.

There is also one patch which removes an extraneous comment I discovered while working on this. It was obviously kept around from an original copy-and-modify implementation, and bears no relation to the current driver code in the freescale driver.

Jacob Keller (8):
clarify implementation of ethtool's get_ts_info op [TRIVIAL] freescale: remove incorrect copied comment
bnx2x: only report most generic filters in get_ts_info
i40e: only report generic filters in get_ts_info
igb: only report generic filters in get_ts_info
ixgbe: only report generic filters in get_ts_info
siena: only report generic filters in get_ts_info
dp83640: only report generic filters in ts_info

 Documentation/networking/timestamping.txt           |  7 +++++++
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c | 11 +----------
 drivers/net/ethernet/freescale/fec_ptp.c            |  6 ------
 drivers/net/ethernet/intel/i40e/i40e_ethtool.c      | 13
++-----------
 drivers/net/ethernet/intel/igb/igb_ethtool.c        |  4 ----
 drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c    |  8 --------
 drivers/net/ethernet/sfc/siena.c                    |  6 +-----
 drivers/net/phy/dp83640.c                           | 10 +---------
 include/uapi/linux/ethtool.h                        |  5 +++++
 9 files changed, 17 insertions(+), 53 deletions(-)

Quoted 52 lines · Jacob E

This patch series attempts to clarify some expected behavior for drivers
when implementing SIOCSHWSTAMP and Ethtool's get_ts_info ioctl.

The SIOCSHWTSTAMP ioctl has several available filters for Rx timestamps
ranging from as specific as HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ_MESSAGE
up to as general as HWTSTAMP_FILTER_ALL. It is expressly allowed for a driver to timestamp more than the requested packets, as long as at least
the requested packets are timestamped. Many drivers do this by upscaling
from the more specific filters into the most generic supported filters.
In this case, some drivers also only report in the Ethtool ioctl those filters which are generic. Since the generic filters are more valuable to users of the Rx timestamps, and it is obvious that HWTSTAMP_FILTER_PTP_V2_EVENT will timestamp SYNC and DELAY_REQ messages,
this patch series clarifies that this behavior is ok. In addition, I provided patches to implement this behavior in get_ts_info for all drivers which currently upscale their hwtstamp ioctl return value.

I did not modify SIOCSHWTSTAMP semantics, and only modified ethtool output. In addition, I left alone drivers which do not actually upscale
their filters. In this way only the filters which are *not* upscaled are
reported in ethtool output.

The intention of this change is to report only the most useful filters to ethtool op output. It should not impact userspace as user applications most often check for the most general filters first and only try the very specific filters as a fallback. I tried to Cc the driver owners where I knew them.

There is also one patch which removes an extraneous comment I discovered while working on this. It was obviously kept around from an original copy-and-modify implementation, and bears no relation to the current driver code in the freescale driver.

Jacob Keller (8):
clarify implementation of ethtool's get_ts_info op [TRIVIAL] freescale: remove incorrect copied comment
bnx2x: only report most generic filters in get_ts_info
i40e: only report generic filters in get_ts_info
igb: only report generic filters in get_ts_info
ixgbe: only report generic filters in get_ts_info
siena: only report generic filters in get_ts_info
dp83640: only report generic filters in ts_info

Quoted 11 lines

 Documentation/networking/timestamping.txt           |  7 +++++++
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c | 11 +----------
 drivers/net/ethernet/freescale/fec_ptp.c            |  6 ------
 drivers/net/ethernet/intel/i40e/i40e_ethtool.c      | 13
++-----------
 drivers/net/ethernet/intel/igb/igb_ethtool.c        |  4 ----
 drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c    |  8 --------
 drivers/net/ethernet/sfc/siena.c                    |  6 +-----
 drivers/net/phy/dp83640.c                           | 10 +---------
 include/uapi/linux/ethtool.h                        |  5 +++++
 9 files changed, 17 insertions(+), 53 deletions(-)

I have applied your series to my queue, not sure what validation can be done on the non-Intel driver changes.