net: ptp: introduce .supported_extts_flags to ptp_clock_info

The PTP_EXTTS_REQUEST(2) ioctl has a flags field which specifies how the
external timestamp request should behave. This includes which edge of the
signal to timestamp, as well as a specialized "offset" mode. It is expected
that more flags will be added in the future.

Driver authors routinely do not check the flags, often accepting requests
with flags which they do not support. Even drivers which do check flags may
not be future-proofed to reject flags not yet defined. Thus, any future
flag additions often require manually updating drivers to reject these
flags.

This approach of hoping we catch flag checks during review, or playing
whack-a-mole after the fact is the wrong approach.

Introduce the "supported_extts_flags" field to the ptp_clock_info
structure. This field defines the set of flags the device actually
supports.

Update the core character device logic to check this field and reject
unsupported requests. Getting this right is somewhat tricky. First, to
avoid unnecessary repetition and make basic functionality work when
.supported_extts_flags is 0, the core always accepts the PTP_ENABLE_FEATURE
flag. This flag is used to set the 'on' parameter to the .enable function
and is thus always 'supported' by all drivers.

For backwards compatibility, the PTP_RISING_EDGE and PTP_FALLING_EDGE flags
are merely "hints" when using the old PTP_EXTTS_REQUEST ioctl, and are not
expected to be enforced. If the user issues PTP_EXTTS_REQUEST2, the
PTP_STRICT_FLAGS flag is added which is supposed to inform the driver to
strictly validate the flags and reject unsupported requests. To handle
this, first check if the driver reports PTP_STRICT_FLAGS support. If it
does not, then always allow the PTP_RISING_EDGE and PTP_FALLING_EDGE flags.
This keeps backwards compatibility with the original PTP_EXTTS_REQUEST
ioctl where these flags are not guaranteed to be honored.

This way, drivers which do not set the supported_extts_flags will continue
to accept requests for the original PTP_EXTTS_REQUEST ioctl. The core will
automatically reject requests with new flags, and correctly reject requests
with PTP_STRICT_FLAGS, where the driver is supposed to strictly validate
the flags.

Update the various drivers, refactoring their validation logic into the
.supported_extts_flags field. For consistency and readability,
PTP_ENABLE_FEATURE is not set in the supported flags list, and
PTP_EXTTS_EDGES is expanded to PTP_RISING_EDGE | PTP_FALLING_EDGE in all
cases.

Note the following driver files set n_ext_ts to a non-zero value but did
not check flags at all:

 • drivers/net/ethernet/freescale/dpaa2/dpaa2-ptp.c
 • drivers/net/ethernet/freescale/enetc/enetc_ptp.c
 • drivers/net/ethernet/intel/i40e/i40e_ptp.c
 • drivers/net/ethernet/marvell/octeontx2/nic/otx2_ptp.c
 • drivers/net/ethernet/renesas/ravb_ptp.c
 • drivers/net/ethernet/renesas/rtsn.c
 • drivers/net/ethernet/renesas/rtsn.h
 • drivers/net/ethernet/ti/am65-cpts.c
 • drivers/net/ethernet/ti/cpts.h
 • drivers/net/ethernet/ti/icssg/icss_iep.c
 • drivers/net/ethernet/xscale/ptp_ixp46x.c
 • drivers/net/phy/bcm-phy-ptp.c
 • drivers/ptp/ptp_ocp.c
 • drivers/ptp/ptp_pch.c
 • drivers/ptp/ptp_qoriq.c

These drivers behavior does change slightly: they will now reject the
PTP_EXTTS_REQUEST2 ioctl, because they do not strictly validate their
flags. This also makes them no longer incorrectly accept PTP_EXT_OFFSET.

Also note that the renesas ravb driver does not support PTP_STRICT_FLAGS.
We could leave the .supported_extts_flags as 0, but I added the
PTP_RISING_EDGE | PTP_FALLING_EDGE since the driver previously manually
validated these flags. This is equivalent to 0 because the core will allow
these flags regardless unless PTP_STRICT_FLAGS is also set.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20250414-jk-supported-perout-flags-v2-1-f6b17d15475c@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 3 insertions, 7 deletions

diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
index 946edbad4302..0c6c0cc78fac 100644
--- a/drivers/net/ethernet/intel/igc/igc_ptp.c
+++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
@@ -257,13 +257,6 @@ static int igc_ptp_feature_enable_i225(struct ptp_clock_info *ptp,
 
 	switch (rq->type) {
 	case PTP_CLK_REQ_EXTTS:
-		/* Reject requests with unsupported flags */
-		if (rq->extts.flags & ~(PTP_ENABLE_FEATURE |
-					PTP_RISING_EDGE |
-					PTP_FALLING_EDGE |
-					PTP_STRICT_FLAGS))
-			return -EOPNOTSUPP;
-
 		/* Reject requests failing to enable both edges. */
 		if ((rq->extts.flags & PTP_STRICT_FLAGS) &&
 		    (rq->extts.flags & PTP_ENABLE_FEATURE) &&
@@ -1146,6 +1139,9 @@ void igc_ptp_init(struct igc_adapter *adapter)
 		adapter->ptp_caps.pin_config = adapter->sdp_config;
 		adapter->ptp_caps.n_ext_ts = IGC_N_EXTTS;
 		adapter->ptp_caps.n_per_out = IGC_N_PEROUT;
+		adapter->ptp_caps.supported_extts_flags = PTP_RISING_EDGE |
+							  PTP_FALLING_EDGE |
+							  PTP_STRICT_FLAGS;
 		adapter->ptp_caps.n_pins = IGC_N_SDP;
 		adapter->ptp_caps.verify = igc_ptp_verify_pin;