Re: [PATCH net] net: ethernet: ti: am65-cpts: fix support for PTP_EXTTS_REQUEST2 ioctl

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- [Medium] Adding PTP_STRICT_FLAGS to am65_ptp_info.supported_extts_flags
  in drivers/net/ethernet/ti/am65-cpts.c also changes the legacy…

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net: ethernet: ti: am65-cpts: fix support for PTP_EXTTS_REQUEST2 ioctl

This patch sets .supported_extts_flags for am65-cpts to
PTP_RISING_EDGE | PTP_STRICT_FLAGS. The PTP core then stops rejecting every
PTP_EXTTS_REQUEST2 for this driver. After the change, PTP_EXTTS_REQUEST2
succeeds for the rising edge and fails with -EOPNOTSUPP for the falling
edge or for both edges.

> diff --git a/drivers/net/ethernet/ti/am65-cpts.c b/drivers/net/ethernet/ti/am65-cpts.c
> index efbf2ef976a3..df5659ead72f 100644
> --- a/drivers/net/ethernet/ti/am65-cpts.c
> +++ b/drivers/net/ethernet/ti/am65-cpts.c
> @@ -779,6 +779,7 @@ static long am65_cpts_ts_work(struct ptp_clock_info *ptp);
>  static struct ptp_clock_info am65_ptp_info = {
>  	.owner		= THIS_MODULE,
>  	.name		= "CTPS timer",
> +	.supported_extts_flags = PTP_RISING_EDGE | PTP_STRICT_FLAGS,

[Severity: Medium]
Does this also change what the legacy PTP_EXTTS_REQUEST ioctl accepts?

In ptp_extts_request(), the v1 branch keeps the edge bits and never sets
PTP_STRICT_FLAGS. Whether the edge bits count only as hints depends just on
the driver's mask:

drivers/ptp/ptp_chardev.c:ptp_extts_request() {
    ...
	} else {
		req.extts.flags &= PTP_EXTTS_V1_VALID_FLAGS;
		memset(req.extts.rsv, 0, sizeof(req.extts.rsv));
	}
    ...
	if (!(supported_extts_flags & PTP_STRICT_FLAGS))
		supported_extts_flags |= PTP_EXTTS_EDGES;
	/* Reject unsupported flags */
	if (req.extts.flags & ~supported_extts_flags)
		return -EOPNOTSUPP;
    ...
}

Before this patch, supported_extts_flags was 0 for am65-cpts. A v1 request
with PTP_ENABLE_FEATURE | PTP_FALLING_EDGE, or with both edges set, was
accepted and reached am65_cpts_extts_enable(), which ignores the flags.

Now the mask has PTP_STRICT_FLAGS but not PTP_FALLING_EDGE, so those same
v1 requests return -EOPNOTSUPP before ops->enable() is ever called.

The same check runs when PTP_ENABLE_FEATURE is clear. Through either ioctl,
a disable request that still carries PTP_FALLING_EDGE is now rejected.

One in-tree example is tools/testing/selftests/ptp/testptp.c run with
-e N -E 2 or -E 3. That sends a legacy request with PTP_FALLING_EDGE set:

			extts_request.flags = PTP_ENABLE_FEATURE | edge;
			if (ioctl(fd, PTP_EXTTS_REQUEST, &extts_request)) {
				perror("PTP_EXTTS_REQUEST");

On am65-cpts this worked before the patch. It now fails with
"PTP_EXTTS_REQUEST: Operation not supported".

Rejecting falling edge requests that the hardware can't honour matches how
the core treats other strict, rising-only drivers. However, the commit
message says:

    Only the PTP_EXTTS_REQUEST ioctl still works.

This suggests v1 behaviour does not change. The patch has a Fixes: tag and
is likely to go to stable. Could the commit message say that v1 requests
carrying PTP_FALLING_EDGE are now rejected as well?

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261020003525.1237742-1-jjc%40jclark.com