net: ptp: introduce .supported_perout_flags to ptp_clock_info

The PTP_PEROUT_REQUEST2 ioctl has gained support for flags specifying
specific output behavior including PTP_PEROUT_ONE_SHOT,
PTP_PEROUT_DUTY_CYCLE, PTP_PEROUT_PHASE.

Driver authors are notorious for not checking the flags of the request.
This results in misinterpreting the request, generating an output signal
that does not match the requested value. It is anticipated that even more
flags will be added in the future, resulting in even more broken requests.

Expecting these issues to be caught during review or playing whack-a-mole
after the fact is not a great solution.

Instead, introduce the supported_perout_flags field in the ptp_clock_info
structure. Update the core character device logic to explicitly reject any
request which has a flag not on this list.

This ensures that drivers must 'opt in' to the flags they support. Drivers
which don't set the .supported_perout_flags field will not need to check
that unsupported flags aren't passed, as the core takes care of this.

Update the drivers which do support flags to set this new field.

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

 • drivers/ptp/ptp_clockmatrix.c
 • drivers/ptp/ptp_idt82p33.c
 • drivers/ptp/ptp_fc3.c
 • drivers/net/ethernet/ti/am65-cpts.c
 • drivers/net/ethernet/aquantia/atlantic/aq_ptp.c
 • drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
 • drivers/net/dsa/sja1105/sja1105_ptp.c
 • drivers/net/ethernet/freescale/dpaa2/dpaa2-ptp.c
 • drivers/net/ethernet/mscc/ocelot_vsc7514.c
 • drivers/net/ethernet/intel/i40e/i40e_ptp.c

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
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-v2-2-f6b17d15475c@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 25cba2e5ee69..eced7e9bf69a 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -69,6 +69,11 @@ struct ptp_system_timestamp {
  * @n_pins:    The number of programmable pins.
  * @pps:       Indicates whether the clock supports a PPS callback.
  *
+ * @supported_perout_flags:  The set of flags the driver supports for the
+ *                           PTP_PEROUT_REQUEST ioctl. The PTP core will
+ *                           reject a request with any flag not specified
+ *                           here.
+ *
  * @supported_extts_flags:  The set of flags the driver supports for the
  *                          PTP_EXTTS_REQUEST ioctl. The PTP core will use
  *                          this list to reject unsupported requests.
@@ -185,6 +190,7 @@ struct ptp_clock_info {
 	int n_per_out;
 	int n_pins;
 	int pps;
+	unsigned int supported_perout_flags;
 	unsigned int supported_extts_flags;
 	struct ptp_pin_desc *pin_config;
 	int (*adjfine)(struct ptp_clock_info *ptp, long scaled_ppm);