Merge branch 'net-ptp-driver-opt-in-for-supported-ptp-ioctl-flags'

Jacob Keller says:

====================
net: ptp: driver opt-in for supported PTP ioctl flags

Both the PTP_EXTTS_REQUEST(2) and PTP_PEROUT_REQUEST(2) ioctls take flags
from userspace to modify their behavior. Drivers are supposed to check
these flags, rejecting requests for flags they do not support.

Many drivers today do not check these flags, despite many attempts to
squash individual drivers as these mistakes are discovered. Additionally,
any new flags added can require updating every driver if their validation
checks are poorly implemented.

It is clear that driver authors will not reliably check for unsupported
flags. The root of the issue is that drivers must essentially opt out of
every flag, rather than opt in to the ones they support.

Instead, lets introduce .supported_perout_flags and .supported_extts_flags
to the ptp_clock_info structure. This is a pattern taken from several
ethtool ioctls which enabled validation to move out of the drivers and into
the shared ioctl handlers. This pattern has worked quite well and makes it
much more difficult for drivers to accidentally accept flags they do not
support.

With this approach, drivers which do not set the supported fields will have
the core automatically reject any request which has flags. Drivers must opt
in to each flag they support by adding it to the list, with the sole
exception being the PTP_ENABLE_FEATURE flag of the PTP_EXTTS_REQUEST ioctl
since it is entirely handled by the ptp_chardev.c file.

This change will ensure that all current and future drivers are safe for
extension when we need to extend these ioctls.

I opted to keep all the driver changes into one patch per ioctl type. The
changes are relatively small and straight forward. Splitting it per-driver
would make the series large, and also break flags between the introduction
of the supported field and setting it in each driver.

The non-Intel drivers are compile-tested only, and I would appreciate
confirmation and testing from their respective maintainers. (It is also
likely that I missed some of the driver authors especially for drivers
which didn't make any checks at all and do not set either of the supported
flags yet)

v1: https://lore.kernel.org/20250408-jk-supported-perout-flags-v1-0-d2f8e3df64f3@intel.com
====================

Link: https://patch.msgid.link/20250414-jk-supported-perout-flags-v2-0-f6b17d15475c@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 0d68d09bedd1..eced7e9bf69a 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -68,6 +68,22 @@ struct ptp_system_timestamp {
  * @n_per_out: The number of programmable periodic signals.
  * @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.
+ *                          PTP_ENABLE_FEATURE is assumed and does not need to
+ *                          be included. If PTP_STRICT_FLAGS is *not* set,
+ *                          then both PTP_RISING_EDGE and PTP_FALLING_EDGE
+ *                          will be assumed. Note that PTP_STRICT_FLAGS must
+ *                          be set if the drivers wants to honor
+ *                          PTP_EXTTS_REQUEST2 and any future flags.
+ *
  * @pin_config: Array of length 'n_pins'. If the number of
  *              programmable pins is nonzero, then drivers must
  *              allocate and initialize this array.
@@ -174,6 +190,8 @@ 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);
 	int (*adjphase)(struct ptp_clock_info *ptp, s32 phase);