netdev - Re: [PATCH net 2/5] renesas: reject PTP_STRICT

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Message-ID: <20250318135947.GR688833@kernel.org>
Date: Tue, 18 Mar 2025 13:59:47 +0000
From: Simon Horman <horms@...nel.org>
To: Jacob Keller <jacob.e.keller@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Ruud Bos <kernel.hbk@...il.com>,
	Paul Barker <paul.barker.ct@...renesas.com>,
	Niklas Söderlund <niklas.soderlund@...natech.se>,
	Bryan Whitehead <bryan.whitehead@...rochip.com>,
	UNGLinuxDriver@...rochip.com,
	Raju Lakkaraju <Raju.Lakkaraju@...rochip.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Jonathan Lemon <jonathan.lemon@...il.com>,
	Lasse Johnsen <l@...johnsen.me>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Subject: Re: [PATCH net 2/5] renesas: reject PTP_STRICT_FLAGS as unsupported

+ Shimoda-san

On Mon, Mar 10, 2025 at 03:16:37PM -0700, Jacob Keller wrote:
> The ravb_ptp_extts() function checks the flags coming from the
> PTP_EXTTS_REQUEST ioctl, to ensure that future flags are not accepted on
> accident.
> 
> This was updated to 'honor' the PTP_STRICT_FLAGS in commit 6138e687c7b6
> ("ptp: Introduce strict checking of external time stamp options.").
> However, the driver does not *actually* validate the flags.
> 
> I originally fixed this driver to reject future flags in commit
> 592025a03b34 ("renesas: reject unsupported external timestamp flags"). It
> is still unclear whether this hardware timestamps the rising, falling, or
> both edges of the input signal.
> 
> Accepting requests with PTP_STRICT_FLAGS is a bug, as this could lead to
> users mistakenly assuming a request with PTP_RISING_EDGE actually
> timestamps the rising edge only.
> 
> Reject requests with PTP_STRICT_FLAGS (and hence all PTP_EXTTS_REQUEST2
> requests) until someone with access to the datasheet or hardware knowledge
> can confirm the timestamping behavior and update this driver.
> 
> Fixes: 6138e687c7b6 ("ptp: Introduce strict checking of external time stamp options.")
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>

Adding Shimoda-san who may be able to help coordinate a review if
Niklas and Paul are unavailable for some reason.

> ---
>  drivers/net/ethernet/renesas/ravb_ptp.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
> index 6e4ef7af27bf31ab2aad8e06a65e0ede6046e3c0..b4365906669f3bd40953813e263aeaafd2e1eb70 100644
> --- a/drivers/net/ethernet/renesas/ravb_ptp.c
> +++ b/drivers/net/ethernet/renesas/ravb_ptp.c
> @@ -179,8 +179,7 @@ static int ravb_ptp_extts(struct ptp_clock_info *ptp,
>  	/* Reject requests with unsupported flags */
>  	if (req->flags & ~(PTP_ENABLE_FEATURE |
>  			   PTP_RISING_EDGE |
> -			   PTP_FALLING_EDGE |
> -			   PTP_STRICT_FLAGS))
> +			   PTP_FALLING_EDGE))
>  		return -EOPNOTSUPP;
>  
>  	if (req->index)
> 
> -- 
> 2.48.1.397.gec9d649cc640
> 
>