Re: [PATCH v3 14/14] can: peak_usb: advertise timestamping capabilities and add ioctl support

From: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: linux-can@vger.kernel.org,
	Stephane Grosjean <s.grosjean@peak-system.com>,
	Jimmy Assarsson <extja@kvaser.com>,
	Oliver Hartkopp <socketcan@hartkopp.net>,
	Dario Binacchi <dario.binacchi@amarulasolutions.com>,
	Max Staudt <max@enpas.org>
Subject: Re: [PATCH v3 14/14] can: peak_usb: advertise timestamping capabilities and add ioctl support
Date: Wed, 27 Jul 2022 17:29:25 +0900	[thread overview]
Message-ID: <CAMZ6RqL0sNAFtLiiopeaA2Oyqq15=dhdOnLivTWngPxGyAFHQw@mail.gmail.com> (raw)
In-Reply-To: <20220727080634.l6uttnbrmwbabh3o@pengutronix.de>

On Wed. 27 Jul. 2022 at 17:10, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> On 26.07.2022 19:24:54, Vincent Mailhol wrote:
> > Currently, userland has no method to query which timestamping features
> > are supported by the peak_usb driver (aside maybe of getting RX
> > messages and obseverse whever or not hardware timestamps stay at
> > zero).
> >
> > The canonical way for a network driver to advertise what kind of
> > timestamping it supports is to implement
> > ethtool_ops::get_ts_info(). Here, we use the CAN specific
> > can_ethtool_op_get_ts_info_hwts() function to achieve this.
> >
> > In addition, the driver currently does not support the hardware
> > timestamps ioctls. According to [1], SIOCSHWTSTAMP is "must" and
> > SIOCGHWTSTAMP is "should". This patch fills up that gap by
> > implementing net_device_ops::ndo_eth_ioctl() using the CAN specific
> > function can_eth_ioctl_hwts().
> >
> > [1] kernel doc Timestamping, section 3.1: "Hardware Timestamping
> > Implementation: Device Drivers"
> > Link: https://docs.kernel.org/networking/timestamping.html#hardware-timestamping-implementation-device-drivers
> >
> > CC: Stephane Grosjean <s.grosjean@peak-system.com>
> > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> > ---
> >
> > Hi Stéphane, as far as I understand, the pcan_usb and the pacn_usb_pro
>                                                             ^^^^
>                                                             pcan
>
> > support hardware timestamps but the pcan_usb_fd doesn't. If not the
> > case, let me know.
> >
> > This is not tested. If you find any issue or if you want to modify,
> > feel free to pick up that patch and resend it.
>
> I have a:
>
> | Bus 002 Device 009: ID 0c72:0012 PEAK System PCAN-USB FD
>
> It supports hardware RX timestamps (Debian kernel 5.18.0-2-amd64) only:
>
> |  (1970-01-01 01:00:00.000000)  peakfd0  TX - -  002   [1]  01
> |  (1970-01-01 02:17:09.473817)  peakfd0  RX - -  002   [1]  3C
> |  (1970-01-01 01:00:00.000000)  peakfd0  TX - -  002   [1]  02
> |  (1970-01-01 02:17:09.673980)  peakfd0  RX - -  002   [1]  3D

Thanks for the confirmation. So this means that all Peak hardware
supports the hardware timestamping. This will greatly simplify the
logic. No need to have two different struct ethtool_ops. I will
prepare a v4.

Yours sincerely,
Vincent Mailhol