From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
To: Marc Kleine-Budde <mkl@pengutronix.de>,
linux-can@vger.kernel.org,
Jeroen Hofstee <jhofstee@victronenergy.com>
Cc: Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
Wolfgang Grandegger <wg@grandegger.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org (open list:NETWORKING DRIVERS),
linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v3 1/1] can: dev: add software tx timestamps
Date: Sun, 10 Jan 2021 21:49:03 +0900 [thread overview]
Message-ID: <20210110124903.109773-2-mailhol.vincent@wanadoo.fr> (raw)
In-Reply-To: <20210110124903.109773-1-mailhol.vincent@wanadoo.fr>
Call skb_tx_timestamp() within can_put_echo_skb() so that a software
tx timestamp gets attached on the skb.
There two main reasons to include this call in can_put_echo_skb():
* It easily allow to enable the tx timestamp on all devices with
just one small change.
* According to Documentation/networking/timestamping.rst, the tx
timestamps should be generated in the device driver as close as
possible, but always prior to passing the packet to the network
interface. During the call to can_put_echo_skb(), the skb gets
cloned meaning that the driver should not dereference the skb
variable anymore after can_put_echo_skb() returns. This makes
can_put_echo_skb() the very last place we can use the skb without
having to access the echo_skb[] array.
Remarks:
* By default, skb_tx_timestamp() does nothing. It needs to be
activated by passing the SOF_TIMESTAMPING_TX_SOFTWARE flag either
through socket options or control messages.
* The hardware rx timestamp of a local loopback message is the
hardware tx timestamp. This means that there are no needs to
implement SOF_TIMESTAMPING_TX_HARDWARE for CAN sockets.
References:
Support for the error queue in CAN RAW sockets (which is needed for tx
timestamps) was introduced in:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eb88531bdbfaafb827192d1fc6c5a3fcc4fadd96
Put the call to skb_tx_timestamp() just before adding it to the array:
https://lkml.org/lkml/2021/1/10/54
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
drivers/net/can/dev.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 3486704c8a95..850759c7677f 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -481,6 +481,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->dev = dev;
+ skb_tx_timestamp(skb);
/* save this skb for tx interrupt echo handling */
priv->echo_skb[idx] = skb;
--
2.26.2
next prev parent reply other threads:[~2021-01-10 12:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-10 12:49 [PATCH v3 0/1] Add software TX timestamps to the CAN devices Vincent Mailhol
2021-01-10 12:49 ` Vincent Mailhol [this message]
2021-01-11 8:10 ` [PATCH v3 1/1] can: dev: add software tx timestamps Marc Kleine-Budde
2021-01-11 17:11 ` Richard Cochran
2021-01-12 0:00 ` Vincent MAILHOL
2021-01-12 2:14 ` Richard Cochran
2021-01-12 6:38 ` Vincent MAILHOL
2021-01-12 7:58 ` Marc Kleine-Budde
2021-01-12 9:58 ` Vincent MAILHOL
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210110124903.109773-2-mailhol.vincent@wanadoo.fr \
--to=mailhol.vincent@wanadoo.fr \
--cc=davem@davemloft.net \
--cc=jhofstee@victronenergy.com \
--cc=kuba@kernel.org \
--cc=linux-can@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mkl@pengutronix.de \
--cc=netdev@vger.kernel.org \
--cc=wg@grandegger.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).