netdev - Re: [PATCH v7 4/7] can: Add Nuvoton NCT6694 CANFD support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250207-fair-active-robin-30025a-mkl@pengutronix.de>
Date: Fri, 7 Feb 2025 16:51:19 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc: Ming Yu <a0282524688@...il.com>, tmyu0@...oton.com, lee@...nel.org, 
	linus.walleij@...aro.org, brgl@...ev.pl, andi.shyti@...nel.org, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	wim@...ux-watchdog.org, linux@...ck-us.net, jdelvare@...e.com, 
	alexandre.belloni@...tlin.com, linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-i2c@...r.kernel.org, linux-can@...r.kernel.org, netdev@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-hwmon@...r.kernel.org, linux-rtc@...r.kernel.org, 
	linux-usb@...r.kernel.org
Subject: Re: [PATCH v7 4/7] can: Add Nuvoton NCT6694 CANFD support

On 08.02.2025 00:00:43, Vincent Mailhol wrote:
> On 07/02/2025 at 21:15, Marc Kleine-Budde wrote:
> > On 07.02.2025 15:44:59, Ming Yu wrote:
> 
> (...)
> 
> >> +static netdev_tx_t nct6694_can_start_xmit(struct sk_buff *skb,
> >> +					  struct net_device *ndev)
> >> +{
> >> +	struct nct6694_can_priv *priv = netdev_priv(ndev);
> >> +
> >> +	if (can_dev_dropped_skb(ndev, skb))
> >> +		return NETDEV_TX_OK;
> >> +
> >> +	netif_stop_queue(ndev);
> >> +	can_put_echo_skb(skb, ndev, 0, 0);
> >> +	queue_work(priv->wq, &priv->tx_work);
> 
> What is the reason to use a work queue here? xmit() is not a hard IRQ.
> Also, the other USB CAN devices just directly send the USB message in
> their xmit() without the need to rely on such worker.
> 
> Sorry if this was discussed in the past, I can not remember if this
> question has already been raised.

AFAICS xmit uses nct6694_write_msg(), which uses several usb_bulk_msg(),
that can only be used from task context.

You can build a chain of usb_fill_bulk_urb(), usb_submit_urb(),
callbacks instead, but that's hard to read compared to blocking
usb_bulk_msg()s.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)