linux-kernel - Re: [PATCH v3 4/7] can: Add Nuvoton NCT6694 CAN support

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Message-ID: <CAOoeyxWOD8=zosrHzhamG6RfFW=MzxEAa1hYXe1zXD1kBLkgrA@mail.gmail.com>
Date: Mon, 23 Dec 2024 17:03:59 +0800
From: Ming Yu <a0282524688@...il.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: tmyu0@...oton.com, lee@...nel.org, linus.walleij@...aro.org, brgl@...ev.pl, 
	andi.shyti@...nel.org, mailhol.vincent@...adoo.fr, 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
Subject: Re: [PATCH v3 4/7] can: Add Nuvoton NCT6694 CAN support

Hi Marc,

> > > +struct nct6694_can_priv {
> > > +     struct can_priv can;    /* must be the first member */
> > > +     struct net_device *ndev;
> > > +     struct nct6694 *nct6694;
> > > +     struct mutex lock;
> >
> > What does lock protect?
> >
>
> The lock is used to protect tx_buf and rx_buf for each CAN device.
>
> > > +     struct sk_buff *tx_skb;
> > > +     struct workqueue_struct *wq;
> > > +     struct work_struct tx_work;
> > > +     unsigned char *tx_buf;
> > void *
> > > +     unsigned char *rx_buf;
> > void *
> > > +     unsigned char can_idx;
> > > +     bool tx_busy;
> >
> > IMHO it makes no sense to have tx_skb and tx_busy
> >
>
> Okay! I will revisit these to evaluate whether they are still necessary.
>
> > > +};
> > > +

I think there needs to be a tx_skb to record the skb passed by
start_xmit(), otherwise it can't handle the can_frame in tx_work. If
this is not necessary, could you please explain?
In addition, the tx flow is based on the implementation in
https://elixir.bootlin.com/linux/v6.12.6/source/drivers/net/can/spi/mcp251x.c

Thanks,
Ming