linux-kernel - Re: [PATCH v2 3/4] can: Add driver for CAST CAN Bus Controller

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Message-ID: <9cf40a68-a07f-46d5-bc2c-302ae0e99ab0@lunn.ch>
Date: Mon, 23 Sep 2024 14:12:39 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Hal Feng <hal.feng@...rfivetech.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Emil Renner Berthing <emil.renner.berthing@...onical.com>,
	William Qiu <william.qiu@...rfivetech.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] can: Add driver for CAST CAN Bus Controller

> > > +	reset_test = ccan_read_reg_8bit(priv, CCAN_CFG_STAT);
> > > +
> > > +	if (!(reset_test & CCAN_RST_MASK)) {
> > > +		netdev_alert(ndev, "Not in reset mode, cannot set bit
> > timing\n");
> > > +		return -EPERM;
> > > +	}
> > 
> > 
> > You don't see nedev_alert() used very often. If this is fatal then netdev_err().
> > 
> > Also, EPERM? man 3 errno say:
> > 
> >        EPERM           Operation not permitted (POSIX.1-2001).
> > 
> > Why is this a permission issue?
> 
> Will use netdev_err() and return -EWOULDBLOCK instead.

I'm not sure that is any better.

       EAGAIN          Resource  temporarily unavailable (may be the same value
                       as EWOULDBLOCK) (POSIX.1-2001).

This is generally used when the kernel expects user space to try a
system call again, and it might then work. Is that what you expect
here?

> > > +static irqreturn_t ccan_interrupt(int irq, void *dev_id) {
> > > +	struct net_device *ndev = (struct net_device *)dev_id;
> > 
> > dev_id is a void *, so you don't need the cast.
> 
> OK, drop it.

Please look at the whole patch. There might be other instances where a
void * is used with a cast, which can be removed. This was just the
first i spotted.

	Andrew