linux-kernel - Re: [PATCH v11 1/5] can: m_can: Create a m

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Message-ID: <8b53474d-9dbf-4b81-defd-1587e022990b@pengutronix.de>
Date:   Wed, 8 May 2019 16:35:46 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Dan Murphy <dmurphy@...com>, wg@...ndegger.com, davem@...emloft.net
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 1/5] can: m_can: Create a m_can platform framework

On 3/19/19 6:26 PM, Dan Murphy wrote:
> Create a m_can platform framework that peripheral
> devices can register to and use common code and register sets.
> The peripheral devices may provide read/write and configuration
> support of the IP.
> 
> Acked-by: Wolfgang Grandegger <wg@...ndegger.com>
> Signed-off-by: Dan Murphy <dmurphy@...com>

[...]

> -/* m_can private data structure */
> -struct m_can_priv {
> -	struct can_priv can;	/* must be the first member */
> -	struct napi_struct napi;
> -	struct net_device *dev;
> -	struct device *device;
> -	struct clk *hclk;
> -	struct clk *cclk;
> -	void __iomem *base;
> -	u32 irqstatus;
> -	int version;
> -
> -	/* message ram configuration */
> -	void __iomem *mram_base;
> -	struct mram_cfg mcfg[MRAM_CFG_NUM];
> -};
> +static u32 m_can_read(struct m_can_priv *priv, enum m_can_reg reg)
> +{
> +	if (priv->ops->read_reg)
> +		return priv->ops->read_reg(priv, reg);
> +	else
> +		return -EINVAL;
> +}

How do you plan to check the return value here?
What's the difference between a register value of 0xffffffe9 and
returning -EINVAL?

>  
> -static inline u32 m_can_read(const struct m_can_priv *priv, enum m_can_reg reg)
> +static int m_can_write(struct m_can_priv *priv, enum m_can_reg reg, u32 val)
>  {
> -	return readl(priv->base + reg);
> +	if (priv->ops->write_reg)
> +		return priv->ops->write_reg(priv, reg, val);
> +	else
> +		return -EINVAL;
>  }

I don't see anyone checking the return value. Better just dereference
the pointer and the kernel will produce a nice backtrace.

Same should be done for all read and write variants.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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