netdev - Re: [PATCH v4 04/12] can: m_can: Add rx coalescing ethtool support

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Date: Wed, 21 Jun 2023 16:22:12 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Markus Schneider-Pargmann <msp@...libre.com>
Cc: Marc Kleine-Budde <mkl@...gutronix.de>,
	Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	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>,
	linux-can@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Julien Panis <jpanis@...libre.com>
Subject: Re: [PATCH v4 04/12] can: m_can: Add rx coalescing ethtool support

On Wed, Jun 21, 2023 at 11:23:42AM +0200, Markus Schneider-Pargmann wrote:

...

> +static int m_can_set_coalesce(struct net_device *dev,
> +			      struct ethtool_coalesce *ec,
> +			      struct kernel_ethtool_coalesce *kec,
> +			      struct netlink_ext_ack *ext_ack)
> +{
> +	struct m_can_classdev *cdev = netdev_priv(dev);
> +
> +	if (cdev->can.state != CAN_STATE_STOPPED) {
> +		netdev_err(dev, "Device is in use, please shut it down first\n");
> +		return -EBUSY;
> +	}
> +
> +	if (ec->rx_max_coalesced_frames_irq > cdev->mcfg[MRAM_RXF0].num) {
> +		netdev_err(dev, "rx-frames-irq %u greater than the RX FIFO %u\n",
> +			   ec->rx_max_coalesced_frames_irq,
> +			   cdev->mcfg[MRAM_RXF0].num);
> +		return -EINVAL;
> +	}
> +	if (ec->rx_max_coalesced_frames_irq == 0 != ec->rx_coalesce_usecs_irq == 0) {

Hi Markus,

For a W=1 build GCC 12.3.0 suggests, rather forcefully, that it would like
some more parentheses here.

 drivers/net/can/m_can/m_can.c: In function 'm_can_set_coalesce':
 drivers/net/can/m_can/m_can.c:1978:45: warning: suggest parentheses around comparison in operand of '!=' [-Wparentheses]
  1978 |         if (ec->rx_max_coalesced_frames_irq == 0 != ec->rx_coalesce_usecs_irq == 0) {
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
 drivers/net/can/m_can/m_can.c:1978:50: warning: suggest parentheses around comparison in operand of '==' [-Wparentheses]
  1978 |         if (ec->rx_max_coalesced_frames_irq == 0 != ec->rx_coalesce_usecs_irq == 0) {
       |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

> +		netdev_err(dev, "rx-frames-irq and rx-usecs-irq can only be set together\n");
> +		return -EINVAL;
> +	}
> +
> +	cdev->rx_max_coalesced_frames_irq = ec->rx_max_coalesced_frames_irq;
> +	cdev->rx_coalesce_usecs_irq = ec->rx_coalesce_usecs_irq;
> +
> +	return 0;
> +}

...