linux-kernel - Re: [PATCH v4 01/12] can: m_can: Write transmit header and data in one transaction

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Message-ID: <ZJMG2ovqLXjMjgZg@corigine.com>
Date:   Wed, 21 Jun 2023 16:19:06 +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 01/12] can: m_can: Write transmit header and data in
 one transaction

On Wed, Jun 21, 2023 at 11:23:39AM +0200, Markus Schneider-Pargmann wrote:
> Combine header and data before writing to the transmit fifo to reduce
> the overhead for peripheral chips.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> ---
>  drivers/net/can/m_can/m_can.c | 34 +++++++++++++++++++++-------------
>  1 file changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..5251073987ee 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -317,6 +317,12 @@ struct id_and_dlc {
>  	u32 dlc;
>  };
>  
> +struct m_can_fifo_element {
> +	u32 id;
> +	u32 dlc;
> +	u8 data[CANFD_MAX_DLEN];
> +};
> +
>  static inline u32 m_can_read(struct m_can_classdev *cdev, enum m_can_reg reg)
>  {
>  	return cdev->ops->read_reg(cdev, reg);
> @@ -1622,6 +1628,8 @@ static int m_can_next_echo_skb_occupied(struct net_device *dev, int putidx)
>  static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
>  {
>  	struct canfd_frame *cf = (struct canfd_frame *)cdev->tx_skb->data;
> +	u8 len_padded = DIV_ROUND_UP(cf->len, 4);
> +	struct m_can_fifo_element fifo_element;
>  	struct net_device *dev = cdev->net;
>  	struct sk_buff *skb = cdev->tx_skb;
>  	struct id_and_dlc fifo_header;

Hi Markus,

GCC 12.3.0 complains that fifo_header is not (no longer) used.

 drivers/net/can/m_can/m_can.c:1635:20: warning: unused variable 'fifo_header' [-Wunused-variable]
         struct id_and_dlc fifo_header;

-- 
pw-bot: changes-requested