netdev - Re: [PATCH] stmmac: debugfs entry name is not be changed when udev rename device name.

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Message-Id: <20200104.201833.91020607861340266.davem@davemloft.net>
Date:   Sat, 04 Jan 2020 20:18:33 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     jiping.ma2@...driver.com
Cc:     peppe.cavallaro@...com, alexandre.torgue@...com,
        joabreu@...opsys.com, mcoquelin.stm32@...il.com,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] stmmac: debugfs entry name is not be changed when udev
 rename device name.

From: Jiping Ma <jiping.ma2@...driver.com>
Date: Thu, 2 Jan 2020 09:35:44 +0800

> Add one notifier for udev changes net device name.
> 
> Signed-off-by: Jiping Ma <jiping.ma2@...driver.com>
> ---
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 28 +++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index b14f46a57154..3b05cb80eed7 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4038,6 +4038,31 @@ static int stmmac_dma_cap_show(struct seq_file *seq, void *v)
>  }
>  DEFINE_SHOW_ATTRIBUTE(stmmac_dma_cap);
>  
> +/* Use network device events to rename debugfs file entries.
> + */
> +static int stmmac_device_event(struct notifier_block *unused,
> +			       unsigned long event, void *ptr)
> +{
> +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> +	struct stmmac_priv *priv = netdev_priv(dev);
> +
> +	switch (event) {
> +	case NETDEV_CHANGENAME:

This notifier gets called for every single netdevice in the entire
system.

You cannot just assume that the device that gets passed in here is
an stmmac device.

Look at how other drivers handle this to see how to do it correctly.

Thank you.