netdev - Re: [PATCH v3 net-next 07/21] net: usb: aqc111: Add support for getting and setting of MAC address

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Date:   Thu, 5 Nov 2020 08:43:40 +0530
From:   Anant Thazhemadam <anant.thazhemadam@...il.com>
To:     Igor Russkikh <Igor.Russkikh@...antia.com>
Cc:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        Dmitry Bezrukov <Dmitry.Bezrukov@...antia.com>
Subject: Re: [PATCH v3 net-next 07/21] net: usb: aqc111: Add support for
 getting and setting of MAC address

Hi,

I only recently browsed through the code, and had some queries regarding
the changes introduced by this commit.

On 21/11/18 3:43 pm, Igor Russkikh wrote:
> From: Dmitry Bezrukov <dmitry.bezrukov@...antia.com>
>
> Signed-off-by: Dmitry Bezrukov <dmitry.bezrukov@...antia.com>
> Signed-off-by: Igor Russkikh <igor.russkikh@...antia.com>
> ---
>  drivers/net/usb/aqc111.c | 47 ++++++++++++++++++++++++++++++++++++++++
>  drivers/net/usb/aqc111.h |  1 +
>  2 files changed, 48 insertions(+)
>
> diff --git a/drivers/net/usb/aqc111.c b/drivers/net/usb/aqc111.c
> index e33be16b506c..390ed6cbc3fd 100644
> --- a/drivers/net/usb/aqc111.c
> +++ b/drivers/net/usb/aqc111.c
> @@ -11,6 +11,7 @@
>  #include <linux/netdevice.h>
>  #include <linux/mii.h>
>  #include <linux/usb.h>
> +#include <linux/if_vlan.h>
>  #include <linux/usb/cdc.h>
>  #include <linux/usb/usbnet.h>
>  
> @@ -204,11 +205,43 @@ static void aqc111_set_phy_speed(struct usbnet *dev, u8 autoneg, u16 speed)
>  	aqc111_write32_cmd(dev, AQ_PHY_OPS, 0, 0, &aqc111_data->phy_cfg);
>  }
>  
> +static int aqc111_set_mac_addr(struct net_device *net, void *p)
> +{
> +	struct usbnet *dev = netdev_priv(net);
> +	int ret = 0;
> +
> +	ret = eth_mac_addr(net, p);
> +	if (ret < 0)
> +		return ret;
> +

When eth_mac_addr() fails, from what I can see, it returns either -EBUSY, or
-EADDRNOTAVAIL.
Wouldn't it be a better idea to set a random MAC address instead, when
-EADDRNOTAVAIL is returned, so that the interface still comes up and is
usable?

I'm only asking because this feels similar to the discussion that can be found here.
    https://lkml.org/lkml/2020/10/2/305

> +	/* Set the MAC address */
> +	return aqc111_write_cmd(dev, AQ_ACCESS_MAC, SFR_NODE_ID, ETH_ALEN,
> +				ETH_ALEN, net->dev_addr);
> +}
> +
>  static const struct net_device_ops aqc111_netdev_ops = {
>  	.ndo_open		= usbnet_open,
>  	.ndo_stop		= usbnet_stop,
> +	.ndo_set_mac_address	= aqc111_set_mac_addr,
> +	.ndo_validate_addr	= eth_validate_addr,
>  };
>  
> +static int aqc111_read_perm_mac(struct usbnet *dev)
> +{
> +	u8 buf[ETH_ALEN];
> +	int ret;
> +
> +	ret = aqc111_read_cmd(dev, AQ_FLASH_PARAMETERS, 0, 0, ETH_ALEN, buf);
> +	if (ret < 0)
> +		goto out;
> +
> +	ether_addr_copy(dev->net->perm_addr, buf);
> +
> +	return 0;
> +out:
> +	return ret;
> +}
> +
>  static void aqc111_read_fw_version(struct usbnet *dev,
>  				   struct aqc111_data *aqc111_data)
>  {
> @@ -251,6 +284,12 @@ static int aqc111_bind(struct usbnet *dev, struct usb_interface *intf)
>  	/* store aqc111_data pointer in device data field */
>  	dev->driver_priv = aqc111_data;
>  
> +	/* Init the MAC address */
> +	ret = aqc111_read_perm_mac(dev);
> +	if (ret)
> +		goto out;
> +
> +	ether_addr_copy(dev->net->dev_addr, dev->net->perm_addr);
>  	dev->net->netdev_ops = &aqc111_netdev_ops;
>  
>  	aqc111_read_fw_version(dev, aqc111_data);
> @@ -259,6 +298,10 @@ static int aqc111_bind(struct usbnet *dev, struct usb_interface *intf)
>  					 SPEED_5000 : SPEED_1000;
>  
>  	return 0;
> +
> +out:
> +	kfree(aqc111_data);
> +	return ret;
>  }
>  
>  static void aqc111_unbind(struct usbnet *dev, struct usb_interface *intf)
> @@ -467,6 +510,10 @@ static int aqc111_reset(struct usbnet *dev)
>  	aqc111_write32_cmd(dev, AQ_PHY_OPS, 0, 0,
>  			   &aqc111_data->phy_cfg);
>  
> +	/* Set the MAC address */
> +	aqc111_write_cmd(dev, AQ_ACCESS_MAC, SFR_NODE_ID, ETH_ALEN,
> +			 ETH_ALEN, dev->net->dev_addr);
> +

There's a chance that aqc111_write_cmd() can end up writing only a
part of the required amount of data too.
Wouldn't it be a better idea to enforce a sanity check here, and set a
random mac address instead if this write fails?

>  	reg8 = 0xFF;
>  	aqc111_write_cmd(dev, AQ_ACCESS_MAC, SFR_BM_INT_MASK, 1, 1, &reg8);
>  
> diff --git a/drivers/net/usb/aqc111.h b/drivers/net/usb/aqc111.h
> index f3b45d8ca4e3..0c8e1ee29893 100644
> --- a/drivers/net/usb/aqc111.h
> +++ b/drivers/net/usb/aqc111.h
> @@ -11,6 +11,7 @@
>  #define __LINUX_USBNET_AQC111_H
>  
>  #define AQ_ACCESS_MAC			0x01
> +#define AQ_FLASH_PARAMETERS		0x20
>  #define AQ_PHY_POWER			0x31
>  #define AQ_PHY_OPS			0x61
>

If any of these changes sound like a good idea, I'd be happy to write a
patch implementing them. :)

Thanks,
Anant