linux-kernel - Re: [PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac

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Date:   Thu, 19 Jul 2018 17:35:40 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Lukas Wunner <lukas@...ner.de>, Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        David Lechner <david@...hnology.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

2018-07-19 14:37 GMT+02:00 Dan Carpenter <dan.carpenter@...cle.com>:
> On Thu, Jul 19, 2018 at 12:06:51PM +0200, Bartosz Golaszewski wrote:
>> It looks simpler as long as you don't add all the new routines
>> resulting from this approach. I've just tried to quickly implement
>> this solution and it resulted in much bigger and duplicated code
>> (checking the validity of mac_addr, copying it etc.). I would prefer
>> the current approach and would like to read someone else's opinion on
>> that.
>
> It's not too bad.  There is two extra ether_addr_copy() calls and one
> extra is_valid_ether_addr().  There are two extra alen declarations and
> one extra addr declaration.  The functions don't share *that* much code.
>
> regards,
> dan carpenter
>
> diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
> index fd8faa0dfa61..8ab7289a5069 100644
> --- a/net/ethernet/eth.c
> +++ b/net/ethernet/eth.c
> @@ -54,6 +54,8 @@
>  #include <linux/if_ether.h>
>  #include <linux/of_net.h>
>  #include <linux/pci.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/mtd/mtd.h>
>  #include <net/dst.h>
>  #include <net/arp.h>
>  #include <net/sock.h>
> @@ -525,7 +527,7 @@ unsigned char * __weak arch_get_platform_mac_address(void)
>         return NULL;
>  }
>
> -int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
> +static int of_eth_get_mac_address(struct device *dev, u8 *mac_addr)
>  {
>         const unsigned char *addr;
>         struct device_node *dp;
> @@ -547,4 +549,82 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
>         ether_addr_copy(mac_addr, addr);
>         return 0;
>  }
> +
> +static int nvmem_eth_get_mac_address(struct device *dev, u8 *mac_addr)
> +{
> +       struct nvmem_cell *nvmem;
> +       unsigned char *addr;
> +       size_t alen;
> +       int ret = 0;
> +
> +       nvmem = nvmem_cell_get(dev, "mac-address");
> +       if (PTR_ERR(nvmem) == -EPROBE_DEFER)
> +               /* We may have a lookup registered for MAC address but the
> +                * corresponding nvmem provider hasn't been registered yet.
> +                */
> +               return -EPROBE_DEFER;
> +       if (IS_ERR(nvmem))
> +               return PTR_ERR(nvmem);
> +       addr = nvmem_cell_read(nvmem, &alen);
> +       if (IS_ERR(addr)) {
> +               ret = PTR_ERR(addr);
> +               goto put_nvmem;
> +       }
> +       if (alen != ETH_ALEN || !is_valid_ether_addr(addr)) {
> +               ret = -EINVAL;
> +               goto free_addr;
> +       }
> +       ether_addr_copy(mac_addr, addr);
> +free_addr:
> +       kfree(addr);
> +put_nvmem:
> +       nvmem_cell_put(nvmem);
> +       return ret;
> +}
> +
> +static int mtd_eth_get_mac_address(struct device *dev, u8 *mac_addr)
> +{
> +       struct mtd_info *mtd;
> +       u8 addrbuf[ETH_ALEN];
> +       size_t alen;
> +       int ret;
> +
> +       /* This function should go away as soon as MTD gets nvmem support. */
> +       if (!IS_ENABLED(CONFIG_MTD))
> +               return -ENODEV;
> +
> +       mtd = get_mtd_device_nm("MAC-Address");
> +       if (IS_ERR(mtd))
> +               return PTR_ERR(mtd);
> +       ret = mtd_read(mtd, 0, ETH_ALEN, &alen, addrbuf);
> +       if (ret)
> +               goto put_mtd;
> +       if (!is_valid_ether_addr(addrbuf)) {
> +               ret = -EINVAL;
> +               goto put_mtd;
> +       }
> +       ether_addr_copy(mac_addr, addrbuf);
> +put_mtd:
> +       put_mtd_device(mtd);
> +       return ret;
> +}
> +
> +int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
> +{
> +       int ret;
> +
> +       ret = of_eth_get_mac_address(dev, mac_addr);
> +       if (!ret)
> +               return 0;
> +       ret = nvmem_eth_get_mac_address(dev, mac_addr);
> +       if (ret == -EPROBE_DEFER)
> +               return -EPROBE_DEFER;
> +       if (!ret)
> +               return 0;
> +       ret = mtd_eth_get_mac_address(dev, mac_addr);
> +       if (!ret)
> +               return 0;
> +
> +       return -ENODEV;
> +}
>  EXPORT_SYMBOL(eth_platform_get_mac_address);

Please take a look at v3 - I did it a bit differently but the idea is the same.

Bart