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From:   Rob Herring <robh+dt@kernel.org>
Date:   Tue, 6 Apr 2021 20:13:15 -0500
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Subject: Re: [PATCH 2/2] of: net: fix of_get_mac_addr_nvmem() for PCI and DSA nodes
To:     Michael Walle <michael@walle.cc>
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On Mon, Apr 5, 2021 at 11:47 AM Michael Walle <michael@walle.cc> wrote:
>
> of_get_mac_address() already supports fetching the MAC address by an
> nvmem provider. But until now, it was just working for platform devices.
> Esp. it was not working for DSA ports and PCI devices. It gets more
> common that PCI devices have a device tree binding since SoCs contain
> integrated root complexes.
>
> Use the nvmem of_* binding to fetch the nvmem cells by a struct
> device_node. We still have to try to read the cell by device first
> because there might be a nvmem_cell_lookup associated with that device.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> Please note, that I've kept the nvmem_get_mac_address() which operates
> on a device. The new of_get_mac_addr_nvmem() is almost identical and
> there are no users of the former function right now, but it seems to be
> the "newer" version to get the MAC address for a "struct device". Thus
> I've kept it. Please advise, if I should kill it though.

It seems kind of backwards from how we normally design this type of
API where the API with a struct device will call a firmware specific
version if there's a firmware handle. But certainly, I don't think we
should be operating on platform device if we can help it.

>  drivers/of/of_net.c | 37 +++++++++++++++++++++++++++++++------
>  1 file changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
> index 2344ad7fff5e..2323c6063eaf 100644
> --- a/drivers/of/of_net.c
> +++ b/drivers/of/of_net.c
> @@ -11,6 +11,7 @@
>  #include <linux/phy.h>
>  #include <linux/export.h>
>  #include <linux/device.h>
> +#include <linux/nvmem-consumer.h>
>
>  /**
>   * of_get_phy_mode - Get phy mode for given device_node
> @@ -56,18 +57,42 @@ static int of_get_mac_addr(struct device_node *np, const char *name, u8 *addr)
>         return -ENODEV;
>  }
>
> -static int of_get_mac_addr_nvmem(struct device_node *np, u8 addr)
> +static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
>  {
>         struct platform_device *pdev = of_find_device_by_node(np);
> +       struct nvmem_cell *cell;
> +       const void *mac;
> +       size_t len;
>         int ret;
>
> -       if (!pdev)
> -               return -ENODEV;
> +       /* Try lookup by device first, there might be a nvmem_cell_lookup
> +        * associated with a given device.
> +        */
> +       if (pdev) {
> +               ret = nvmem_get_mac_address(&pdev->dev, addr);
> +               put_device(&pdev->dev);
> +               return ret;
> +       }
> +
> +       cell = of_nvmem_cell_get(np, "mac-address");
> +       if (IS_ERR(cell))
> +               return PTR_ERR(cell);
> +
> +       mac = nvmem_cell_read(cell, &len);
> +       nvmem_cell_put(cell);
> +
> +       if (IS_ERR(mac))
> +               return PTR_ERR(mac);
> +
> +       if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
> +               kfree(mac);
> +               return -EINVAL;
> +       }
>
> -       ret = nvmem_get_mac_address(&pdev->dev, addr);
> -       put_device(&pdev->dev);
> +       ether_addr_copy(addr, mac);
> +       kfree(mac);
>
> -       return ret;
> +       return 0;
>  }
>
>  /**
> --
> 2.20.1
>