Subject: Re: [PATCH v2 1/4] of_net: Add NVMEM support to of_get_mac_address

From: Rob Herring <[email-masked]>
Date: Wed, 1 May 2019 15:19:25 -0500

On Sun, Apr 28, 2019 at 02:53:19PM +0200, Petr Štetiar wrote:
> Many embedded devices have information such as MAC addresses stored
> inside NVMEMs like EEPROMs and so on. Currently there are only two
> drivers in the tree which benefit from NVMEM bindings.
> 
> Adding support for NVMEM into every other driver would mean adding a lot
> of repetitive code. This patch allows us to configure MAC addresses in
> various devices like ethernet and wireless adapters directly from
> of_get_mac_address, which is already used by almost every driver in the
> tree.
> 
> Predecessor of this patch which used directly MTD layer has originated
> in OpenWrt some time ago and supports already about 497 use cases in 357
> device tree files.
> 
> Cc: Alban Bedel <[email-masked]>
> Signed-off-by: Felix Fietkau <[email-masked]>
> Signed-off-by: John Crispin <[email-masked]>
> Signed-off-by: Petr Štetiar <[email-masked]>
> ---
> 
>  Changes since v1:
> 
>   * moved handling of nvmem after mac-address and local-mac-address properties
> 
>  drivers/of/of_net.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
> index d820f3e..8ce4f47 100644
> --- a/drivers/of/of_net.c
> +++ b/drivers/of/of_net.c
> @@ -8,6 +8,7 @@
>  #include <linux/etherdevice.h>
>  #include <linux/kernel.h>
>  #include <linux/of_net.h>
> +#include <linux/of_platform.h>
>  #include <linux/phy.h>
>  #include <linux/export.h>
>  
> @@ -47,12 +48,45 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
>  	return NULL;
>  }
>  
> +static const void *of_get_mac_addr_nvmem(struct device_node *np)
> +{
> +	int r;
> +	u8 mac[ETH_ALEN];
> +	struct property *pp;
> +	struct platform_device *pdev = of_find_device_by_node(np);
> +
> +	if (!pdev)
> +		return NULL;
> +
> +	r = nvmem_get_mac_address(&pdev->dev, &mac);
> +	if (r < 0)
> +		return NULL;
> +
> +	pp = kzalloc(sizeof(*pp), GFP_KERNEL);
> +	if (!pp)
> +		return NULL;
> +
> +	pp->name = "nvmem-mac-address";
> +	pp->length = ETH_ALEN;
> +	pp->value = kmemdup(mac, ETH_ALEN, GFP_KERNEL);
> +	if (!pp->value || of_add_property(np, pp))
> +		goto free;

Why add this to the DT? You have the struct device ptr, so just use 
devm_kzalloc() if you need an allocation.

> +
> +	return pp->value;
> +free:
> +	kfree(pp->value);
> +	kfree(pp);
> +
> +	return NULL;
> +}
> +
>  /**
>   * Search the device tree for the best MAC address to use.  'mac-address' is
>   * checked first, because that is supposed to contain to "most recent" MAC
>   * address. If that isn't set, then 'local-mac-address' is checked next,
> - * because that is the default address.  If that isn't set, then the obsolete
> - * 'address' is checked, just in case we're using an old device tree.
> + * because that is the default address.  If that isn't set, try to get MAC
> + * address from nvmem cell named 'mac-address'. If that isn't set, then the
> + * obsolete 'address' is checked, just in case we're using an old device tree.
>   *
>   * Note that the 'address' property is supposed to contain a virtual address of
>   * the register set, but some DTS files have redefined that property to be the
> @@ -77,6 +111,10 @@ const void *of_get_mac_address(struct device_node *np)
>  	if (addr)
>  		return addr;
>  
> +	addr = of_get_mac_addr_nvmem(np);
> +	if (addr)
> +		return addr;
> +
>  	return of_get_mac_addr(np, "address");
>  }
>  EXPORT_SYMBOL(of_get_mac_address);
> -- 
> 1.9.1
>