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Date:   Wed, 17 Apr 2019 07:00:45 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Petr Štetiar <ynezz@...e.cz>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Frank Rowand <frowand.list@...il.com>,
        John Crispin <john@...ozen.org>, Felix Fietkau <nbd@....name>
Subject: Re: [PATCH] of_net: add mtd-mac-address support to
 of_get_mac_address()

On 16.04.2019 22:05, Petr Štetiar wrote:
> From: John Crispin <john@...ozen.org>
> 
> Many embedded devices have information such as MAC addresses stored
> inside MTD devices. This patch allows us to add a property inside a node
> describing a network interface. The new property points at a MTD
> partition with an offset where the MAC address can be found.
> 
> This patch has originated in OpenWrt some time ago, so in order to
> consider usefulness of this patch, here are some real-world numbers
> which hopefully speak for themselves:
> 
>  * mtd-mac-address                used 497 times in 357 device tree files
>  * mtd-mac-address-increment      used  74 times in  58 device tree files
>  * mtd-mac-address-increment-byte used   1 time  in   1 device tree file
> 
> Signed-off-by: John Crispin <john@...ozen.org>
> Signed-off-by: Felix Fietkau <nbd@....name>
> [cleanup of the patch for upstream submission]
> Signed-off-by: Petr Štetiar <ynezz@...e.cz>
> ---
>  Documentation/devicetree/bindings/net/ethernet.txt |  5 ++
>  drivers/of/of_net.c                                | 82 +++++++++++++++++++++-
>  2 files changed, 86 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/ethernet.txt b/Documentation/devicetree/bindings/net/ethernet.txt
> index cfc376b..8a7891e 100644
> --- a/Documentation/devicetree/bindings/net/ethernet.txt
> +++ b/Documentation/devicetree/bindings/net/ethernet.txt
> @@ -10,6 +10,11 @@ Documentation/devicetree/bindings/phy/phy-bindings.txt.
>    the boot program; should be used in cases where the MAC address assigned to
>    the device by the boot program is different from the "local-mac-address"
>    property;
> +- mtd-mac-address: specify a MTD partition + offset containing array of 6 bytes
> +- mtd-mac-address-increment: specify number by which we should increment the
> +  MAC address stored in the MTD partition
> +- mtd-mac-address-increment-byte: specify octet/byte(0-5) in the MAC address,
> +  where we should increment the value, defaults to octet 5 (the last one)
>  - nvmem-cells: phandle, reference to an nvmem node for the MAC address;
>  - nvmem-cell-names: string, should be "mac-address" if nvmem is to be used;
>  - max-speed: number, specifies maximum speed in Mbit/s supported by the device;
> diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
> index 810ab0f..01b24d6 100644
> --- a/drivers/of/of_net.c
> +++ b/drivers/of/of_net.c
> @@ -11,6 +11,7 @@
>  #include <linux/of_net.h>
>  #include <linux/phy.h>
>  #include <linux/export.h>
> +#include <linux/mtd/mtd.h>
>  
>  /**
>   * of_get_phy_mode - Get phy mode for given device_node
> @@ -39,7 +40,7 @@ int of_get_phy_mode(struct device_node *np)
>  }
>  EXPORT_SYMBOL_GPL(of_get_phy_mode);
>  
> -static const void *of_get_mac_addr(struct device_node *np, const char *name)
> +static void *of_get_mac_addr(struct device_node *np, const char *name)
>  {
>  	struct property *pp = of_find_property(np, name, NULL);
>  
> @@ -48,6 +49,78 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
>  	return NULL;
>  }
>  
> +static const void *of_get_mac_address_mtd(struct device_node *np)
> +{
> +#ifdef CONFIG_MTD
> +	void *addr;
> +	size_t retlen;
> +	int size, ret;
> +	u8 mac[ETH_ALEN];
> +	phandle phandle;
> +	const char *part;
> +	const __be32 *list;
> +	struct mtd_info *mtd;
> +	struct property *prop;
> +	u32 mac_inc = 0;
> +	u32 inc_idx = ETH_ALEN-1;
> +	struct device_node *mtd_np = NULL;
> +
> +	list = of_get_property(np, "mtd-mac-address", &size);
> +	if (!list || (size != (2 * sizeof(*list))))
> +		return NULL;
> +
> +	phandle = be32_to_cpup(list++);
> +	if (phandle)
> +		mtd_np = of_find_node_by_phandle(phandle);
> +
> +	if (!mtd_np)
> +		return NULL;
> +
> +	part = of_get_property(mtd_np, "label", NULL);
> +	if (!part)
> +		part = mtd_np->name;
> +
> +	mtd = get_mtd_device_nm(part);
> +	if (IS_ERR(mtd))
> +		return NULL;
> +
> +	ret = mtd_read(mtd, be32_to_cpup(list), ETH_ALEN, &retlen, mac);

ret doesn't seem to be checked. And checking retlen wouldn't be bad too.

> +	put_mtd_device(mtd);
> +
> +	of_property_read_u32(np, "mtd-mac-address-increment-byte", &inc_idx);
> +	if (inc_idx > ETH_ALEN-1)
> +		return NULL;
> +
> +	if (!of_property_read_u32(np, "mtd-mac-address-increment", &mac_inc))
> +		mac[inc_idx] += mac_inc;
> +
> +	if (!is_valid_ether_addr(mac))
> +		return NULL;
> +
> +	addr = of_get_mac_addr(np, "mac-address");
> +	if (addr) {
> +		memcpy(addr, mac, ETH_ALEN);
> +		return addr;
> +	}
> +
> +	prop = kzalloc(sizeof(*prop), GFP_KERNEL);
> +	if (!prop)
> +		return NULL;
> +
> +	prop->name = "mac-address";
> +	prop->length = ETH_ALEN;
> +	prop->value = kmemdup(mac, ETH_ALEN, GFP_KERNEL);
> +	if (!prop->value || of_add_property(np, prop))
> +		goto free;
> +
> +	return prop->value;
> +free:
> +	kfree(prop->value);
> +	kfree(prop);
> +#endif
> +	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
> @@ -65,11 +138,18 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
>   * addresses.  Some older U-Boots only initialized 'local-mac-address'.  In
>   * this case, the real MAC is in 'local-mac-address', and 'mac-address' exists
>   * but is all zeros.
> + *
> + * If a mtd-mac-address property exists, try to fetch the MAC address from the
> + * specified MTD device, and store it as a 'mac-address' property.
>  */
>  const void *of_get_mac_address(struct device_node *np)
>  {
>  	const void *addr;
>  
> +	addr = of_get_mac_address_mtd(np);
> +	if (addr)
> +		return addr;
> +
>  	addr = of_get_mac_addr(np, "mac-address");
>  	if (addr)
>  		return addr;
> 

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