[PATCH v2 0/3] net: extend eth_platform_get_mac_address()

[PATCH v2 0/3] net: extend eth_platform_get_mac_address()

[Bartosz Golaszewski]

This is a follow-up to a series I posted a while ago the goal of which
was to replace the at24 platform data with device properties. To do so
we need to somehow remove reading the MAC address from relevant board
files.

In my patches I used nvmem and MTD to read the MAC address from within
the davinci emac driver. It was suggested that we generalize it further
but since MTD doesn't support nvmem yet, the best we can do is to move
this code over to net core code.

The following patches modify the eth_platform_get_mac_address()
function which seems to be the best candidate for this code.

The first patch calls is_valid_ether_addr() on the read address so
that we're sure it's correct.

The last two patches add nvmem and MTD support to the function. In
order to stay compatible with existing users, nvmem and MTD will be
tried last - after device tree and arch-specific callback.

If this series gets accepted I will modify my previous patches to
use it instead of handcoding the same operations in davinci_emac.

v1 -> v2:
- dropped patches 1 & 2
- improved the MAC address verification and fixed a potential buffer
  overflow in patch 2/3

Bartosz Golaszewski (3):
  net: fortify eth_platform_get_mac_address()
  net: add support for nvmem to eth_platform_get_mac_address()
  net: add MTD support to eth_platform_get_mac_address()

 net/ethernet/eth.c | 47 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

-- 
2.17.1

[PATCH v2 1/3] net: fortify eth_platform_get_mac_address()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

We'll soon have more sources from which to read the MAC address in this
routine. Make sure the address is correct before returning it.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 net/ethernet/eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index ee28440f57c5..39af03894598 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -541,7 +541,7 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 	if (!addr)
 		addr = arch_get_platform_mac_address();
 
-	if (!addr)
+	if (!addr || !is_valid_ether_addr(addr))
 		return -ENODEV;
 
 	ether_addr_copy(mac_addr, addr);
-- 
2.17.1

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Many non-DT platforms read the MAC address from EEPROM. Usually it's
either done with callbacks defined in board files or from SoC-specific
ethernet drivers.

In order to generalize this, try to read the MAC from nvmem in
eth_platform_get_mac_address() using a standard lookup name:
"mac-address".

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 net/ethernet/eth.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 39af03894598..af3b4b1b77eb 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -54,6 +54,7 @@
 #include <linux/if_ether.h>
 #include <linux/of_net.h>
 #include <linux/pci.h>
+#include <linux/nvmem-consumer.h>
 #include <net/dst.h>
 #include <net/arp.h>
 #include <net/sock.h>
@@ -527,8 +528,11 @@ unsigned char * __weak arch_get_platform_mac_address(void)
 
 int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 {
+	unsigned char addrbuf[ETH_ALEN];
 	const unsigned char *addr;
+	struct nvmem_cell *nvmem;
 	struct device_node *dp;
+	size_t alen;
 
 	if (dev_is_pci(dev))
 		dp = pci_device_to_OF_node(to_pci_dev(dev));
@@ -541,6 +545,29 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 	if (!addr)
 		addr = arch_get_platform_mac_address();
 
+	if (!addr) {
+		nvmem = nvmem_cell_get(dev, "mac-address");
+		if (IS_ERR(nvmem) && 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)) {
+			addr = nvmem_cell_read(nvmem, &alen);
+			if (!IS_ERR(addr)) {
+				if (alen == ETH_ALEN)
+					ether_addr_copy(addrbuf, addr);
+
+				kfree(addr);
+				addr = alen == ETH_ALEN ? addrbuf : NULL;
+			}
+
+			nvmem_cell_put(nvmem);
+		}
+	}
+
 	if (!addr || !is_valid_ether_addr(addr))
 		return -ENODEV;
 
-- 
2.17.1

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Dan Carpenter]

On Thu, Jul 19, 2018 at 10:20:27AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> Many non-DT platforms read the MAC address from EEPROM. Usually it's
> either done with callbacks defined in board files or from SoC-specific
> ethernet drivers.
> 
> In order to generalize this, try to read the MAC from nvmem in
> eth_platform_get_mac_address() using a standard lookup name:
> "mac-address".
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---
>  net/ethernet/eth.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
> index 39af03894598..af3b4b1b77eb 100644
> --- a/net/ethernet/eth.c
> +++ b/net/ethernet/eth.c
> @@ -54,6 +54,7 @@
>  #include <linux/if_ether.h>
>  #include <linux/of_net.h>
>  #include <linux/pci.h>
> +#include <linux/nvmem-consumer.h>
>  #include <net/dst.h>
>  #include <net/arp.h>
>  #include <net/sock.h>
> @@ -527,8 +528,11 @@ unsigned char * __weak arch_get_platform_mac_address(void)
>  
>  int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
>  {
> +	unsigned char addrbuf[ETH_ALEN];
>  	const unsigned char *addr;
> +	struct nvmem_cell *nvmem;
>  	struct device_node *dp;
> +	size_t alen;
>  
>  	if (dev_is_pci(dev))
>  		dp = pci_device_to_OF_node(to_pci_dev(dev));
> @@ -541,6 +545,29 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
>  	if (!addr)
>  		addr = arch_get_platform_mac_address();
>  
> +	if (!addr) {
> +		nvmem = nvmem_cell_get(dev, "mac-address");
> +		if (IS_ERR(nvmem) && 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)) {
> +			addr = nvmem_cell_read(nvmem, &alen);
> +			if (!IS_ERR(addr)) {
                                    ^^^^
Never do success handling.  Always error handling.  Otherwise the code
is indent a lot and the error handling is far from the call.

> +				if (alen == ETH_ALEN)
> +					ether_addr_copy(addrbuf, addr);
> +
> +				kfree(addr);
> +				addr = alen == ETH_ALEN ? addrbuf : NULL;
> +			}
> +
> +			nvmem_cell_put(nvmem);
> +		}
> +	}
> +
>  	if (!addr || !is_valid_ether_addr(addr))
                                          ^^^^
Instead of handling the error we dereference the error pointer here.

*frowny face*

>  		return -ENODEV;
>  
> --

Maybe this?

	if (!addr) {
		nvmem = nvmem_cell_get(dev, "mac-address");
		if (PTR_ERR(nvmem) == -EPROBE_DEFER)
			return -EPROBE_DEFER;
		if (IS_ERR(nvmem))
			return -ENODEV;
		addr = nvmem_cell_read(nvmem, &alen);
		if (IS_ERR(addr))
			return PTR_ERR(addr);
		if (alen != ETH_ALEN) {
			kfree(addr);
			return -ENODEV;
		}
		ether_addr_copy(addrbuf, addr);
		kfree(addr);
		addr = addrbuf;
	}
	if (!is_valid_ether_addr(addr))
		return -ENODEV;
	ether_addr_copy(mac_addr, addr);
	return 0;

regards,
dan carpenter

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Bartosz Golaszewski]

2018-07-19 10:48 GMT+02:00 Dan Carpenter <dan.carpenter@oracle.com>:
> On Thu, Jul 19, 2018 at 10:20:27AM +0200, Bartosz Golaszewski wrote:
>> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>>
>> Many non-DT platforms read the MAC address from EEPROM. Usually it's
>> either done with callbacks defined in board files or from SoC-specific
>> ethernet drivers.
>>
>> In order to generalize this, try to read the MAC from nvmem in
>> eth_platform_get_mac_address() using a standard lookup name:
>> "mac-address".
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>> ---
>>  net/ethernet/eth.c | 27 +++++++++++++++++++++++++++
>>  1 file changed, 27 insertions(+)
>>
>> diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
>> index 39af03894598..af3b4b1b77eb 100644
>> --- a/net/ethernet/eth.c
>> +++ b/net/ethernet/eth.c
>> @@ -54,6 +54,7 @@
>>  #include <linux/if_ether.h>
>>  #include <linux/of_net.h>
>>  #include <linux/pci.h>
>> +#include <linux/nvmem-consumer.h>
>>  #include <net/dst.h>
>>  #include <net/arp.h>
>>  #include <net/sock.h>
>> @@ -527,8 +528,11 @@ unsigned char * __weak arch_get_platform_mac_address(void)
>>
>>  int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
>>  {
>> +     unsigned char addrbuf[ETH_ALEN];
>>       const unsigned char *addr;
>> +     struct nvmem_cell *nvmem;
>>       struct device_node *dp;
>> +     size_t alen;
>>
>>       if (dev_is_pci(dev))
>>               dp = pci_device_to_OF_node(to_pci_dev(dev));
>> @@ -541,6 +545,29 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
>>       if (!addr)
>>               addr = arch_get_platform_mac_address();
>>
>> +     if (!addr) {
>> +             nvmem = nvmem_cell_get(dev, "mac-address");
>> +             if (IS_ERR(nvmem) && 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)) {
>> +                     addr = nvmem_cell_read(nvmem, &alen);
>> +                     if (!IS_ERR(addr)) {
>                                     ^^^^
> Never do success handling.  Always error handling.  Otherwise the code
> is indent a lot and the error handling is far from the call.
>
>> +                             if (alen == ETH_ALEN)
>> +                                     ether_addr_copy(addrbuf, addr);
>> +
>> +                             kfree(addr);
>> +                             addr = alen == ETH_ALEN ? addrbuf : NULL;
>> +                     }
>> +
>> +                     nvmem_cell_put(nvmem);
>> +             }
>> +     }
>> +
>>       if (!addr || !is_valid_ether_addr(addr))
>                                           ^^^^
> Instead of handling the error we dereference the error pointer here.
>

True - we should add a check for IS_ERR(addr) here.

> *frowny face*
>
>>               return -ENODEV;
>>
>> --
>
> Maybe this?
>
>         if (!addr) {
>                 nvmem = nvmem_cell_get(dev, "mac-address");
>                 if (PTR_ERR(nvmem) == -EPROBE_DEFER)
>                         return -EPROBE_DEFER;
>                 if (IS_ERR(nvmem))
>                         return -ENODEV;
>                 addr = nvmem_cell_read(nvmem, &alen);
>                 if (IS_ERR(addr))
>                         return PTR_ERR(addr);
>                 if (alen != ETH_ALEN) {
>                         kfree(addr);
>                         return -ENODEV;
>                 }
>                 ether_addr_copy(addrbuf, addr);
>                 kfree(addr);
>                 addr = addrbuf;
>         }
>         if (!is_valid_ether_addr(addr))
>                 return -ENODEV;
>         ether_addr_copy(mac_addr, addr);
>         return 0;
>

I would normally go this way but here we don't want to bail out when
we encounter an error but rather continue on to the next possible
source of a MAC address. We'll get -ENODEV from nvmem_cell_get() if
the lookup fails for "mac-address" but instead of returning an error
code we should then check if we can read the MAC from MTD.

Bart

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Dan Carpenter]

Maybe it would be simpler as three separate functions:

int of_eth_get_mac_address() <- rename existing function to this
int nvmem_eth_get_mac_address() <- patch 2
int mtd_eth_nvmem_get_mac_address() patch 3

	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 == -EPROBEDEFER)
		return ret;
	if (!ret)
		return 0;
	ret = mtd_eth_nvmem_get_mac_address(dev, mac_addr);
	if (!ret)
		return 0;

	return -ENODEV;

regards,
dan carpenter

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Bartosz Golaszewski]

2018-07-19 11:09 GMT+02:00 Dan Carpenter <dan.carpenter@oracle.com>:
>
> Maybe it would be simpler as three separate functions:
>
> int of_eth_get_mac_address() <- rename existing function to this
> int nvmem_eth_get_mac_address() <- patch 2
> int mtd_eth_nvmem_get_mac_address() patch 3
>
>         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 == -EPROBEDEFER)
>                 return ret;
>         if (!ret)
>                 return 0;
>         ret = mtd_eth_nvmem_get_mac_address(dev, mac_addr);
>         if (!ret)
>                 return 0;
>
>         return -ENODEV;
>
> regards,
> dan carpenter

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.

Thanks,
Bart
>

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Dan Carpenter]

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);

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Bartosz Golaszewski]

2018-07-19 14:37 GMT+02:00 Dan Carpenter <dan.carpenter@oracle.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

[PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac_address()

[Russell King - ARM Linux]

On Thu, Jul 19, 2018 at 11:48:37AM +0300, Dan Carpenter wrote:
> On Thu, Jul 19, 2018 at 10:20:27AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > 
> > Many non-DT platforms read the MAC address from EEPROM. Usually it's
> > either done with callbacks defined in board files or from SoC-specific
> > ethernet drivers.
> > 
> > In order to generalize this, try to read the MAC from nvmem in
> > eth_platform_get_mac_address() using a standard lookup name:
> > "mac-address".
> > 
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > ---
> >  net/ethernet/eth.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> > 
> > diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
> > index 39af03894598..af3b4b1b77eb 100644
> > --- a/net/ethernet/eth.c
> > +++ b/net/ethernet/eth.c
> > @@ -54,6 +54,7 @@
> >  #include <linux/if_ether.h>
> >  #include <linux/of_net.h>
> >  #include <linux/pci.h>
> > +#include <linux/nvmem-consumer.h>
> >  #include <net/dst.h>
> >  #include <net/arp.h>
> >  #include <net/sock.h>
> > @@ -527,8 +528,11 @@ unsigned char * __weak arch_get_platform_mac_address(void)
> >  
> >  int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
> >  {
> > +	unsigned char addrbuf[ETH_ALEN];
> >  	const unsigned char *addr;
> > +	struct nvmem_cell *nvmem;
> >  	struct device_node *dp;
> > +	size_t alen;
> >  
> >  	if (dev_is_pci(dev))
> >  		dp = pci_device_to_OF_node(to_pci_dev(dev));
> > @@ -541,6 +545,29 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
> >  	if (!addr)
> >  		addr = arch_get_platform_mac_address();
> >  
> > +	if (!addr) {
> > +		nvmem = nvmem_cell_get(dev, "mac-address");
> > +		if (IS_ERR(nvmem) && 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)) {
> > +			addr = nvmem_cell_read(nvmem, &alen);
> > +			if (!IS_ERR(addr)) {
>                                     ^^^^
> Never do success handling.  Always error handling.  Otherwise the code
> is indent a lot and the error handling is far from the call.
> 
> > +				if (alen == ETH_ALEN)
> > +					ether_addr_copy(addrbuf, addr);
> > +
> > +				kfree(addr);
> > +				addr = alen == ETH_ALEN ? addrbuf : NULL;
> > +			}
> > +
> > +			nvmem_cell_put(nvmem);
> > +		}
> > +	}
> > +
> >  	if (!addr || !is_valid_ether_addr(addr))
>                                           ^^^^
> Instead of handling the error we dereference the error pointer here.
> 
> *frowny face*
> 
> >  		return -ENODEV;
> >  
> > --
> 
> Maybe this?
> 
> 	if (!addr) {
> 		nvmem = nvmem_cell_get(dev, "mac-address");
> 		if (PTR_ERR(nvmem) == -EPROBE_DEFER)
> 			return -EPROBE_DEFER;
> 		if (IS_ERR(nvmem))
> 			return -ENODEV;
> 		addr = nvmem_cell_read(nvmem, &alen);
> 		if (IS_ERR(addr))
> 			return PTR_ERR(addr);

The problem with doing it this way is... error handling is Hard(tm).
You missed the call to nvmem_cell_put() here.

> 		if (alen != ETH_ALEN) {
> 			kfree(addr);

and again here.

> 			return -ENODEV;
> 		}
> 		ether_addr_copy(addrbuf, addr);
> 		kfree(addr);
> 		addr = addrbuf;

and here.

> 	}
> 	if (!is_valid_ether_addr(addr))
> 		return -ENODEV;
> 	ether_addr_copy(mac_addr, addr);
> 	return 0;

Without checking the semantics, a possible solution to that could be:

	if (!addr) {
		nvmem = nvmem_cell_get(dev, "mac-address");
		if (PTR_ERR(nvmem) == -EPROBE_DEFER)
			return -EPROBE_DEFER;
		if (IS_ERR(nvmem))
			return -ENODEV;
		addr = nvmem_cell_read(nvmem, &alen);
+		nvmem_cell_put(nvmem);
		if (IS_ERR(addr))
			return PTR_ERR(addr);
		if (alen != ETH_ALEN) {
			kfree(addr);
			return -ENODEV;
		}
		ether_addr_copy(addrbuf, addr);
		kfree(addr);
		addr = addrbuf;
	}
	if (!is_valid_ether_addr(addr))
		return -ENODEV;
	ether_addr_copy(mac_addr, addr);
	return 0;

A potential better solution would be to put this code in a separate
function, and then do:

	if (!addr)
		addr = eth_platform_get_nvmem_mac_address(dev, addrbuf);

which returns either NULL or addrbuf depending on whether it failed or
succeeded, which would probably end up with cleaner code.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

[PATCH v2 3/3] net: add MTD support to eth_platform_get_mac_address()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

MTD doesn't support nvmem yet. Some platforms use MTD to read the MAC
address from SPI flash. If we want this function to generalize reading
the MAC address, we need to separately try to use MTD.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 net/ethernet/eth.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index af3b4b1b77eb..addbb3375e3b 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -55,6 +55,7 @@
 #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>
@@ -568,6 +569,23 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 		}
 	}
 
+#ifdef CONFIG_MTD
+	/* NOTE: this should go away as soon as MTD gets nvmem support. */
+	if (!addr) {
+		struct mtd_info *mtd;
+		int rv;
+
+		mtd = get_mtd_device_nm("MAC-Address");
+		if (!IS_ERR(mtd)) {
+			rv = mtd_read(mtd, 0, ETH_ALEN, &alen, addrbuf);
+			if (rv == 0)
+				addr = addrbuf;
+
+			put_mtd_device(mtd);
+		}
+	}
+#endif /* CONFIG_MTD */
+
 	if (!addr || !is_valid_ether_addr(addr))
 		return -ENODEV;
 
-- 
2.17.1