[U-Boot] [PATCH 09/14] net: Add ability to set MAC address via EEPROM
Olliver Schinagl
oliver at schinagl.nl
Tue Nov 29 17:45:21 CET 2016
Hey Michal,
On 28-11-16 09:21, Michal Simek wrote:
> On 25.11.2016 16:30, Olliver Schinagl wrote:
>> This patch allows Kconfig to enable and set parameters to make it
>> possible to read the MAC address from an EEPROM. The net core layer then
>> uses this information to read MAC addresses from this EEPROM.
>>
>> Besides the various tuneables as to how to access the eeprom (bus,
>> address, addressing mode/length, 2 configurable that are EEPROM generic
>> (e.g. SPI or some other form of access) which are:
>>
>> NET_ETHADDR_EEPROM_OFFSET, indicating where in the EEPROM the start of
>> the MAC address is. The default is 8 allowing for 8 bytes before the MAC
>> for other purposes (header MAGIC for example).
>>
>> NET_ETHADDR_EEPROM_CRC8, indicating the MAC is appended with a CRC8-CCIT
>> checksum that should be verified.
>>
>> Currently only I2C eeproms have been tested and thus only those options
>> are available, but shouldn't be a limit. NET_ETHADDR_EEPROM_SPI can be
>> just as created and added.
>>
>> The code currently first checks if there is a non-zero MAC address in
>> the eeprom. If that fails to be the case, the read_rom_hwaddr can be
>> used by a board to supply the MAC in other ways.
>>
>> If both these fails, the other code is still in place to query the
>> environent, which then can be used to override the hardware supplied
>> data.
>>
>> Signed-off-by: Olliver Schinagl <oliver at schinagl.nl>
>> ---
>> doc/README.enetaddr | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>> include/net.h | 14 ++++++++
>> net/Kconfig | 59 +++++++++++++++++++++++++++++++
>> net/eth-uclass.c | 9 +++--
>> net/eth_common.c | 34 ++++++++++++++++++
>> net/eth_legacy.c | 2 ++
>> 6 files changed, 214 insertions(+), 3 deletions(-)
>>
>> diff --git a/doc/README.enetaddr b/doc/README.enetaddr
>> index 50e4899..89c1f7d 100644
>> --- a/doc/README.enetaddr
>> +++ b/doc/README.enetaddr
>> @@ -47,6 +47,105 @@ Correct flow of setting up the MAC address (summarized):
>> Previous behavior had the MAC address always being programmed into hardware
>> in the device's init() function.
>>
>> +--------
>> + EEPROM
>> +--------
>> +
>> +Boards may come with an EEPROM specifically to store configuration bits, such
>> +as a MAC address. Using CONFIG_NET_ETHADDR_EEPROM enables this feature.
>> +Depending on the board, the EEPROM may be connected on various methods, but
>> +currently, only the I2C bus can be used via CONFIG_NET_ETHADDR_EEPROM_I2C.
>> +
>> +The following config options are available,
>> +CONFIG_NET_ETHADDR_EEPROM_I2C_BUS is the I2C bus on which the eeprom is present.
>> +CONFIG_NET_ETHADDR_EEPROM_I2C_ADDR sets the address of the EEPROM, which
>> +defaults to the very common 0x50. Small size EEPROM's generally use single byte
>> +addressing but larger EEPROM's may use double byte addressing, which can be
>> +configured using CONFIG_NET_ETHADDR_EEPROM_ADDRLEN.
>> +
>> +Within the EEPROM, the MAC address can be stored on any arbitrary offset,
>> +CONFIG_NET_ETHADDR_EEPROM_OFFSET sets this to 8 as a default however, allowing
>> +the first 8 bytes to be used for an optional data, for example a configuration
>> +struct where the mac address is part of.
>> +
>> +Appending the 6 (ARP_HLEN) bytes is a CRC8 byte over the previous ARP_HLEN
>> +bytes. Whether to check this CRC8 or not is dependent on
>> +CONFIG_NET_ETHADDR_EEPROM_CRC8.
>> +
>> +To keep things nicely aligned, a final 'reserved' byte is added to the mac
>> +address + crc8 combo.
>> +
>> +A board may want to store more information in its eeprom, using the following
>> +example layout, this can be achieved.
>> +
>> +struct mac_addr {
>> + uint8_t mac[ARP_HLEN];
>> + uint8_t crc8;
>> + uint8_t reserved;
>> +};
>> +
>> +struct config_eeprom {
>> + uint32_t magic;
>> + uint8_t version;
>> + uint8_t reserved[2];
>> + uint8_t mac_cnt;
>> + struct mac_addr[mac_cnt];
>> +};
>> +
>> +Filling this in:
>> +struct config_eeprom eeprom = {
>> + .magic = { 'M', 'g', 'i', 'c' },
>> + .reserved = { 0x00, 0x00 },
>> + .mac_cnt = 2,
>> + .mac_addr = {
>> + {
>> + .mac = {
>> + 0x01, 0x23, 0x45,
>> + 0x67, 0x89, 0xab,
>> + },
>> + .crc8 = 0xbe,
>> + .reserved = 0x00,
>> + }, {
>> + .mac = {
>> + 0xba, 0x98, 0x76,
>> + 0x54, 0x32, 0x10,
>> + },
>> + .crc8 = 0x82,
>> + .reserved = 0x00,
>> + },
>> + },
>> +};
>> +
>> +The eeprom content would look like this.
>> +
>> +00000000 4d 67 69 63 01 00 00 02 01 23 45 67 89 ab be 00 |Mgic.....#Eg....|
>> +00000010 ba 98 76 54 32 10 82 00 |..vT2...|
>> +
>> +This can be done from linux using the i2c-tools:
>> +
>> +i2cset I2CBUS 0x50 0x08 0x01
>> +i2cset I2CBUS 0x50 0x09 0x23
>> +i2cset I2CBUS 0x50 0x0a 0x45
>> +i2cset I2CBUS 0x50 0x0b 0x67
>> +i2cset I2CBUS 0x50 0x0c 0x89
>> +i2cset I2CBUS 0x50 0x0d 0xab
>> +i2cset I2CBUS 0x50 0x0e 0xbe
>> +
>> +Alternativly this can be done from the u-boot console as:
>> +
>> +u-boot> mm.b 0
>> +00000000: 00 ? 01
>> +00000001: 23 ? 23
>> +00000002: 45 ? 45
>> +00000003: 67 ? 67
>> +00000004: 89 ? 89
>> +00000005: ab ? ab
>> +00000006: be ? be
>> +00000007: 00 ? q
>> +i2c dev I2CBUS
>> +i2c write 0 50 8 7
>> +i2c md 50 8
>> +
>> -------
>> Usage
>> -------
>> diff --git a/include/net.h b/include/net.h
>> index 08f8af8..e50ab5d 100644
>> --- a/include/net.h
>> +++ b/include/net.h
>> @@ -248,6 +248,20 @@ int eth_getenv_enetaddr(const char *name, uchar *enetaddr);
>> int eth_setenv_enetaddr(const char *name, const uchar *enetaddr);
>>
>> /**
>> + * eeprom_read_enetaddr() - Read the hardware address from an eeprom
>> + *
>> + * This function tries to read the MAC address from an eeprom as can be read
>> + * in docs/README.enetaddr.
>> + *
>> + * @index: index of the interface to get the hwaddr for
>> + * @enetaddr: pointer for the found hwaddr. Needs to be atleast ARP_HLEN
>> + * @return: 0 on success, non-zero is error status. Additionally hwaddr
>> + * is set to 00:00:00:00:00. This is also the case if
>> + * CONFIG_NET_ETHADDR_EEPROM is not set.
>> + */
>> +int eeprom_read_enetaddr(const int index, unsigned char *enetaddr);
>> +
>> +/**
>> * eth_setenv_enetaddr_by_index() - set the MAC address environment variable
>> *
>> * This sets up an environment variable with the given MAC address (@enetaddr).
>> diff --git a/net/Kconfig b/net/Kconfig
>> index 414c549..f699e1c 100644
>> --- a/net/Kconfig
>> +++ b/net/Kconfig
>> @@ -7,6 +7,65 @@ menuconfig NET
>>
>> if NET
>>
>> +config NET_ETHADDR_EEPROM
>> + bool "Get ethaddr from eeprom"
>> + help
>> + Selecting this will try to get the Ethernet address from an onboard
>> + EEPROM and set into the environment if and only if the environment
>> + does currently not already hold a MAC address. For more information
>> + see doc/README.enetaddr.
>> +
>> +config NET_ETHADDR_EEPROM_I2C
>> + depends on NET_ETHADDR_EEPROM
>> + bool "EEPROM on I2C bus"
>> + help
>> + This switch enables checks for an EEPROM on the I2C bus. Naturally
>> + this will only work if there is an actual EEPROM connected on the
>> + I2C bus and the bus and device are properly configured via the
>> + options below.
>> +
>> +config NET_ETHADDR_EEPROM_I2C_BUS
>> + depends on NET_ETHADDR_EEPROM_I2C
>> + int "I2C bus"
>> + default 0
>> + help
>> + Select the bus on which the EEPROM is present, defaults to bus 0.
>> + Remember to also make the selected bus available via I2Cn_ENABLE.
>> +
>> +config NET_ETHADDR_EEPROM_I2C_ADDR
>> + depends on NET_ETHADDR_EEPROM_I2C
>> + hex "EEPROM address"
>> + default 0x50
>> + help
>> + Select the address of the EEPROM, defaults to address 0x50.
>> +
>> +config NET_ETHADDR_EEPROM_I2C_ADDRLEN
>> + depends on NET_ETHADDR_EEPROM_I2C
>> + int "EEPROM address length"
>> + default 1
>> + help
>> + Number of bytes to be used for the I2C address length. Typically 1,
>> + 2 for large memories, 0 for register type devices with only one
>> + register.
>> +
>> +config NET_ETHADDR_EEPROM_OFFSET
>> + depends on NET_ETHADDR_EEPROM
>> + int "EEPROM offset"
>> + default 8
>> + help
>> + Select the byte offset of the MAC address within the page,
>> + defaults to byte 8.
> I would prefer to all these values to be in hex because i2c commands are
> also taking values in hex.
You are completly right and this is indeed my mistake. I will fix it for v2.
Incidently I put them on 0x50 in my own config files for this exact
reason. I probably did not realise I could make it default to hex :)
>
>> +
>> +config NET_ETHADDR_EEPROM_CRC8
>> + depends on NET_ETHADDR_EEPROM
>> + bool "Check CRC8 of MAC"
>> + default y
>> + help
>> + Optionally, it is possible to run a CRC-8-CCITT check on the MAC
>> + address. To do so, the MAC address is stored with a CRC8 byte append.
>> + This option enables the CRC check of the MAC address against the CRC
>> + byte.
>> +
> Would it be possible to have default n here?
> I would guess that more boards don't have this CRC8 sums.
I agree, but most boards will not use this by default yet. If you enable
this feature for your board, I strongly strongly recommend enabeling
this feature as well. Thus disable it by user request.
Reason why I strongly recommend to enable it: If i have an unprogrammed
eeprom, it comes filled with 0xffffffff. Which is interpreted as a
correct mac address. What if i have random garbage in the eeprom (or a
user change one bit by accident). I still have a valid mac address.
Using the crc8 to validate the mac address makes this a lot more safe.
Olliver
>
> Thanks,
> Michal
>
>
>
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