[U-Boot] [PATCH v3] Retrieve MAC address from EEPROM

[Michal Simek]

On 8.11.2016 16:54, Olliver Schinagl wrote:
> This patch-series introduces methods to retrieve the MAC address from an
> onboard EEPROM using the read_rom_hwaddr hook.
> 
> The reason we might want to read the MAC address from an EEPROM instead of
> storing the entire environment is mostly a size thing. Our default environment
> already is bigger then the EEPROM so it is understandable that someone might
> not give up the entire eeprom just for the u-boot environment. Especially if
> only board specific things might be stored in the eeprom (MAC, serial, product
> number etc). Additionally it is a board thing and a MAC address might be
> programmed at the factory before ever seeing any software.
> 
> The current idea of the eeprom layout, is to skip the first 8 bytes, so that
> other information can be stored there if needed, for example a header with some
> magic to identify the EEPROM. Or equivalent purposes.
> 
> After those 8 bytes the MAC address follows the first macaddress. The macaddress
> is appended by a CRC8 byte and then padded to make for nice 8 bytes. Following
> the first macaddress one can store a second, or a third etc etc mac addresses.
> 
> The CRC8 is optional (via a define) but is strongly recommended to have. It
> helps preventing user error and more importantly, checks if the bytes read are
> actually a user inserted address. E.g. only writing 1 macaddress into the eeprom
> but trying to consume 2.
> 
> Hans de Goede and I talked about retrieving the MAC from the EEPROM for sunxi
> based boards a while ago, but hopefully this patch makes possible to have
> something slightly more generic, even if only the configuration options.
> Additionally the EEPROM layout could be recommended by u-boot as well.
> 
> Since the Olimex OLinuXino sunxi boards all seem to have an eeprom, I started
> my work on one of these and tested the implementation with one of our own real
> MAC addresses.
> 
> What still needs disussing I think, is the patches that remove the
> 'setup_environment' function in board.c. I think we have put functionality in
> boards.c which does not belong. Injecting ethernet addresses into the
> environment instead of using the net_op hooks as well as parsing the fdt to get
> overrides from. I think especially this last point should be done at a higher
> level, if possible at all.
> 
> I explicitly did not use the wiser eth_validate_ethaddr_str(),
> eth_parse_enetaddr() and the ARP_HLEN define as it was quite painful
> (dependancies) to get these functions into the tools. I would suggest to merge
> as is, and if someone wants to improve these simple tools to use these functions
> to happily do so.
> 
> These patches where tested on Olimex OLinuXino Lime1 (A10/A20), Lime2 (NAND
> and eMMC) and A20-OLinuXino-MICRO-4G variants and have been in use
> internally on our production systems since v2 of this patch set.
> 
> As a recommendation, I would suggest for the zynq to adopt the config defines,
> as they are nice and generic and suggest to also implement the 8 byte offset,
> crc8 and pad bytes.

Yes, Zynq and ZynqMP is using this feature. I am also aware about using
qspi OTP region for storing information like this.

Thanks,
Michal