[U-Boot] [PATCH v2 1/5] net: Add ability to set MAC address via EEPROM to Kconfig

[Olliver Schinagl]

This patch allows Kconfig to enable and set parameters to make it
possible to read the MAC address from an EEPROM. This patch only sets up
some environment variables, it is up to the specific boards to actually
use these defines.

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.

Signed-off-by: Olliver Schinagl <o.schinagl at ultimaker.com>
---
 doc/README.enetaddr | 34 +++++++++++++++++++++++++++++++
 net/Kconfig         | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/doc/README.enetaddr b/doc/README.enetaddr
index 50e4899..1dc4119 100644
--- a/doc/README.enetaddr
+++ b/doc/README.enetaddr
@@ -47,6 +47,40 @@ 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
+--------
+
+When there is an EEPROM available on a board, but the EEPROM is not large enough
+to store the whole environment, it may be desired to store a MAC address in the
+onboard EEPROM. 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 is available via CONFIG_NET_ETHADDR_EEPROM_I2C.
+CONFIG_NET_ETHADDR_EEPROM_I2C_BUS I2C bus on which the eeprom is present and
+CONFIG_NET_ETHADDR_EEPROM_I2C_ADDR set 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 header magic.
+
+Appending the 6 MAC bytes a CRC8 byte over the previous 6 bytes. Whether to check
+this CRC8 or not is dependent on CONFIG_NET_ETHADDR_EEPROM_CRC8.
+
+After the 6 bytes used for the MAC address, the 8th byte is used to indicate
+the ID of the network interface this MAC address is for. 0xff here means 'for
+the first available interface' and 0x00 means the first network interface, 0x01
+the second, etc. It is up to the platform however to enforce this.
+
+Layout example:
+
+00000000  21 4d 61 67 69 63 2e 21  01 23 45 67 89 ab be ff |!Magic.!.#Eg....|
+
+where the Header magic (!Magic.!) is spread over the first 8 bytes, and the MAC
+address '01-23-45-67-89-ab' with the CRC8 checksum 0xbe for any interface (0xff)
+
 -------
  Usage
 -------
diff --git a/net/Kconfig b/net/Kconfig
index a44a783..aced51e 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -7,6 +7,64 @@ 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.
+
+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.
+
+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.
+
 config NET_RANDOM_ETHADDR
 	bool "Random ethaddr if unset"
 	select LIB_RAND
-- 
2.6.2