x86 Linux Kernel and Integration

Most x86 platforms will “just work” with the stock ONIE x86 kernel, but some platform specific modifications may be necessary.

Kernel Modifications

To add support to the kernel for a particular platform, the following Linux kernel files must be created or modified:

File Purpose
linux/drivers/platform/x86/vendor_machine.c Platform support C file. Basic initialization and reset.
linux/drivers/platform/x86/Kconfig Kernel configuration fragment that allows the new platform to be selected.
linux/drivers/platform/x86/Makefile Makefile fragment detailing what C file to compile when the platform is selected.

What needs to go into the platform-specific kernel files varies from platform to platform. Some common reasons for adding platform specific kernel code:

  • Special reset sequence, perhaps requiring access to a specific CPLD.
  • Mapping GPIO lines to specific things, like I2C multiplexers or front panel LEDs.

The resulting stg kernel patches are stored in the $MACHINE/kernel directory. Patches placed here will automatically be applied by the build system.

See the Patching ONIE Using stgit section for information about how to create stg patches.

Board EEPROM Access – onie-syseeprom

On x86 platforms the onie-syseeprom is used to access the board EEPROM. The syntax of the command follows:

ONIE:/ # onie-syseeprom -h
Display and program the system EEPROM data block.
Usage: sys-eeprom [-h][-l] [-e] [-s <code>=<value>,...]
   With no arguments display the EEPROM contents.
   -h --help
      Display usage
   -l --list
      List the understood TLV codes and names.
   -e --erase
      Reset the EEPROM data.
   -g --get <code>
      Look up a TLV by code and write the value to stdout.
   -s --set <code>=<value>,<code>=<value>...
      Set a TLV code to a value.
      If no value, TLV is deleted.

See the Board EEPROM Information Format section for more about the format of the EEPROM data and available TLV fields.

In order for the tool to work, however, each platform must define how to access its EEPROM. At a minimum, each platform must define the following in sys_eeprom_platform.h:

SYS_EEPROM_SIZE       : size of usable eeprom
SYS_EEPROM_I2C_ADDR   : address on the bus

The following may also be defined in sys_eeprom_platform.h, or else the defaults will take over:

SYS_EEPROM_MAX_SIZE : Total size of the eeprom
SYS_EEPROM_OFFSET   : offset from where the ONIE TLV header starts

For details, see the onie-syseeprom patch, onie/patches/i2ctools/i2ctools-sys-eeprom.patch.

On the x86 architecture the onie-sysinfo command uses the onie-syseeprom command to generate parts of its output. See the System Information section for more about the onie-sysinfo command.