xref: /openbmc/linux/Documentation/ABI/testing/sysfs-kernel-boot_params (revision 34433332)

What:		/sys/kernel/boot_params
Date:		December 2013
Contact:	Dave Young <dyoung@redhat.com>
Description:	The /sys/kernel/boot_params directory contains two
		files: "data" and "version" and one subdirectory "setup_data".
		It is used to export the kernel boot parameters of an x86
		platform to userspace for kexec and debugging purpose.

		If there's no setup_data in boot_params the subdirectory will
		not be created.

		"data" file is the binary representation of struct boot_params.

		"version" file is the string representation of boot
		protocol version.

		"setup_data" subdirectory contains the setup_data data
		structure in boot_params. setup_data is maintained in kernel
		as a link list. In "setup_data" subdirectory there's one
		subdirectory for each link list node named with the number
		of the list nodes. The list node subdirectory contains two
		files "type" and "data". "type" file is the string
		representation of setup_data type. "data" file is the binary
		representation of setup_data payload.

		The whole boot_params directory structure is like below::

		  /sys/kernel/boot_params
		  |__ data
		  |__ setup_data
		  |   |__ 0
		  |   |   |__ data
		  |   |   |__ type
		  |   |__ 1
		  |       |__ data
		  |       |__ type
		  |__ version

Users:		Kexec