xref: /openbmc/linux/Documentation/ABI/testing/dell-smbios-wmi (revision f2645fa3)

What:		/dev/wmi/dell-smbios
Date:		November 2017
KernelVersion:	4.15
Contact:	"Mario Limonciello" <mario.limonciello@dell.com>
Description:
		Perform SMBIOS calls on supported Dell machines.
		through the Dell ACPI-WMI interface.

		IOCTL's and buffer formats are defined in:
		<uapi/linux/wmi.h>

		1) To perform an SMBIOS call from userspace, you'll need to
		first determine the minimum size of the calling interface
		buffer for your machine.
		Platforms that contain larger buffers can return larger
		objects from the system firmware.
		Commonly this size is either 4k or 32k.

		To determine the size of the buffer read() a u64 dword from
		the WMI character device /dev/wmi/dell-smbios.

		2) After you've determined the minimum size of the calling
		interface buffer, you can allocate a structure that represents
		the structure documented above.

		3) In the 'length' object store the size of the buffer you
		determined above and allocated.

		4) In this buffer object, prepare as necessary for the SMBIOS
		call you're interested in.  Typically SMBIOS buffers have
		"class", "select", and "input" defined to values that coincide
		with the data you are interested in.
		Documenting class/select/input values is outside of the scope
		of this documentation. Check with the libsmbios project for
		further documentation on these values.

		6) Run the call by using ioctl() as described in the header.

		7) The output will be returned in the buffer object.

		8) Be sure to free up your allocated object.