.\"	$OpenBSD: efi.4,v 1.3 2024/05/05 19:13:13 kn Exp $
.\"
.\" Copyright (c) 2018 Mark Kettenis <kettenis@openbsd.org>
.\" Copyright (c) 2024 Klemens Nanni <kn@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: May 5 2024 $
.Dt EFI 4
.Os
.Sh NAME
.Nm efi
.Nd Unified Extensible Firmware Interface
.Sh SYNOPSIS
.Cd "# amd64"
.Cd "efi* at bios?"
.Pp
.Cd "# arm64"
.Cd "efi* at fdt?"
.Sh DESCRIPTION
The
.Nm
driver provides support for EFI runtime services offered by UEFI
firmware implementations.
It can read and write the Real Time Clock and provides userland applications
.Xr ioctl 2
access to the System Resource Table and to read and write variables.
.Sh IOCTLS
.Nm
supports the following
.Xr ioctl 2
commands, available through
.In dev/efi/efi.h
.In dev/efi/efiio.h :
.Bl -tag -width xxxx
.It Dv EFIIOC_GET_TABLE Fa "struct efi_get_table_ioc *"
.Bd -literal
struct efi_get_table_ioc {
	void *buf;          /* Pointer to userspace buffer */
	struct uuid uuid;   /* UUID to look up */
	size_t table_len;   /* Table size */
	size_t buf_len;     /* Size of the buffer */
};
.Ed
.Pp
Read a table.
.It Dv EFIIOC_VAR_GET Fa "struct efi_var_ioc *"
.Bd -literal
struct efi_var_ioc {
	uint16_t *name;     /* User pointer to name, in UCS2 chars */
	size_t namesize;    /* Number of *bytes* in the name
	                       including terminator */
	struct uuid vendor; /* Vendor's UUID for variable */
	uint32_t attrib;    /* Attributes */
	void *data;         /* User pointer to value */
	size_t datasize;    /* Number of *bytes* in the value */
};
.Ed
.Pp
Read a variable.
.It Dv EFIIOC_VAR_NEXT Fa "struct efi_var_ioc *"
Enumerate all variables.
The first command must use the empty name.
Further ones must denote the previous variable's name and UUID.
.It Dv EFIIOC_VAR_SET Fa "struct efi_var_ioc *"
Write a variable.
Delete it if
.Va datasize
is zero.
.El
.Sh FILES
.Bl -tag -width /dev/efi -compact
.It Pa /dev/efi
.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr intro 4
.Sh HISTORY
The
.Nm
device driver first appeared for arm64 in
.Ox 6.3 .
Support for amd64, the ESRT and EFI variables appeared in
.Ox 7.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Mark Kettenis Aq Mt kettenis@openbsd.org .
Support for the ESRT and EFI variables is heavily based on work done by
.An Sergii Dmytruk Aq Mt sergii.dmytruk@3meb.com .