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.\"	$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>
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.\" purpose with or without fee is hereby granted, provided that the above
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.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 .