.\" Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright notice,
.\"    this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of VegaOS nor the names of its
.\"    contributors may be used to endorse or promote products derived from
.\"    this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.Dd October 4, 2023
.Dt MMIO 9
.Os
.Sh NAME
.Nm mmio - vega MMIO interface
.Sh SYNOPSIS
.In sys/mmio.h

.Bd -literal
static inline void mmio_write8(void *addr, uint8_t val);
static inline void mmio_write16(void *addr, uint16_t val);
static inline void mmio_write32(void *addr, uint32_t val);
#if __SIZEOF_SIZE_T__ == 8
static inline void mmio_write64(void *addr, uint64_t val);
#endif
__extension__
.Ed

.Sh DESCRIPTION
In short, MMIO is a method of writing to registers
of an I/O device via a mapped porition of memory. MMIO
should NOT be done on your own when doing Vega kernel programming.
Instead, rely on Vega's MMIO interface and use
.Ft mmio_read<n>()
and
.Ft mmio_write<n>()
functions. Where `n` is 8 to 32 on 32-bit machines, and to 64
on 64-bit machines.

The
.Ft addr
argument can be either a physical address or virtual
address; however, it is recommended to use virtual addresses
for the sake of consistency.

.Sh AUTHORS
.An Ian Moffett Aq Mt ian@osmora.org