163 lines
4.6 KiB
Groff
163 lines
4.6 KiB
Groff
.\" $NetBSD: spi.9,v 1.2 2019/02/23 17:37:10 wiz Exp $
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.\"
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.\" Copyright (c) 2019 The NetBSD Foundation
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.\" All rights reserved.
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.\"
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.\" Written by Michael van Elst
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd February 23, 2019
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.Dt SPI 9
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.Os
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.Sh NAME
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.Nm spi_configure ,
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.Nm spi_transfer ,
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.Nm spi_transfer_init ,
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.Nm spi_chunk_init ,
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.Nm spi_transfer_add ,
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.Nm spi_wait ,
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.Nm spi_done ,
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.Nm spi_send ,
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.Nm spi_recv ,
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.Nm spi_send_recv
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.Nd Serial Peripheral Interface (SPI) kernel interface
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.Sh SYNOPSIS
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.In dev/spi/spivar.h
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.Ft int
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.Fo spi_configure
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.Fa "struct spi_handle *sh"
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.Fa "int mode"
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.Fa "int speed"
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.Fc
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.Ft int
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.Fo spi_transfer
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.Fa "struct spi_handle *sh"
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.Fa "struct spi_transfer *st"
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.Fc
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.Ft void
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.Fo spi_transfer_init
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.Fa "struct spi_transfer *st"
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.Fc
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.Ft void
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.Fo spi_chunk_init
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.Fa "struct spi_chunk *chunk"
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.Fa "int cnt"
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.Fa "const uint8_t *wptr"
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.Fa "uint8_t *rptr"
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.Fc
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.Ft void
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.Fo spi_transfer_add
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.Fa "struct spi_transfer *st"
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.Fa "struct spi_chunk *chunk"
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.Fc
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.Ft void
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.Fo spi_wait
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.Fa "struct spi_transfer *st"
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.Fc
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.Ft void
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.Fo spi_done
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.Fa "struct spi_transfer *st"
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.Fa "int err"
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.Fc
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.Ft int
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.Fo spi_recv
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.Fa "struct spi_handle *sh"
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.Fa "int cnt"
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.Fa "uint8_t *data"
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.Fc
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.Ft int
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.Fo spi_send
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.Fa "struct spi_handle *sh"
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.Fa "int cnt"
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.Fa "const uint8_t *data"
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.Fc
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.Ft int
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.Fo spi_send_recv
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.Fa "struct spi_handle *sh"
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.Fa "int scnt"
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.Fa "const uint8_t *snd"
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.Fa "int rcnt"
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.Fa "const uint8_t *rcv"
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.Fc
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.Sh DESCRIPTION
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SPI is a 4-wire synchronous full-duplex serial bus.
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It is commonly used for connecting devices such as EEPROMs,
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displays, and other types of integrated circuits.
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The
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.Nm spi
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interface provides a means of communicating with SPI-connected devices.
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.Sh FUNCTIONS
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The following functions comprise the API provided to drivers of
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SPI-connected devices.
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.Pp
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The
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.Fa struct spi_handle
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corresponding to the device is passed in the driver attachment.
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.Bl -tag -width spi_transfer_init
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.It Fn spi_configure "sh" "mode" "speed"
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Sets mode and speed for subsequent communication with a SPI slave.
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.It Fn spi_transfer "sh" "st"
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Queue transfer to SPI controller.
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.Fn spi_transfer
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returns an errno value when the transfer couldn't be queued.
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.It Fn spi_transfer_init "st"
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Initialize a transfer structure.
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.It Fn spi_chunk_init "chunk" "cnt" "wptr" rptr"
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Initialize a chunk structure, each chunk corresponds to
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a possibly bi-directional transfer where the same amount
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of bytes is shifted in and out.
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.It Fn spi_transfer_add "st" "chunk"
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Append a chunk to transfer structure.
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.It Fn spi_wait "st"
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Wait for a transfer to complete.
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When the transfer has failed for some reason, the field
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.Va st->st_errno
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is set to a non-zero value.
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.It Fn spi_done "st" "err"
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Called back machine-dependent backend to signal completion
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of a transfer.
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.El
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.Pp
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For simplicity there are convenience functions that combine
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common operations.
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These functions return an errno value when the transfer failed.
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.Bl -tag -width spi_transfer_init
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.It Fn spi_recv "sh" "cnt" "data"
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Prepares a chunk for receiving data, queues a transfer and
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waits for it to complete.
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.It Fn spi_send "sh" "cnt" "data"
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Prepares a chunk for sending data, queues a transfer and
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waits for it to complete.
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.It Fn spi_send_recv "sh" "scnt" "snd" "rcnt" "rcv"
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Prepares two chunks for sending data first and then receiving
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an answer, queues a transfer and waits for it to complete.
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This is not a full-duplex operation.
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.El
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.Sh SEE ALSO
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.Xr spi 4
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.Sh HISTORY
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The
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.Nm spi
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API first appeared in
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.Nx 4.0 .
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