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/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
* include/linux/spi/spidev.h
* Copyright (C) 2006 SWAPP
* Andrea Paterniani <>
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#ifndef SPIDEV_H
#define SPIDEV_H
#include <linux/types.h>
#include <linux/ioctl.h>
#include <linux/spi/spi.h>
/* IOCTL commands */
#define SPI_IOC_MAGIC 'k'
* struct spi_ioc_transfer - describes a single SPI transfer
* @tx_buf: Holds pointer to userspace buffer with transmit data, or null.
* If no data is provided, zeroes are shifted out.
* @rx_buf: Holds pointer to userspace buffer for receive data, or null.
* @len: Length of tx and rx buffers, in bytes.
* @speed_hz: Temporary override of the device's bitrate.
* @bits_per_word: Temporary override of the device's wordsize.
* @delay_usecs: If nonzero, how long to delay after the last bit transfer
* before optionally deselecting the device before the next transfer.
* @cs_change: True to deselect device before starting the next transfer.
* @word_delay_usecs: If nonzero, how long to wait between words within one
* transfer. This property needs explicit support in the SPI controller,
* otherwise it is silently ignored.
* This structure is mapped directly to the kernel spi_transfer structure;
* the fields have the same meanings, except of course that the pointers
* are in a different address space (and may be of different sizes in some
* cases, such as 32-bit i386 userspace over a 64-bit x86_64 kernel).
* Zero-initialize the structure, including currently unused fields, to
* accommodate potential future updates.
* SPI_IOC_MESSAGE gives userspace the equivalent of kernel spi_sync().
* Pass it an array of related transfers, they'll execute together.
* Each transfer may be half duplex (either direction) or full duplex.
* struct spi_ioc_transfer mesg[4];
* ...
* status = ioctl(fd, SPI_IOC_MESSAGE(4), mesg);
* So for example one transfer might send a nine bit command (right aligned
* in a 16-bit word), the next could read a block of 8-bit data before
* terminating that command by temporarily deselecting the chip; the next
* could send a different nine bit command (re-selecting the chip), and the
* last transfer might write some register values.
struct spi_ioc_transfer {
__u64 tx_buf;
__u64 rx_buf;
__u32 len;
__u32 speed_hz;
__u16 delay_usecs;
__u8 bits_per_word;
__u8 cs_change;
__u8 tx_nbits;
__u8 rx_nbits;
__u8 word_delay_usecs;
__u8 pad;
/* If the contents of 'struct spi_ioc_transfer' ever change
* incompatibly, then the ioctl number (currently 0) must change;
* ioctls with constant size fields get a bit more in the way of
* error checking than ones (like this) where that field varies.
* NOTE: struct layout is the same in 64bit and 32bit userspace.
/* not all platforms use <asm-generic/ioctl.h> or _IOC_TYPECHECK() ... */
#define SPI_MSGSIZE(N) \
((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \
? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
/* Read / Write of SPI mode (SPI_MODE_0..SPI_MODE_3) (limited to 8 bits) */
#define SPI_IOC_RD_MODE _IOR(SPI_IOC_MAGIC, 1, __u8)
#define SPI_IOC_WR_MODE _IOW(SPI_IOC_MAGIC, 1, __u8)
/* Read / Write SPI bit justification */
/* Read / Write SPI device word length (1..N) */
/* Read / Write SPI device default max speed hz */
/* Read / Write of the SPI mode field */
#define SPI_IOC_RD_MODE32 _IOR(SPI_IOC_MAGIC, 5, __u32)
#define SPI_IOC_WR_MODE32 _IOW(SPI_IOC_MAGIC, 5, __u32)
#endif /* SPIDEV_H */