path: root/include/linux/spi/spi.h

/*
 * Copyright (C) 2005 David Brownell
 *
 * 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
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * 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 __LINUX_SPI_H
#define __LINUX_SPI_H

#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/slab.h>
#include <linux/kthread.h>

/*
 * INTERFACES between SPI master-side drivers and SPI infrastructure.
 * (There's no SPI slave support for Linux yet...)
 */
extern struct bus_type spi_bus_type;

/**
 * struct spi_device - Master side proxy for an SPI slave device
 * @dev: Driver model representation of the device.
 * @master: SPI controller used with the device.
 * @max_speed_hz: Maximum clock rate to be used with this chip
 *	(on this board); may be changed by the device's driver.
 *	The spi_transfer.speed_hz can override this for each transfer.
 * @chip_select: Chipselect, distinguishing chips handled by @master.
 * @mode: The spi mode defines how data is clocked out and in.
 *	This may be changed by the device's driver.
 *	The "active low" default for chipselect mode can be overridden
 *	(by specifying SPI_CS_HIGH) as can the "MSB first" default for
 *	each word in a transfer (by specifying SPI_LSB_FIRST).
 * @bits_per_word: Data transfers involve one or more words; word sizes
 *	like eight or 12 bits are common.  In-memory wordsizes are
 *	powers of two bytes (e.g. 20 bit samples use 32 bits).
 *	This may be changed by the device's driver, or left at the
 *	default (0) indicating protocol words are eight bit bytes.
 *	The spi_transfer.bits_per_word can override this for each transfer.
 * @irq: Negative, or the number passed to request_irq() to receive
 *	interrupts from this device.
 * @controller_state: Controller's runtime state
 * @controller_data: Board-specific definitions for controller, such as
 *	FIFO initialization parameters; from board_info.controller_data
 * @modalias: Name of the driver to use with this device, or an alias
 *	for that name.  This appears in the sysfs "modalias" attribute
 *	for driver coldplugging, and in uevents used for hotplugging
 *
 * A @spi_device is used to interchange data between an SPI slave
 * (usually a discrete chip) and CPU memory.
 *
 * In @dev, the platform_data is used to hold information about this
 * device that's meaningful to the device's protocol driver, but not
 * to its controller.  One example might be an identifier for a chip
 * variant with slightly different functionality; another might be
 * information about how this particular board wires the chip's pins.
 */
struct spi_device {
	struct device		dev;
	struct spi_master	*master;
	u32			max_speed_hz;
	u8			chip_select;
	u8			mode;
#define	SPI_CPHA	0x01			/* clock phase */
#define	SPI_CPOL	0x02			/* clock polarity */
#define	SPI_MODE_0	(0|0)			/* (original MicroWire) */
#define	SPI_MODE_1	(0|SPI_CPHA)
#define	SPI_MODE_2	(SPI_CPOL|0)
#define	SPI_MODE_3	(SPI_CPOL|SPI_CPHA)
#define	SPI_CS_HIGH	0x04			/* chipselect active high? */
#define	SPI_LSB_FIRST	0x08			/* per-word bits-on-wire */
#define	SPI_3WIRE	0x10			/* SI/SO signals shared */
#define	SPI_LOOP	0x20			/* loopback mode */
#define	SPI_NO_CS	0x40			/* 1 dev/bus, no chipselect */
#define	SPI_READY	0x80			/* slave pulls low to pause */
	u8			bits_per_word;
	int			irq;
	void			*controller_state;
	void			*controller_data;
	char			modalias[SPI_NAME_SIZE];

	/*
	 * likely need more hooks for more protocol options affecting how
	 * the controller talks to each chip, like:
	 *  - memory packing (12 bit samples into low bits, others zeroed)
	 *  - priority
	 *  - drop chipselect after each word
	 *  - chipselect delays
	 *  - ...
	 */
};

static inline struct spi_device *to_spi_device(struct device *dev)
{
	return dev ? container_of(dev, struct spi_device, dev) : NULL;
}

/* most drivers won't need to care about device refcounting */
static inline struct spi_device *spi_dev_get(struct spi_device *spi)
{
	return (spi && get_device(&spi->dev)) ? spi : NULL;
}

static inline void spi_dev_put(struct spi_device *spi)
{
	if (spi)
		put_device(&spi->dev);
}

/* ctldata is for the bus_master driver's runtime state */
static inline void *spi_get_ctldata(struct spi_device *spi)
{
	return spi->controller_state;
}

static inline void spi_set_ctldata(struct spi_device *spi, void *state)
{
	spi->controller_state = state;
}

/* device driver data */

static inline void spi_set_drvdata(struct spi_device *spi, void *data)
{
	dev_set_drvdata(&spi->dev, data);
}

static inline void *spi_get_drvdata(struct spi_device *spi)
{
	return dev_get_drvdata(&spi->dev);
}

struct spi_message;



/**
 * struct spi_driver - Host side "protocol" driver
 * @id_table: List of SPI devices supported by this driver
 * @probe: Binds this driver to the spi device.  Drivers can verify
 *	that the device is actually present, and may need to configure
 *	characteristics (such as bits_per_word) which weren't needed for
 *	the initial configuration done during system setup.
 * @remove: Unbinds this driver from the spi device
 * @shutdown: Standard shutdown callback used during system state
 *	transitions such as powerdown/halt and kexec
 * @suspend: Standard suspend callback used during system state transitions
 * @resume: Standard resume callback used during system state transitions
 * @driver: SPI device drivers should initialize the name and owner
 *	field of this structure.
 *
 * This represents the kind of device driver that uses SPI messages to
 * interact with the hardware at the other end of a SPI link.  It's called
 * a "protocol" driver because it works through messages rather than talking
 * directly to SPI hardware (which is what the underlying SPI controller
 * driver does to pass those messages).  These protocols are defined in the
 * specification for the device(s) supported by the driver.
 *
 * As a rule, those device protocols represent the lowest level interface
 * supported by a driver, and it will support upper level interfaces too.
 * Examples of such upper levels include frameworks like MTD, networking,
 * MMC, RTC, filesystem character device nodes, and hardware monitoring.
 */
struct spi_driver {
	const struct spi_device_id *id_table;
	int			(*probe)(struct spi_device *spi);
	int			(*remove)(struct spi_device *spi);
	void			(*shutdown)(struct spi_device *spi);
	int			(*suspend)(struct spi_device *spi, pm_message_t mesg);
	int			(*resume)(struct spi_device *spi);
	struct device_driver	driver;
};

static inline struct spi_driver *to_spi_driver(struct device_driver *drv)
{
	return drv ? container_of(drv, struct spi_driver, driver) : NULL;
}

extern int spi_register_driver(struct spi_driver *sdrv);

/**
 * spi_unregister_driver - reverse effect of spi_register_driver
 * @sdrv: the driver to unregister
 * Context: can sleep
 */
static inline void spi_unregister_driver(struct spi_driver *sdrv)
{
	if (sdrv)
		driver_unregister(&sdrv->driver);
}

/**
 * module_spi_driver() - Helper macro for registering a SPI driver
 * @__spi_driver: spi_driver struct
 *
 * Helper macro for SPI drivers which do not do anything special in module
 * init/exit. This eliminates a lot of boilerplate. Each module may only
 * use this macro once, and calling it replaces module_init() and module_exit()
 */
#define module_spi_driver(__spi_driver) \
	module_driver(__spi_driver, spi_register_driver, \
			spi_unregister_driver)

/**
 * struct spi_master - interface to SPI master controller
 * @dev: device interface to this driver
 * @list: link with the global spi_master list
 * @bus_num: board-specific (and often SOC-specific) identifier for a
 *	given SPI controller.
 * @num_chipselect: chipselects are used to distinguish individual
 *	SPI slaves, and are numbered from zero to num_chipselects.
 *	each slave has a chipselect signal, but it's common that not
 *	every chipselect is connected to a slave.
 * @dma_alignment: SPI controller constraint on DMA buffers alignment.
 * @mode_bits: flags understood by this controller driver
 * @flags: other constraints relevant to this driver
 * @bus_lock_spinlock: spinlock for SPI bus locking
 * @bus_lock_mutex: mutex for SPI bus locking
 * @bus_lock_flag: indicates that the SPI bus is locked for exclusive use
 * @setup: updates the device mode and clocking records used by a
 *	device's SPI controller; protocol code may call this.  This
 *	must fail if an unrecognized or unsupported mode is requested.
 *	It's always safe to call this unless transfers are pending on
 *	the device whose settings are being modified.
 * @transfer: adds a message to the controller's transfer queue.
 * @cleanup: frees controller-specific state
 * @queued: whether this master is providing an internal message queue
 * @kworker: thread struct for message pump
 * @kworker_task: pointer to task for message pump kworker thread
 * @pump_messages: work struct for scheduling work to the message pump
 * @queue_lock: spinlock to syncronise access to message queue
 * @queue: message queue
 * @cur_msg: the currently in-flight message
 * @busy: message pump is busy
 * @running: message pump is running
 * @rt: whether this queue is set to run as a realtime task
 * @prepare_transfer_hardware: a message will soon arrive from the queue
 *	so the subsystem requests the driver to prepare the transfer hardware
 *	by issuing this call
 * @transfer_one_message: the subsystem calls the driver to transfer a single
 *	message while queuing transfers that arrive in the meantime. When the
 *	driver is finished with this message, it must call
 *	spi_finalize_current_message() so the subsystem can issue the next
 *	transfer
 * @unprepare_transfer_hardware: there are currently no more messages on the
 *	queue so the subsystem notifies the driver that it may relax the
 *	hardware by issuing this call
 *
 * Each SPI master controller can communicate with one or more @spi_device
 * children.  These make a small bus, sharing MOSI, MISO and SCK signals
 * but not chip select signals.  Each device may be configured to use a
 * different clock rate, since those shared signals are ignored unless
 * the chip is selected.
 *
 * The driver for an SPI controller manages access to those devices through
 * a queue of spi_message transactions, copying data between CPU memory and
 * an SPI slave device.  For each such message it queues, it calls the
 * message's completion function when the transaction completes.
 */
struct spi_master {
	struct device	dev;

	struct list_head list;

	/* other than negative (== assign one dynamically), bus_num is fully
	 * board-specific.  usually that simplifies to being SOC-specific.
	 * example:  one SOC has three SPI controllers, numbered 0..2,
	 * and one board's schematics might show it using SPI-2.  software
	 * would normally use bus_num=2 for that controller.
	 */
	s16			bus_num;

	/* chipselects will be integral to many controllers; some others
	 * might use board-specific GPIOs.
	 */
	u16			num_chipselect;

	/* some SPI controllers pose alignment requirements on DMAable
	 * buffers; let protocol drivers know about these requirements.
	 */
	u16			dma_alignment;

	/* spi_device.mode flags understood by this controller driver */
	u16			mode_bits;

	/* other constraints relevant to this driver */
	u16			flags;
#define SPI_MASTER_HALF_DUPLEX	BIT(0)		/* can't do full duplex */
#define SPI_MASTER_NO_RX	BIT(1)		/* can't do buffer read */
#define SPI_MASTER_NO_TX	BIT(2)		/* can't do buffer write */

	/* lock and mutex for SPI bus locking */
	spinlock_t		bus_lock_spinlock;
	struct mutex		bus_lock_mutex;

	/* flag indicating that the SPI bus is locked for exclusive use */
	bool			bus_lock_flag;

	/* Setup mode and clock, etc (spi driver may call many times).
	 *
	 * IMPORTANT:  this may be called when transfers to another
	 * device are active.  DO NOT UPDATE SHARED REGISTERS in ways
	 * which could break those transfers.
	 */
	int			(*setup)(struct spi_device *spi);