2 * Copyright (C) 2005 David Brownell
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 #include <linux/device.h>
23 #include <linux/mod_devicetable.h>
24 #include <linux/slab.h>
25 #include <linux/kthread.h>
28 * INTERFACES between SPI master-side drivers and SPI infrastructure.
29 * (There's no SPI slave support for Linux yet...)
31 extern struct bus_type spi_bus_type;
34 * struct spi_device - Master side proxy for an SPI slave device
35 * @dev: Driver model representation of the device.
36 * @master: SPI controller used with the device.
37 * @max_speed_hz: Maximum clock rate to be used with this chip
38 * (on this board); may be changed by the device's driver.
39 * The spi_transfer.speed_hz can override this for each transfer.
40 * @chip_select: Chipselect, distinguishing chips handled by @master.
41 * @mode: The spi mode defines how data is clocked out and in.
42 * This may be changed by the device's driver.
43 * The "active low" default for chipselect mode can be overridden
44 * (by specifying SPI_CS_HIGH) as can the "MSB first" default for
45 * each word in a transfer (by specifying SPI_LSB_FIRST).
46 * @bits_per_word: Data transfers involve one or more words; word sizes
47 * like eight or 12 bits are common. In-memory wordsizes are
48 * powers of two bytes (e.g. 20 bit samples use 32 bits).
49 * This may be changed by the device's driver, or left at the
50 * default (0) indicating protocol words are eight bit bytes.
51 * The spi_transfer.bits_per_word can override this for each transfer.
52 * @irq: Negative, or the number passed to request_irq() to receive
53 * interrupts from this device.
54 * @controller_state: Controller's runtime state
55 * @controller_data: Board-specific definitions for controller, such as
56 * FIFO initialization parameters; from board_info.controller_data
57 * @modalias: Name of the driver to use with this device, or an alias
58 * for that name. This appears in the sysfs "modalias" attribute
59 * for driver coldplugging, and in uevents used for hotplugging
61 * A @spi_device is used to interchange data between an SPI slave
62 * (usually a discrete chip) and CPU memory.
64 * In @dev, the platform_data is used to hold information about this
65 * device that's meaningful to the device's protocol driver, but not
66 * to its controller. One example might be an identifier for a chip
67 * variant with slightly different functionality; another might be
68 * information about how this particular board wires the chip's pins.
72 struct spi_master *master;
76 #define SPI_CPHA 0x01 /* clock phase */
77 #define SPI_CPOL 0x02 /* clock polarity */
78 #define SPI_MODE_0 (0|0) /* (original MicroWire) */
79 #define SPI_MODE_1 (0|SPI_CPHA)
80 #define SPI_MODE_2 (SPI_CPOL|0)
81 #define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
82 #define SPI_CS_HIGH 0x04 /* chipselect active high? */
83 #define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
84 #define SPI_3WIRE 0x10 /* SI/SO signals shared */
85 #define SPI_LOOP 0x20 /* loopback mode */
86 #define SPI_NO_CS 0x40 /* 1 dev/bus, no chipselect */
87 #define SPI_READY 0x80 /* slave pulls low to pause */
90 void *controller_state;
91 void *controller_data;
92 char modalias[SPI_NAME_SIZE];
95 * likely need more hooks for more protocol options affecting how
96 * the controller talks to each chip, like:
97 * - memory packing (12 bit samples into low bits, others zeroed)
99 * - drop chipselect after each word
100 * - chipselect delays
105 static inline struct spi_device *to_spi_device(struct device *dev)
107 return dev ? container_of(dev, struct spi_device, dev) : NULL;
110 /* most drivers won't need to care about device refcounting */
111 static inline struct spi_device *spi_dev_get(struct spi_device *spi)
113 return (spi && get_device(&spi->dev)) ? spi : NULL;
116 static inline void spi_dev_put(struct spi_device *spi)
119 put_device(&spi->dev);
122 /* ctldata is for the bus_master driver's runtime state */
123 static inline void *spi_get_ctldata(struct spi_device *spi)
125 return spi->controller_state;
128 static inline void spi_set_ctldata(struct spi_device *spi, void *state)
130 spi->controller_state = state;
133 /* device driver data */
135 static inline void spi_set_drvdata(struct spi_device *spi, void *data)
137 dev_set_drvdata(&spi->dev, data);
140 static inline void *spi_get_drvdata(struct spi_device *spi)
142 return dev_get_drvdata(&spi->dev);
150 * struct spi_driver - Host side "protocol" driver
151 * @id_table: List of SPI devices supported by this driver
152 * @probe: Binds this driver to the spi device. Drivers can verify
153 * that the device is actually present, and may need to configure
154 * characteristics (such as bits_per_word) which weren't needed for
155 * the initial configuration done during system setup.
156 * @remove: Unbinds this driver from the spi device
157 * @shutdown: Standard shutdown callback used during system state
158 * transitions such as powerdown/halt and kexec
159 * @suspend: Standard suspend callback used during system state transitions
160 * @resume: Standard resume callback used during system state transitions
161 * @driver: SPI device drivers should initialize the name and owner
162 * field of this structure.
164 * This represents the kind of device driver that uses SPI messages to
165 * interact with the hardware at the other end of a SPI link. It's called
166 * a "protocol" driver because it works through messages rather than talking
167 * directly to SPI hardware (which is what the underlying SPI controller
168 * driver does to pass those messages). These protocols are defined in the
169 * specification for the device(s) supported by the driver.
171 * As a rule, those device protocols represent the lowest level interface
172 * supported by a driver, and it will support upper level interfaces too.
173 * Examples of such upper levels include frameworks like MTD, networking,
174 * MMC, RTC, filesystem character device nodes, and hardware monitoring.
177 const struct spi_device_id *id_table;
178 int (*probe)(struct spi_device *spi);
179 int (*remove)(struct spi_device *spi);
180 void (*shutdown)(struct spi_device *spi);
181 int (*suspend)(struct spi_device *spi, pm_message_t mesg);
182 int (*resume)(struct spi_device *spi);
183 struct device_driver driver;
186 static inline struct spi_driver *to_spi_driver(struct device_driver *drv)
188 return drv ? container_of(drv, struct spi_driver, driver) : NULL;
191 extern int spi_register_driver(struct spi_driver *sdrv);
194 * spi_unregister_driver - reverse effect of spi_register_driver
195 * @sdrv: the driver to unregister
198 static inline void spi_unregister_driver(struct spi_driver *sdrv)
201 driver_unregister(&sdrv->driver);
205 * module_spi_driver() - Helper macro for registering a SPI driver
206 * @__spi_driver: spi_driver struct
208 * Helper macro for SPI drivers which do not do anything special in module
209 * init/exit. This eliminates a lot of boilerplate. Each module may only
210 * use this macro once, and calling it replaces module_init() and module_exit()
212 #define module_spi_driver(__spi_driver) \
213 module_driver(__spi_driver, spi_register_driver, \
214 spi_unregister_driver)
217 * struct spi_master - interface to SPI master controller
218 * @dev: device interface to this driver
219 * @list: link with the global spi_master list
220 * @bus_num: board-specific (and often SOC-specific) identifier for a
221 * given SPI controller.
222 * @num_chipselect: chipselects are used to distinguish individual
223 * SPI slaves, and are numbered from zero to num_chipselects.
224 * each slave has a chipselect signal, but it's common that not
225 * every chipselect is connected to a slave.
226 * @dma_alignment: SPI controller constraint on DMA buffers alignment.
227 * @mode_bits: flags understood by this controller driver
228 * @flags: other constraints relevant to this driver
229 * @bus_lock_spinlock: spinlock for SPI bus locking
230 * @bus_lock_mutex: mutex for SPI bus locking
231 * @bus_lock_flag: indicates that the SPI bus is locked for exclusive use
232 * @setup: updates the device mode and clocking records used by a
233 * device's SPI controller; protocol code may call this. This
234 * must fail if an unrecognized or unsupported mode is requested.
235 * It's always safe to call this unless transfers are pending on
236 * the device whose settings are being modified.
237 * @transfer: adds a message to the controller's transfer queue.
238 * @cleanup: frees controller-specific state
239 * @queued: whether this master is providing an internal message queue
240 * @kworker: thread struct for message pump
241 * @kworker_task: pointer to task for message pump kworker thread
242 * @pump_messages: work struct for scheduling work to the message pump
243 * @queue_lock: spinlock to syncronise access to message queue
244 * @queue: message queue
245 * @cur_msg: the currently in-flight message
246 * @busy: message pump is busy
247 * @running: message pump is running
248 * @rt: whether this queue is set to run as a realtime task
249 * @prepare_transfer_hardware: a message will soon arrive from the queue
250 * so the subsystem requests the driver to prepare the transfer hardware
251 * by issuing this call
252 * @transfer_one_message: the subsystem calls the driver to transfer a single
253 * message while queuing transfers that arrive in the meantime. When the
254 * driver is finished with this message, it must call
255 * spi_finalize_current_message() so the subsystem can issue the next
257 * @prepare_transfer_hardware: there are currently no more messages on the
258 * queue so the subsystem notifies the driver that it may relax the
259 * hardware by issuing this call
261 * Each SPI master controller can communicate with one or more @spi_device
262 * children. These make a small bus, sharing MOSI, MISO and SCK signals
263 * but not chip select signals. Each device may be configured to use a
264 * different clock rate, since those shared signals are ignored unless
265 * the chip is selected.
267 * The driver for an SPI controller manages access to those devices through
268 * a queue of spi_message transactions, copying data between CPU memory and
269 * an SPI slave device. For each such message it queues, it calls the
270 * message's completion function when the transaction completes.
275 struct list_head list;
277 /* other than negative (== assign one dynamically), bus_num is fully
278 * board-specific. usually that simplifies to being SOC-specific.
279 * example: one SOC has three SPI controllers, numbered 0..2,
280 * and one board's schematics might show it using SPI-2. software
281 * would normally use bus_num=2 for that controller.
285 /* chipselects will be integral to many controllers; some others
286 * might use board-specific GPIOs.
290 /* some SPI controllers pose alignment requirements on DMAable
291 * buffers; let protocol drivers know about these requirements.
295 /* spi_device.mode flags understood by this controller driver */
298 /* other constraints relevant to this driver */
300 #define SPI_MASTER_HALF_DUPLEX BIT(0) /* can't do full duplex */
301 #define SPI_MASTER_NO_RX BIT(1) /* can't do buffer read */
302 #define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */
304 /* lock and mutex for SPI bus locking */
305 spinlock_t bus_lock_spinlock;
306 struct mutex bus_lock_mutex;
308 /* flag indicating that the SPI bus is locked for exclusive use */
311 /* Setup mode and clock, etc (spi driver may call many times).
313 * IMPORTANT: this may be called when transfers to another
314 * device are active. DO NOT UPDATE SHARED REGISTERS in ways
315 * which could break those transfers.
317 int (*setup)(struct spi_device *spi);
319 /* bidirectional bulk transfers
321 * + The transfer() method may not sleep; its main role is
322 * just to add the message to the queue.
323 * + For now there's no remove-from-queue operation, or
324 * any other request management
325 * + To a given spi_device, message queueing is pure fifo
327 * + The master's main job is to process its message queue,
328 * selecting a chip then transferring data
329 * + If there are multiple spi_device children, the i/o queue
330 * arbitration algorithm is unspecified (round robin, fifo,
331 * priority, reservations, preemption, etc)
333 * + Chipselect stays active during the entire message
334 * (unless modified by spi_transfer.cs_change != 0).
335 * + The message transfers use clock and SPI mode parameters
336 * previously established by setup() for this device
338 int (*transfer)(struct spi_device *spi,
339 struct spi_message *mesg);
341 /* called on release() to free memory provided by spi_master */
342 void (*cleanup)(struct spi_device *spi);
345 * These hooks are for drivers that want to use the generic
346 * master transfer queueing mechanism. If these are used, the
347 * transfer() function above must NOT be specified by the driver.
348 * Over time we expect SPI drivers to be phased over to this API.
351 struct kthread_worker kworker;
352 struct task_struct *kworker_task;
353 struct kthread_work pump_messages;
354 spinlock_t queue_lock;
355 struct list_head queue;
356 struct spi_message *cur_msg;
361 int (*prepare_transfer_hardware)(struct spi_master *master);
362 int (*transfer_one_message)(struct spi_master *master,
363 struct spi_message *mesg);
364 int (*unprepare_transfer_hardware)(struct spi_master *master);
367 static inline void *spi_master_get_devdata(struct spi_master *master)
369 return dev_get_drvdata(&master->dev);
372 static inline void spi_master_set_devdata(struct spi_master *master, void *data)
374 dev_set_drvdata(&master->dev, data);
377 static inline struct spi_master *spi_master_get(struct spi_master *master)
379 if (!master || !get_device(&master->dev))
384 static inline void spi_master_put(struct spi_master *master)
387 put_device(&master->dev);
390 /* PM calls that need to be issued by the driver */
391 extern int spi_master_suspend(struct spi_master *master);
392 extern int spi_master_resume(struct spi_master *master);
394 /* Calls the driver make to interact with the message queue */
395 extern struct spi_message *spi_get_next_queued_message(struct spi_master *master);
396 extern void spi_finalize_current_message(struct spi_master *master);
398 /* the spi driver core manages memory for the spi_master classdev */
399 extern struct spi_master *
400 spi_alloc_master(struct device *host, unsigned size);
402 extern int spi_register_master(struct spi_master *master);
403 extern void spi_unregister_master(struct spi_master *master);
405 extern struct spi_master *spi_busnum_to_master(u16 busnum);
407 /*---------------------------------------------------------------------------*/
410 * I/O INTERFACE between SPI controller and protocol drivers
412 * Protocol drivers use a queue of spi_messages, each transferring data
413 * between the controller and memory buffers.
415 * The spi_messages themselves consist of a series of read+write transfer
416 * segments. Those segments always read the same number of bits as they
417 * write; but one or the other is easily ignored by passing a null buffer
418 * pointer. (This is unlike most types of I/O API, because SPI hardware
421 * NOTE: Allocation of spi_transfer and spi_message memory is entirely
422 * up to the protocol driver, which guarantees the integrity of both (as
423 * well as the data buffers) for as long as the message is queued.
427 * struct spi_transfer - a read/write buffer pair
428 * @tx_buf: data to be written (dma-safe memory), or NULL
429 * @rx_buf: data to be read (dma-safe memory), or NULL
430 * @tx_dma: DMA address of tx_buf, if @spi_message.is_dma_mapped
431 * @rx_dma: DMA address of rx_buf, if @spi_message.is_dma_mapped
432 * @len: size of rx and tx buffers (in bytes)
433 * @speed_hz: Select a speed other than the device default for this
434 * transfer. If 0 the default (from @spi_device) is used.
435 * @bits_per_word: select a bits_per_word other than the device default
436 * for this transfer. If 0 the default (from @spi_device) is used.
437 * @cs_change: affects chipselect after this transfer completes
438 * @delay_usecs: microseconds to delay after this transfer before
439 * (optionally) changing the chipselect status, then starting
440 * the next transfer or completing this @spi_message.
441 * @transfer_list: transfers are sequenced through @spi_message.transfers
443 * SPI transfers always write the same number of bytes as they read.
444 * Protocol drivers should always provide @rx_buf and/or @tx_buf.
445 * In some cases, they may also want to provide DMA addresses for
446 * the data being transferred; that may reduce overhead, when the
447 * underlying driver uses dma.
449 * If the transmit buffer is null, zeroes will be shifted out
450 * while filling @rx_buf. If the receive buffer is null, the data
451 * shifted in will be discarded. Only "len" bytes shift out (or in).
452 * It's an error to try to shift out a partial word. (For example, by
453 * shifting out three bytes with word size of sixteen or twenty bits;
454 * the former uses two bytes per word, the latter uses four bytes.)
456 * In-memory data values are always in native CPU byte order, translated
457 * from the wire byte order (big-endian except with SPI_LSB_FIRST). So
458 * for example when bits_per_word is sixteen, buffers are 2N bytes long
459 * (@len = 2N) and hold N sixteen bit words in CPU byte order.
461 * When the word size of the SPI transfer is not a power-of-two multiple
462 * of eight bits, those in-memory words include extra bits. In-memory
463 * words are always seen by protocol drivers as right-justified, so the
464 * undefined (rx) or unused (tx) bits are always the most significant bits.
466 * All SPI transfers start with the relevant chipselect active. Normally
467 * it stays selected until after the last transfer in a message. Drivers
468 * can affect the chipselect signal using cs_change.
470 * (i) If the transfer isn't the last one in the message, this flag is
471 * used to make the chipselect briefly go inactive in the middle of the
472 * message. Toggling chipselect in this way may be needed to terminate
473 * a chip command, letting a single spi_message perform all of group of
474 * chip transactions together.
476 * (ii) When the transfer is the last one in the message, the chip may
477 * stay selected until the next transfer. On multi-device SPI busses
478 * with nothing blocking messages going to other devices, this is just
479 * a performance hint; starting a message to another device deselects
480 * this one. But in other cases, this can be used to ensure correctness.
481 * Some devices need protocol transactions to be built from a series of
482 * spi_message submissions, where the content of one message is determined
483 * by the results of previous messages and where the whole transaction
484 * ends when the chipselect goes intactive.
486 * The code that submits an spi_message (and its spi_transfers)
487 * to the lower layers is responsible for managing its memory.
488 * Zero-initialize every field you don't set up explicitly, to
489 * insulate against future API updates. After you submit a message
490 * and its transfers, ignore them until its completion callback.
492 struct spi_transfer {
493 /* it's ok if tx_buf == rx_buf (right?)
494 * for MicroWire, one buffer must be null
495 * buffers must work with dma_*map_single() calls, unless
496 * spi_message.is_dma_mapped reports a pre-existing mapping
505 unsigned cs_change:1;
510 struct list_head transfer_list;
514 * struct spi_message - one multi-segment SPI transaction
515 * @transfers: list of transfer segments in this transaction
516 * @spi: SPI device to which the transaction is queued
517 * @is_dma_mapped: if true, the caller provided both dma and cpu virtual
518 * addresses for each transfer buffer
519 * @complete: called to report transaction completions
520 * @context: the argument to complete() when it's called
521 * @actual_length: the total number of bytes that were transferred in all
522 * successful segments
523 * @status: zero for success, else negative errno
524 * @queue: for use by whichever driver currently owns the message
525 * @state: for use by whichever driver currently owns the message
527 * A @spi_message is used to execute an atomic sequence of data transfers,
528 * each represented by a struct spi_transfer. The sequence is "atomic"
529 * in the sense that no other spi_message may use that SPI bus until that
530 * sequence completes. On some systems, many such sequences can execute as
531 * as single programmed DMA transfer. On all systems, these messages are
532 * queued, and might complete after transactions to other devices. Messages
533 * sent to a given spi_device are alway executed in FIFO order.
535 * The code that submits an spi_message (and its spi_transfers)
536 * to the lower layers is responsible for managing its memory.
537 * Zero-initialize every field you don't set up explicitly, to
538 * insulate against future API updates. After you submit a message
539 * and its transfers, ignore them until its completion callback.
542 struct list_head transfers;
544 struct spi_device *spi;
546 unsigned is_dma_mapped:1;
548 /* REVISIT: we might want a flag affecting the behavior of the
549 * last transfer ... allowing things like "read 16 bit length L"
550 * immediately followed by "read L bytes". Basically imposing
551 * a specific message scheduling algorithm.
553 * Some controller drivers (message-at-a-time queue processing)
554 * could provide that as their default scheduling algorithm. But
555 * others (with multi-message pipelines) could need a flag to
556 * tell them about such special cases.
559 /* completion is reported through a callback */
560 void (*complete)(void *context);
562 unsigned actual_length;
565 /* for optional use by whatever driver currently owns the
566 * spi_message ... between calls to spi_async and then later
567 * complete(), that's the spi_master controller driver.
569 struct list_head queue;
573 static inline void spi_message_init(struct spi_message *m)
575 memset(m, 0, sizeof *m);
576 INIT_LIST_HEAD(&m->transfers);
580 spi_message_add_tail(struct spi_transfer *t, struct spi_message *m)
582 list_add_tail(&t->transfer_list, &m->transfers);
586 spi_transfer_del(struct spi_transfer *t)
588 list_del(&t->transfer_list);
591 /* It's fine to embed message and transaction structures in other data
592 * structures so long as you don't free them while they're in use.
595 static inline struct spi_message *spi_message_alloc(unsigned ntrans, gfp_t flags)
597 struct spi_message *m;
599 m = kzalloc(sizeof(struct spi_message)
600 + ntrans * sizeof(struct spi_transfer),
604 struct spi_transfer *t = (struct spi_transfer *)(m + 1);
606 INIT_LIST_HEAD(&m->transfers);
607 for (i = 0; i < ntrans; i++, t++)
608 spi_message_add_tail(t, m);
613 static inline void spi_message_free(struct spi_message *m)
618 extern int spi_setup(struct spi_device *spi);
619 extern int spi_async(struct spi_device *spi, struct spi_message *message);
620 extern int spi_async_locked(struct spi_device *spi,
621 struct spi_message *message);
623 /*---------------------------------------------------------------------------*/
625 /* All these synchronous SPI transfer routines are utilities layered
626 * over the core async transfer primitive. Here, "synchronous" means
627 * they will sleep uninterruptibly until the async transfer completes.
630 extern int spi_sync(struct spi_device *spi, struct spi_message *message);
631 extern int spi_sync_locked(struct spi_device *spi, struct spi_message *message);
632 extern int spi_bus_lock(struct spi_master *master);
633 extern int spi_bus_unlock(struct spi_master *master);
636 * spi_write - SPI synchronous write
637 * @spi: device to which data will be written
639 * @len: data buffer size
642 * This writes the buffer and returns zero or a negative error code.
643 * Callable only from contexts that can sleep.
646 spi_write(struct spi_device *spi, const void *buf, size_t len)
648 struct spi_transfer t = {
652 struct spi_message m;
654 spi_message_init(&m);
655 spi_message_add_tail(&t, &m);
656 return spi_sync(spi, &m);
660 * spi_read - SPI synchronous read
661 * @spi: device from which data will be read
663 * @len: data buffer size
666 * This reads the buffer and returns zero or a negative error code.
667 * Callable only from contexts that can sleep.
670 spi_read(struct spi_device *spi, void *buf, size_t len)
672 struct spi_transfer t = {
676 struct spi_message m;
678 spi_message_init(&m);
679 spi_message_add_tail(&t, &m);
680 return spi_sync(spi, &m);
683 /* this copies txbuf and rxbuf data; for small transfers only! */
684 extern int spi_write_then_read(struct spi_device *spi,
685 const void *txbuf, unsigned n_tx,
686 void *rxbuf, unsigned n_rx);
689 * spi_w8r8 - SPI synchronous 8 bit write followed by 8 bit read
690 * @spi: device with which data will be exchanged
691 * @cmd: command to be written before data is read back
694 * This returns the (unsigned) eight bit number returned by the
695 * device, or else a negative error code. Callable only from
696 * contexts that can sleep.
698 static inline ssize_t spi_w8r8(struct spi_device *spi, u8 cmd)
703 status = spi_write_then_read(spi, &cmd, 1, &result, 1);
705 /* return negative errno or unsigned value */
706 return (status < 0) ? status : result;
710 * spi_w8r16 - SPI synchronous 8 bit write followed by 16 bit read
711 * @spi: device with which data will be exchanged
712 * @cmd: command to be written before data is read back
715 * This returns the (unsigned) sixteen bit number returned by the
716 * device, or else a negative error code. Callable only from
717 * contexts that can sleep.
719 * The number is returned in wire-order, which is at least sometimes
722 static inline ssize_t spi_w8r16(struct spi_device *spi, u8 cmd)
727 status = spi_write_then_read(spi, &cmd, 1, (u8 *) &result, 2);
729 /* return negative errno or unsigned value */
730 return (status < 0) ? status : result;
733 /*---------------------------------------------------------------------------*/
736 * INTERFACE between board init code and SPI infrastructure.
738 * No SPI driver ever sees these SPI device table segments, but
739 * it's how the SPI core (or adapters that get hotplugged) grows
740 * the driver model tree.
742 * As a rule, SPI devices can't be probed. Instead, board init code
743 * provides a table listing the devices which are present, with enough
744 * information to bind and set up the device's driver. There's basic
745 * support for nonstatic configurations too; enough to handle adding
746 * parport adapters, or microcontrollers acting as USB-to-SPI bridges.
750 * struct spi_board_info - board-specific template for a SPI device
751 * @modalias: Initializes spi_device.modalias; identifies the driver.
752 * @platform_data: Initializes spi_device.platform_data; the particular
753 * data stored there is driver-specific.
754 * @controller_data: Initializes spi_device.controller_data; some
755 * controllers need hints about hardware setup, e.g. for DMA.
756 * @irq: Initializes spi_device.irq; depends on how the board is wired.
757 * @max_speed_hz: Initializes spi_device.max_speed_hz; based on limits
758 * from the chip datasheet and board-specific signal quality issues.
759 * @bus_num: Identifies which spi_master parents the spi_device; unused
760 * by spi_new_device(), and otherwise depends on board wiring.
761 * @chip_select: Initializes spi_device.chip_select; depends on how
762 * the board is wired.
763 * @mode: Initializes spi_device.mode; based on the chip datasheet, board
764 * wiring (some devices support both 3WIRE and standard modes), and
765 * possibly presence of an inverter in the chipselect path.
767 * When adding new SPI devices to the device tree, these structures serve
768 * as a partial device template. They hold information which can't always
769 * be determined by drivers. Information that probe() can establish (such
770 * as the default transfer wordsize) is not included here.
772 * These structures are used in two places. Their primary role is to
773 * be stored in tables of board-specific device descriptors, which are
774 * declared early in board initialization and then used (much later) to
775 * populate a controller's device tree after the that controller's driver
776 * initializes. A secondary (and atypical) role is as a parameter to
777 * spi_new_device() call, which happens after those controller drivers
778 * are active in some dynamic board configuration models.
780 struct spi_board_info {
781 /* the device name and module name are coupled, like platform_bus;
782 * "modalias" is normally the driver name.
784 * platform_data goes to spi_device.dev.platform_data,
785 * controller_data goes to spi_device.controller_data,
788 char modalias[SPI_NAME_SIZE];
789 const void *platform_data;
790 void *controller_data;
793 /* slower signaling on noisy or low voltage boards */
797 /* bus_num is board specific and matches the bus_num of some
798 * spi_master that will probably be registered later.
800 * chip_select reflects how this chip is wired to that master;
801 * it's less than num_chipselect.
806 /* mode becomes spi_device.mode, and is essential for chips
807 * where the default of SPI_CS_HIGH = 0 is wrong.
811 /* ... may need additional spi_device chip config data here.
812 * avoid stuff protocol drivers can set; but include stuff
813 * needed to behave without being bound to a driver:
814 * - quirks like clock rate mattering when not selected
820 spi_register_board_info(struct spi_board_info const *info, unsigned n);
822 /* board init code may ignore whether SPI is configured or not */
824 spi_register_board_info(struct spi_board_info const *info, unsigned n)
829 /* If you're hotplugging an adapter with devices (parport, usb, etc)
830 * use spi_new_device() to describe each device. You can also call
831 * spi_unregister_device() to start making that device vanish, but
832 * normally that would be handled by spi_unregister_master().
834 * You can also use spi_alloc_device() and spi_add_device() to use a two
835 * stage registration sequence for each spi_device. This gives the caller
836 * some more control over the spi_device structure before it is registered,
837 * but requires that caller to initialize fields that would otherwise
838 * be defined using the board info.
840 extern struct spi_device *
841 spi_alloc_device(struct spi_master *master);
844 spi_add_device(struct spi_device *spi);
846 extern struct spi_device *
847 spi_new_device(struct spi_master *, struct spi_board_info *);
850 spi_unregister_device(struct spi_device *spi)
853 device_unregister(&spi->dev);
856 extern const struct spi_device_id *
857 spi_get_device_id(const struct spi_device *sdev);
859 #endif /* __LINUX_SPI_H */