2 * spi.c - SPI init/core code
4 * Copyright (C) 2005 David Brownell
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 #include <linux/kernel.h>
22 #include <linux/device.h>
23 #include <linux/init.h>
24 #include <linux/cache.h>
25 #include <linux/mutex.h>
26 #include <linux/of_device.h>
27 #include <linux/slab.h>
28 #include <linux/mod_devicetable.h>
29 #include <linux/spi/spi.h>
30 #include <linux/of_spi.h>
33 /* SPI bustype and spi_master class are registered after board init code
34 * provides the SPI device tables, ensuring that both are present by the
35 * time controller driver registration causes spi_devices to "enumerate".
37 static void spidev_release(struct device
*dev
)
39 struct spi_device
*spi
= to_spi_device(dev
);
41 /* spi masters may cleanup for released devices */
42 if (spi
->master
->cleanup
)
43 spi
->master
->cleanup(spi
);
45 spi_master_put(spi
->master
);
50 modalias_show(struct device
*dev
, struct device_attribute
*a
, char *buf
)
52 const struct spi_device
*spi
= to_spi_device(dev
);
54 return sprintf(buf
, "%s\n", spi
->modalias
);
57 static struct device_attribute spi_dev_attrs
[] = {
62 /* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
63 * and the sysfs version makes coldplug work too.
66 static const struct spi_device_id
*spi_match_id(const struct spi_device_id
*id
,
67 const struct spi_device
*sdev
)
70 if (!strcmp(sdev
->modalias
, id
->name
))
77 const struct spi_device_id
*spi_get_device_id(const struct spi_device
*sdev
)
79 const struct spi_driver
*sdrv
= to_spi_driver(sdev
->dev
.driver
);
81 return spi_match_id(sdrv
->id_table
, sdev
);
83 EXPORT_SYMBOL_GPL(spi_get_device_id
);
85 static int spi_match_device(struct device
*dev
, struct device_driver
*drv
)
87 const struct spi_device
*spi
= to_spi_device(dev
);
88 const struct spi_driver
*sdrv
= to_spi_driver(drv
);
90 /* Attempt an OF style match */
91 if (of_driver_match_device(dev
, drv
))
95 return !!spi_match_id(sdrv
->id_table
, spi
);
97 return strcmp(spi
->modalias
, drv
->name
) == 0;
100 static int spi_uevent(struct device
*dev
, struct kobj_uevent_env
*env
)
102 const struct spi_device
*spi
= to_spi_device(dev
);
104 add_uevent_var(env
, "MODALIAS=%s%s", SPI_MODULE_PREFIX
, spi
->modalias
);
110 static int spi_suspend(struct device
*dev
, pm_message_t message
)
113 struct spi_driver
*drv
= to_spi_driver(dev
->driver
);
115 /* suspend will stop irqs and dma; no more i/o */
118 value
= drv
->suspend(to_spi_device(dev
), message
);
120 dev_dbg(dev
, "... can't suspend\n");
125 static int spi_resume(struct device
*dev
)
128 struct spi_driver
*drv
= to_spi_driver(dev
->driver
);
130 /* resume may restart the i/o queue */
133 value
= drv
->resume(to_spi_device(dev
));
135 dev_dbg(dev
, "... can't resume\n");
141 #define spi_suspend NULL
142 #define spi_resume NULL
145 struct bus_type spi_bus_type
= {
147 .dev_attrs
= spi_dev_attrs
,
148 .match
= spi_match_device
,
149 .uevent
= spi_uevent
,
150 .suspend
= spi_suspend
,
151 .resume
= spi_resume
,
153 EXPORT_SYMBOL_GPL(spi_bus_type
);
156 static int spi_drv_probe(struct device
*dev
)
158 const struct spi_driver
*sdrv
= to_spi_driver(dev
->driver
);
160 return sdrv
->probe(to_spi_device(dev
));
163 static int spi_drv_remove(struct device
*dev
)
165 const struct spi_driver
*sdrv
= to_spi_driver(dev
->driver
);
167 return sdrv
->remove(to_spi_device(dev
));
170 static void spi_drv_shutdown(struct device
*dev
)
172 const struct spi_driver
*sdrv
= to_spi_driver(dev
->driver
);
174 sdrv
->shutdown(to_spi_device(dev
));
178 * spi_register_driver - register a SPI driver
179 * @sdrv: the driver to register
182 int spi_register_driver(struct spi_driver
*sdrv
)
184 sdrv
->driver
.bus
= &spi_bus_type
;
186 sdrv
->driver
.probe
= spi_drv_probe
;
188 sdrv
->driver
.remove
= spi_drv_remove
;
190 sdrv
->driver
.shutdown
= spi_drv_shutdown
;
191 return driver_register(&sdrv
->driver
);
193 EXPORT_SYMBOL_GPL(spi_register_driver
);
195 /*-------------------------------------------------------------------------*/
197 /* SPI devices should normally not be created by SPI device drivers; that
198 * would make them board-specific. Similarly with SPI master drivers.
199 * Device registration normally goes into like arch/.../mach.../board-YYY.c
200 * with other readonly (flashable) information about mainboard devices.
204 struct list_head list
;
205 unsigned n_board_info
;
206 struct spi_board_info board_info
[0];
209 static LIST_HEAD(board_list
);
210 static DEFINE_MUTEX(board_lock
);
213 * spi_alloc_device - Allocate a new SPI device
214 * @master: Controller to which device is connected
217 * Allows a driver to allocate and initialize a spi_device without
218 * registering it immediately. This allows a driver to directly
219 * fill the spi_device with device parameters before calling
220 * spi_add_device() on it.
222 * Caller is responsible to call spi_add_device() on the returned
223 * spi_device structure to add it to the SPI master. If the caller
224 * needs to discard the spi_device without adding it, then it should
225 * call spi_dev_put() on it.
227 * Returns a pointer to the new device, or NULL.
229 struct spi_device
*spi_alloc_device(struct spi_master
*master
)
231 struct spi_device
*spi
;
232 struct device
*dev
= master
->dev
.parent
;
234 if (!spi_master_get(master
))
237 spi
= kzalloc(sizeof *spi
, GFP_KERNEL
);
239 dev_err(dev
, "cannot alloc spi_device\n");
240 spi_master_put(master
);
244 spi
->master
= master
;
245 spi
->dev
.parent
= dev
;
246 spi
->dev
.bus
= &spi_bus_type
;
247 spi
->dev
.release
= spidev_release
;
248 device_initialize(&spi
->dev
);
251 EXPORT_SYMBOL_GPL(spi_alloc_device
);
254 * spi_add_device - Add spi_device allocated with spi_alloc_device
255 * @spi: spi_device to register
257 * Companion function to spi_alloc_device. Devices allocated with
258 * spi_alloc_device can be added onto the spi bus with this function.
260 * Returns 0 on success; negative errno on failure
262 int spi_add_device(struct spi_device
*spi
)
264 static DEFINE_MUTEX(spi_add_lock
);
265 struct device
*dev
= spi
->master
->dev
.parent
;
269 /* Chipselects are numbered 0..max; validate. */
270 if (spi
->chip_select
>= spi
->master
->num_chipselect
) {
271 dev_err(dev
, "cs%d >= max %d\n",
273 spi
->master
->num_chipselect
);
277 /* Set the bus ID string */
278 dev_set_name(&spi
->dev
, "%s.%u", dev_name(&spi
->master
->dev
),
282 /* We need to make sure there's no other device with this
283 * chipselect **BEFORE** we call setup(), else we'll trash
284 * its configuration. Lock against concurrent add() calls.
286 mutex_lock(&spi_add_lock
);
288 d
= bus_find_device_by_name(&spi_bus_type
, NULL
, dev_name(&spi
->dev
));
290 dev_err(dev
, "chipselect %d already in use\n",
297 /* Drivers may modify this initial i/o setup, but will
298 * normally rely on the device being setup. Devices
299 * using SPI_CS_HIGH can't coexist well otherwise...
301 status
= spi_setup(spi
);
303 dev_err(dev
, "can't %s %s, status %d\n",
304 "setup", dev_name(&spi
->dev
), status
);
308 /* Device may be bound to an active driver when this returns */
309 status
= device_add(&spi
->dev
);
311 dev_err(dev
, "can't %s %s, status %d\n",
312 "add", dev_name(&spi
->dev
), status
);
314 dev_dbg(dev
, "registered child %s\n", dev_name(&spi
->dev
));
317 mutex_unlock(&spi_add_lock
);
320 EXPORT_SYMBOL_GPL(spi_add_device
);
323 * spi_new_device - instantiate one new SPI device
324 * @master: Controller to which device is connected
325 * @chip: Describes the SPI device
328 * On typical mainboards, this is purely internal; and it's not needed
329 * after board init creates the hard-wired devices. Some development
330 * platforms may not be able to use spi_register_board_info though, and
331 * this is exported so that for example a USB or parport based adapter
332 * driver could add devices (which it would learn about out-of-band).
334 * Returns the new device, or NULL.
336 struct spi_device
*spi_new_device(struct spi_master
*master
,
337 struct spi_board_info
*chip
)
339 struct spi_device
*proxy
;
342 /* NOTE: caller did any chip->bus_num checks necessary.
344 * Also, unless we change the return value convention to use
345 * error-or-pointer (not NULL-or-pointer), troubleshootability
346 * suggests syslogged diagnostics are best here (ugh).
349 proxy
= spi_alloc_device(master
);
353 WARN_ON(strlen(chip
->modalias
) >= sizeof(proxy
->modalias
));
355 proxy
->chip_select
= chip
->chip_select
;
356 proxy
->max_speed_hz
= chip
->max_speed_hz
;
357 proxy
->mode
= chip
->mode
;
358 proxy
->irq
= chip
->irq
;
359 strlcpy(proxy
->modalias
, chip
->modalias
, sizeof(proxy
->modalias
));
360 proxy
->dev
.platform_data
= (void *) chip
->platform_data
;
361 proxy
->controller_data
= chip
->controller_data
;
362 proxy
->controller_state
= NULL
;
364 status
= spi_add_device(proxy
);
372 EXPORT_SYMBOL_GPL(spi_new_device
);
375 * spi_register_board_info - register SPI devices for a given board
376 * @info: array of chip descriptors
377 * @n: how many descriptors are provided
380 * Board-specific early init code calls this (probably during arch_initcall)
381 * with segments of the SPI device table. Any device nodes are created later,
382 * after the relevant parent SPI controller (bus_num) is defined. We keep
383 * this table of devices forever, so that reloading a controller driver will
384 * not make Linux forget about these hard-wired devices.
386 * Other code can also call this, e.g. a particular add-on board might provide
387 * SPI devices through its expansion connector, so code initializing that board
388 * would naturally declare its SPI devices.
390 * The board info passed can safely be __initdata ... but be careful of
391 * any embedded pointers (platform_data, etc), they're copied as-is.
394 spi_register_board_info(struct spi_board_info
const *info
, unsigned n
)
396 struct boardinfo
*bi
;
398 bi
= kmalloc(sizeof(*bi
) + n
* sizeof *info
, GFP_KERNEL
);
401 bi
->n_board_info
= n
;
402 memcpy(bi
->board_info
, info
, n
* sizeof *info
);
404 mutex_lock(&board_lock
);
405 list_add_tail(&bi
->list
, &board_list
);
406 mutex_unlock(&board_lock
);
411 static void scan_boardinfo(struct spi_master
*master
)
413 struct boardinfo
*bi
;
415 mutex_lock(&board_lock
);
416 list_for_each_entry(bi
, &board_list
, list
) {
417 struct spi_board_info
*chip
= bi
->board_info
;
420 for (n
= bi
->n_board_info
; n
> 0; n
--, chip
++) {
421 if (chip
->bus_num
!= master
->bus_num
)
423 /* NOTE: this relies on spi_new_device to
424 * issue diagnostics when given bogus inputs
426 (void) spi_new_device(master
, chip
);
429 mutex_unlock(&board_lock
);
432 /*-------------------------------------------------------------------------*/
434 static void spi_master_release(struct device
*dev
)
436 struct spi_master
*master
;
438 master
= container_of(dev
, struct spi_master
, dev
);
442 static struct class spi_master_class
= {
443 .name
= "spi_master",
444 .owner
= THIS_MODULE
,
445 .dev_release
= spi_master_release
,
450 * spi_alloc_master - allocate SPI master controller
451 * @dev: the controller, possibly using the platform_bus
452 * @size: how much zeroed driver-private data to allocate; the pointer to this
453 * memory is in the driver_data field of the returned device,
454 * accessible with spi_master_get_devdata().
457 * This call is used only by SPI master controller drivers, which are the
458 * only ones directly touching chip registers. It's how they allocate
459 * an spi_master structure, prior to calling spi_register_master().
461 * This must be called from context that can sleep. It returns the SPI
462 * master structure on success, else NULL.
464 * The caller is responsible for assigning the bus number and initializing
465 * the master's methods before calling spi_register_master(); and (after errors
466 * adding the device) calling spi_master_put() to prevent a memory leak.
468 struct spi_master
*spi_alloc_master(struct device
*dev
, unsigned size
)
470 struct spi_master
*master
;
475 master
= kzalloc(size
+ sizeof *master
, GFP_KERNEL
);
479 device_initialize(&master
->dev
);
480 master
->dev
.class = &spi_master_class
;
481 master
->dev
.parent
= get_device(dev
);
482 spi_master_set_devdata(master
, &master
[1]);
486 EXPORT_SYMBOL_GPL(spi_alloc_master
);
489 * spi_register_master - register SPI master controller
490 * @master: initialized master, originally from spi_alloc_master()
493 * SPI master controllers connect to their drivers using some non-SPI bus,
494 * such as the platform bus. The final stage of probe() in that code
495 * includes calling spi_register_master() to hook up to this SPI bus glue.
497 * SPI controllers use board specific (often SOC specific) bus numbers,
498 * and board-specific addressing for SPI devices combines those numbers
499 * with chip select numbers. Since SPI does not directly support dynamic
500 * device identification, boards need configuration tables telling which
501 * chip is at which address.
503 * This must be called from context that can sleep. It returns zero on
504 * success, else a negative error code (dropping the master's refcount).
505 * After a successful return, the caller is responsible for calling
506 * spi_unregister_master().
508 int spi_register_master(struct spi_master
*master
)
510 static atomic_t dyn_bus_id
= ATOMIC_INIT((1<<15) - 1);
511 struct device
*dev
= master
->dev
.parent
;
512 int status
= -ENODEV
;
518 /* even if it's just one always-selected device, there must
519 * be at least one chipselect
521 if (master
->num_chipselect
== 0)
524 /* convention: dynamically assigned bus IDs count down from the max */
525 if (master
->bus_num
< 0) {
526 master
->bus_num
= atomic_dec_return(&dyn_bus_id
);
530 spin_lock_init(&master
->bus_lock_spinlock
);
531 mutex_init(&master
->bus_lock_mutex
);
532 master
->bus_lock_flag
= 0;
534 /* register the device, then userspace will see it.
535 * registration fails if the bus ID is in use.
537 dev_set_name(&master
->dev
, "spi%u", master
->bus_num
);
538 status
= device_add(&master
->dev
);
541 dev_dbg(dev
, "registered master %s%s\n", dev_name(&master
->dev
),
542 dynamic
? " (dynamic)" : "");
544 /* populate children from any spi device tables */
545 scan_boardinfo(master
);
548 /* Register devices from the device tree */
549 of_register_spi_devices(master
);
553 EXPORT_SYMBOL_GPL(spi_register_master
);
556 static int __unregister(struct device
*dev
, void *null
)
558 spi_unregister_device(to_spi_device(dev
));
563 * spi_unregister_master - unregister SPI master controller
564 * @master: the master being unregistered
567 * This call is used only by SPI master controller drivers, which are the
568 * only ones directly touching chip registers.
570 * This must be called from context that can sleep.
572 void spi_unregister_master(struct spi_master
*master
)
576 dummy
= device_for_each_child(&master
->dev
, NULL
, __unregister
);
577 device_unregister(&master
->dev
);
579 EXPORT_SYMBOL_GPL(spi_unregister_master
);
581 static int __spi_master_match(struct device
*dev
, void *data
)
583 struct spi_master
*m
;
586 m
= container_of(dev
, struct spi_master
, dev
);
587 return m
->bus_num
== *bus_num
;
591 * spi_busnum_to_master - look up master associated with bus_num
592 * @bus_num: the master's bus number
595 * This call may be used with devices that are registered after
596 * arch init time. It returns a refcounted pointer to the relevant
597 * spi_master (which the caller must release), or NULL if there is
598 * no such master registered.
600 struct spi_master
*spi_busnum_to_master(u16 bus_num
)
603 struct spi_master
*master
= NULL
;
605 dev
= class_find_device(&spi_master_class
, NULL
, &bus_num
,
608 master
= container_of(dev
, struct spi_master
, dev
);
609 /* reference got in class_find_device */
612 EXPORT_SYMBOL_GPL(spi_busnum_to_master
);
615 /*-------------------------------------------------------------------------*/
617 /* Core methods for SPI master protocol drivers. Some of the
618 * other core methods are currently defined as inline functions.
622 * spi_setup - setup SPI mode and clock rate
623 * @spi: the device whose settings are being modified
624 * Context: can sleep, and no requests are queued to the device
626 * SPI protocol drivers may need to update the transfer mode if the
627 * device doesn't work with its default. They may likewise need
628 * to update clock rates or word sizes from initial values. This function
629 * changes those settings, and must be called from a context that can sleep.
630 * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
631 * effect the next time the device is selected and data is transferred to
632 * or from it. When this function returns, the spi device is deselected.
634 * Note that this call will fail if the protocol driver specifies an option
635 * that the underlying controller or its driver does not support. For
636 * example, not all hardware supports wire transfers using nine bit words,
637 * LSB-first wire encoding, or active-high chipselects.
639 int spi_setup(struct spi_device
*spi
)
644 /* help drivers fail *cleanly* when they need options
645 * that aren't supported with their current master
647 bad_bits
= spi
->mode
& ~spi
->master
->mode_bits
;
649 dev_dbg(&spi
->dev
, "setup: unsupported mode bits %x\n",
654 if (!spi
->bits_per_word
)
655 spi
->bits_per_word
= 8;
657 status
= spi
->master
->setup(spi
);
659 dev_dbg(&spi
->dev
, "setup mode %d, %s%s%s%s"
660 "%u bits/w, %u Hz max --> %d\n",
661 (int) (spi
->mode
& (SPI_CPOL
| SPI_CPHA
)),
662 (spi
->mode
& SPI_CS_HIGH
) ? "cs_high, " : "",
663 (spi
->mode
& SPI_LSB_FIRST
) ? "lsb, " : "",
664 (spi
->mode
& SPI_3WIRE
) ? "3wire, " : "",
665 (spi
->mode
& SPI_LOOP
) ? "loopback, " : "",
666 spi
->bits_per_word
, spi
->max_speed_hz
,
671 EXPORT_SYMBOL_GPL(spi_setup
);
673 static int __spi_async(struct spi_device
*spi
, struct spi_message
*message
)
675 struct spi_master
*master
= spi
->master
;
677 /* Half-duplex links include original MicroWire, and ones with
678 * only one data pin like SPI_3WIRE (switches direction) or where
679 * either MOSI or MISO is missing. They can also be caused by
680 * software limitations.
682 if ((master
->flags
& SPI_MASTER_HALF_DUPLEX
)
683 || (spi
->mode
& SPI_3WIRE
)) {
684 struct spi_transfer
*xfer
;
685 unsigned flags
= master
->flags
;
687 list_for_each_entry(xfer
, &message
->transfers
, transfer_list
) {
688 if (xfer
->rx_buf
&& xfer
->tx_buf
)
690 if ((flags
& SPI_MASTER_NO_TX
) && xfer
->tx_buf
)
692 if ((flags
& SPI_MASTER_NO_RX
) && xfer
->rx_buf
)
698 message
->status
= -EINPROGRESS
;
699 return master
->transfer(spi
, message
);
703 * spi_async - asynchronous SPI transfer
704 * @spi: device with which data will be exchanged
705 * @message: describes the data transfers, including completion callback
706 * Context: any (irqs may be blocked, etc)
708 * This call may be used in_irq and other contexts which can't sleep,
709 * as well as from task contexts which can sleep.
711 * The completion callback is invoked in a context which can't sleep.
712 * Before that invocation, the value of message->status is undefined.
713 * When the callback is issued, message->status holds either zero (to
714 * indicate complete success) or a negative error code. After that
715 * callback returns, the driver which issued the transfer request may
716 * deallocate the associated memory; it's no longer in use by any SPI
717 * core or controller driver code.
719 * Note that although all messages to a spi_device are handled in
720 * FIFO order, messages may go to different devices in other orders.
721 * Some device might be higher priority, or have various "hard" access
722 * time requirements, for example.
724 * On detection of any fault during the transfer, processing of
725 * the entire message is aborted, and the device is deselected.
726 * Until returning from the associated message completion callback,
727 * no other spi_message queued to that device will be processed.
728 * (This rule applies equally to all the synchronous transfer calls,
729 * which are wrappers around this core asynchronous primitive.)
731 int spi_async(struct spi_device
*spi
, struct spi_message
*message
)
733 struct spi_master
*master
= spi
->master
;
737 spin_lock_irqsave(&master
->bus_lock_spinlock
, flags
);
739 if (master
->bus_lock_flag
)
742 ret
= __spi_async(spi
, message
);
744 spin_unlock_irqrestore(&master
->bus_lock_spinlock
, flags
);
748 EXPORT_SYMBOL_GPL(spi_async
);
751 * spi_async_locked - version of spi_async with exclusive bus usage
752 * @spi: device with which data will be exchanged
753 * @message: describes the data transfers, including completion callback
754 * Context: any (irqs may be blocked, etc)
756 * This call may be used in_irq and other contexts which can't sleep,
757 * as well as from task contexts which can sleep.
759 * The completion callback is invoked in a context which can't sleep.
760 * Before that invocation, the value of message->status is undefined.
761 * When the callback is issued, message->status holds either zero (to
762 * indicate complete success) or a negative error code. After that
763 * callback returns, the driver which issued the transfer request may
764 * deallocate the associated memory; it's no longer in use by any SPI
765 * core or controller driver code.
767 * Note that although all messages to a spi_device are handled in
768 * FIFO order, messages may go to different devices in other orders.
769 * Some device might be higher priority, or have various "hard" access
770 * time requirements, for example.
772 * On detection of any fault during the transfer, processing of
773 * the entire message is aborted, and the device is deselected.
774 * Until returning from the associated message completion callback,
775 * no other spi_message queued to that device will be processed.
776 * (This rule applies equally to all the synchronous transfer calls,
777 * which are wrappers around this core asynchronous primitive.)
779 int spi_async_locked(struct spi_device
*spi
, struct spi_message
*message
)
781 struct spi_master
*master
= spi
->master
;
785 spin_lock_irqsave(&master
->bus_lock_spinlock
, flags
);
787 ret
= __spi_async(spi
, message
);
789 spin_unlock_irqrestore(&master
->bus_lock_spinlock
, flags
);
794 EXPORT_SYMBOL_GPL(spi_async_locked
);
797 /*-------------------------------------------------------------------------*/
799 /* Utility methods for SPI master protocol drivers, layered on
800 * top of the core. Some other utility methods are defined as
804 static void spi_complete(void *arg
)
809 static int __spi_sync(struct spi_device
*spi
, struct spi_message
*message
,
812 DECLARE_COMPLETION_ONSTACK(done
);
814 struct spi_master
*master
= spi
->master
;
816 message
->complete
= spi_complete
;
817 message
->context
= &done
;
820 mutex_lock(&master
->bus_lock_mutex
);
822 status
= spi_async_locked(spi
, message
);
825 mutex_unlock(&master
->bus_lock_mutex
);
828 wait_for_completion(&done
);
829 status
= message
->status
;
831 message
->context
= NULL
;
836 * spi_sync - blocking/synchronous SPI data transfers
837 * @spi: device with which data will be exchanged
838 * @message: describes the data transfers
841 * This call may only be used from a context that may sleep. The sleep
842 * is non-interruptible, and has no timeout. Low-overhead controller
843 * drivers may DMA directly into and out of the message buffers.
845 * Note that the SPI device's chip select is active during the message,
846 * and then is normally disabled between messages. Drivers for some
847 * frequently-used devices may want to minimize costs of selecting a chip,
848 * by leaving it selected in anticipation that the next message will go
849 * to the same chip. (That may increase power usage.)
851 * Also, the caller is guaranteeing that the memory associated with the
852 * message will not be freed before this call returns.
854 * It returns zero on success, else a negative error code.
856 int spi_sync(struct spi_device
*spi
, struct spi_message
*message
)
858 return __spi_sync(spi
, message
, 0);
860 EXPORT_SYMBOL_GPL(spi_sync
);
863 * spi_sync_locked - version of spi_sync with exclusive bus usage
864 * @spi: device with which data will be exchanged
865 * @message: describes the data transfers
868 * This call may only be used from a context that may sleep. The sleep
869 * is non-interruptible, and has no timeout. Low-overhead controller
870 * drivers may DMA directly into and out of the message buffers.
872 * This call should be used by drivers that require exclusive access to the
873 * SPI bus. It has to be preceeded by a spi_bus_lock call. The SPI bus must
874 * be released by a spi_bus_unlock call when the exclusive access is over.
876 * It returns zero on success, else a negative error code.
878 int spi_sync_locked(struct spi_device
*spi
, struct spi_message
*message
)
880 return __spi_sync(spi
, message
, 1);
882 EXPORT_SYMBOL_GPL(spi_sync_locked
);
885 * spi_bus_lock - obtain a lock for exclusive SPI bus usage
886 * @master: SPI bus master that should be locked for exclusive bus access
889 * This call may only be used from a context that may sleep. The sleep
890 * is non-interruptible, and has no timeout.
892 * This call should be used by drivers that require exclusive access to the
893 * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
894 * exclusive access is over. Data transfer must be done by spi_sync_locked
895 * and spi_async_locked calls when the SPI bus lock is held.
897 * It returns zero on success, else a negative error code.
899 int spi_bus_lock(struct spi_master
*master
)
903 mutex_lock(&master
->bus_lock_mutex
);
905 spin_lock_irqsave(&master
->bus_lock_spinlock
, flags
);
906 master
->bus_lock_flag
= 1;
907 spin_unlock_irqrestore(&master
->bus_lock_spinlock
, flags
);
909 /* mutex remains locked until spi_bus_unlock is called */
913 EXPORT_SYMBOL_GPL(spi_bus_lock
);
916 * spi_bus_unlock - release the lock for exclusive SPI bus usage
917 * @master: SPI bus master that was locked for exclusive bus access
920 * This call may only be used from a context that may sleep. The sleep
921 * is non-interruptible, and has no timeout.
923 * This call releases an SPI bus lock previously obtained by an spi_bus_lock
926 * It returns zero on success, else a negative error code.
928 int spi_bus_unlock(struct spi_master
*master
)
930 master
->bus_lock_flag
= 0;
932 mutex_unlock(&master
->bus_lock_mutex
);
936 EXPORT_SYMBOL_GPL(spi_bus_unlock
);
938 /* portable code must never pass more than 32 bytes */
939 #define SPI_BUFSIZ max(32,SMP_CACHE_BYTES)
944 * spi_write_then_read - SPI synchronous write followed by read
945 * @spi: device with which data will be exchanged
946 * @txbuf: data to be written (need not be dma-safe)
947 * @n_tx: size of txbuf, in bytes
948 * @rxbuf: buffer into which data will be read (need not be dma-safe)
949 * @n_rx: size of rxbuf, in bytes
952 * This performs a half duplex MicroWire style transaction with the
953 * device, sending txbuf and then reading rxbuf. The return value
954 * is zero for success, else a negative errno status code.
955 * This call may only be used from a context that may sleep.
957 * Parameters to this routine are always copied using a small buffer;
958 * portable code should never use this for more than 32 bytes.
959 * Performance-sensitive or bulk transfer code should instead use
960 * spi_{async,sync}() calls with dma-safe buffers.
962 int spi_write_then_read(struct spi_device
*spi
,
963 const u8
*txbuf
, unsigned n_tx
,
964 u8
*rxbuf
, unsigned n_rx
)
966 static DEFINE_MUTEX(lock
);
969 struct spi_message message
;
970 struct spi_transfer x
[2];
973 /* Use preallocated DMA-safe buffer. We can't avoid copying here,
974 * (as a pure convenience thing), but we can keep heap costs
975 * out of the hot path ...
977 if ((n_tx
+ n_rx
) > SPI_BUFSIZ
)
980 spi_message_init(&message
);
981 memset(x
, 0, sizeof x
);
984 spi_message_add_tail(&x
[0], &message
);
988 spi_message_add_tail(&x
[1], &message
);
991 /* ... unless someone else is using the pre-allocated buffer */
992 if (!mutex_trylock(&lock
)) {
993 local_buf
= kmalloc(SPI_BUFSIZ
, GFP_KERNEL
);
999 memcpy(local_buf
, txbuf
, n_tx
);
1000 x
[0].tx_buf
= local_buf
;
1001 x
[1].rx_buf
= local_buf
+ n_tx
;
1004 status
= spi_sync(spi
, &message
);
1006 memcpy(rxbuf
, x
[1].rx_buf
, n_rx
);
1008 if (x
[0].tx_buf
== buf
)
1009 mutex_unlock(&lock
);
1015 EXPORT_SYMBOL_GPL(spi_write_then_read
);
1017 /*-------------------------------------------------------------------------*/
1019 static int __init
spi_init(void)
1023 buf
= kmalloc(SPI_BUFSIZ
, GFP_KERNEL
);
1029 status
= bus_register(&spi_bus_type
);
1033 status
= class_register(&spi_master_class
);
1039 bus_unregister(&spi_bus_type
);
1047 /* board_info is normally registered in arch_initcall(),
1048 * but even essential drivers wait till later
1050 * REVISIT only boardinfo really needs static linking. the rest (device and
1051 * driver registration) _could_ be dynamically linked (modular) ... costs
1052 * include needing to have boardinfo data structures be much more public.
1054 postcore_initcall(spi_init
);