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/slab.h>
27 #include <linux/mod_devicetable.h>
28 #include <linux/spi/spi.h>
29 #include <linux/of_spi.h>
32 /* SPI bustype and spi_master class are registered after board init code
33 * provides the SPI device tables, ensuring that both are present by the
34 * time controller driver registration causes spi_devices to "enumerate".
36 static void spidev_release(struct device *dev)
38 struct spi_device *spi = to_spi_device(dev);
40 /* spi masters may cleanup for released devices */
41 if (spi->master->cleanup)
42 spi->master->cleanup(spi);
44 spi_master_put(spi->master);
49 modalias_show(struct device *dev, struct device_attribute *a, char *buf)
51 const struct spi_device *spi = to_spi_device(dev);
53 return sprintf(buf, "%s\n", spi->modalias);
56 static struct device_attribute spi_dev_attrs[] = {
61 /* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
62 * and the sysfs version makes coldplug work too.
65 static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,
66 const struct spi_device *sdev)
69 if (!strcmp(sdev->modalias, id->name))
76 const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev)
78 const struct spi_driver *sdrv = to_spi_driver(sdev->dev.driver);
80 return spi_match_id(sdrv->id_table, sdev);
82 EXPORT_SYMBOL_GPL(spi_get_device_id);
84 static int spi_match_device(struct device *dev, struct device_driver *drv)
86 const struct spi_device *spi = to_spi_device(dev);
87 const struct spi_driver *sdrv = to_spi_driver(drv);
90 return !!spi_match_id(sdrv->id_table, spi);
92 return strcmp(spi->modalias, drv->name) == 0;
95 static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
97 const struct spi_device *spi = to_spi_device(dev);
99 add_uevent_var(env, "MODALIAS=%s%s", SPI_MODULE_PREFIX, spi->modalias);
105 static int spi_suspend(struct device *dev, pm_message_t message)
108 struct spi_driver *drv = to_spi_driver(dev->driver);
110 /* suspend will stop irqs and dma; no more i/o */
113 value = drv->suspend(to_spi_device(dev), message);
115 dev_dbg(dev, "... can't suspend\n");
120 static int spi_resume(struct device *dev)
123 struct spi_driver *drv = to_spi_driver(dev->driver);
125 /* resume may restart the i/o queue */
128 value = drv->resume(to_spi_device(dev));
130 dev_dbg(dev, "... can't resume\n");
136 #define spi_suspend NULL
137 #define spi_resume NULL
140 struct bus_type spi_bus_type = {
142 .dev_attrs = spi_dev_attrs,
143 .match = spi_match_device,
144 .uevent = spi_uevent,
145 .suspend = spi_suspend,
146 .resume = spi_resume,
148 EXPORT_SYMBOL_GPL(spi_bus_type);
151 static int spi_drv_probe(struct device *dev)
153 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
155 return sdrv->probe(to_spi_device(dev));
158 static int spi_drv_remove(struct device *dev)
160 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
162 return sdrv->remove(to_spi_device(dev));
165 static void spi_drv_shutdown(struct device *dev)
167 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
169 sdrv->shutdown(to_spi_device(dev));
173 * spi_register_driver - register a SPI driver
174 * @sdrv: the driver to register
177 int spi_register_driver(struct spi_driver *sdrv)
179 sdrv->driver.bus = &spi_bus_type;
181 sdrv->driver.probe = spi_drv_probe;
183 sdrv->driver.remove = spi_drv_remove;
185 sdrv->driver.shutdown = spi_drv_shutdown;
186 return driver_register(&sdrv->driver);
188 EXPORT_SYMBOL_GPL(spi_register_driver);
190 /*-------------------------------------------------------------------------*/
192 /* SPI devices should normally not be created by SPI device drivers; that
193 * would make them board-specific. Similarly with SPI master drivers.
194 * Device registration normally goes into like arch/.../mach.../board-YYY.c
195 * with other readonly (flashable) information about mainboard devices.
199 struct list_head list;
200 unsigned n_board_info;
201 struct spi_board_info board_info[0];
204 static LIST_HEAD(board_list);
205 static DEFINE_MUTEX(board_lock);
208 * spi_alloc_device - Allocate a new SPI device
209 * @master: Controller to which device is connected
212 * Allows a driver to allocate and initialize a spi_device without
213 * registering it immediately. This allows a driver to directly
214 * fill the spi_device with device parameters before calling
215 * spi_add_device() on it.
217 * Caller is responsible to call spi_add_device() on the returned
218 * spi_device structure to add it to the SPI master. If the caller
219 * needs to discard the spi_device without adding it, then it should
220 * call spi_dev_put() on it.
222 * Returns a pointer to the new device, or NULL.
224 struct spi_device *spi_alloc_device(struct spi_master *master)
226 struct spi_device *spi;
227 struct device *dev = master->dev.parent;
229 if (!spi_master_get(master))
232 spi = kzalloc(sizeof *spi, GFP_KERNEL);
234 dev_err(dev, "cannot alloc spi_device\n");
235 spi_master_put(master);
239 spi->master = master;
240 spi->dev.parent = dev;
241 spi->dev.bus = &spi_bus_type;
242 spi->dev.release = spidev_release;
243 device_initialize(&spi->dev);
246 EXPORT_SYMBOL_GPL(spi_alloc_device);
249 * spi_add_device - Add spi_device allocated with spi_alloc_device
250 * @spi: spi_device to register
252 * Companion function to spi_alloc_device. Devices allocated with
253 * spi_alloc_device can be added onto the spi bus with this function.
255 * Returns 0 on success; negative errno on failure
257 int spi_add_device(struct spi_device *spi)
259 static DEFINE_MUTEX(spi_add_lock);
260 struct device *dev = spi->master->dev.parent;
264 /* Chipselects are numbered 0..max; validate. */
265 if (spi->chip_select >= spi->master->num_chipselect) {
266 dev_err(dev, "cs%d >= max %d\n",
268 spi->master->num_chipselect);
272 /* Set the bus ID string */
273 dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev),
277 /* We need to make sure there's no other device with this
278 * chipselect **BEFORE** we call setup(), else we'll trash
279 * its configuration. Lock against concurrent add() calls.
281 mutex_lock(&spi_add_lock);
283 d = bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev));
285 dev_err(dev, "chipselect %d already in use\n",
292 /* Drivers may modify this initial i/o setup, but will
293 * normally rely on the device being setup. Devices
294 * using SPI_CS_HIGH can't coexist well otherwise...
296 status = spi_setup(spi);
298 dev_err(dev, "can't %s %s, status %d\n",
299 "setup", dev_name(&spi->dev), status);
303 /* Device may be bound to an active driver when this returns */
304 status = device_add(&spi->dev);
306 dev_err(dev, "can't %s %s, status %d\n",
307 "add", dev_name(&spi->dev), status);
309 dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));
312 mutex_unlock(&spi_add_lock);
315 EXPORT_SYMBOL_GPL(spi_add_device);
318 * spi_new_device - instantiate one new SPI device
319 * @master: Controller to which device is connected
320 * @chip: Describes the SPI device
323 * On typical mainboards, this is purely internal; and it's not needed
324 * after board init creates the hard-wired devices. Some development
325 * platforms may not be able to use spi_register_board_info though, and
326 * this is exported so that for example a USB or parport based adapter
327 * driver could add devices (which it would learn about out-of-band).
329 * Returns the new device, or NULL.
331 struct spi_device *spi_new_device(struct spi_master *master,
332 struct spi_board_info *chip)
334 struct spi_device *proxy;
337 /* NOTE: caller did any chip->bus_num checks necessary.
339 * Also, unless we change the return value convention to use
340 * error-or-pointer (not NULL-or-pointer), troubleshootability
341 * suggests syslogged diagnostics are best here (ugh).
344 proxy = spi_alloc_device(master);
348 WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));
350 proxy->chip_select = chip->chip_select;
351 proxy->max_speed_hz = chip->max_speed_hz;
352 proxy->mode = chip->mode;
353 proxy->irq = chip->irq;
354 strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
355 proxy->dev.platform_data = (void *) chip->platform_data;
356 proxy->controller_data = chip->controller_data;
357 proxy->controller_state = NULL;
359 status = spi_add_device(proxy);
367 EXPORT_SYMBOL_GPL(spi_new_device);
370 * spi_register_board_info - register SPI devices for a given board
371 * @info: array of chip descriptors
372 * @n: how many descriptors are provided
375 * Board-specific early init code calls this (probably during arch_initcall)
376 * with segments of the SPI device table. Any device nodes are created later,
377 * after the relevant parent SPI controller (bus_num) is defined. We keep
378 * this table of devices forever, so that reloading a controller driver will
379 * not make Linux forget about these hard-wired devices.
381 * Other code can also call this, e.g. a particular add-on board might provide
382 * SPI devices through its expansion connector, so code initializing that board
383 * would naturally declare its SPI devices.
385 * The board info passed can safely be __initdata ... but be careful of
386 * any embedded pointers (platform_data, etc), they're copied as-is.
389 spi_register_board_info(struct spi_board_info const *info, unsigned n)
391 struct boardinfo *bi;
393 bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
396 bi->n_board_info = n;
397 memcpy(bi->board_info, info, n * sizeof *info);
399 mutex_lock(&board_lock);
400 list_add_tail(&bi->list, &board_list);
401 mutex_unlock(&board_lock);
405 /* FIXME someone should add support for a __setup("spi", ...) that
406 * creates board info from kernel command lines
409 static void scan_boardinfo(struct spi_master *master)
411 struct boardinfo *bi;
413 mutex_lock(&board_lock);
414 list_for_each_entry(bi, &board_list, list) {
415 struct spi_board_info *chip = bi->board_info;
418 for (n = bi->n_board_info; n > 0; n--, chip++) {
419 if (chip->bus_num != master->bus_num)
421 /* NOTE: this relies on spi_new_device to
422 * issue diagnostics when given bogus inputs
424 (void) spi_new_device(master, chip);
427 mutex_unlock(&board_lock);
430 /*-------------------------------------------------------------------------*/
432 static void spi_master_release(struct device *dev)
434 struct spi_master *master;
436 master = container_of(dev, struct spi_master, dev);
440 static struct class spi_master_class = {
441 .name = "spi_master",
442 .owner = THIS_MODULE,
443 .dev_release = spi_master_release,
448 * spi_alloc_master - allocate SPI master controller
449 * @dev: the controller, possibly using the platform_bus
450 * @size: how much zeroed driver-private data to allocate; the pointer to this
451 * memory is in the driver_data field of the returned device,
452 * accessible with spi_master_get_devdata().
455 * This call is used only by SPI master controller drivers, which are the
456 * only ones directly touching chip registers. It's how they allocate
457 * an spi_master structure, prior to calling spi_register_master().
459 * This must be called from context that can sleep. It returns the SPI
460 * master structure on success, else NULL.
462 * The caller is responsible for assigning the bus number and initializing
463 * the master's methods before calling spi_register_master(); and (after errors
464 * adding the device) calling spi_master_put() to prevent a memory leak.
466 struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
468 struct spi_master *master;
473 master = kzalloc(size + sizeof *master, GFP_KERNEL);
477 device_initialize(&master->dev);
478 master->dev.class = &spi_master_class;
479 master->dev.parent = get_device(dev);
480 spi_master_set_devdata(master, &master[1]);
484 EXPORT_SYMBOL_GPL(spi_alloc_master);
487 * spi_register_master - register SPI master controller
488 * @master: initialized master, originally from spi_alloc_master()
491 * SPI master controllers connect to their drivers using some non-SPI bus,
492 * such as the platform bus. The final stage of probe() in that code
493 * includes calling spi_register_master() to hook up to this SPI bus glue.
495 * SPI controllers use board specific (often SOC specific) bus numbers,
496 * and board-specific addressing for SPI devices combines those numbers
497 * with chip select numbers. Since SPI does not directly support dynamic
498 * device identification, boards need configuration tables telling which
499 * chip is at which address.
501 * This must be called from context that can sleep. It returns zero on
502 * success, else a negative error code (dropping the master's refcount).
503 * After a successful return, the caller is responsible for calling
504 * spi_unregister_master().
506 int spi_register_master(struct spi_master *master)
508 static atomic_t dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
509 struct device *dev = master->dev.parent;
510 int status = -ENODEV;
516 /* even if it's just one always-selected device, there must
517 * be at least one chipselect
519 if (master->num_chipselect == 0)
522 /* convention: dynamically assigned bus IDs count down from the max */
523 if (master->bus_num < 0) {
524 /* FIXME switch to an IDR based scheme, something like
525 * I2C now uses, so we can't run out of "dynamic" IDs
527 master->bus_num = atomic_dec_return(&dyn_bus_id);
531 spin_lock_init(&master->bus_lock_spinlock);
532 mutex_init(&master->bus_lock_mutex);
533 master->bus_lock_flag = 0;
535 /* register the device, then userspace will see it.
536 * registration fails if the bus ID is in use.
538 dev_set_name(&master->dev, "spi%u", master->bus_num);
539 status = device_add(&master->dev);
542 dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
543 dynamic ? " (dynamic)" : "");
545 /* populate children from any spi device tables */
546 scan_boardinfo(master);
549 /* Register devices from the device tree */
550 of_register_spi_devices(master);
554 EXPORT_SYMBOL_GPL(spi_register_master);
557 static int __unregister(struct device *dev, void *master_dev)
559 /* note: before about 2.6.14-rc1 this would corrupt memory: */
560 if (dev != master_dev)
561 spi_unregister_device(to_spi_device(dev));
566 * spi_unregister_master - unregister SPI master controller
567 * @master: the master being unregistered
570 * This call is used only by SPI master controller drivers, which are the
571 * only ones directly touching chip registers.
573 * This must be called from context that can sleep.
575 void spi_unregister_master(struct spi_master *master)
579 dummy = device_for_each_child(master->dev.parent, &master->dev,
581 device_unregister(&master->dev);
583 EXPORT_SYMBOL_GPL(spi_unregister_master);
585 static int __spi_master_match(struct device *dev, void *data)
587 struct spi_master *m;
590 m = container_of(dev, struct spi_master, dev);
591 return m->bus_num == *bus_num;
595 * spi_busnum_to_master - look up master associated with bus_num
596 * @bus_num: the master's bus number
599 * This call may be used with devices that are registered after
600 * arch init time. It returns a refcounted pointer to the relevant
601 * spi_master (which the caller must release), or NULL if there is
602 * no such master registered.
604 struct spi_master *spi_busnum_to_master(u16 bus_num)
607 struct spi_master *master = NULL;
609 dev = class_find_device(&spi_master_class, NULL, &bus_num,
612 master = container_of(dev, struct spi_master, dev);
613 /* reference got in class_find_device */
616 EXPORT_SYMBOL_GPL(spi_busnum_to_master);
619 /*-------------------------------------------------------------------------*/
621 /* Core methods for SPI master protocol drivers. Some of the
622 * other core methods are currently defined as inline functions.
626 * spi_setup - setup SPI mode and clock rate
627 * @spi: the device whose settings are being modified
628 * Context: can sleep, and no requests are queued to the device
630 * SPI protocol drivers may need to update the transfer mode if the
631 * device doesn't work with its default. They may likewise need
632 * to update clock rates or word sizes from initial values. This function
633 * changes those settings, and must be called from a context that can sleep.
634 * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
635 * effect the next time the device is selected and data is transferred to
636 * or from it. When this function returns, the spi device is deselected.
638 * Note that this call will fail if the protocol driver specifies an option
639 * that the underlying controller or its driver does not support. For
640 * example, not all hardware supports wire transfers using nine bit words,
641 * LSB-first wire encoding, or active-high chipselects.
643 int spi_setup(struct spi_device *spi)
648 /* help drivers fail *cleanly* when they need options
649 * that aren't supported with their current master
651 bad_bits = spi->mode & ~spi->master->mode_bits;
653 dev_dbg(&spi->dev, "setup: unsupported mode bits %x\n",
658 if (!spi->bits_per_word)
659 spi->bits_per_word = 8;
661 status = spi->master->setup(spi);
663 dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s"
664 "%u bits/w, %u Hz max --> %d\n",
665 (int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
666 (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
667 (spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
668 (spi->mode & SPI_3WIRE) ? "3wire, " : "",
669 (spi->mode & SPI_LOOP) ? "loopback, " : "",
670 spi->bits_per_word, spi->max_speed_hz,
675 EXPORT_SYMBOL_GPL(spi_setup);
677 static int __spi_async(struct spi_device *spi, struct spi_message *message)
679 struct spi_master *master = spi->master;
681 /* Half-duplex links include original MicroWire, and ones with
682 * only one data pin like SPI_3WIRE (switches direction) or where
683 * either MOSI or MISO is missing. They can also be caused by
684 * software limitations.
686 if ((master->flags & SPI_MASTER_HALF_DUPLEX)
687 || (spi->mode & SPI_3WIRE)) {
688 struct spi_transfer *xfer;
689 unsigned flags = master->flags;
691 list_for_each_entry(xfer, &message->transfers, transfer_list) {
692 if (xfer->rx_buf && xfer->tx_buf)
694 if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
696 if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
702 message->status = -EINPROGRESS;
703 return master->transfer(spi, message);
707 * spi_async - asynchronous SPI transfer
708 * @spi: device with which data will be exchanged
709 * @message: describes the data transfers, including completion callback
710 * Context: any (irqs may be blocked, etc)
712 * This call may be used in_irq and other contexts which can't sleep,
713 * as well as from task contexts which can sleep.
715 * The completion callback is invoked in a context which can't sleep.
716 * Before that invocation, the value of message->status is undefined.
717 * When the callback is issued, message->status holds either zero (to
718 * indicate complete success) or a negative error code. After that
719 * callback returns, the driver which issued the transfer request may
720 * deallocate the associated memory; it's no longer in use by any SPI
721 * core or controller driver code.
723 * Note that although all messages to a spi_device are handled in
724 * FIFO order, messages may go to different devices in other orders.
725 * Some device might be higher priority, or have various "hard" access
726 * time requirements, for example.
728 * On detection of any fault during the transfer, processing of
729 * the entire message is aborted, and the device is deselected.
730 * Until returning from the associated message completion callback,
731 * no other spi_message queued to that device will be processed.
732 * (This rule applies equally to all the synchronous transfer calls,
733 * which are wrappers around this core asynchronous primitive.)
735 int spi_async(struct spi_device *spi, struct spi_message *message)
737 struct spi_master *master = spi->master;
741 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
743 if (master->bus_lock_flag)
746 ret = __spi_async(spi, message);
748 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
752 EXPORT_SYMBOL_GPL(spi_async);
755 * spi_async_locked - version of spi_async with exclusive bus usage
756 * @spi: device with which data will be exchanged
757 * @message: describes the data transfers, including completion callback
758 * Context: any (irqs may be blocked, etc)
760 * This call may be used in_irq and other contexts which can't sleep,
761 * as well as from task contexts which can sleep.
763 * The completion callback is invoked in a context which can't sleep.
764 * Before that invocation, the value of message->status is undefined.
765 * When the callback is issued, message->status holds either zero (to
766 * indicate complete success) or a negative error code. After that
767 * callback returns, the driver which issued the transfer request may
768 * deallocate the associated memory; it's no longer in use by any SPI
769 * core or controller driver code.
771 * Note that although all messages to a spi_device are handled in
772 * FIFO order, messages may go to different devices in other orders.
773 * Some device might be higher priority, or have various "hard" access
774 * time requirements, for example.
776 * On detection of any fault during the transfer, processing of
777 * the entire message is aborted, and the device is deselected.
778 * Until returning from the associated message completion callback,
779 * no other spi_message queued to that device will be processed.
780 * (This rule applies equally to all the synchronous transfer calls,
781 * which are wrappers around this core asynchronous primitive.)
783 int spi_async_locked(struct spi_device *spi, struct spi_message *message)
785 struct spi_master *master = spi->master;
789 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
791 ret = __spi_async(spi, message);
793 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
798 EXPORT_SYMBOL_GPL(spi_async_locked);
801 /*-------------------------------------------------------------------------*/
803 /* Utility methods for SPI master protocol drivers, layered on
804 * top of the core. Some other utility methods are defined as
808 static void spi_complete(void *arg)
813 static int __spi_sync(struct spi_device *spi, struct spi_message *message,
816 DECLARE_COMPLETION_ONSTACK(done);
818 struct spi_master *master = spi->master;
820 message->complete = spi_complete;
821 message->context = &done;
824 mutex_lock(&master->bus_lock_mutex);
826 status = spi_async_locked(spi, message);
829 mutex_unlock(&master->bus_lock_mutex);
832 wait_for_completion(&done);
833 status = message->status;
835 message->context = NULL;
840 * spi_sync - blocking/synchronous SPI data transfers
841 * @spi: device with which data will be exchanged
842 * @message: describes the data transfers
845 * This call may only be used from a context that may sleep. The sleep
846 * is non-interruptible, and has no timeout. Low-overhead controller
847 * drivers may DMA directly into and out of the message buffers.
849 * Note that the SPI device's chip select is active during the message,
850 * and then is normally disabled between messages. Drivers for some
851 * frequently-used devices may want to minimize costs of selecting a chip,
852 * by leaving it selected in anticipation that the next message will go
853 * to the same chip. (That may increase power usage.)
855 * Also, the caller is guaranteeing that the memory associated with the
856 * message will not be freed before this call returns.
858 * It returns zero on success, else a negative error code.
860 int spi_sync(struct spi_device *spi, struct spi_message *message)
862 return __spi_sync(spi, message, 0);
864 EXPORT_SYMBOL_GPL(spi_sync);
867 * spi_sync_locked - version of spi_sync with exclusive bus usage
868 * @spi: device with which data will be exchanged
869 * @message: describes the data transfers
872 * This call may only be used from a context that may sleep. The sleep
873 * is non-interruptible, and has no timeout. Low-overhead controller
874 * drivers may DMA directly into and out of the message buffers.
876 * This call should be used by drivers that require exclusive access to the
877 * SPI bus. It has to be preceeded by a spi_bus_lock call. The SPI bus must
878 * be released by a spi_bus_unlock call when the exclusive access is over.
880 * It returns zero on success, else a negative error code.
882 int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
884 return __spi_sync(spi, message, 1);
886 EXPORT_SYMBOL_GPL(spi_sync_locked);
889 * spi_bus_lock - obtain a lock for exclusive SPI bus usage
890 * @master: SPI bus master that should be locked for exclusive bus access
893 * This call may only be used from a context that may sleep. The sleep
894 * is non-interruptible, and has no timeout.
896 * This call should be used by drivers that require exclusive access to the
897 * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
898 * exclusive access is over. Data transfer must be done by spi_sync_locked
899 * and spi_async_locked calls when the SPI bus lock is held.
901 * It returns zero on success, else a negative error code.
903 int spi_bus_lock(struct spi_master *master)
907 mutex_lock(&master->bus_lock_mutex);
909 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
910 master->bus_lock_flag = 1;
911 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
913 /* mutex remains locked until spi_bus_unlock is called */
917 EXPORT_SYMBOL_GPL(spi_bus_lock);
920 * spi_bus_unlock - release the lock for exclusive SPI bus usage
921 * @master: SPI bus master that was locked for exclusive bus access
924 * This call may only be used from a context that may sleep. The sleep
925 * is non-interruptible, and has no timeout.
927 * This call releases an SPI bus lock previously obtained by an spi_bus_lock
930 * It returns zero on success, else a negative error code.
932 int spi_bus_unlock(struct spi_master *master)
934 master->bus_lock_flag = 0;
936 mutex_unlock(&master->bus_lock_mutex);
940 EXPORT_SYMBOL_GPL(spi_bus_unlock);
942 /* portable code must never pass more than 32 bytes */
943 #define SPI_BUFSIZ max(32,SMP_CACHE_BYTES)
948 * spi_write_then_read - SPI synchronous write followed by read
949 * @spi: device with which data will be exchanged
950 * @txbuf: data to be written (need not be dma-safe)
951 * @n_tx: size of txbuf, in bytes
952 * @rxbuf: buffer into which data will be read (need not be dma-safe)
953 * @n_rx: size of rxbuf, in bytes
956 * This performs a half duplex MicroWire style transaction with the
957 * device, sending txbuf and then reading rxbuf. The return value
958 * is zero for success, else a negative errno status code.
959 * This call may only be used from a context that may sleep.
961 * Parameters to this routine are always copied using a small buffer;
962 * portable code should never use this for more than 32 bytes.
963 * Performance-sensitive or bulk transfer code should instead use
964 * spi_{async,sync}() calls with dma-safe buffers.
966 int spi_write_then_read(struct spi_device *spi,
967 const u8 *txbuf, unsigned n_tx,
968 u8 *rxbuf, unsigned n_rx)
970 static DEFINE_MUTEX(lock);
973 struct spi_message message;
974 struct spi_transfer x[2];
977 /* Use preallocated DMA-safe buffer. We can't avoid copying here,
978 * (as a pure convenience thing), but we can keep heap costs
979 * out of the hot path ...
981 if ((n_tx + n_rx) > SPI_BUFSIZ)
984 spi_message_init(&message);
985 memset(x, 0, sizeof x);
988 spi_message_add_tail(&x[0], &message);
992 spi_message_add_tail(&x[1], &message);
995 /* ... unless someone else is using the pre-allocated buffer */
996 if (!mutex_trylock(&lock)) {
997 local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
1003 memcpy(local_buf, txbuf, n_tx);
1004 x[0].tx_buf = local_buf;
1005 x[1].rx_buf = local_buf + n_tx;
1008 status = spi_sync(spi, &message);
1010 memcpy(rxbuf, x[1].rx_buf, n_rx);
1012 if (x[0].tx_buf == buf)
1013 mutex_unlock(&lock);
1019 EXPORT_SYMBOL_GPL(spi_write_then_read);
1021 /*-------------------------------------------------------------------------*/
1023 static int __init spi_init(void)
1027 buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
1033 status = bus_register(&spi_bus_type);
1037 status = class_register(&spi_master_class);
1043 bus_unregister(&spi_bus_type);
1051 /* board_info is normally registered in arch_initcall(),
1052 * but even essential drivers wait till later
1054 * REVISIT only boardinfo really needs static linking. the rest (device and
1055 * driver registration) _could_ be dynamically linked (modular) ... costs
1056 * include needing to have boardinfo data structures be much more public.
1058 postcore_initcall(spi_init);