4 * Copyright (C) 2005 David Brownell
5 * Copyright (C) 2008 Secret Lab Technologies Ltd.
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 #include <linux/kernel.h>
23 #include <linux/kmod.h>
24 #include <linux/device.h>
25 #include <linux/init.h>
26 #include <linux/cache.h>
27 #include <linux/mutex.h>
28 #include <linux/of_device.h>
29 #include <linux/of_irq.h>
30 #include <linux/slab.h>
31 #include <linux/mod_devicetable.h>
32 #include <linux/spi/spi.h>
33 #include <linux/of_gpio.h>
34 #include <linux/pm_runtime.h>
35 #include <linux/export.h>
36 #include <linux/sched/rt.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/ioport.h>
40 #include <linux/acpi.h>
42 static void spidev_release(struct device *dev)
44 struct spi_device *spi = to_spi_device(dev);
46 /* spi masters may cleanup for released devices */
47 if (spi->master->cleanup)
48 spi->master->cleanup(spi);
50 spi_master_put(spi->master);
55 modalias_show(struct device *dev, struct device_attribute *a, char *buf)
57 const struct spi_device *spi = to_spi_device(dev);
59 return sprintf(buf, "%s%s\n", SPI_MODULE_PREFIX, spi->modalias);
62 static struct device_attribute spi_dev_attrs[] = {
67 /* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
68 * and the sysfs version makes coldplug work too.
71 static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,
72 const struct spi_device *sdev)
75 if (!strcmp(sdev->modalias, id->name))
82 const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev)
84 const struct spi_driver *sdrv = to_spi_driver(sdev->dev.driver);
86 return spi_match_id(sdrv->id_table, sdev);
88 EXPORT_SYMBOL_GPL(spi_get_device_id);
90 static int spi_match_device(struct device *dev, struct device_driver *drv)
92 const struct spi_device *spi = to_spi_device(dev);
93 const struct spi_driver *sdrv = to_spi_driver(drv);
95 /* Attempt an OF style match */
96 if (of_driver_match_device(dev, drv))
100 if (acpi_driver_match_device(dev, drv))
104 return !!spi_match_id(sdrv->id_table, spi);
106 return strcmp(spi->modalias, drv->name) == 0;
109 static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
111 const struct spi_device *spi = to_spi_device(dev);
113 add_uevent_var(env, "MODALIAS=%s%s", SPI_MODULE_PREFIX, spi->modalias);
117 #ifdef CONFIG_PM_SLEEP
118 static int spi_legacy_suspend(struct device *dev, pm_message_t message)
121 struct spi_driver *drv = to_spi_driver(dev->driver);
123 /* suspend will stop irqs and dma; no more i/o */
126 value = drv->suspend(to_spi_device(dev), message);
128 dev_dbg(dev, "... can't suspend\n");
133 static int spi_legacy_resume(struct device *dev)
136 struct spi_driver *drv = to_spi_driver(dev->driver);
138 /* resume may restart the i/o queue */
141 value = drv->resume(to_spi_device(dev));
143 dev_dbg(dev, "... can't resume\n");
148 static int spi_pm_suspend(struct device *dev)
150 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
153 return pm_generic_suspend(dev);
155 return spi_legacy_suspend(dev, PMSG_SUSPEND);
158 static int spi_pm_resume(struct device *dev)
160 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
163 return pm_generic_resume(dev);
165 return spi_legacy_resume(dev);
168 static int spi_pm_freeze(struct device *dev)
170 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
173 return pm_generic_freeze(dev);
175 return spi_legacy_suspend(dev, PMSG_FREEZE);
178 static int spi_pm_thaw(struct device *dev)
180 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
183 return pm_generic_thaw(dev);
185 return spi_legacy_resume(dev);
188 static int spi_pm_poweroff(struct device *dev)
190 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
193 return pm_generic_poweroff(dev);
195 return spi_legacy_suspend(dev, PMSG_HIBERNATE);
198 static int spi_pm_restore(struct device *dev)
200 const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
203 return pm_generic_restore(dev);
205 return spi_legacy_resume(dev);
208 #define spi_pm_suspend NULL
209 #define spi_pm_resume NULL
210 #define spi_pm_freeze NULL
211 #define spi_pm_thaw NULL
212 #define spi_pm_poweroff NULL
213 #define spi_pm_restore NULL
216 static const struct dev_pm_ops spi_pm = {
217 .suspend = spi_pm_suspend,
218 .resume = spi_pm_resume,
219 .freeze = spi_pm_freeze,
221 .poweroff = spi_pm_poweroff,
222 .restore = spi_pm_restore,
224 pm_generic_runtime_suspend,
225 pm_generic_runtime_resume,
230 struct bus_type spi_bus_type = {
232 .dev_attrs = spi_dev_attrs,
233 .match = spi_match_device,
234 .uevent = spi_uevent,
237 EXPORT_SYMBOL_GPL(spi_bus_type);
240 static int spi_drv_probe(struct device *dev)
242 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
244 return sdrv->probe(to_spi_device(dev));
247 static int spi_drv_remove(struct device *dev)
249 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
251 return sdrv->remove(to_spi_device(dev));
254 static void spi_drv_shutdown(struct device *dev)
256 const struct spi_driver *sdrv = to_spi_driver(dev->driver);
258 sdrv->shutdown(to_spi_device(dev));
262 * spi_register_driver - register a SPI driver
263 * @sdrv: the driver to register
266 int spi_register_driver(struct spi_driver *sdrv)
268 sdrv->driver.bus = &spi_bus_type;
270 sdrv->driver.probe = spi_drv_probe;
272 sdrv->driver.remove = spi_drv_remove;
274 sdrv->driver.shutdown = spi_drv_shutdown;
275 return driver_register(&sdrv->driver);
277 EXPORT_SYMBOL_GPL(spi_register_driver);
279 /*-------------------------------------------------------------------------*/
281 /* SPI devices should normally not be created by SPI device drivers; that
282 * would make them board-specific. Similarly with SPI master drivers.
283 * Device registration normally goes into like arch/.../mach.../board-YYY.c
284 * with other readonly (flashable) information about mainboard devices.
288 struct list_head list;
289 struct spi_board_info board_info;
292 static LIST_HEAD(board_list);
293 static LIST_HEAD(spi_master_list);
296 * Used to protect add/del opertion for board_info list and
297 * spi_master list, and their matching process
299 static DEFINE_MUTEX(board_lock);
302 * spi_alloc_device - Allocate a new SPI device
303 * @master: Controller to which device is connected
306 * Allows a driver to allocate and initialize a spi_device without
307 * registering it immediately. This allows a driver to directly
308 * fill the spi_device with device parameters before calling
309 * spi_add_device() on it.
311 * Caller is responsible to call spi_add_device() on the returned
312 * spi_device structure to add it to the SPI master. If the caller
313 * needs to discard the spi_device without adding it, then it should
314 * call spi_dev_put() on it.
316 * Returns a pointer to the new device, or NULL.
318 struct spi_device *spi_alloc_device(struct spi_master *master)
320 struct spi_device *spi;
321 struct device *dev = master->dev.parent;
323 if (!spi_master_get(master))
326 spi = kzalloc(sizeof *spi, GFP_KERNEL);
328 dev_err(dev, "cannot alloc spi_device\n");
329 spi_master_put(master);
333 spi->master = master;
334 spi->dev.parent = &master->dev;
335 spi->dev.bus = &spi_bus_type;
336 spi->dev.release = spidev_release;
337 spi->cs_gpio = -ENOENT;
338 device_initialize(&spi->dev);
341 EXPORT_SYMBOL_GPL(spi_alloc_device);
344 * spi_add_device - Add spi_device allocated with spi_alloc_device
345 * @spi: spi_device to register
347 * Companion function to spi_alloc_device. Devices allocated with
348 * spi_alloc_device can be added onto the spi bus with this function.
350 * Returns 0 on success; negative errno on failure
352 int spi_add_device(struct spi_device *spi)
354 static DEFINE_MUTEX(spi_add_lock);
355 struct spi_master *master = spi->master;
356 struct device *dev = master->dev.parent;
360 /* Chipselects are numbered 0..max; validate. */
361 if (spi->chip_select >= master->num_chipselect) {
362 dev_err(dev, "cs%d >= max %d\n",
364 master->num_chipselect);
368 /* Set the bus ID string */
369 dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev),
373 /* We need to make sure there's no other device with this
374 * chipselect **BEFORE** we call setup(), else we'll trash
375 * its configuration. Lock against concurrent add() calls.
377 mutex_lock(&spi_add_lock);
379 d = bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev));
381 dev_err(dev, "chipselect %d already in use\n",
388 if (master->cs_gpios)
389 spi->cs_gpio = master->cs_gpios[spi->chip_select];
391 /* Drivers may modify this initial i/o setup, but will
392 * normally rely on the device being setup. Devices
393 * using SPI_CS_HIGH can't coexist well otherwise...
395 status = spi_setup(spi);
397 dev_err(dev, "can't setup %s, status %d\n",
398 dev_name(&spi->dev), status);
402 /* Device may be bound to an active driver when this returns */
403 status = device_add(&spi->dev);
405 dev_err(dev, "can't add %s, status %d\n",
406 dev_name(&spi->dev), status);
408 dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));
411 mutex_unlock(&spi_add_lock);
414 EXPORT_SYMBOL_GPL(spi_add_device);
417 * spi_new_device - instantiate one new SPI device
418 * @master: Controller to which device is connected
419 * @chip: Describes the SPI device
422 * On typical mainboards, this is purely internal; and it's not needed
423 * after board init creates the hard-wired devices. Some development
424 * platforms may not be able to use spi_register_board_info though, and
425 * this is exported so that for example a USB or parport based adapter
426 * driver could add devices (which it would learn about out-of-band).
428 * Returns the new device, or NULL.
430 struct spi_device *spi_new_device(struct spi_master *master,
431 struct spi_board_info *chip)
433 struct spi_device *proxy;
436 /* NOTE: caller did any chip->bus_num checks necessary.
438 * Also, unless we change the return value convention to use
439 * error-or-pointer (not NULL-or-pointer), troubleshootability
440 * suggests syslogged diagnostics are best here (ugh).
443 proxy = spi_alloc_device(master);
447 WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));
449 proxy->chip_select = chip->chip_select;
450 proxy->max_speed_hz = chip->max_speed_hz;
451 proxy->mode = chip->mode;
452 proxy->irq = chip->irq;
453 strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
454 proxy->dev.platform_data = (void *) chip->platform_data;
455 proxy->controller_data = chip->controller_data;
456 proxy->controller_state = NULL;
458 status = spi_add_device(proxy);
466 EXPORT_SYMBOL_GPL(spi_new_device);
468 static void spi_match_master_to_boardinfo(struct spi_master *master,
469 struct spi_board_info *bi)
471 struct spi_device *dev;
473 if (master->bus_num != bi->bus_num)
476 dev = spi_new_device(master, bi);
478 dev_err(master->dev.parent, "can't create new device for %s\n",
483 * spi_register_board_info - register SPI devices for a given board
484 * @info: array of chip descriptors
485 * @n: how many descriptors are provided
488 * Board-specific early init code calls this (probably during arch_initcall)
489 * with segments of the SPI device table. Any device nodes are created later,
490 * after the relevant parent SPI controller (bus_num) is defined. We keep
491 * this table of devices forever, so that reloading a controller driver will
492 * not make Linux forget about these hard-wired devices.
494 * Other code can also call this, e.g. a particular add-on board might provide
495 * SPI devices through its expansion connector, so code initializing that board
496 * would naturally declare its SPI devices.
498 * The board info passed can safely be __initdata ... but be careful of
499 * any embedded pointers (platform_data, etc), they're copied as-is.
501 int spi_register_board_info(struct spi_board_info const *info, unsigned n)
503 struct boardinfo *bi;
506 bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
510 for (i = 0; i < n; i++, bi++, info++) {
511 struct spi_master *master;
513 memcpy(&bi->board_info, info, sizeof(*info));
514 mutex_lock(&board_lock);
515 list_add_tail(&bi->list, &board_list);
516 list_for_each_entry(master, &spi_master_list, list)
517 spi_match_master_to_boardinfo(master, &bi->board_info);
518 mutex_unlock(&board_lock);
524 /*-------------------------------------------------------------------------*/
527 * spi_pump_messages - kthread work function which processes spi message queue
528 * @work: pointer to kthread work struct contained in the master struct
530 * This function checks if there is any spi message in the queue that
531 * needs processing and if so call out to the driver to initialize hardware
532 * and transfer each message.
535 static void spi_pump_messages(struct kthread_work *work)
537 struct spi_master *master =
538 container_of(work, struct spi_master, pump_messages);
540 bool was_busy = false;
543 /* Lock queue and check for queue work */
544 spin_lock_irqsave(&master->queue_lock, flags);
545 if (list_empty(&master->queue) || !master->running) {
547 spin_unlock_irqrestore(&master->queue_lock, flags);
550 master->busy = false;
551 spin_unlock_irqrestore(&master->queue_lock, flags);
552 if (master->unprepare_transfer_hardware &&
553 master->unprepare_transfer_hardware(master))
554 dev_err(&master->dev,
555 "failed to unprepare transfer hardware\n");
556 if (master->auto_runtime_pm) {
557 pm_runtime_mark_last_busy(master->dev.parent);
558 pm_runtime_put_autosuspend(master->dev.parent);
563 /* Make sure we are not already running a message */
564 if (master->cur_msg) {
565 spin_unlock_irqrestore(&master->queue_lock, flags);
568 /* Extract head of queue */
570 list_entry(master->queue.next, struct spi_message, queue);
572 list_del_init(&master->cur_msg->queue);
577 spin_unlock_irqrestore(&master->queue_lock, flags);
579 if (!was_busy && master->auto_runtime_pm) {
580 ret = pm_runtime_get_sync(master->dev.parent);
582 dev_err(&master->dev, "Failed to power device: %d\n",
588 if (!was_busy && master->prepare_transfer_hardware) {
589 ret = master->prepare_transfer_hardware(master);
591 dev_err(&master->dev,
592 "failed to prepare transfer hardware\n");
594 if (master->auto_runtime_pm)
595 pm_runtime_put(master->dev.parent);
600 ret = master->transfer_one_message(master, master->cur_msg);
602 dev_err(&master->dev,
603 "failed to transfer one message from queue\n");
608 static int spi_init_queue(struct spi_master *master)
610 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
612 INIT_LIST_HEAD(&master->queue);
613 spin_lock_init(&master->queue_lock);
615 master->running = false;
616 master->busy = false;
618 init_kthread_worker(&master->kworker);
619 master->kworker_task = kthread_run(kthread_worker_fn,
620 &master->kworker, "%s",
621 dev_name(&master->dev));
622 if (IS_ERR(master->kworker_task)) {
623 dev_err(&master->dev, "failed to create message pump task\n");
626 init_kthread_work(&master->pump_messages, spi_pump_messages);
629 * Master config will indicate if this controller should run the
630 * message pump with high (realtime) priority to reduce the transfer
631 * latency on the bus by minimising the delay between a transfer
632 * request and the scheduling of the message pump thread. Without this
633 * setting the message pump thread will remain at default priority.
636 dev_info(&master->dev,
637 "will run message pump with realtime priority\n");
638 sched_setscheduler(master->kworker_task, SCHED_FIFO, ¶m);
645 * spi_get_next_queued_message() - called by driver to check for queued
647 * @master: the master to check for queued messages
649 * If there are more messages in the queue, the next message is returned from
652 struct spi_message *spi_get_next_queued_message(struct spi_master *master)
654 struct spi_message *next;
657 /* get a pointer to the next message, if any */
658 spin_lock_irqsave(&master->queue_lock, flags);
659 if (list_empty(&master->queue))
662 next = list_entry(master->queue.next,
663 struct spi_message, queue);
664 spin_unlock_irqrestore(&master->queue_lock, flags);
668 EXPORT_SYMBOL_GPL(spi_get_next_queued_message);
671 * spi_finalize_current_message() - the current message is complete
672 * @master: the master to return the message to
674 * Called by the driver to notify the core that the message in the front of the
675 * queue is complete and can be removed from the queue.
677 void spi_finalize_current_message(struct spi_master *master)
679 struct spi_message *mesg;
682 spin_lock_irqsave(&master->queue_lock, flags);
683 mesg = master->cur_msg;
684 master->cur_msg = NULL;
686 queue_kthread_work(&master->kworker, &master->pump_messages);
687 spin_unlock_irqrestore(&master->queue_lock, flags);
691 mesg->complete(mesg->context);
693 EXPORT_SYMBOL_GPL(spi_finalize_current_message);
695 static int spi_start_queue(struct spi_master *master)
699 spin_lock_irqsave(&master->queue_lock, flags);
701 if (master->running || master->busy) {
702 spin_unlock_irqrestore(&master->queue_lock, flags);
706 master->running = true;
707 master->cur_msg = NULL;
708 spin_unlock_irqrestore(&master->queue_lock, flags);
710 queue_kthread_work(&master->kworker, &master->pump_messages);
715 static int spi_stop_queue(struct spi_master *master)
718 unsigned limit = 500;
721 spin_lock_irqsave(&master->queue_lock, flags);
724 * This is a bit lame, but is optimized for the common execution path.
725 * A wait_queue on the master->busy could be used, but then the common
726 * execution path (pump_messages) would be required to call wake_up or
727 * friends on every SPI message. Do this instead.
729 while ((!list_empty(&master->queue) || master->busy) && limit--) {
730 spin_unlock_irqrestore(&master->queue_lock, flags);
732 spin_lock_irqsave(&master->queue_lock, flags);
735 if (!list_empty(&master->queue) || master->busy)
738 master->running = false;
740 spin_unlock_irqrestore(&master->queue_lock, flags);
743 dev_warn(&master->dev,
744 "could not stop message queue\n");
750 static int spi_destroy_queue(struct spi_master *master)
754 ret = spi_stop_queue(master);
757 * flush_kthread_worker will block until all work is done.
758 * If the reason that stop_queue timed out is that the work will never
759 * finish, then it does no good to call flush/stop thread, so
763 dev_err(&master->dev, "problem destroying queue\n");
767 flush_kthread_worker(&master->kworker);
768 kthread_stop(master->kworker_task);
774 * spi_queued_transfer - transfer function for queued transfers
775 * @spi: spi device which is requesting transfer
776 * @msg: spi message which is to handled is queued to driver queue
778 static int spi_queued_transfer(struct spi_device *spi, struct spi_message *msg)
780 struct spi_master *master = spi->master;
783 spin_lock_irqsave(&master->queue_lock, flags);
785 if (!master->running) {
786 spin_unlock_irqrestore(&master->queue_lock, flags);
789 msg->actual_length = 0;
790 msg->status = -EINPROGRESS;
792 list_add_tail(&msg->queue, &master->queue);
794 queue_kthread_work(&master->kworker, &master->pump_messages);
796 spin_unlock_irqrestore(&master->queue_lock, flags);
800 static int spi_master_initialize_queue(struct spi_master *master)
804 master->queued = true;
805 master->transfer = spi_queued_transfer;
807 /* Initialize and start queue */
808 ret = spi_init_queue(master);
810 dev_err(&master->dev, "problem initializing queue\n");
813 ret = spi_start_queue(master);
815 dev_err(&master->dev, "problem starting queue\n");
816 goto err_start_queue;
823 spi_destroy_queue(master);
827 /*-------------------------------------------------------------------------*/
829 #if defined(CONFIG_OF)
831 * of_register_spi_devices() - Register child devices onto the SPI bus
832 * @master: Pointer to spi_master device
834 * Registers an spi_device for each child node of master node which has a 'reg'
837 static void of_register_spi_devices(struct spi_master *master)
839 struct spi_device *spi;
840 struct device_node *nc;
844 if (!master->dev.of_node)
847 for_each_available_child_of_node(master->dev.of_node, nc) {
848 /* Alloc an spi_device */
849 spi = spi_alloc_device(master);
851 dev_err(&master->dev, "spi_device alloc error for %s\n",
857 /* Select device driver */
858 if (of_modalias_node(nc, spi->modalias,
859 sizeof(spi->modalias)) < 0) {
860 dev_err(&master->dev, "cannot find modalias for %s\n",
867 rc = of_property_read_u32(nc, "reg", &value);
869 dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
874 spi->chip_select = value;
876 /* Mode (clock phase/polarity/etc.) */
877 if (of_find_property(nc, "spi-cpha", NULL))
878 spi->mode |= SPI_CPHA;
879 if (of_find_property(nc, "spi-cpol", NULL))
880 spi->mode |= SPI_CPOL;
881 if (of_find_property(nc, "spi-cs-high", NULL))
882 spi->mode |= SPI_CS_HIGH;
883 if (of_find_property(nc, "spi-3wire", NULL))
884 spi->mode |= SPI_3WIRE;
886 /* Device DUAL/QUAD mode */
887 if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
892 spi->mode |= SPI_TX_DUAL;
895 spi->mode |= SPI_TX_QUAD;
898 dev_err(&master->dev,
899 "spi-tx-bus-width %d not supported\n",
906 if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
911 spi->mode |= SPI_RX_DUAL;
914 spi->mode |= SPI_RX_QUAD;
917 dev_err(&master->dev,
918 "spi-rx-bus-width %d not supported\n",
926 rc = of_property_read_u32(nc, "spi-max-frequency", &value);
928 dev_err(&master->dev, "%s has no valid 'spi-max-frequency' property (%d)\n",
933 spi->max_speed_hz = value;
936 spi->irq = irq_of_parse_and_map(nc, 0);
938 /* Store a pointer to the node in the device structure */
940 spi->dev.of_node = nc;
942 /* Register the new device */
943 request_module("%s%s", SPI_MODULE_PREFIX, spi->modalias);
944 rc = spi_add_device(spi);
946 dev_err(&master->dev, "spi_device register error %s\n",
954 static void of_register_spi_devices(struct spi_master *master) { }
958 static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
960 struct spi_device *spi = data;
962 if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) {
963 struct acpi_resource_spi_serialbus *sb;
965 sb = &ares->data.spi_serial_bus;
966 if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_SPI) {
967 spi->chip_select = sb->device_selection;
968 spi->max_speed_hz = sb->connection_speed;
970 if (sb->clock_phase == ACPI_SPI_SECOND_PHASE)
971 spi->mode |= SPI_CPHA;
972 if (sb->clock_polarity == ACPI_SPI_START_HIGH)
973 spi->mode |= SPI_CPOL;
974 if (sb->device_polarity == ACPI_SPI_ACTIVE_HIGH)
975 spi->mode |= SPI_CS_HIGH;
977 } else if (spi->irq < 0) {
980 if (acpi_dev_resource_interrupt(ares, 0, &r))
984 /* Always tell the ACPI core to skip this resource */
988 static acpi_status acpi_spi_add_device(acpi_handle handle, u32 level,
989 void *data, void **return_value)
991 struct spi_master *master = data;
992 struct list_head resource_list;
993 struct acpi_device *adev;
994 struct spi_device *spi;
997 if (acpi_bus_get_device(handle, &adev))
999 if (acpi_bus_get_status(adev) || !adev->status.present)
1002 spi = spi_alloc_device(master);
1004 dev_err(&master->dev, "failed to allocate SPI device for %s\n",
1005 dev_name(&adev->dev));
1006 return AE_NO_MEMORY;
1009 ACPI_HANDLE_SET(&spi->dev, handle);
1012 INIT_LIST_HEAD(&resource_list);
1013 ret = acpi_dev_get_resources(adev, &resource_list,
1014 acpi_spi_add_resource, spi);
1015 acpi_dev_free_resource_list(&resource_list);
1017 if (ret < 0 || !spi->max_speed_hz) {
1022 strlcpy(spi->modalias, dev_name(&adev->dev), sizeof(spi->modalias));
1023 if (spi_add_device(spi)) {
1024 dev_err(&master->dev, "failed to add SPI device %s from ACPI\n",
1025 dev_name(&adev->dev));
1032 static void acpi_register_spi_devices(struct spi_master *master)
1037 handle = ACPI_HANDLE(master->dev.parent);
1041 status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
1042 acpi_spi_add_device, NULL,
1044 if (ACPI_FAILURE(status))
1045 dev_warn(&master->dev, "failed to enumerate SPI slaves\n");
1048 static inline void acpi_register_spi_devices(struct spi_master *master) {}
1049 #endif /* CONFIG_ACPI */
1051 static void spi_master_release(struct device *dev)
1053 struct spi_master *master;
1055 master = container_of(dev, struct spi_master, dev);
1059 static struct class spi_master_class = {
1060 .name = "spi_master",
1061 .owner = THIS_MODULE,
1062 .dev_release = spi_master_release,
1068 * spi_alloc_master - allocate SPI master controller
1069 * @dev: the controller, possibly using the platform_bus
1070 * @size: how much zeroed driver-private data to allocate; the pointer to this
1071 * memory is in the driver_data field of the returned device,
1072 * accessible with spi_master_get_devdata().
1073 * Context: can sleep
1075 * This call is used only by SPI master controller drivers, which are the
1076 * only ones directly touching chip registers. It's how they allocate
1077 * an spi_master structure, prior to calling spi_register_master().
1079 * This must be called from context that can sleep. It returns the SPI
1080 * master structure on success, else NULL.
1082 * The caller is responsible for assigning the bus number and initializing
1083 * the master's methods before calling spi_register_master(); and (after errors
1084 * adding the device) calling spi_master_put() and kfree() to prevent a memory
1087 struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
1089 struct spi_master *master;
1094 master = kzalloc(size + sizeof *master, GFP_KERNEL);
1098 device_initialize(&master->dev);
1099 master->bus_num = -1;
1100 master->num_chipselect = 1;
1101 master->dev.class = &spi_master_class;
1102 master->dev.parent = get_device(dev);
1103 spi_master_set_devdata(master, &master[1]);
1107 EXPORT_SYMBOL_GPL(spi_alloc_master);
1110 static int of_spi_register_master(struct spi_master *master)
1113 struct device_node *np = master->dev.of_node;
1118 nb = of_gpio_named_count(np, "cs-gpios");
1119 master->num_chipselect = max(nb, (int)master->num_chipselect);
1121 /* Return error only for an incorrectly formed cs-gpios property */
1122 if (nb == 0 || nb == -ENOENT)
1127 cs = devm_kzalloc(&master->dev,
1128 sizeof(int) * master->num_chipselect,
1130 master->cs_gpios = cs;
1132 if (!master->cs_gpios)
1135 for (i = 0; i < master->num_chipselect; i++)
1138 for (i = 0; i < nb; i++)
1139 cs[i] = of_get_named_gpio(np, "cs-gpios", i);
1144 static int of_spi_register_master(struct spi_master *master)
1151 * spi_register_master - register SPI master controller
1152 * @master: initialized master, originally from spi_alloc_master()
1153 * Context: can sleep
1155 * SPI master controllers connect to their drivers using some non-SPI bus,
1156 * such as the platform bus. The final stage of probe() in that code
1157 * includes calling spi_register_master() to hook up to this SPI bus glue.
1159 * SPI controllers use board specific (often SOC specific) bus numbers,
1160 * and board-specific addressing for SPI devices combines those numbers
1161 * with chip select numbers. Since SPI does not directly support dynamic
1162 * device identification, boards need configuration tables telling which
1163 * chip is at which address.
1165 * This must be called from context that can sleep. It returns zero on
1166 * success, else a negative error code (dropping the master's refcount).
1167 * After a successful return, the caller is responsible for calling
1168 * spi_unregister_master().
1170 int spi_register_master(struct spi_master *master)
1172 static atomic_t dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
1173 struct device *dev = master->dev.parent;
1174 struct boardinfo *bi;
1175 int status = -ENODEV;
1181 status = of_spi_register_master(master);
1185 /* even if it's just one always-selected device, there must
1186 * be at least one chipselect
1188 if (master->num_chipselect == 0)
1191 if ((master->bus_num < 0) && master->dev.of_node)
1192 master->bus_num = of_alias_get_id(master->dev.of_node, "spi");
1194 /* convention: dynamically assigned bus IDs count down from the max */
1195 if (master->bus_num < 0) {
1196 /* FIXME switch to an IDR based scheme, something like
1197 * I2C now uses, so we can't run out of "dynamic" IDs
1199 master->bus_num = atomic_dec_return(&dyn_bus_id);
1203 spin_lock_init(&master->bus_lock_spinlock);
1204 mutex_init(&master->bus_lock_mutex);
1205 master->bus_lock_flag = 0;
1207 /* register the device, then userspace will see it.
1208 * registration fails if the bus ID is in use.
1210 dev_set_name(&master->dev, "spi%u", master->bus_num);
1211 status = device_add(&master->dev);
1214 dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
1215 dynamic ? " (dynamic)" : "");
1217 /* If we're using a queued driver, start the queue */
1218 if (master->transfer)
1219 dev_info(dev, "master is unqueued, this is deprecated\n");
1221 status = spi_master_initialize_queue(master);
1223 device_del(&master->dev);
1228 mutex_lock(&board_lock);
1229 list_add_tail(&master->list, &spi_master_list);
1230 list_for_each_entry(bi, &board_list, list)
1231 spi_match_master_to_boardinfo(master, &bi->board_info);
1232 mutex_unlock(&board_lock);
1234 /* Register devices from the device tree and ACPI */
1235 of_register_spi_devices(master);
1236 acpi_register_spi_devices(master);
1240 EXPORT_SYMBOL_GPL(spi_register_master);
1242 static int __unregister(struct device *dev, void *null)
1244 spi_unregister_device(to_spi_device(dev));
1249 * spi_unregister_master - unregister SPI master controller
1250 * @master: the master being unregistered
1251 * Context: can sleep
1253 * This call is used only by SPI master controller drivers, which are the
1254 * only ones directly touching chip registers.
1256 * This must be called from context that can sleep.
1258 void spi_unregister_master(struct spi_master *master)
1262 if (master->queued) {
1263 if (spi_destroy_queue(master))
1264 dev_err(&master->dev, "queue remove failed\n");
1267 mutex_lock(&board_lock);
1268 list_del(&master->list);
1269 mutex_unlock(&board_lock);
1271 dummy = device_for_each_child(&master->dev, NULL, __unregister);
1272 device_unregister(&master->dev);
1274 EXPORT_SYMBOL_GPL(spi_unregister_master);
1276 int spi_master_suspend(struct spi_master *master)
1280 /* Basically no-ops for non-queued masters */
1281 if (!master->queued)
1284 ret = spi_stop_queue(master);
1286 dev_err(&master->dev, "queue stop failed\n");
1290 EXPORT_SYMBOL_GPL(spi_master_suspend);
1292 int spi_master_resume(struct spi_master *master)
1296 if (!master->queued)
1299 ret = spi_start_queue(master);
1301 dev_err(&master->dev, "queue restart failed\n");
1305 EXPORT_SYMBOL_GPL(spi_master_resume);
1307 static int __spi_master_match(struct device *dev, const void *data)
1309 struct spi_master *m;
1310 const u16 *bus_num = data;
1312 m = container_of(dev, struct spi_master, dev);
1313 return m->bus_num == *bus_num;
1317 * spi_busnum_to_master - look up master associated with bus_num
1318 * @bus_num: the master's bus number
1319 * Context: can sleep
1321 * This call may be used with devices that are registered after
1322 * arch init time. It returns a refcounted pointer to the relevant
1323 * spi_master (which the caller must release), or NULL if there is
1324 * no such master registered.
1326 struct spi_master *spi_busnum_to_master(u16 bus_num)
1329 struct spi_master *master = NULL;
1331 dev = class_find_device(&spi_master_class, NULL, &bus_num,
1332 __spi_master_match);
1334 master = container_of(dev, struct spi_master, dev);
1335 /* reference got in class_find_device */
1338 EXPORT_SYMBOL_GPL(spi_busnum_to_master);
1341 /*-------------------------------------------------------------------------*/
1343 /* Core methods for SPI master protocol drivers. Some of the
1344 * other core methods are currently defined as inline functions.
1348 * spi_setup - setup SPI mode and clock rate
1349 * @spi: the device whose settings are being modified
1350 * Context: can sleep, and no requests are queued to the device
1352 * SPI protocol drivers may need to update the transfer mode if the
1353 * device doesn't work with its default. They may likewise need
1354 * to update clock rates or word sizes from initial values. This function
1355 * changes those settings, and must be called from a context that can sleep.
1356 * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
1357 * effect the next time the device is selected and data is transferred to
1358 * or from it. When this function returns, the spi device is deselected.
1360 * Note that this call will fail if the protocol driver specifies an option
1361 * that the underlying controller or its driver does not support. For
1362 * example, not all hardware supports wire transfers using nine bit words,
1363 * LSB-first wire encoding, or active-high chipselects.
1365 int spi_setup(struct spi_device *spi)
1370 /* check mode to prevent that DUAL and QUAD set at the same time
1372 if (((spi->mode & SPI_TX_DUAL) && (spi->mode & SPI_TX_QUAD)) ||
1373 ((spi->mode & SPI_RX_DUAL) && (spi->mode & SPI_RX_QUAD))) {
1375 "setup: can not select dual and quad at the same time\n");
1378 /* if it is SPI_3WIRE mode, DUAL and QUAD should be forbidden
1380 if ((spi->mode & SPI_3WIRE) && (spi->mode &
1381 (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)))
1383 /* help drivers fail *cleanly* when they need options
1384 * that aren't supported with their current master
1386 bad_bits = spi->mode & ~spi->master->mode_bits;
1388 dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
1393 if (!spi->bits_per_word)
1394 spi->bits_per_word = 8;
1396 if (spi->master->setup)
1397 status = spi->master->setup(spi);
1399 dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s"
1400 "%u bits/w, %u Hz max --> %d\n",
1401 (int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
1402 (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
1403 (spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
1404 (spi->mode & SPI_3WIRE) ? "3wire, " : "",
1405 (spi->mode & SPI_LOOP) ? "loopback, " : "",
1406 spi->bits_per_word, spi->max_speed_hz,
1411 EXPORT_SYMBOL_GPL(spi_setup);
1413 static int __spi_async(struct spi_device *spi, struct spi_message *message)
1415 struct spi_master *master = spi->master;
1416 struct spi_transfer *xfer;
1418 if (list_empty(&message->transfers))
1420 if (!message->complete)
1423 /* Half-duplex links include original MicroWire, and ones with
1424 * only one data pin like SPI_3WIRE (switches direction) or where
1425 * either MOSI or MISO is missing. They can also be caused by
1426 * software limitations.
1428 if ((master->flags & SPI_MASTER_HALF_DUPLEX)
1429 || (spi->mode & SPI_3WIRE)) {
1430 unsigned flags = master->flags;
1432 list_for_each_entry(xfer, &message->transfers, transfer_list) {
1433 if (xfer->rx_buf && xfer->tx_buf)
1435 if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
1437 if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
1443 * Set transfer bits_per_word and max speed as spi device default if
1444 * it is not set for this transfer.
1445 * Set transfer tx_nbits and rx_nbits as single transfer default
1446 * (SPI_NBITS_SINGLE) if it is not set for this transfer.
1448 list_for_each_entry(xfer, &message->transfers, transfer_list) {
1449 message->frame_length += xfer->len;
1450 if (!xfer->bits_per_word)
1451 xfer->bits_per_word = spi->bits_per_word;
1452 if (!xfer->speed_hz) {
1453 xfer->speed_hz = spi->max_speed_hz;
1454 if (master->max_speed_hz &&
1455 xfer->speed_hz > master->max_speed_hz)
1456 xfer->speed_hz = master->max_speed_hz;
1459 if (master->bits_per_word_mask) {
1460 /* Only 32 bits fit in the mask */
1461 if (xfer->bits_per_word > 32)
1463 if (!(master->bits_per_word_mask &
1464 BIT(xfer->bits_per_word - 1)))
1468 if (xfer->speed_hz && master->min_speed_hz &&
1469 xfer->speed_hz < master->min_speed_hz)
1471 if (xfer->speed_hz && master->max_speed_hz &&
1472 xfer->speed_hz > master->max_speed_hz)
1475 if (xfer->tx_buf && !xfer->tx_nbits)
1476 xfer->tx_nbits = SPI_NBITS_SINGLE;
1477 if (xfer->rx_buf && !xfer->rx_nbits)
1478 xfer->rx_nbits = SPI_NBITS_SINGLE;
1479 /* check transfer tx/rx_nbits:
1480 * 1. keep the value is not out of single, dual and quad
1481 * 2. keep tx/rx_nbits is contained by mode in spi_device
1482 * 3. if SPI_3WIRE, tx/rx_nbits should be in single
1485 if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
1486 xfer->tx_nbits != SPI_NBITS_DUAL &&
1487 xfer->tx_nbits != SPI_NBITS_QUAD)
1489 if ((xfer->tx_nbits == SPI_NBITS_DUAL) &&
1490 !(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD)))
1492 if ((xfer->tx_nbits == SPI_NBITS_QUAD) &&
1493 !(spi->mode & SPI_TX_QUAD))
1495 if ((spi->mode & SPI_3WIRE) &&
1496 (xfer->tx_nbits != SPI_NBITS_SINGLE))
1499 /* check transfer rx_nbits */
1501 if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
1502 xfer->rx_nbits != SPI_NBITS_DUAL &&
1503 xfer->rx_nbits != SPI_NBITS_QUAD)
1505 if ((xfer->rx_nbits == SPI_NBITS_DUAL) &&
1506 !(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD)))
1508 if ((xfer->rx_nbits == SPI_NBITS_QUAD) &&
1509 !(spi->mode & SPI_RX_QUAD))
1511 if ((spi->mode & SPI_3WIRE) &&
1512 (xfer->rx_nbits != SPI_NBITS_SINGLE))
1518 message->status = -EINPROGRESS;
1519 return master->transfer(spi, message);
1523 * spi_async - asynchronous SPI transfer
1524 * @spi: device with which data will be exchanged
1525 * @message: describes the data transfers, including completion callback
1526 * Context: any (irqs may be blocked, etc)
1528 * This call may be used in_irq and other contexts which can't sleep,
1529 * as well as from task contexts which can sleep.
1531 * The completion callback is invoked in a context which can't sleep.
1532 * Before that invocation, the value of message->status is undefined.
1533 * When the callback is issued, message->status holds either zero (to
1534 * indicate complete success) or a negative error code. After that
1535 * callback returns, the driver which issued the transfer request may
1536 * deallocate the associated memory; it's no longer in use by any SPI
1537 * core or controller driver code.
1539 * Note that although all messages to a spi_device are handled in
1540 * FIFO order, messages may go to different devices in other orders.
1541 * Some device might be higher priority, or have various "hard" access
1542 * time requirements, for example.
1544 * On detection of any fault during the transfer, processing of
1545 * the entire message is aborted, and the device is deselected.
1546 * Until returning from the associated message completion callback,
1547 * no other spi_message queued to that device will be processed.
1548 * (This rule applies equally to all the synchronous transfer calls,
1549 * which are wrappers around this core asynchronous primitive.)
1551 int spi_async(struct spi_device *spi, struct spi_message *message)
1553 struct spi_master *master = spi->master;
1555 unsigned long flags;
1557 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
1559 if (master->bus_lock_flag)
1562 ret = __spi_async(spi, message);
1564 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
1568 EXPORT_SYMBOL_GPL(spi_async);
1571 * spi_async_locked - version of spi_async with exclusive bus usage
1572 * @spi: device with which data will be exchanged
1573 * @message: describes the data transfers, including completion callback
1574 * Context: any (irqs may be blocked, etc)
1576 * This call may be used in_irq and other contexts which can't sleep,
1577 * as well as from task contexts which can sleep.
1579 * The completion callback is invoked in a context which can't sleep.
1580 * Before that invocation, the value of message->status is undefined.
1581 * When the callback is issued, message->status holds either zero (to
1582 * indicate complete success) or a negative error code. After that
1583 * callback returns, the driver which issued the transfer request may
1584 * deallocate the associated memory; it's no longer in use by any SPI
1585 * core or controller driver code.
1587 * Note that although all messages to a spi_device are handled in
1588 * FIFO order, messages may go to different devices in other orders.
1589 * Some device might be higher priority, or have various "hard" access
1590 * time requirements, for example.
1592 * On detection of any fault during the transfer, processing of
1593 * the entire message is aborted, and the device is deselected.
1594 * Until returning from the associated message completion callback,
1595 * no other spi_message queued to that device will be processed.
1596 * (This rule applies equally to all the synchronous transfer calls,
1597 * which are wrappers around this core asynchronous primitive.)
1599 int spi_async_locked(struct spi_device *spi, struct spi_message *message)
1601 struct spi_master *master = spi->master;
1603 unsigned long flags;
1605 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
1607 ret = __spi_async(spi, message);
1609 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
1614 EXPORT_SYMBOL_GPL(spi_async_locked);
1617 /*-------------------------------------------------------------------------*/
1619 /* Utility methods for SPI master protocol drivers, layered on
1620 * top of the core. Some other utility methods are defined as
1624 static void spi_complete(void *arg)
1629 static int __spi_sync(struct spi_device *spi, struct spi_message *message,
1632 DECLARE_COMPLETION_ONSTACK(done);
1634 struct spi_master *master = spi->master;
1636 message->complete = spi_complete;
1637 message->context = &done;
1640 mutex_lock(&master->bus_lock_mutex);
1642 status = spi_async_locked(spi, message);
1645 mutex_unlock(&master->bus_lock_mutex);
1648 wait_for_completion(&done);
1649 status = message->status;
1651 message->context = NULL;
1656 * spi_sync - blocking/synchronous SPI data transfers
1657 * @spi: device with which data will be exchanged
1658 * @message: describes the data transfers
1659 * Context: can sleep
1661 * This call may only be used from a context that may sleep. The sleep
1662 * is non-interruptible, and has no timeout. Low-overhead controller
1663 * drivers may DMA directly into and out of the message buffers.
1665 * Note that the SPI device's chip select is active during the message,
1666 * and then is normally disabled between messages. Drivers for some
1667 * frequently-used devices may want to minimize costs of selecting a chip,
1668 * by leaving it selected in anticipation that the next message will go
1669 * to the same chip. (That may increase power usage.)
1671 * Also, the caller is guaranteeing that the memory associated with the
1672 * message will not be freed before this call returns.
1674 * It returns zero on success, else a negative error code.
1676 int spi_sync(struct spi_device *spi, struct spi_message *message)
1678 return __spi_sync(spi, message, 0);
1680 EXPORT_SYMBOL_GPL(spi_sync);
1683 * spi_sync_locked - version of spi_sync with exclusive bus usage
1684 * @spi: device with which data will be exchanged
1685 * @message: describes the data transfers
1686 * Context: can sleep
1688 * This call may only be used from a context that may sleep. The sleep
1689 * is non-interruptible, and has no timeout. Low-overhead controller
1690 * drivers may DMA directly into and out of the message buffers.
1692 * This call should be used by drivers that require exclusive access to the
1693 * SPI bus. It has to be preceded by a spi_bus_lock call. The SPI bus must
1694 * be released by a spi_bus_unlock call when the exclusive access is over.
1696 * It returns zero on success, else a negative error code.
1698 int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
1700 return __spi_sync(spi, message, 1);
1702 EXPORT_SYMBOL_GPL(spi_sync_locked);
1705 * spi_bus_lock - obtain a lock for exclusive SPI bus usage
1706 * @master: SPI bus master that should be locked for exclusive bus access
1707 * Context: can sleep
1709 * This call may only be used from a context that may sleep. The sleep
1710 * is non-interruptible, and has no timeout.
1712 * This call should be used by drivers that require exclusive access to the
1713 * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
1714 * exclusive access is over. Data transfer must be done by spi_sync_locked
1715 * and spi_async_locked calls when the SPI bus lock is held.
1717 * It returns zero on success, else a negative error code.
1719 int spi_bus_lock(struct spi_master *master)
1721 unsigned long flags;
1723 mutex_lock(&master->bus_lock_mutex);
1725 spin_lock_irqsave(&master->bus_lock_spinlock, flags);
1726 master->bus_lock_flag = 1;
1727 spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
1729 /* mutex remains locked until spi_bus_unlock is called */
1733 EXPORT_SYMBOL_GPL(spi_bus_lock);
1736 * spi_bus_unlock - release the lock for exclusive SPI bus usage
1737 * @master: SPI bus master that was locked for exclusive bus access
1738 * Context: can sleep
1740 * This call may only be used from a context that may sleep. The sleep
1741 * is non-interruptible, and has no timeout.
1743 * This call releases an SPI bus lock previously obtained by an spi_bus_lock
1746 * It returns zero on success, else a negative error code.
1748 int spi_bus_unlock(struct spi_master *master)
1750 master->bus_lock_flag = 0;
1752 mutex_unlock(&master->bus_lock_mutex);
1756 EXPORT_SYMBOL_GPL(spi_bus_unlock);
1758 /* portable code must never pass more than 32 bytes */
1759 #define SPI_BUFSIZ max(32,SMP_CACHE_BYTES)
1764 * spi_write_then_read - SPI synchronous write followed by read
1765 * @spi: device with which data will be exchanged
1766 * @txbuf: data to be written (need not be dma-safe)
1767 * @n_tx: size of txbuf, in bytes
1768 * @rxbuf: buffer into which data will be read (need not be dma-safe)
1769 * @n_rx: size of rxbuf, in bytes
1770 * Context: can sleep
1772 * This performs a half duplex MicroWire style transaction with the
1773 * device, sending txbuf and then reading rxbuf. The return value
1774 * is zero for success, else a negative errno status code.
1775 * This call may only be used from a context that may sleep.
1777 * Parameters to this routine are always copied using a small buffer;
1778 * portable code should never use this for more than 32 bytes.
1779 * Performance-sensitive or bulk transfer code should instead use
1780 * spi_{async,sync}() calls with dma-safe buffers.
1782 int spi_write_then_read(struct spi_device *spi,
1783 const void *txbuf, unsigned n_tx,
1784 void *rxbuf, unsigned n_rx)
1786 static DEFINE_MUTEX(lock);
1789 struct spi_message message;
1790 struct spi_transfer x[2];
1793 /* Use preallocated DMA-safe buffer if we can. We can't avoid
1794 * copying here, (as a pure convenience thing), but we can
1795 * keep heap costs out of the hot path unless someone else is
1796 * using the pre-allocated buffer or the transfer is too large.
1798 if ((n_tx + n_rx) > SPI_BUFSIZ || !mutex_trylock(&lock)) {
1799 local_buf = kmalloc(max((unsigned)SPI_BUFSIZ, n_tx + n_rx),
1800 GFP_KERNEL | GFP_DMA);
1807 spi_message_init(&message);
1808 memset(x, 0, sizeof x);
1811 spi_message_add_tail(&x[0], &message);
1815 spi_message_add_tail(&x[1], &message);
1818 memcpy(local_buf, txbuf, n_tx);
1819 x[0].tx_buf = local_buf;
1820 x[1].rx_buf = local_buf + n_tx;
1823 status = spi_sync(spi, &message);
1825 memcpy(rxbuf, x[1].rx_buf, n_rx);
1827 if (x[0].tx_buf == buf)
1828 mutex_unlock(&lock);
1834 EXPORT_SYMBOL_GPL(spi_write_then_read);
1836 /*-------------------------------------------------------------------------*/
1838 static int __init spi_init(void)
1842 buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
1848 status = bus_register(&spi_bus_type);
1852 status = class_register(&spi_master_class);
1858 bus_unregister(&spi_bus_type);
1866 /* board_info is normally registered in arch_initcall(),
1867 * but even essential drivers wait till later
1869 * REVISIT only boardinfo really needs static linking. the rest (device and
1870 * driver registration) _could_ be dynamically linked (modular) ... costs
1871 * include needing to have boardinfo data structures be much more public.
1873 postcore_initcall(spi_init);