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 /* register the device, then userspace will see it.
532 * registration fails if the bus ID is in use.
534 dev_set_name(&master
->dev
, "spi%u", master
->bus_num
);
535 status
= device_add(&master
->dev
);
538 dev_dbg(dev
, "registered master %s%s\n", dev_name(&master
->dev
),
539 dynamic
? " (dynamic)" : "");
541 /* populate children from any spi device tables */
542 scan_boardinfo(master
);
545 /* Register devices from the device tree */
546 of_register_spi_devices(master
);
550 EXPORT_SYMBOL_GPL(spi_register_master
);
553 static int __unregister(struct device
*dev
, void *master_dev
)
555 /* note: before about 2.6.14-rc1 this would corrupt memory: */
556 if (dev
!= master_dev
)
557 spi_unregister_device(to_spi_device(dev
));
562 * spi_unregister_master - unregister SPI master controller
563 * @master: the master being unregistered
566 * This call is used only by SPI master controller drivers, which are the
567 * only ones directly touching chip registers.
569 * This must be called from context that can sleep.
571 void spi_unregister_master(struct spi_master
*master
)
575 dummy
= device_for_each_child(master
->dev
.parent
, &master
->dev
,
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
);
674 * spi_async - asynchronous SPI transfer
675 * @spi: device with which data will be exchanged
676 * @message: describes the data transfers, including completion callback
677 * Context: any (irqs may be blocked, etc)
679 * This call may be used in_irq and other contexts which can't sleep,
680 * as well as from task contexts which can sleep.
682 * The completion callback is invoked in a context which can't sleep.
683 * Before that invocation, the value of message->status is undefined.
684 * When the callback is issued, message->status holds either zero (to
685 * indicate complete success) or a negative error code. After that
686 * callback returns, the driver which issued the transfer request may
687 * deallocate the associated memory; it's no longer in use by any SPI
688 * core or controller driver code.
690 * Note that although all messages to a spi_device are handled in
691 * FIFO order, messages may go to different devices in other orders.
692 * Some device might be higher priority, or have various "hard" access
693 * time requirements, for example.
695 * On detection of any fault during the transfer, processing of
696 * the entire message is aborted, and the device is deselected.
697 * Until returning from the associated message completion callback,
698 * no other spi_message queued to that device will be processed.
699 * (This rule applies equally to all the synchronous transfer calls,
700 * which are wrappers around this core asynchronous primitive.)
702 int spi_async(struct spi_device
*spi
, struct spi_message
*message
)
704 struct spi_master
*master
= spi
->master
;
706 /* Half-duplex links include original MicroWire, and ones with
707 * only one data pin like SPI_3WIRE (switches direction) or where
708 * either MOSI or MISO is missing. They can also be caused by
709 * software limitations.
711 if ((master
->flags
& SPI_MASTER_HALF_DUPLEX
)
712 || (spi
->mode
& SPI_3WIRE
)) {
713 struct spi_transfer
*xfer
;
714 unsigned flags
= master
->flags
;
716 list_for_each_entry(xfer
, &message
->transfers
, transfer_list
) {
717 if (xfer
->rx_buf
&& xfer
->tx_buf
)
719 if ((flags
& SPI_MASTER_NO_TX
) && xfer
->tx_buf
)
721 if ((flags
& SPI_MASTER_NO_RX
) && xfer
->rx_buf
)
727 message
->status
= -EINPROGRESS
;
728 return master
->transfer(spi
, message
);
730 EXPORT_SYMBOL_GPL(spi_async
);
733 /*-------------------------------------------------------------------------*/
735 /* Utility methods for SPI master protocol drivers, layered on
736 * top of the core. Some other utility methods are defined as
740 static void spi_complete(void *arg
)
746 * spi_sync - blocking/synchronous SPI data transfers
747 * @spi: device with which data will be exchanged
748 * @message: describes the data transfers
751 * This call may only be used from a context that may sleep. The sleep
752 * is non-interruptible, and has no timeout. Low-overhead controller
753 * drivers may DMA directly into and out of the message buffers.
755 * Note that the SPI device's chip select is active during the message,
756 * and then is normally disabled between messages. Drivers for some
757 * frequently-used devices may want to minimize costs of selecting a chip,
758 * by leaving it selected in anticipation that the next message will go
759 * to the same chip. (That may increase power usage.)
761 * Also, the caller is guaranteeing that the memory associated with the
762 * message will not be freed before this call returns.
764 * It returns zero on success, else a negative error code.
766 int spi_sync(struct spi_device
*spi
, struct spi_message
*message
)
768 DECLARE_COMPLETION_ONSTACK(done
);
771 message
->complete
= spi_complete
;
772 message
->context
= &done
;
773 status
= spi_async(spi
, message
);
775 wait_for_completion(&done
);
776 status
= message
->status
;
778 message
->context
= NULL
;
781 EXPORT_SYMBOL_GPL(spi_sync
);
783 /* portable code must never pass more than 32 bytes */
784 #define SPI_BUFSIZ max(32,SMP_CACHE_BYTES)
789 * spi_write_then_read - SPI synchronous write followed by read
790 * @spi: device with which data will be exchanged
791 * @txbuf: data to be written (need not be dma-safe)
792 * @n_tx: size of txbuf, in bytes
793 * @rxbuf: buffer into which data will be read (need not be dma-safe)
794 * @n_rx: size of rxbuf, in bytes
797 * This performs a half duplex MicroWire style transaction with the
798 * device, sending txbuf and then reading rxbuf. The return value
799 * is zero for success, else a negative errno status code.
800 * This call may only be used from a context that may sleep.
802 * Parameters to this routine are always copied using a small buffer;
803 * portable code should never use this for more than 32 bytes.
804 * Performance-sensitive or bulk transfer code should instead use
805 * spi_{async,sync}() calls with dma-safe buffers.
807 int spi_write_then_read(struct spi_device
*spi
,
808 const u8
*txbuf
, unsigned n_tx
,
809 u8
*rxbuf
, unsigned n_rx
)
811 static DEFINE_MUTEX(lock
);
814 struct spi_message message
;
815 struct spi_transfer x
[2];
818 /* Use preallocated DMA-safe buffer. We can't avoid copying here,
819 * (as a pure convenience thing), but we can keep heap costs
820 * out of the hot path ...
822 if ((n_tx
+ n_rx
) > SPI_BUFSIZ
)
825 spi_message_init(&message
);
826 memset(x
, 0, sizeof x
);
829 spi_message_add_tail(&x
[0], &message
);
833 spi_message_add_tail(&x
[1], &message
);
836 /* ... unless someone else is using the pre-allocated buffer */
837 if (!mutex_trylock(&lock
)) {
838 local_buf
= kmalloc(SPI_BUFSIZ
, GFP_KERNEL
);
844 memcpy(local_buf
, txbuf
, n_tx
);
845 x
[0].tx_buf
= local_buf
;
846 x
[1].rx_buf
= local_buf
+ n_tx
;
849 status
= spi_sync(spi
, &message
);
851 memcpy(rxbuf
, x
[1].rx_buf
, n_rx
);
853 if (x
[0].tx_buf
== buf
)
860 EXPORT_SYMBOL_GPL(spi_write_then_read
);
862 /*-------------------------------------------------------------------------*/
864 static int __init
spi_init(void)
868 buf
= kmalloc(SPI_BUFSIZ
, GFP_KERNEL
);
874 status
= bus_register(&spi_bus_type
);
878 status
= class_register(&spi_master_class
);
884 bus_unregister(&spi_bus_type
);
892 /* board_info is normally registered in arch_initcall(),
893 * but even essential drivers wait till later
895 * REVISIT only boardinfo really needs static linking. the rest (device and
896 * driver registration) _could_ be dynamically linked (modular) ... costs
897 * include needing to have boardinfo data structures be much more public.
899 postcore_initcall(spi_init
);