text: /*
   * SPI init/core code
   *
   * Copyright (C) 2005 David Brownell
   * Copyright (C) 2008 Secret Lab Technologies Ltd.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #include <linux/kernel.h>
  #include <linux/kmod.h>
  #include <linux/device.h>
  #include <linux/init.h>
  #include <linux/cache.h>
  #include <linux/dma-mapping.h>
  #include <linux/dmaengine.h>
  #include <linux/mutex.h>
  #include <linux/of_device.h>
  #include <linux/of_irq.h>
  #include <linux/clk/clk-conf.h>
  #include <linux/slab.h>
  #include <linux/mod_devicetable.h>
  #include <linux/spi/spi.h>
  #include <linux/of_gpio.h>
  #include <linux/pm_runtime.h>
  #include <linux/pm_domain.h>
  #include <linux/export.h>
  #include <linux/sched/rt.h>
  #include <linux/delay.h>
  #include <linux/kthread.h>
  #include <linux/ioport.h>
  #include <linux/acpi.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/spi.h>
  
  static void spidev_release(struct device *dev)
  {
  	struct spi_device	*spi = to_spi_device(dev);
  
  	/* spi masters may cleanup for released devices */
  	if (spi->master->cleanup)
  		spi->master->cleanup(spi);
  
  	spi_master_put(spi->master);
  	kfree(spi);
  }
  
  static ssize_t
  modalias_show(struct device *dev, struct device_attribute *a, char *buf)
  {
  	const struct spi_device	*spi = to_spi_device(dev);
  	int len;
  
  	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
  	if (len != -ENODEV)
  		return len;
  
  	return sprintf(buf, "%s%s\n", SPI_MODULE_PREFIX, spi->modalias);
  }
  static DEVICE_ATTR_RO(modalias);
  
  static struct attribute *spi_dev_attrs[] = {
  	&dev_attr_modalias.attr,
  	NULL,
  };
  ATTRIBUTE_GROUPS(spi_dev);
  
  /* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
   * and the sysfs version makes coldplug work too.
   */
  
  static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,
  						const struct spi_device *sdev)
  {
  	while (id->name[0]) {
  		if (!strcmp(sdev->modalias, id->name))
  			return id;
  		id++;
  	}
  	return NULL;
  }
  
  const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev)
  {
  	const struct spi_driver *sdrv = to_spi_driver(sdev->dev.driver);
  
  	return spi_match_id(sdrv->id_table, sdev);
  }
  EXPORT_SYMBOL_GPL(spi_get_device_id);
  
  static int spi_match_device(struct device *dev, struct device_driver *drv)
  {
  	const struct spi_device	*spi = to_spi_device(dev);
  	const struct spi_driver	*sdrv = to_spi_driver(drv);
  
  	/* Attempt an OF style match */
  	if (of_driver_match_device(dev, drv))
  		return 1;
  
  	/* Then try ACPI */
  	if (acpi_driver_match_device(dev, drv))
  		return 1;
  
  	if (sdrv->id_table)
  		return !!spi_match_id(sdrv->id_table, spi);
  
  	return strcmp(spi->modalias, drv->name) == 0;
  }
  
  static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	const struct spi_device		*spi = to_spi_device(dev);
  	int rc;
  
  	rc = acpi_device_uevent_modalias(dev, env);
  	if (rc != -ENODEV)
  		return rc;
  
  	add_uevent_var(env, "MODALIAS=%s%s", SPI_MODULE_PREFIX, spi->modalias);
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int spi_legacy_suspend(struct device *dev, pm_message_t message)
  {
  	int			value = 0;
  	struct spi_driver	*drv = to_spi_driver(dev->driver);
  
  	/* suspend will stop irqs and dma; no more i/o */
  	if (drv) {
  		if (drv->suspend)
  			value = drv->suspend(to_spi_device(dev), message);
  		else
  			dev_dbg(dev, "... can't suspend\n");
  	}
  	return value;
  }
  
  static int spi_legacy_resume(struct device *dev)
  {
  	int			value = 0;
  	struct spi_driver	*drv = to_spi_driver(dev->driver);
  
  	/* resume may restart the i/o queue */
  	if (drv) {
  		if (drv->resume)
  			value = drv->resume(to_spi_device(dev));
  		else
  			dev_dbg(dev, "... can't resume\n");
  	}
  	return value;
  }
  
  static int spi_pm_suspend(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_suspend(dev);
  	else
  		return spi_legacy_suspend(dev, PMSG_SUSPEND);
  }
  
  static int spi_pm_resume(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_resume(dev);
  	else
  		return spi_legacy_resume(dev);
  }
  
  static int spi_pm_freeze(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_freeze(dev);
  	else
  		return spi_legacy_suspend(dev, PMSG_FREEZE);
  }
  
  static int spi_pm_thaw(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_thaw(dev);
  	else
  		return spi_legacy_resume(dev);
  }
  
  static int spi_pm_poweroff(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_poweroff(dev);
  	else
  		return spi_legacy_suspend(dev, PMSG_HIBERNATE);
  }
  
  static int spi_pm_restore(struct device *dev)
  {
  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
  
  	if (pm)
  		return pm_generic_restore(dev);
  	else
  		return spi_legacy_resume(dev);
  }
  #else
  #define spi_pm_suspend	NULL
  #define spi_pm_resume	NULL
  #define spi_pm_freeze	NULL
  #define spi_pm_thaw	NULL
  #define spi_pm_poweroff	NULL
  #define spi_pm_restore	NULL
  #endif
  
  static const struct dev_pm_ops spi_pm = {
  	.suspend = spi_pm_suspend,
  	.resume = spi_pm_resume,
  	.freeze = spi_pm_freeze,
  	.thaw = spi_pm_thaw,
  	.poweroff = spi_pm_poweroff,
  	.restore = spi_pm_restore,
  	SET_RUNTIME_PM_OPS(
  		pm_generic_runtime_suspend,
  		pm_generic_runtime_resume,
  		NULL
  	)
  };
  
  struct bus_type spi_bus_type = {
  	.name		= "spi",
  	.dev_groups	= spi_dev_groups,
  	.match		= spi_match_device,
  	.uevent		= spi_uevent,
  	.pm		= &spi_pm,
  };
  EXPORT_SYMBOL_GPL(spi_bus_type);
  
  
  static int spi_drv_probe(struct device *dev)
  {
  	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
  	int ret;
  
  	ret = of_clk_set_defaults(dev->of_node, false);
  	if (ret)
  		return ret;
  
  	ret = dev_pm_domain_attach(dev, true);
  	if (ret != -EPROBE_DEFER) {
  		ret = sdrv->probe(to_spi_device(dev));
  		if (ret)
  			dev_pm_domain_detach(dev, true);
  	}
  
  	return ret;
  }
  
  static int spi_drv_remove(struct device *dev)
  {
  	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
  	int ret;
  
  	ret = sdrv->remove(to_spi_device(dev));
  	dev_pm_domain_detach(dev, true);
  
  	return ret;
  }
  
  static void spi_drv_shutdown(struct device *dev)
  {
  	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
  
  	sdrv->shutdown(to_spi_device(dev));
  }
  
  /**
   * spi_register_driver - register a SPI driver
   * @sdrv: the driver to register
   * Context: can sleep
   */
  int spi_register_driver(struct spi_driver *sdrv)
  {
  	sdrv->driver.bus = &spi_bus_type;
  	if (sdrv->probe)
  		sdrv->driver.probe = spi_drv_probe;
  	if (sdrv->remove)
  		sdrv->driver.remove = spi_drv_remove;
  	if (sdrv->shutdown)
  		sdrv->driver.shutdown = spi_drv_shutdown;
  	return driver_register(&sdrv->driver);
  }
  EXPORT_SYMBOL_GPL(spi_register_driver);
  
  /*-------------------------------------------------------------------------*/
  
  /* SPI devices should normally not be created by SPI device drivers; that
   * would make them board-specific.  Similarly with SPI master drivers.
   * Device registration normally goes into like arch/.../mach.../board-YYY.c
   * with other readonly (flashable) information about mainboard devices.
   */
  
  struct boardinfo {
  	struct list_head	list;
  	struct spi_board_info	board_info;
  };
  
  static LIST_HEAD(board_list);
  static LIST_HEAD(spi_master_list);
  
  /*
   * Used to protect add/del opertion for board_info list and
   * spi_master list, and their matching process
   */
  static DEFINE_MUTEX(board_lock);
  
  /**
   * spi_alloc_device - Allocate a new SPI device
   * @master: Controller to which device is connected
   * Context: can sleep
   *
   * Allows a driver to allocate and initialize a spi_device without
   * registering it immediately.  This allows a driver to directly
   * fill the spi_device with device parameters before calling
   * spi_add_device() on it.
   *
   * Caller is responsible to call spi_add_device() on the returned
   * spi_device structure to add it to the SPI master.  If the caller
   * needs to discard the spi_device without adding it, then it should
   * call spi_dev_put() on it.
   *
   * Returns a pointer to the new device, or NULL.
   */
  struct spi_device *spi_alloc_device(struct spi_master *master)
  {
  	struct spi_device	*spi;
  
  	if (!spi_master_get(master))
  		return NULL;
  
  	spi = kzalloc(sizeof(*spi), GFP_KERNEL);
  	if (!spi) {
  		spi_master_put(master);
  		return NULL;
  	}
  
  	spi->master = master;
  	spi->dev.parent = &master->dev;
  	spi->dev.bus = &spi_bus_type;
  	spi->dev.release = spidev_release;
  	spi->cs_gpio = -ENOENT;
  	device_initialize(&spi->dev);
  	return spi;
  }
  EXPORT_SYMBOL_GPL(spi_alloc_device);
  
  static void spi_dev_set_name(struct spi_device *spi)
  {
  	struct acpi_device *adev = ACPI_COMPANION(&spi->dev);
  
  	if (adev) {
  		dev_set_name(&spi->dev, "spi-%s", acpi_dev_name(adev));
  		return;
  	}
  
  	dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev),
  		     spi->chip_select);
  }
  
  static int spi_dev_check(struct device *dev, void *data)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	struct spi_device *new_spi = data;
  
  	if (spi->master == new_spi->master &&
  	    spi->chip_select == new_spi->chip_select)
  		return -EBUSY;
  	return 0;
  }
  
  /**
   * spi_add_device - Add spi_device allocated with spi_alloc_device
   * @spi: spi_device to register
   *
   * Companion function to spi_alloc_device.  Devices allocated with
   * spi_alloc_device can be added onto the spi bus with this function.
   *
   * Returns 0 on success; negative errno on failure
   */
  int spi_add_device(struct spi_device *spi)
  {
  	static DEFINE_MUTEX(spi_add_lock);
  	struct spi_master *master = spi->master;
  	struct device *dev = master->dev.parent;
  	int status;
  
  	/* Chipselects are numbered 0..max; validate. */
  	if (spi->chip_select >= master->num_chipselect) {
  		dev_err(dev, "cs%d >= max %d\n",
  			spi->chip_select,
  			master->num_chipselect);
  		return -EINVAL;
  	}
  
  	/* Set the bus ID string */
  	spi_dev_set_name(spi);
  
  	/* We need to make sure there's no other device with this
  	 * chipselect **BEFORE** we call setup(), else we'll trash
  	 * its configuration.  Lock against concurrent add() calls.
  	 */
  	mutex_lock(&spi_add_lock);
  
  	status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
  	if (status) {
  		dev_err(dev, "chipselect %d already in use\n",
  				spi->chip_select);
  		goto done;
  	}
  
  	if (master->cs_gpios)
  		spi->cs_gpio = master->cs_gpios[spi->chip_select];
  
  	/* Drivers may modify this initial i/o setup, but will
  	 * normally rely on the device being setup.  Devices
  	 * using SPI_CS_HIGH can't coexist well otherwise...
  	 */
  	status = spi_setup(spi);
  	if (status < 0) {
  		dev_err(dev, "can't setup %s, status %d\n",
  				dev_name(&spi->dev), status);
  		goto done;
  	}
  
  	/* Device may be bound to an active driver when this returns */
  	status = device_add(&spi->dev);
  	if (status < 0)
  		dev_err(dev, "can't add %s, status %d\n",
  				dev_name(&spi->dev), status);
  	else
  		dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));
  
  done:
  	mutex_unlock(&spi_add_lock);
  	return status;
  }
  EXPORT_SYMBOL_GPL(spi_add_device);
  
  /**
   * spi_new_device - instantiate one new SPI device
   * @master: Controller to which device is connected
   * @chip: Describes the SPI device
   * Context: can sleep
   *
   * On typical mainboards, this is purely internal; and it's not needed
   * after board init creates the hard-wired devices.  Some development
   * platforms may not be able to use spi_register_board_info though, and
   * this is exported so that for example a USB or parport based adapter
   * driver could add devices (which it would learn about out-of-band).
   *
   * Returns the new device, or NULL.
   */
  struct spi_device *spi_new_device(struct spi_master *master,
  				  struct spi_board_info *chip)
  {
  	struct spi_device	*proxy;
  	int			status;
  
  	/* NOTE:  caller did any chip->bus_num checks necessary.
  	 *
  	 * Also, unless we change the return value convention to use
  	 * error-or-pointer (not NULL-or-pointer), troubleshootability
  	 * suggests syslogged diagnostics are best here (ugh).
  	 */
  
  	proxy = spi_alloc_device(master);
  	if (!proxy)
  		return NULL;
  
  	WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));
  
  	proxy->chip_select = chip->chip_select;
  	proxy->max_speed_hz = chip->max_speed_hz;
  	proxy->mode = chip->mode;
  	proxy->irq = chip->irq;
  	strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
  	proxy->dev.platform_data = (void *) chip->platform_data;
  	proxy->controller_data = chip->controller_data;
  	proxy->controller_state = NULL;
  
  	status = spi_add_device(proxy);
  	if (status < 0) {
  		spi_dev_put(proxy);
  		return NULL;
  	}
  
  	return proxy;
  }
  EXPORT_SYMBOL_GPL(spi_new_device);
  
  static void spi_match_master_to_boardinfo(struct spi_master *master,
  				struct spi_board_info *bi)
  {
  	struct spi_device *dev;
  
  	if (master->bus_num != bi->bus_num)
  		return;
  
  	dev = spi_new_device(master, bi);
  	if (!dev)
  		dev_err(master->dev.parent, "can't create new device for %s\n",
  			bi->modalias);
  }
  
  /**
   * spi_register_board_info - register SPI devices for a given board
   * @info: array of chip descriptors
   * @n: how many descriptors are provided
   * Context: can sleep
   *
   * Board-specific early init code calls this (probably during arch_initcall)
   * with segments of the SPI device table.  Any device nodes are created later,
   * after the relevant parent SPI controller (bus_num) is defined.  We keep
   * this table of devices forever, so that reloading a controller driver will
   * not make Linux forget about these hard-wired devices.
   *
   * Other code can also call this, e.g. a particular add-on board might provide
   * SPI devices through its expansion connector, so code initializing that board
   * would naturally declare its SPI devices.
   *
   * The board info passed can safely be __initdata ... but be careful of
   * any embedded pointers (platform_data, etc), they're copied as-is.
   */
  int spi_register_board_info(struct spi_board_info const *info, unsigned n)
  {
  	struct boardinfo *bi;
  	int i;
  
  	if (!n)
  		return -EINVAL;
  
  	bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
  	if (!bi)
  		return -ENOMEM;
  
  	for (i = 0; i < n; i++, bi++, info++) {
  		struct spi_master *master;
  
  		memcpy(&bi->board_info, info, sizeof(*info));
  		mutex_lock(&board_lock);
  		list_add_tail(&bi->list, &board_list);
  		list_for_each_entry(master, &spi_master_list, list)
  			spi_match_master_to_boardinfo(master, &bi->board_info);
  		mutex_unlock(&board_lock);
  	}
  
  	return 0;
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void spi_set_cs(struct spi_device *spi, bool enable)
  {
  	if (spi->mode & SPI_CS_HIGH)
  		enable = !enable;
  
  	if (spi->cs_gpio >= 0)
  		gpio_set_value(spi->cs_gpio, !enable);
  	else if (spi->master->set_cs)
  		spi->master->set_cs(spi, !enable);
  }
  
  #ifdef CONFIG_HAS_DMA
  static int spi_map_buf(struct spi_master *master, struct device *dev,
  		       struct sg_table *sgt, void *buf, size_t len,
  		       enum dma_data_direction dir)
  {
  	const bool vmalloced_buf = is_vmalloc_addr(buf);
  	const int desc_len = vmalloced_buf ? PAGE_SIZE : master->max_dma_len;
  	const int sgs = DIV_ROUND_UP(len, desc_len);
  	struct page *vm_page;
  	void *sg_buf;
  	size_t min;
  	int i, ret;
  
  	ret = sg_alloc_table(sgt, sgs, GFP_KERNEL);
  	if (ret != 0)
  		return ret;
  
  	for (i = 0; i < sgs; i++) {
  		min = min_t(size_t, len, desc_len);
  
  		if (vmalloced_buf) {
  			vm_page = vmalloc_to_page(buf);
  			if (!vm_page) {
  				sg_free_table(sgt);
  				return -ENOMEM;
  			}
  			sg_set_page(&sgt->sgl[i], vm_page,
  				    min, offset_in_page(buf));
  		} else {
  			sg_buf = buf;
  			sg_set_buf(&sgt->sgl[i], sg_buf, min);
  		}
  
  
  		buf += min;
  		len -= min;
  	}
  
  	ret = dma_map_sg(dev, sgt->sgl, sgt->nents, dir);
  	if (!ret)
  		ret = -ENOMEM;
  	if (ret < 0) {
  		sg_free_table(sgt);
  		return ret;
  	}
  
  	sgt->nents = ret;
  
  	return 0;
  }
  
  static void spi_unmap_buf(struct spi_master *master, struct device *dev,
  			  struct sg_table *sgt, enum dma_data_direction dir)
  {
  	if (sgt->orig_nents) {
  		dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
  		sg_free_table(sgt);
  	}
  }
  
  static int __spi_map_msg(struct spi_master *master, struct spi_message *msg)
  {
  	struct device *tx_dev, *rx_dev;
  	struct spi_transfer *xfer;
  	int ret;
  
  	if (!master->can_dma)
  		return 0;
  
  	tx_dev = master->dma_tx->device->dev;
  	rx_dev = master->dma_rx->device->dev;
  
  	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
  		if (!master->can_dma(master, msg->spi, xfer))
  			continue;
  
  		if (xfer->tx_buf != NULL) {
  			ret = spi_map_buf(master, tx_dev, &xfer->tx_sg,
  					  (void *)xfer->tx_buf, xfer->len,
  					  DMA_TO_DEVICE);
  			if (ret != 0)
  				return ret;
  		}
  
  		if (xfer->rx_buf != NULL) {
  			ret = spi_map_buf(master, rx_dev, &xfer->rx_sg,
  					  xfer->rx_buf, xfer->len,
  					  DMA_FROM_DEVICE);
  			if (ret != 0) {
  				spi_unmap_buf(master, tx_dev, &xfer->tx_sg,
  					      DMA_TO_DEVICE);
  				return ret;
  			}
  		}
  	}
  
  	master->cur_msg_mapped = true;
  
  	return 0;
  }
  
  static int spi_unmap_msg(struct spi_master *master, struct spi_message *msg)
  {
  	struct spi_transfer *xfer;
  	struct device *tx_dev, *rx_dev;
  
  	if (!master->cur_msg_mapped || !master->can_dma)
  		return 0;
  
  	tx_dev = master->dma_tx->device->dev;
  	rx_dev = master->dma_rx->device->dev;
  
  	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
  		if (!master->can_dma(master, msg->spi, xfer))
  			continue;
  
  		spi_unmap_buf(master, rx_dev, &xfer->rx_sg, DMA_FROM_DEVICE);
  		spi_unmap_buf(master, tx_dev, &xfer->tx_sg, DMA_TO_DEVICE);
  	}
  
  	return 0;
  }
  #else /* !CONFIG_HAS_DMA */
  static inline int __spi_map_msg(struct spi_master *master,
  				struct spi_message *msg)
  {
  	return 0;
  }
  
  static inline int spi_unmap_msg(struct spi_master *master,
  				struct spi_message *msg)
  {
  	return 0;
  }
  #endif /* !CONFIG_HAS_DMA */
  
  static int spi_map_msg(struct spi_master *master, struct spi_message *msg)
  {
  	struct spi_transfer *xfer;
  	void *tmp;
  	unsigned int max_tx, max_rx;
  
  	if (master->flags & (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX)) {
  		max_tx = 0;
  		max_rx = 0;
  
  		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
  			if ((master->flags & SPI_MASTER_MUST_TX) &&
  			    !xfer->tx_buf)
  				max_tx = max(xfer->len, max_tx);
  			if ((master->flags & SPI_MASTER_MUST_RX) &&
  			    !xfer->rx_buf)
  				max_rx = max(xfer->len, max_rx);
  		}
  
  		if (max_tx) {
  			tmp = krealloc(master->dummy_tx, max_tx,
  				       GFP_KERNEL | GFP_DMA);
  			if (!tmp)
  				return -ENOMEM;
  			master->dummy_tx = tmp;
  			memset(tmp, 0, max_tx);
  		}
  
  		if (max_rx) {
  			tmp = krealloc(master->dummy_rx, max_rx,
  				       GFP_KERNEL | GFP_DMA);
  			if (!tmp)
  				return -ENOMEM;
  			master->dummy_rx = tmp;
  		}
  
  		if (max_tx || max_rx) {
  			list_for_each_entry(xfer, &msg->transfers,
  					    transfer_list) {
  				if (!xfer->tx_buf)
  					xfer->tx_buf = master->dummy_tx;
  				if (!xfer->rx_buf)
  					xfer->rx_buf = master->dummy_rx;
  			}
  		}
  	}
  
  	return __spi_map_msg(master, msg);
  }
  
  /*
   * spi_transfer_one_message - Default implementation of transfer_one_message()
   *
   * This is a standard implementation of transfer_one_message() for
   * drivers which impelment a transfer_one() operation.  It provides
   * standard handling of delays and chip select management.
   */
  static int spi_transfer_one_message(struct spi_master *master,
  				    struct spi_message *msg)
  {
  	struct spi_transfer *xfer;
  	bool keep_cs = false;
  	int ret = 0;
  	int ms = 1;
  
  	spi_set_cs(msg->spi, true);
  
  	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
  		trace_spi_transfer_start(msg, xfer);
  
  		if (xfer->tx_buf || xfer->rx_buf) {
  			reinit_completion(&master->xfer_completion);
  
  			ret = master->transfer_one(master, msg->spi, xfer);
  			if (ret < 0) {
  				dev_err(&msg->spi->dev,
  					"SPI transfer failed: %d\n", ret);
  				goto out;
  			}
  
  			if (ret > 0) {
  				ret = 0;
  				ms = xfer->len * 8 * 1000 / xfer->speed_hz;
  				ms += ms + 100; /* some tolerance */
  
  				ms = wait_for_completion_timeout(&master->xfer_completion,
  								 msecs_to_jiffies(ms));
  			}
  
  			if (ms == 0) {
  				dev_err(&msg->spi->dev,
  					"SPI transfer timed out\n");
  				msg->status = -ETIMEDOUT;
  			}
  		} else {
  			if (xfer->len)
  				dev_err(&msg->spi->dev,
  					"Bufferless transfer has length %u\n",
  					xfer->len);
  		}
  
  		trace_spi_transfer_stop(msg, xfer);
  
  		if (msg->status != -EINPROGRESS)
  			goto out;
  
  		if (xfer->delay_usecs)
  			udelay(xfer->delay_usecs);
  
  		if (xfer->cs_change) {
  			if (list_is_last(&xfer->transfer_list,
  					 &msg->transfers)) {
  				keep_cs = true;
  			} else {
  				spi_set_cs(msg->spi, false);
  				udelay(10);
  				spi_set_cs(msg->spi, true);
  			}
  		}
  
  		msg->actual_length += xfer->len;
  	}
  
  out:
  	if (ret != 0 || !keep_cs)
  		spi_set_cs(msg->spi, false);
  
  	if (msg->status == -EINPROGRESS)
  		msg->status = ret;
  
  	spi_finalize_current_message(master);
  
  	return ret;
  }
  
  /**
   * spi_finalize_current_transfer - report completion of a transfer
   * @master: the master reporting completion
   *
   * Called by SPI drivers using the core transfer_one_message()
   * implementation to notify it that the current interrupt driven
   * transfer has finished and the next one may be scheduled.
   */
  void spi_finalize_current_transfer(struct spi_master *master)
  {
  	complete(&master->xfer_completion);
  }
  EXPORT_SYMBOL_GPL(spi_finalize_current_transfer);
  
  /**
   * spi_pump_messages - kthread work function which processes spi message queue
   * @work: pointer to kthread work struct contained in the master struct
   *
   * This function checks if there is any spi message in the queue that
   * needs processing and if so call out to the driver to initialize hardware
   * and transfer each message.
   *
   */
  static void spi_pump_messages(struct kthread_work *work)
  {
  	struct spi_master *master =
  		container_of(work, struct spi_master, pump_messages);
  	unsigned long flags;
  	bool was_busy = false;
  	int ret;
  
  	/* Lock queue and check for queue work */
  	spin_lock_irqsave(&master->queue_lock, flags);
  	if (list_empty(&master->queue) || !master->running) {
  		if (!master->busy) {
  			spin_unlock_irqrestore(&master->queue_lock, flags);
  			return;
  		}
  		master->busy = false;
  		spin_unlock_irqrestore(&master->queue_lock, flags);
  		kfree(master->dummy_rx);
  		master->dummy_rx = NULL;
  		kfree(master->dummy_tx);
  		master->dummy_tx = NULL;
  		if (master->unprepare_transfer_hardware &&
  		    master->unprepare_transfer_hardware(master))
  			dev_err(&master->dev,
  				"failed to unprepare transfer hardware\n");
  		if (master->auto_runtime_pm) {
  			pm_runtime_mark_last_busy(master->dev.parent);
  			pm_runtime_put_autosuspend(master->dev.parent);
  		}
  		trace_spi_master_idle(master);
  		return;
  	}
  
  	/* Make sure we are not already running a message */
  	if (master->cur_msg) {
  		spin_unlock_irqrestore(&master->queue_lock, flags);
  		return;
  	}
  	/* Extract head of queue */
  	master->cur_msg =
  		list_first_entry(&master->queue, struct spi_message, queue);
  
  	list_del_init(&master->cur_msg->queue);
  	if (master->busy)
  		was_busy = true;
  	else
  		master->busy = true;
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  
  	if (!was_busy && master->auto_runtime_pm) {
  		ret = pm_runtime_get_sync(master->dev.parent);
  		if (ret < 0) {
  			dev_err(&master->dev, "Failed to power device: %d\n",
  				ret);
  			return;
  		}
  	}
  
  	if (!was_busy)
  		trace_spi_master_busy(master);
  
  	if (!was_busy && master->prepare_transfer_hardware) {
  		ret = master->prepare_transfer_hardware(master);
  		if (ret) {
  			dev_err(&master->dev,
  				"failed to prepare transfer hardware\n");
  
  			if (master->auto_runtime_pm)
  				pm_runtime_put(master->dev.parent);
  			return;
  		}
  	}
  
  	trace_spi_message_start(master->cur_msg);
  
  	if (master->prepare_message) {
  		ret = master->prepare_message(master, master->cur_msg);
  		if (ret) {
  			dev_err(&master->dev,
  				"failed to prepare message: %d\n", ret);
  			master->cur_msg->status = ret;
  			spi_finalize_current_message(master);
  			return;
  		}
  		master->cur_msg_prepared = true;
  	}
  
  	ret = spi_map_msg(master, master->cur_msg);
  	if (ret) {
  		master->cur_msg->status = ret;
  		spi_finalize_current_message(master);
  		return;
  	}
  
  	ret = master->transfer_one_message(master, master->cur_msg);
  	if (ret) {
  		dev_err(&master->dev,
  			"failed to transfer one message from queue\n");
  		return;
  	}
  }
  
  static int spi_init_queue(struct spi_master *master)
  {
  	struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
  
  	INIT_LIST_HEAD(&master->queue);
  	spin_lock_init(&master->queue_lock);
  
  	master->running = false;
  	master->busy = false;
  
  	init_kthread_worker(&master->kworker);
  	master->kworker_task = kthread_run(kthread_worker_fn,
  					   &master->kworker, "%s",
  					   dev_name(&master->dev));
  	if (IS_ERR(master->kworker_task)) {
  		dev_err(&master->dev, "failed to create message pump task\n");
  		return PTR_ERR(master->kworker_task);
  	}
  	init_kthread_work(&master->pump_messages, spi_pump_messages);
  
  	/*
  	 * Master config will indicate if this controller should run the
  	 * message pump with high (realtime) priority to reduce the transfer
  	 * latency on the bus by minimising the delay between a transfer
  	 * request and the scheduling of the message pump thread. Without this
  	 * setting the message pump thread will remain at default priority.
  	 */
  	if (master->rt) {
  		dev_info(&master->dev,
  			"will run message pump with realtime priority\n");
  		sched_setscheduler(master->kworker_task, SCHED_FIFO, &param);
  	}
  
  	return 0;
  }
  
  /**
   * spi_get_next_queued_message() - called by driver to check for queued
   * messages
   * @master: the master to check for queued messages
   *
   * If there are more messages in the queue, the next message is returned from
   * this call.
   */
  struct spi_message *spi_get_next_queued_message(struct spi_master *master)
  {
  	struct spi_message *next;
  	unsigned long flags;
  
  	/* get a pointer to the next message, if any */
  	spin_lock_irqsave(&master->queue_lock, flags);
  	next = list_first_entry_or_null(&master->queue, struct spi_message,
  					queue);
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  
  	return next;
  }
  EXPORT_SYMBOL_GPL(spi_get_next_queued_message);
  
  /**
   * spi_finalize_current_message() - the current message is complete
   * @master: the master to return the message to
   *
   * Called by the driver to notify the core that the message in the front of the
   * queue is complete and can be removed from the queue.
   */
  void spi_finalize_current_message(struct spi_master *master)
  {
  	struct spi_message *mesg;
  	unsigned long flags;
  	int ret;
  
  	spin_lock_irqsave(&master->queue_lock, flags);
  	mesg = master->cur_msg;
  	master->cur_msg = NULL;
  
  	queue_kthread_work(&master->kworker, &master->pump_messages);
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  
  	spi_unmap_msg(master, mesg);
  
  	if (master->cur_msg_prepared && master->unprepare_message) {
  		ret = master->unprepare_message(master, mesg);
  		if (ret) {
  			dev_err(&master->dev,
  				"failed to unprepare message: %d\n", ret);
  		}
  	}
  	master->cur_msg_prepared = false;
  
  	mesg->state = NULL;
  	if (mesg->complete)
  		mesg->complete(mesg->context);
  
  	trace_spi_message_done(mesg);
  }
  EXPORT_SYMBOL_GPL(spi_finalize_current_message);
  
  static int spi_start_queue(struct spi_master *master)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&master->queue_lock, flags);
  
  	if (master->running || master->busy) {
  		spin_unlock_irqrestore(&master->queue_lock, flags);
  		return -EBUSY;
  	}
  
  	master->running = true;
  	master->cur_msg = NULL;
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  
  	queue_kthread_work(&master->kworker, &master->pump_messages);
  
  	return 0;
  }
  
  static int spi_stop_queue(struct spi_master *master)
  {
  	unsigned long flags;
  	unsigned limit = 500;
  	int ret = 0;
  
  	spin_lock_irqsave(&master->queue_lock, flags);
  
  	/*
  	 * This is a bit lame, but is optimized for the common execution path.
  	 * A wait_queue on the master->busy could be used, but then the common
  	 * execution path (pump_messages) would be required to call wake_up or
  	 * friends on every SPI message. Do this instead.
  	 */
  	while ((!list_empty(&master->queue) || master->busy) && limit--) {
  		spin_unlock_irqrestore(&master->queue_lock, flags);
  		usleep_range(10000, 11000);
  		spin_lock_irqsave(&master->queue_lock, flags);
  	}
  
  	if (!list_empty(&master->queue) || master->busy)
  		ret = -EBUSY;
  	else
  		master->running = false;
  
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  
  	if (ret) {
  		dev_warn(&master->dev,
  			 "could not stop message queue\n");
  		return ret;
  	}
  	return ret;
  }
  
  static int spi_destroy_queue(struct spi_master *master)
  {
  	int ret;
  
  	ret = spi_stop_queue(master);
  
  	/*
  	 * flush_kthread_worker will block until all work is done.
  	 * If the reason that stop_queue timed out is that the work will never
  	 * finish, then it does no good to call flush/stop thread, so
  	 * return anyway.
  	 */
  	if (ret) {
  		dev_err(&master->dev, "problem destroying queue\n");
  		return ret;
  	}
  
  	flush_kthread_worker(&master->kworker);
  	kthread_stop(master->kworker_task);
  
  	return 0;
  }
  
  /**
   * spi_queued_transfer - transfer function for queued transfers
   * @spi: spi device which is requesting transfer
   * @msg: spi message which is to handled is queued to driver queue
   */
  static int spi_queued_transfer(struct spi_device *spi, struct spi_message *msg)
  {
  	struct spi_master *master = spi->master;
  	unsigned long flags;
  
  	spin_lock_irqsave(&master->queue_lock, flags);
  
  	if (!master->running) {
  		spin_unlock_irqrestore(&master->queue_lock, flags);
  		return -ESHUTDOWN;
  	}
  	msg->actual_length = 0;
  	msg->status = -EINPROGRESS;
  
  	list_add_tail(&msg->queue, &master->queue);
  	if (!master->busy)
  		queue_kthread_work(&master->kworker, &master->pump_messages);
  
  	spin_unlock_irqrestore(&master->queue_lock, flags);
  	return 0;
  }
  
  static int spi_master_initialize_queue(struct spi_master *master)
  {
  	int ret;
  
  	master->transfer = spi_queued_transfer;
  	if (!master->transfer_one_message)
  		master->transfer_one_message = spi_transfer_one_message;
  
  	/* Initialize and start queue */
  	ret = spi_init_queue(master);
  	if (ret) {
  		dev_err(&master->dev, "problem initializing queue\n");
  		goto err_init_queue;
  	}
  	master->queued = true;
  	ret = spi_start_queue(master);
  	if (ret) {
  		dev_err(&master->dev, "problem starting queue\n");
  		goto err_start_queue;
  	}
  
  	return 0;
  
  err_start_queue:
  	spi_destroy_queue(master);
  err_init_queue:
  	return ret;
  }
  
  /*-------------------------------------------------------------------------*/
  
  #if defined(CONFIG_OF)
  static struct spi_device *
  of_register_spi_device(struct spi_master *master, struct device_node *nc)
  {
  	struct spi_device *spi;
  	int rc;
  	u32 value;
  
  	/* Alloc an spi_device */
  	spi = spi_alloc_device(master);
  	if (!spi) {
  		dev_err(&master->dev, "spi_device alloc error for %s\n",
  			nc->full_name);
  		rc = -ENOMEM;
  		goto err_out;
  	}
  
  	/* Select device driver */
  	rc = of_modalias_node(nc, spi->modalias,
  				sizeof(spi->modalias));
  	if (rc < 0) {
  		dev_err(&master->dev, "cannot find modalias for %s\n",
  			nc->full_name);
  		goto err_out;
  	}
  
  	/* Device address */
  	rc = of_property_read_u32(nc, "reg", &value);
  	if (rc) {
  		dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
  			nc->full_name, rc);
  		goto err_out;
  	}
  	spi->chip_select = value;
  
  	/* Mode (clock phase/polarity/etc.) */
  	if (of_find_property(nc, "spi-cpha", NULL))
  		spi->mode |= SPI_CPHA;
  	if (of_find_property(nc, "spi-cpol", NULL))
  		spi->mode |= SPI_CPOL;
  	if (of_find_property(nc, "spi-cs-high", NULL))
  		spi->mode |= SPI_CS_HIGH;
  	if (of_find_property(nc, "spi-3wire", NULL))
  		spi->mode |= SPI_3WIRE;
  	if (of_find_property(nc, "spi-lsb-first", NULL))
  		spi->mode |= SPI_LSB_FIRST;
  
  	/* Device DUAL/QUAD mode */
  	if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
  		switch (value) {
  		case 1:
  			break;
  		case 2:
  			spi->mode |= SPI_TX_DUAL;
  			break;
  		case 4:
  			spi->mode |= SPI_TX_QUAD;
  			break;
  		default:
  			dev_warn(&master->dev,
  				"spi-tx-bus-width %d not supported\n",
  				value);
  			break;
  		}
  	}
  
  	if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
  		switch (value) {
  		case 1:
  			break;
  		case 2:
  			spi->mode |= SPI_RX_DUAL;
  			break;
  		case 4:
  			spi->mode |= SPI_RX_QUAD;
  			break;
  		default:
  			dev_warn(&master->dev,
  				"spi-rx-bus-width %d not supported\n",
  				value);
  			break;
  		}
  	}
  
  	/* Device speed */
  	rc = of_property_read_u32(nc, "spi-max-frequency", &value);
  	if (rc) {
  		dev_err(&master->dev, "%s has no valid 'spi-max-frequency' property (%d)\n",
  			nc->full_name, rc);
  		goto err_out;
  	}
  	spi->max_speed_hz = value;
  
  	/* IRQ */
  	spi->irq = irq_of_parse_and_map(nc, 0);
  
  	/* Store a pointer to the node in the device structure */
  	of_node_get(nc);
  	spi->dev.of_node = nc;
  
  	/* Register the new device */
  	request_module("%s%s", SPI_MODULE_PREFIX, spi->modalias);
  	rc = spi_add_device(spi);
  	if (rc) {
  		dev_err(&master->dev, "spi_device register error %s\n",
  			nc->full_name);
  		goto err_out;
  	}
  
  	return spi;
  
  err_out:
  	spi_dev_put(spi);
  	return ERR_PTR(rc);
  }
  
  /**
   * of_register_spi_devices() - Register child devices onto the SPI bus
   * @master:	Pointer to spi_master device
   *
   * Registers an spi_device for each child node of master node which has a 'reg'
   * property.
   */
  static void of_register_spi_devices(struct spi_master *master)
  {
  	struct spi_device *spi;
  	struct device_node *nc;
  
  	if (!master->dev.of_node)
  		return;
  
  	for_each_available_child_of_node(master->dev.of_node, nc) {
  		spi = of_register_spi_device(master, nc);
  		if (IS_ERR(spi))
  			dev_warn(&master->dev, "Failed to create SPI device for %s\n",
  				nc->full_name);
  	}
  }
  #else
  static void of_register_spi_devices(struct spi_master *master) { }
  #endif
  
  #ifdef CONFIG_ACPI
  static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
  {
  	struct spi_device *spi = data;
  
  	if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) {
  		struct acpi_resource_spi_serialbus *sb;
  
  		sb = &ares->data.spi_serial_bus;
  		if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_SPI) {
  			spi->chip_select = sb->device_selection;
  			spi->max_speed_hz = sb->connection_speed;
  
  			if (sb->clock_phase == ACPI_SPI_SECOND_PHASE)
  				spi->mode |= SPI_CPHA;
  			if (sb->clock_polarity == ACPI_SPI_START_HIGH)
  				spi->mode |= SPI_CPOL;
  			if (sb->device_polarity == ACPI_SPI_ACTIVE_HIGH)
  				spi->mode |= SPI_CS_HIGH;
  		}
  	} else if (spi->irq < 0) {
  		struct resource r;
  
  		if (acpi_dev_resource_interrupt(ares, 0, &r))
  			spi->irq = r.start;
  	}
  
  	/* Always tell the ACPI core to skip this resource */
  	return 1;
  }
  
  static acpi_status acpi_spi_add_device(acpi_handle handle, u32 level,
  				       void *data, void **return_value)
  {
  	struct spi_master *master = data;
  	struct list_head resource_list;
  	struct acpi_device *adev;
  	struct spi_device *spi;
  	int ret;
  
  	if (acpi_bus_get_device(handle, &adev))
  		return AE_OK;
  	if (acpi_bus_get_status(adev) || !adev->status.present)
  		return AE_OK;
  
  	spi = spi_alloc_device(master);
  	if (!spi) {
  		dev_err(&master->dev, "failed to allocate SPI device for %s\n",
  			dev_name(&adev->dev));
  		return AE_NO_MEMORY;
  	}
  
  	ACPI_COMPANION_SET(&spi->dev, adev);
  	spi->irq = -1;
  
  	INIT_LIST_HEAD(&resource_list);
  	ret = acpi_dev_get_resources(adev, &resource_list,
  				     acpi_spi_add_resource, spi);
  	acpi_dev_free_resource_list(&resource_list);
  
  	if (ret < 0 || !spi->max_speed_hz) {
  		spi_dev_put(spi);
  		return AE_OK;
  	}
  
  	adev->power.flags.ignore_parent = true;
  	strlcpy(spi->modalias, acpi_device_hid(adev), sizeof(spi->modalias));
  	if (spi_add_device(spi)) {
  		adev->power.flags.ignore_parent = false;
  		dev_err(&master->dev, "failed to add SPI device %s from ACPI\n",
  			dev_name(&adev->dev));
  		spi_dev_put(spi);
  	}
  
  	return AE_OK;
  }
  
  static void acpi_register_spi_devices(struct spi_master *master)
  {
  	acpi_status status;
  	acpi_handle handle;
  
  	handle = ACPI_HANDLE(master->dev.parent);
  	if (!handle)
  		return;
  
  	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
  				     acpi_spi_add_device, NULL,
  				     master, NULL);
  	if (ACPI_FAILURE(status))
  		dev_warn(&master->dev, "failed to enumerate SPI slaves\n");
  }
  #else
  static inline void acpi_register_spi_devices(struct spi_master *master) {}
  #endif /* CONFIG_ACPI */
  
  static void spi_master_release(struct device *dev)
  {
  	struct spi_master *master;
  
  	master = container_of(dev, struct spi_master, dev);
  	kfree(master);
  }
  
  static struct class spi_master_class = {
  	.name		= "spi_master",
  	.owner		= THIS_MODULE,
  	.dev_release	= spi_master_release,
  };
  
  
  
  /**
   * spi_alloc_master - allocate SPI master controller
   * @dev: the controller, possibly using the platform_bus
   * @size: how much zeroed driver-private data to allocate; the pointer to this
   *	memory is in the driver_data field of the returned device,
   *	accessible with spi_master_get_devdata().
   * Context: can sleep
   *
   * This call is used only by SPI master controller drivers, which are the
   * only ones directly touching chip registers.  It's how they allocate
   * an spi_master structure, prior to calling spi_register_master().
   *
   * This must be called from context that can sleep.  It returns the SPI
   * master structure on success, else NULL.
   *
   * The caller is responsible for assigning the bus number and initializing
   * the master's methods before calling spi_register_master(); and (after errors
   * adding the device) calling spi_master_put() and kfree() to prevent a memory
   * leak.
   */
  struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
  {
  	struct spi_master	*master;
  
  	if (!dev)
  		return NULL;
  
  	master = kzalloc(size + sizeof(*master), GFP_KERNEL);
  	if (!master)
  		return NULL;
  
  	device_initialize(&master->dev);
  	master->bus_num = -1;
  	master->num_chipselect = 1;
  	master->dev.class = &spi_master_class;
  	master->dev.parent = get_device(dev);
  	spi_master_set_devdata(master, &master[1]);
  
  	return master;
  }
  EXPORT_SYMBOL_GPL(spi_alloc_master);
  
  #ifdef CONFIG_OF
  static int of_spi_register_master(struct spi_master *master)
  {
  	int nb, i, *cs;
  	struct device_node *np = master->dev.of_node;
  
  	if (!np)
  		return 0;
  
  	nb = of_gpio_named_count(np, "cs-gpios");
  	master->num_chipselect = max_t(int, nb, master->num_chipselect);
  
  	/* Return error only for an incorrectly formed cs-gpios property */
  	if (nb == 0 || nb == -ENOENT)
  		return 0;
  	else if (nb < 0)
  		return nb;
  
  	cs = devm_kzalloc(&master->dev,
  			  sizeof(int) * master->num_chipselect,
  			  GFP_KERNEL);
  	master->cs_gpios = cs;
  
  	if (!master->cs_gpios)
  		return -ENOMEM;
  
  	for (i = 0; i < master->num_chipselect; i++)
  		cs[i] = -ENOENT;
  
  	for (i = 0; i < nb; i++)
  		cs[i] = of_get_named_gpio(np, "cs-gpios", i);
  
  	return 0;
  }
  #else
  static int of_spi_register_master(struct spi_master *master)
  {
  	return 0;
  }
  #endif
  
  /**
   * spi_register_master - register SPI master controller
   * @master: initialized master, originally from spi_alloc_master()
   * Context: can sleep
   *
   * SPI master controllers connect to their drivers using some non-SPI bus,
   * such as the platform bus.  The final stage of probe() in that code
   * includes calling spi_register_master() to hook up to this SPI bus glue.
   *
   * SPI controllers use board specific (often SOC specific) bus numbers,
   * and board-specific addressing for SPI devices combines those numbers
   * with chip select numbers.  Since SPI does not directly support dynamic
   * device identification, boards need configuration tables telling which
   * chip is at which address.
   *
   * This must be called from context that can sleep.  It returns zero on
   * success, else a negative error code (dropping the master's refcount).
   * After a successful return, the caller is responsible for calling
   * spi_unregister_master().
   */
  int spi_register_master(struct spi_master *master)
  {
  	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
  	struct device		*dev = master->dev.parent;
  	struct boardinfo	*bi;
  	int			status = -ENODEV;
  	int			dynamic = 0;
  
  	if (!dev)
  		return -ENODEV;
  
  	status = of_spi_register_master(master);
  	if (status)
  		return status;
  
  	/* even if it's just one always-selected device, there must
  	 * be at least one chipselect
  	 */
  	if (master->num_chipselect == 0)
  		return -EINVAL;
  
  	if ((master->bus_num < 0) && master->dev.of_node)
  		master->bus_num = of_alias_get_id(master->dev.of_node, "spi");
  
  	/* convention:  dynamically assigned bus IDs count down from the max */
  	if (master->bus_num < 0) {
  		/* FIXME switch to an IDR based scheme, something like
  		 * I2C now uses, so we can't run out of "dynamic" IDs
  		 */
  		master->bus_num = atomic_dec_return(&dyn_bus_id);
  		dynamic = 1;
  	}
  
  	spin_lock_init(&master->bus_lock_spinlock);
  	mutex_init(&master->bus_lock_mutex);
  	master->bus_lock_flag = 0;
  	init_completion(&master->xfer_completion);
  	if (!master->max_dma_len)
  		master->max_dma_len = INT_MAX;
  
  	/* register the device, then userspace will see it.
  	 * registration fails if the bus ID is in use.
  	 */
  	dev_set_name(&master->dev, "spi%u", master->bus_num);
  	status = device_add(&master->dev);
  	if (status < 0)
  		goto done;
  	dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
  			dynamic ? " (dynamic)" : "");
  
  	/* If we're using a queued driver, start the queue */
  	if (master->transfer)
  		dev_info(dev, "master is unqueued, this is deprecated\n");
  	else {
  		status = spi_master_initialize_queue(master);
  		if (status) {
  			device_del(&master->dev);
  			goto done;
  		}
  	}
  
  	mutex_lock(&board_lock);
  	list_add_tail(&master->list, &spi_master_list);
  	list_for_each_entry(bi, &board_list, list)
  		spi_match_master_to_boardinfo(master, &bi->board_info);
  	mutex_unlock(&board_lock);
  
  	/* Register devices from the device tree and ACPI */
  	of_register_spi_devices(master);
  	acpi_register_spi_devices(master);
  done:
  	return status;
  }
  EXPORT_SYMBOL_GPL(spi_register_master);
  
  static void devm_spi_unregister(struct device *dev, void *res)
  {
  	spi_unregister_master(*(struct spi_master **)res);
  }
  
  /**
   * dev_spi_register_master - register managed SPI master controller
   * @dev:    device managing SPI master
   * @master: initialized master, originally from spi_alloc_master()
   * Context: can sleep
   *
   * Register a SPI device as with spi_register_master() which will
   * automatically be unregister
   */
  int devm_spi_register_master(struct device *dev, struct spi_master *master)
  {
  	struct spi_master **ptr;
  	int ret;
  
  	ptr = devres_alloc(devm_spi_unregister, sizeof(*ptr), GFP_KERNEL);
  	if (!ptr)
  		return -ENOMEM;
  
  	ret = spi_register_master(master);
  	if (!ret) {
  		*ptr = master;
  		devres_add(dev, ptr);
  	} else {
  		devres_free(ptr);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(devm_spi_register_master);
  
  static int __unregister(struct device *dev, void *null)
  {
  	spi_unregister_device(to_spi_device(dev));
  	return 0;
  }
  
  /**
   * spi_unregister_master - unregister SPI master controller
   * @master: the master being unregistered
   * Context: can sleep
   *
   * This call is used only by SPI master controller drivers, which are the
   * only ones directly touching chip registers.
   *
   * This must be called from context that can sleep.
   */
  void spi_unregister_master(struct spi_master *master)
  {
  	int dummy;
  
  	if (master->queued) {
  		if (spi_destroy_queue(master))
  			dev_err(&master->dev, "queue remove failed\n");
  	}
  
  	mutex_lock(&board_lock);
  	list_del(&master->list);
  	mutex_unlock(&board_lock);
  
  	dummy = device_for_each_child(&master->dev, NULL, __unregister);
  	device_unregister(&master->dev);
  }
  EXPORT_SYMBOL_GPL(spi_unregister_master);
  
  int spi_master_suspend(struct spi_master *master)
  {
  	int ret;
  
  	/* Basically no-ops for non-queued masters */
  	if (!master->queued)
  		return 0;
  
  	ret = spi_stop_queue(master);
  	if (ret)
  		dev_err(&master->dev, "queue stop failed\n");
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(spi_master_suspend);
  
  int spi_master_resume(struct spi_master *master)
  {
  	int ret;
  
  	if (!master->queued)
  		return 0;
  
  	ret = spi_start_queue(master);
  	if (ret)
  		dev_err(&master->dev, "queue restart failed\n");
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(spi_master_resume);
  
  static int __spi_master_match(struct device *dev, const void *data)
  {
  	struct spi_master *m;
  	const u16 *bus_num = data;
  
  	m = container_of(dev, struct spi_master, dev);
  	return m->bus_num == *bus_num;
  }
  
  /**
   * spi_busnum_to_master - look up master associated with bus_num
   * @bus_num: the master's bus number
   * Context: can sleep
   *
   * This call may be used with devices that are registered after
   * arch init time.  It returns a refcounted pointer to the relevant
   * spi_master (which the caller must release), or NULL if there is
   * no such master registered.
   */
  struct spi_master *spi_busnum_to_master(u16 bus_num)
  {
  	struct device		*dev;
  	struct spi_master	*master = NULL;
  
  	dev = class_find_device(&spi_master_class, NULL, &bus_num,
  				__spi_master_match);
  	if (dev)
  		master = container_of(dev, struct spi_master, dev);
  	/* reference got in class_find_device */
  	return master;
  }
  EXPORT_SYMBOL_GPL(spi_busnum_to_master);
  
  
  /*-------------------------------------------------------------------------*/
  
  /* Core methods for SPI master protocol drivers.  Some of the
   * other core methods are currently defined as inline functions.
   */
  
  /**
   * spi_setup - setup SPI mode and clock rate
   * @spi: the device whose settings are being modified
   * Context: can sleep, and no requests are queued to the device
   *
   * SPI protocol drivers may need to update the transfer mode if the
   * device doesn't work with its default.  They may likewise need
   * to update clock rates or word sizes from initial values.  This function
   * changes those settings, and must be called from a context that can sleep.
   * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
   * effect the next time the device is selected and data is transferred to
   * or from it.  When this function returns, the spi device is deselected.
   *
   * Note that this call will fail if the protocol driver specifies an option
   * that the underlying controller or its driver does not support.  For
   * example, not all hardware supports wire transfers using nine bit words,
   * LSB-first wire encoding, or active-high chipselects.
   */
  int spi_setup(struct spi_device *spi)
  {
  	unsigned	bad_bits, ugly_bits;
  	int		status = 0;
  
  	/* check mode to prevent that DUAL and QUAD set at the same time
  	 */
  	if (((spi->mode & SPI_TX_DUAL) && (spi->mode & SPI_TX_QUAD)) ||
  		((spi->mode & SPI_RX_DUAL) && (spi->mode & SPI_RX_QUAD))) {
  		dev_err(&spi->dev,
  		"setup: can not select dual and quad at the same time\n");
  		return -EINVAL;
  	}
  	/* if it is SPI_3WIRE mode, DUAL and QUAD should be forbidden
  	 */
  	if ((spi->mode & SPI_3WIRE) && (spi->mode &
  		(SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)))
  		return -EINVAL;
  	/* help drivers fail *cleanly* when they need options
  	 * that aren't supported with their current master
  	 */
  	bad_bits = spi->mode & ~spi->master->mode_bits;
  	ugly_bits = bad_bits &
  		    (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD);
  	if (ugly_bits) {
  		dev_warn(&spi->dev,
  			 "setup: ignoring unsupported mode bits %x\n",
  			 ugly_bits);
  		spi->mode &= ~ugly_bits;
  		bad_bits &= ~ugly_bits;
  	}
  	if (bad_bits) {
  		dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
  			bad_bits);
  		return -EINVAL;
  	}
  
  	if (!spi->bits_per_word)
  		spi->bits_per_word = 8;
  
  	if (!spi->max_speed_hz)
  		spi->max_speed_hz = spi->master->max_speed_hz;
  
  	if (spi->master->setup)
  		status = spi->master->setup(spi);
  
  	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
  			(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
  			(spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
  			(spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
  			(spi->mode & SPI_3WIRE) ? "3wire, " : "",
  			(spi->mode & SPI_LOOP) ? "loopback, " : "",
  			spi->bits_per_word, spi->max_speed_hz,
  			status);
  
  	return status;
  }
  EXPORT_SYMBOL_GPL(spi_setup);
  
  static int __spi_validate(struct spi_device *spi, struct spi_message *message)
  {
  	struct spi_master *master = spi->master;
  	struct spi_transfer *xfer;
  	int w_size;
  
  	if (list_empty(&message->transfers))
  		return -EINVAL;
  
  	/* Half-duplex links include original MicroWire, and ones with
  	 * only one data pin like SPI_3WIRE (switches direction) or where
  	 * either MOSI or MISO is missing.  They can also be caused by
  	 * software limitations.
  	 */
  	if ((master->flags & SPI_MASTER_HALF_DUPLEX)
  			|| (spi->mode & SPI_3WIRE)) {
  		unsigned flags = master->flags;
  
  		list_for_each_entry(xfer, &message->transfers, transfer_list) {
  			if (xfer->rx_buf && xfer->tx_buf)
  				return -EINVAL;
  			if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
  				return -EINVAL;
  			if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
  				return -EINVAL;
  		}
  	}
  
  	/**
  	 * Set transfer bits_per_word and max speed as spi device default if
  	 * it is not set for this transfer.
  	 * Set transfer tx_nbits and rx_nbits as single transfer default
  	 * (SPI_NBITS_SINGLE) if it is not set for this transfer.
  	 */
  	list_for_each_entry(xfer, &message->transfers, transfer_list) {
  		message->frame_length += xfer->len;
  		if (!xfer->bits_per_word)
  			xfer->bits_per_word = spi->bits_per_word;
  
  		if (!xfer->speed_hz)
  			xfer->speed_hz = spi->max_speed_hz;
  
  		if (master->max_speed_hz &&
  		    xfer->speed_hz > master->max_speed_hz)
  			xfer->speed_hz = master->max_speed_hz;
  
  		if (master->bits_per_word_mask) {
  			/* Only 32 bits fit in the mask */
  			if (xfer->bits_per_word > 32)
  				return -EINVAL;
  			if (!(master->bits_per_word_mask &
  					BIT(xfer->bits_per_word - 1)))
  				return -EINVAL;
  		}
  
  		/*
  		 * SPI transfer length should be multiple of SPI word size
  		 * where SPI word size should be power-of-two multiple
  		 */
  		if (xfer->bits_per_word <= 8)
  			w_size = 1;
  		else if (xfer->bits_per_word <= 16)
  			w_size = 2;
  		else
  			w_size = 4;
  
  		/* No partial transfers accepted */
  		if (xfer->len % w_size)
  			return -EINVAL;
  
  		if (xfer->speed_hz && master->min_speed_hz &&
  		    xfer->speed_hz < master->min_speed_hz)
  			return -EINVAL;
  
  		if (xfer->tx_buf && !xfer->tx_nbits)
  			xfer->tx_nbits = SPI_NBITS_SINGLE;
  		if (xfer->rx_buf && !xfer->rx_nbits)
  			xfer->rx_nbits = SPI_NBITS_SINGLE;
  		/* check transfer tx/rx_nbits:
  		 * 1. check the value matches one of single, dual and quad
  		 * 2. check tx/rx_nbits match the mode in spi_device
  		 */
  		if (xfer->tx_buf) {
  			if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
  				xfer->tx_nbits != SPI_NBITS_DUAL &&
  				xfer->tx_nbits != SPI_NBITS_QUAD)
  				return -EINVAL;
  			if ((xfer->tx_nbits == SPI_NBITS_DUAL) &&
  				!(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD)))
  				return -EINVAL;
  			if ((xfer->tx_nbits == SPI_NBITS_QUAD) &&
  				!(spi->mode & SPI_TX_QUAD))
  				return -EINVAL;
  		}
  		/* check transfer rx_nbits */
  		if (xfer->rx_buf) {
  			if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
  				xfer->rx_nbits != SPI_NBITS_DUAL &&
  				xfer->rx_nbits != SPI_NBITS_QUAD)
  				return -EINVAL;
  			if ((xfer->rx_nbits == SPI_NBITS_DUAL) &&
  				!(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD)))
  				return -EINVAL;
  			if ((xfer->rx_nbits == SPI_NBITS_QUAD) &&
  				!(spi->mode & SPI_RX_QUAD))
  				return -EINVAL;
  		}
  	}
  
  	message->status = -EINPROGRESS;
  
  	return 0;
  }
  
  static int __spi_async(struct spi_device *spi, struct spi_message *message)
  {
  	struct spi_master *master = spi->master;
  
  	message->spi = spi;
  
  	trace_spi_message_submit(message);
  
  	return master->transfer(spi, message);
  }
  
  /**
   * spi_async - asynchronous SPI transfer
   * @spi: device with which data will be exchanged
   * @message: describes the data transfers, including completion callback
   * Context: any (irqs may be blocked, etc)
   *
   * This call may be used in_irq and other contexts which can't sleep,
   * as well as from task contexts which can sleep.
   *
   * The completion callback is invoked in a context which can't sleep.
   * Before that invocation, the value of message->status is undefined.
   * When the callback is issued, message->status holds either zero (to
   * indicate complete success) or a negative error code.  After that
   * callback returns, the driver which issued the transfer request may
   * deallocate the associated memory; it's no longer in use by any SPI
   * core or controller driver code.
   *
   * Note that although all messages to a spi_device are handled in
   * FIFO order, messages may go to different devices in other orders.
   * Some device might be higher priority, or have various "hard" access
   * time requirements, for example.
   *
   * On detection of any fault during the transfer, processing of
   * the entire message is aborted, and the device is deselected.
   * Until returning from the associated message completion callback,
   * no other spi_message queued to that device will be processed.
   * (This rule applies equally to all the synchronous transfer calls,
   * which are wrappers around this core asynchronous primitive.)
   */
  int spi_async(struct spi_device *spi, struct spi_message *message)
  {
  	struct spi_master *master = spi->master;
  	int ret;
  	unsigned long flags;
  
  	ret = __spi_validate(spi, message);
  	if (ret != 0)
  		return ret;
  
  	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
  
  	if (master->bus_lock_flag)
  		ret = -EBUSY;
  	else
  		ret = __spi_async(spi, message);
  
  	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(spi_async);
  
  /**
   * spi_async_locked - version of spi_async with exclusive bus usage
   * @spi: device with which data will be exchanged
   * @message: describes the data transfers, including completion callback
   * Context: any (irqs may be blocked, etc)
   *
   * This call may be used in_irq and other contexts which can't sleep,
   * as well as from task contexts which can sleep.
   *
   * The completion callback is invoked in a context which can't sleep.
   * Before that invocation, the value of message->status is undefined.
   * When the callback is issued, message->status holds either zero (to
   * indicate complete success) or a negative error code.  After that
   * callback returns, the driver which issued the transfer request may
   * deallocate the associated memory; it's no longer in use by any SPI
   * core or controller driver code.
   *
   * Note that although all messages to a spi_device are handled in
   * FIFO order, messages may go to different devices in other orders.
   * Some device might be higher priority, or have various "hard" access
   * time requirements, for example.
   *
   * On detection of any fault during the transfer, processing of
   * the entire message is aborted, and the device is deselected.
   * Until returning from the associated message completion callback,
   * no other spi_message queued to that device will be processed.
   * (This rule applies equally to all the synchronous transfer calls,
   * which are wrappers around this core asynchronous primitive.)
   */
  int spi_async_locked(struct spi_device *spi, struct spi_message *message)
  {
  	struct spi_master *master = spi->master;
  	int ret;
  	unsigned long flags;
  
  	ret = __spi_validate(spi, message);
  	if (ret != 0)
  		return ret;
  
  	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
  
  	ret = __spi_async(spi, message);
  
  	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
  
  	return ret;
  
  }
  EXPORT_SYMBOL_GPL(spi_async_locked);
  
  
  /*-------------------------------------------------------------------------*/
  
  /* Utility methods for SPI master protocol drivers, layered on
   * top of the core.  Some other utility methods are defined as
   * inline functions.
   */
  
  static void spi_complete(void *arg)
  {
  	complete(arg);
  }
  
  static int __spi_sync(struct spi_device *spi, struct spi_message *message,
  		      int bus_locked)
  {
  	DECLARE_COMPLETION_ONSTACK(done);
  	int status;
  	struct spi_master *master = spi->master;
  
  	message->complete = spi_complete;
  	message->context = &done;
  
  	if (!bus_locked)
  		mutex_lock(&master->bus_lock_mutex);
  
  	status = spi_async_locked(spi, message);
  
  	if (!bus_locked)
  		mutex_unlock(&master->bus_lock_mutex);
  
  	if (status == 0) {
  		wait_for_completion(&done);
  		status = message->status;
  	}
  	message->context = NULL;
  	return status;
  }
  
  /**
   * spi_sync - blocking/synchronous SPI data transfers
   * @spi: device with which data will be exchanged
   * @message: describes the data transfers
   * Context: can sleep
   *
   * This call may only be used from a context that may sleep.  The sleep
   * is non-interruptible, and has no timeout.  Low-overhead controller
   * drivers may DMA directly into and out of the message buffers.
   *
   * Note that the SPI device's chip select is active during the message,
   * and then is normally disabled between messages.  Drivers for some
   * frequently-used devices may want to minimize costs of selecting a chip,
   * by leaving it selected in anticipation that the next message will go
   * to the same chip.  (That may increase power usage.)
   *
   * Also, the caller is guaranteeing that the memory associated with the
   * message will not be freed before this call returns.
   *
   * It returns zero on success, else a negative error code.
   */
  int spi_sync(struct spi_device *spi, struct spi_message *message)
  {
  	return __spi_sync(spi, message, 0);
  }
  EXPORT_SYMBOL_GPL(spi_sync);
  
  /**
   * spi_sync_locked - version of spi_sync with exclusive bus usage
   * @spi: device with which data will be exchanged
   * @message: describes the data transfers
   * Context: can sleep
   *
   * This call may only be used from a context that may sleep.  The sleep
   * is non-interruptible, and has no timeout.  Low-overhead controller
   * drivers may DMA directly into and out of the message buffers.
   *
   * This call should be used by drivers that require exclusive access to the
   * SPI bus. It has to be preceded by a spi_bus_lock call. The SPI bus must
   * be released by a spi_bus_unlock call when the exclusive access is over.
   *
   * It returns zero on success, else a negative error code.
   */
  int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
  {
  	return __spi_sync(spi, message, 1);
  }
  EXPORT_SYMBOL_GPL(spi_sync_locked);
  
  /**
   * spi_bus_lock - obtain a lock for exclusive SPI bus usage
   * @master: SPI bus master that should be locked for exclusive bus access
   * Context: can sleep
   *
   * This call may only be used from a context that may sleep.  The sleep
   * is non-interruptible, and has no timeout.
   *
   * This call should be used by drivers that require exclusive access to the
   * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
   * exclusive access is over. Data transfer must be done by spi_sync_locked
   * and spi_async_locked calls when the SPI bus lock is held.
   *
   * It returns zero on success, else a negative error code.
   */
  int spi_bus_lock(struct spi_master *master)
  {
  	unsigned long flags;
  
  	mutex_lock(&master->bus_lock_mutex);
  
  	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
  	master->bus_lock_flag = 1;
  	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
  
  	/* mutex remains locked until spi_bus_unlock is called */
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(spi_bus_lock);
  
  /**
   * spi_bus_unlock - release the lock for exclusive SPI bus usage
   * @master: SPI bus master that was locked for exclusive bus access
   * Context: can sleep
   *
   * This call may only be used from a context that may sleep.  The sleep
   * is non-interruptible, and has no timeout.
   *
   * This call releases an SPI bus lock previously obtained by an spi_bus_lock
   * call.
   *
   * It returns zero on success, else a negative error code.
   */
  int spi_bus_unlock(struct spi_master *master)
  {
  	master->bus_lock_flag = 0;
  
  	mutex_unlock(&master->bus_lock_mutex);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(spi_bus_unlock);
  
  /* portable code must never pass more than 32 bytes */
  #define	SPI_BUFSIZ	max(32, SMP_CACHE_BYTES)
  
  static u8	*buf;
  
  /**
   * spi_write_then_read - SPI synchronous write followed by read
   * @spi: device with which data will be exchanged
   * @txbuf: data to be written (need not be dma-safe)
   * @n_tx: size of txbuf, in bytes
   * @rxbuf: buffer into which data will be read (need not be dma-safe)
   * @n_rx: size of rxbuf, in bytes
   * Context: can sleep
   *
   * This performs a half duplex MicroWire style transaction with the
   * device, sending txbuf and then reading rxbuf.  The return value
   * is zero for success, else a negative errno status code.
   * This call may only be used from a context that may sleep.
   *
   * Parameters to this routine are always copied using a small buffer;
   * portable code should never use this for more than 32 bytes.
   * Performance-sensitive or bulk transfer code should instead use
   * spi_{async,sync}() calls with dma-safe buffers.
   */
  int spi_write_then_read(struct spi_device *spi,
  		const void *txbuf, unsigned n_tx,
  		void *rxbuf, unsigned n_rx)
  {
  	static DEFINE_MUTEX(lock);
  
  	int			status;
  	struct spi_message	message;
  	struct spi_transfer	x[2];
  	u8			*local_buf;
  
  	/* Use preallocated DMA-safe buffer if we can.  We can't avoid
  	 * copying here, (as a pure convenience thing), but we can
  	 * keep heap costs out of the hot path unless someone else is
  	 * using the pre-allocated buffer or the transfer is too large.
  	 */
  	if ((n_tx + n_rx) > SPI_BUFSIZ || !mutex_trylock(&lock)) {
  		local_buf = kmalloc(max((unsigned)SPI_BUFSIZ, n_tx + n_rx),
  				    GFP_KERNEL | GFP_DMA);
  		if (!local_buf)
  			return -ENOMEM;
  	} else {
  		local_buf = buf;
  	}
  
  	spi_message_init(&message);
  	memset(x, 0, sizeof(x));
  	if (n_tx) {
  		x[0].len = n_tx;
  		spi_message_add_tail(&x[0], &message);
  	}
  	if (n_rx) {
  		x[1].len = n_rx;
  		spi_message_add_tail(&x[1], &message);
  	}
  
  	memcpy(local_buf, txbuf, n_tx);
  	x[0].tx_buf = local_buf;
  	x[1].rx_buf = local_buf + n_tx;
  
  	/* do the i/o */
  	status = spi_sync(spi, &message);
  	if (status == 0)
  		memcpy(rxbuf, x[1].rx_buf, n_rx);
  
  	if (x[0].tx_buf == buf)
  		mutex_unlock(&lock);
  	else
  		kfree(local_buf);
  
  	return status;
  }
  EXPORT_SYMBOL_GPL(spi_write_then_read);
  
  /*-------------------------------------------------------------------------*/
  
  #if IS_ENABLED(CONFIG_OF_DYNAMIC)
  static int __spi_of_device_match(struct device *dev, void *data)
  {
  	return dev->of_node == data;
  }
  
  /* must call put_device() when done with returned spi_device device */
  static struct spi_device *of_find_spi_device_by_node(struct device_node *node)
  {
  	struct device *dev = bus_find_device(&spi_bus_type, NULL, node,
  						__spi_of_device_match);
  	return dev ? to_spi_device(dev) : NULL;
  }
  
  static int __spi_of_master_match(struct device *dev, const void *data)
  {
  	return dev->of_node == data;
  }
  
  /* the spi masters are not using spi_bus, so we find it with another way */
  static struct spi_master *of_find_spi_master_by_node(struct device_node *node)
  {
  	struct device *dev;
  
  	dev = class_find_device(&spi_master_class, NULL, node,
  				__spi_of_master_match);
  	if (!dev)
  		return NULL;
  
  	/* reference got in class_find_device */
  	return container_of(dev, struct spi_master, dev);
  }
  
  static int of_spi_notify(struct notifier_block *nb, unsigned long action,
  			 void *arg)
  {
  	struct of_reconfig_data *rd = arg;
  	struct spi_master *master;
  	struct spi_device *spi;
  
  	switch (of_reconfig_get_state_change(action, arg)) {
  	case OF_RECONFIG_CHANGE_ADD:
  		master = of_find_spi_master_by_node(rd->dn->parent);
  		if (master == NULL)
  			return NOTIFY_OK;	/* not for us */
  
  		spi = of_register_spi_device(master, rd->dn);
  		put_device(&master->dev);
  
  		if (IS_ERR(spi)) {
  			pr_err("%s: failed to create for '%s'\n",
  					__func__, rd->dn->full_name);
  			return notifier_from_errno(PTR_ERR(spi));
  		}
  		break;
  
  	case OF_RECONFIG_CHANGE_REMOVE:
  		/* find our device by node */
  		spi = of_find_spi_device_by_node(rd->dn);
  		if (spi == NULL)
  			return NOTIFY_OK;	/* no? not meant for us */
  
  		/* unregister takes one ref away */
  		spi_unregister_device(spi);
  
  		/* and put the reference of the find */
  		put_device(&spi->dev);
  		break;
  	}
  
  	return NOTIFY_OK;
  }
  
  static struct notifier_block spi_of_notifier = {
  	.notifier_call = of_spi_notify,
  };
  #else /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
  extern struct notifier_block spi_of_notifier;
  #endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
  
  static int __init spi_init(void)
  {
  	int	status;
  
  	buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
  	if (!buf) {
  		status = -ENOMEM;
  		goto err0;
  	}
  
  	status = bus_register(&spi_bus_type);
  	if (status < 0)
  		goto err1;
  
  	status = class_register(&spi_master_class);
  	if (status < 0)
  		goto err2;
  
  	if (IS_ENABLED(CONFIG_OF_DYNAMIC))
  		WARN_ON(of_reconfig_notifier_register(&spi_of_notifier));
  
  	return 0;
  
  err2:
  	bus_unregister(&spi_bus_type);
  err1:
  	kfree(buf);
  	buf = NULL;
  err0:
  	return status;
  }
  
  /* board_info is normally registered in arch_initcall(),
   * but even essential drivers wait till later
   *
   * REVISIT only boardinfo really needs static linking. the rest (device and
   * driver registration) _could_ be dynamically linked (modular) ... costs
   * include needing to have boardinfo data structures be much more public.
   */
  postcore_initcall(spi_init);
  
  