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spi.c

/*
 * spi.c - SPI init/core code
 *
 * Copyright (C) 2005 David Brownell
 *
 * 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/autoconf.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/cache.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>


/* SPI bustype and spi_master class are registered after board init code
 * provides the SPI device tables, ensuring that both are present by the
 * time controller driver registration causes spi_devices to "enumerate".
 */
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(dev);
}

static ssize_t
modalias_show(struct device *dev, struct device_attribute *a, char *buf)
{
      const struct spi_device *spi = to_spi_device(dev);

      return snprintf(buf, BUS_ID_SIZE + 1, "%s\n", spi->modalias);
}

static struct device_attribute spi_dev_attrs[] = {
      __ATTR_RO(modalias),
      __ATTR_NULL,
};

/* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
 * and the sysfs version makes coldplug work too.
 */

static int spi_match_device(struct device *dev, struct device_driver *drv)
{
      const struct spi_device *spi = to_spi_device(dev);

      return strncmp(spi->modalias, drv->name, BUS_ID_SIZE) == 0;
}

static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
{
      const struct spi_device       *spi = to_spi_device(dev);

      add_uevent_var(env, "MODALIAS=%s", spi->modalias);
      return 0;
}

#ifdef      CONFIG_PM

/*
 * NOTE:  the suspend() method for an spi_master controller driver
 * should verify that all its child devices are marked as suspended;
 * suspend requests delivered through sysfs power/state files don't
 * enforce such constraints.
 */
static int spi_suspend(struct device *dev, pm_message_t message)
{
      int               value;
      struct spi_driver *drv = to_spi_driver(dev->driver);

      if (!drv || !drv->suspend)
            return 0;

      /* suspend will stop irqs and dma; no more i/o */
      value = drv->suspend(to_spi_device(dev), message);
      if (value == 0)
            dev->power.power_state = message;
      return value;
}

static int spi_resume(struct device *dev)
{
      int               value;
      struct spi_driver *drv = to_spi_driver(dev->driver);

      if (!drv || !drv->resume)
            return 0;

      /* resume may restart the i/o queue */
      value = drv->resume(to_spi_device(dev));
      if (value == 0)
            dev->power.power_state = PMSG_ON;
      return value;
}

#else
#define spi_suspend     NULL
#define spi_resume      NULL
#endif

struct bus_type spi_bus_type = {
      .name       = "spi",
      .dev_attrs  = spi_dev_attrs,
      .match            = spi_match_device,
      .uevent           = spi_uevent,
      .suspend    = spi_suspend,
      .resume           = spi_resume,
};
EXPORT_SYMBOL_GPL(spi_bus_type);


static int spi_drv_probe(struct device *dev)
{
      const struct spi_driver       *sdrv = to_spi_driver(dev->driver);

      return sdrv->probe(to_spi_device(dev));
}

static int spi_drv_remove(struct device *dev)
{
      const struct spi_driver       *sdrv = to_spi_driver(dev->driver);

      return sdrv->remove(to_spi_device(dev));
}

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;
      unsigned          n_board_info;
      struct spi_board_info   board_info[0];
};

static LIST_HEAD(board_list);
static DEFINE_MUTEX(board_lock);


/**
 * 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;
      struct device           *dev = master->dev.parent;
      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).
       */

      /* Chipselects are numbered 0..max; validate. */
      if (chip->chip_select >= master->num_chipselect) {
            dev_err(dev, "cs%d > max %d\n",
                  chip->chip_select,
                  master->num_chipselect);
            return NULL;
      }

      if (!spi_master_get(master))
            return NULL;

      proxy = kzalloc(sizeof *proxy, GFP_KERNEL);
      if (!proxy) {
            dev_err(dev, "can't alloc dev for cs%d\n",
                  chip->chip_select);
            goto fail;
      }
      proxy->master = master;
      proxy->chip_select = chip->chip_select;
      proxy->max_speed_hz = chip->max_speed_hz;
      proxy->mode = chip->mode;
      proxy->irq = chip->irq;
      proxy->modalias = chip->modalias;

      snprintf(proxy->dev.bus_id, sizeof proxy->dev.bus_id,
                  "%s.%u", master->dev.bus_id,
                  chip->chip_select);
      proxy->dev.parent = dev;
      proxy->dev.bus = &spi_bus_type;
      proxy->dev.platform_data = (void *) chip->platform_data;
      proxy->controller_data = chip->controller_data;
      proxy->controller_state = NULL;
      proxy->dev.release = spidev_release;

      /* drivers may modify this initial i/o setup */
      status = master->setup(proxy);
      if (status < 0) {
            dev_err(dev, "can't %s %s, status %d\n",
                        "setup", proxy->dev.bus_id, status);
            goto fail;
      }

      /* driver core catches callers that misbehave by defining
       * devices that already exist.
       */
      status = device_register(&proxy->dev);
      if (status < 0) {
            dev_err(dev, "can't %s %s, status %d\n",
                        "add", proxy->dev.bus_id, status);
            goto fail;
      }
      dev_dbg(dev, "registered child %s\n", proxy->dev.bus_id);
      return proxy;

fail:
      spi_master_put(master);
      kfree(proxy);
      return NULL;
}
EXPORT_SYMBOL_GPL(spi_new_device);

/**
 * 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 __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
      struct boardinfo  *bi;

      bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
      if (!bi)
            return -ENOMEM;
      bi->n_board_info = n;
      memcpy(bi->board_info, info, n * sizeof *info);

      mutex_lock(&board_lock);
      list_add_tail(&bi->list, &board_list);
      mutex_unlock(&board_lock);
      return 0;
}

/* FIXME someone should add support for a __setup("spi", ...) that
 * creates board info from kernel command lines
 */

static void scan_boardinfo(struct spi_master *master)
{
      struct boardinfo  *bi;

      mutex_lock(&board_lock);
      list_for_each_entry(bi, &board_list, list) {
            struct spi_board_info   *chip = bi->board_info;
            unsigned          n;

            for (n = bi->n_board_info; n > 0; n--, chip++) {
                  if (chip->bus_num != master->bus_num)
                        continue;
                  /* NOTE: this relies on spi_new_device to
                   * issue diagnostics when given bogus inputs
                   */
                  (void) spi_new_device(master, chip);
            }
      }
      mutex_unlock(&board_lock);
}

/*-------------------------------------------------------------------------*/

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() 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->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);

/**
 * 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;
      int               status = -ENODEV;
      int               dynamic = 0;

      if (!dev)
            return -ENODEV;

      /* even if it's just one always-selected device, there must
       * be at least one chipselect
       */
      if (master->num_chipselect == 0)
            return -EINVAL;

      /* 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;
      }

      /* register the device, then userspace will see it.
       * registration fails if the bus ID is in use.
       */
      snprintf(master->dev.bus_id, sizeof master->dev.bus_id,
            "spi%u", master->bus_num);
      status = device_add(&master->dev);
      if (status < 0)
            goto done;
      dev_dbg(dev, "registered master %s%s\n", master->dev.bus_id,
                  dynamic ? " (dynamic)" : "");

      /* populate children from any spi device tables */
      scan_boardinfo(master);
      status = 0;
done:
      return status;
}
EXPORT_SYMBOL_GPL(spi_register_master);


static int __unregister(struct device *dev, void *master_dev)
{
      /* note: before about 2.6.14-rc1 this would corrupt memory: */
      if (dev != master_dev)
            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;

      dummy = device_for_each_child(master->dev.parent, &master->dev,
                              __unregister);
      device_unregister(&master->dev);
}
EXPORT_SYMBOL_GPL(spi_unregister_master);

/**
 * 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;
      struct spi_master *m;

      down(&spi_master_class.sem);
      list_for_each_entry(dev, &spi_master_class.children, node) {
            m = container_of(dev, struct spi_master, dev);
            if (m->bus_num == bus_num) {
                  master = spi_master_get(m);
                  break;
            }
      }
      up(&spi_master_class.sem);
      return master;
}
EXPORT_SYMBOL_GPL(spi_busnum_to_master);


/*-------------------------------------------------------------------------*/

static void spi_complete(void *arg)
{
      complete(arg);
}

/**
 * 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)
{
      DECLARE_COMPLETION_ONSTACK(done);
      int status;

      message->complete = spi_complete;
      message->context = &done;
      status = spi_async(spi, message);
      if (status == 0) {
            wait_for_completion(&done);
            status = message->status;
      }
      message->context = NULL;
      return status;
}
EXPORT_SYMBOL_GPL(spi_sync);

/* 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
 * @n_rx: size of rxbuf, in bytes (need not be dma-safe)
 * 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 u8 *txbuf, unsigned n_tx,
            u8 *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.  We can't avoid copying here,
       * (as a pure convenience thing), but we can keep heap costs
       * out of the hot path ...
       */
      if ((n_tx + n_rx) > SPI_BUFSIZ)
            return -EINVAL;

      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);
      }

      /* ... unless someone else is using the pre-allocated buffer */
      if (!mutex_trylock(&lock)) {
            local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
            if (!local_buf)
                  return -ENOMEM;
      } else
            local_buf = buf;

      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);

/*-------------------------------------------------------------------------*/

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;
      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.
 */
subsys_initcall(spi_init);


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