linux-imx

/*

 * Simple synchronous userspace interface to SPI devices

 *

 * Copyright (C) 2006 SWAPP

 *  Andrea Paterniani <a.paterniani@swapp-eng.it>

 * Copyright (C) 2007 David Brownell (simplification, cleanup)

 *

 * 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.

 */

​

#include <linux/init.h>

#include <linux/module.h>

#include <linux/ioctl.h>

#include <linux/fs.h>

#include <linux/device.h>

#include <linux/err.h>

#include <linux/list.h>

#include <linux/errno.h>

#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/compat.h>

#include <linux/of.h>

#include <linux/of_device.h>

#include <linux/acpi.h>

​

#include <linux/spi/spi.h>

#include <linux/spi/spidev.h>

​

#include <linux/uaccess.h>

​

​

/*

 * This supports access to SPI devices using normal userspace I/O calls.

 * Note that while traditional UNIX/POSIX I/O semantics are half duplex,

 * and often mask message boundaries, full SPI support requires full duplex

 * transfers.  There are several kinds of internal message boundaries to

 * handle chipselect management and other protocol options.

 *

 * SPI has a character major number assigned.  We allocate minor numbers

 * dynamically using a bitmask.  You must use hotplug tools, such as udev

 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device

 * nodes, since there is no fixed association of minor numbers with any

 * particular SPI bus or device.

 */

#define SPIDEV_MAJOR            153 /* assigned */

#define N_SPI_MINORS            32  /* ... up to 256 */

​

static DECLARE_BITMAP(minors, N_SPI_MINORS);

​

​

/* Bit masks for spi_device.mode management.  Note that incorrect

 * settings for some settings can cause *lots* of trouble for other

 * devices on a shared bus:

 *

 *  - CS_HIGH ... this device will be active when it shouldn't be

 *  - 3WIRE ... when active, it won't behave as it should

 *  - NO_CS ... there will be no explicit message boundaries; this

 *  is completely incompatible with the shared bus model

 *  - READY ... transfers may proceed when they shouldn't.

 *

 * REVISIT should changing those flags be privileged?

 */

#define SPI_MODE_MASK       (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \

                | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \

                | SPI_NO_CS | SPI_READY | SPI_TX_DUAL \

                | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)

​

struct spidev_data {

    dev_t           devt;

    spinlock_t      spi_lock;

    struct spi_device   *spi;

    struct list_head    device_entry;

​

    /* TX/RX buffers are NULL unless this device is open (users > 0) */

    struct mutex        buf_lock;

    unsigned        users;

    u8          *tx_buffer;

    u8          *rx_buffer;

    u32         speed_hz;

};

​

static LIST_HEAD(device_list);

static DEFINE_MUTEX(device_list_lock);

​