mrf24j40.c

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/*
 * Driver for Microchip MRF24J40 802.15.4 Wireless-PAN Networking controller
 *
 * Copyright (C) 2012 Alan Ott <[email protected]>
 *                    Signal 11 Software
 *
 * 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/spi/spi.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <net/wpan-phy.h>
#include <net/mac802154.h>

/* MRF24J40 Short Address Registers */
#define REG_RXMCR    0x00  /* Receive MAC control */
#define REG_PANIDL   0x01  /* PAN ID (low) */
#define REG_PANIDH   0x02  /* PAN ID (high) */
#define REG_SADRL    0x03  /* Short address (low) */
#define REG_SADRH    0x04  /* Short address (high) */
#define REG_EADR0    0x05  /* Long address (low) (high is EADR7) */
#define REG_TXMCR    0x11  /* Transmit MAC control */
#define REG_PACON0   0x16  /* Power Amplifier Control */
#define REG_PACON1   0x17  /* Power Amplifier Control */
#define REG_PACON2   0x18  /* Power Amplifier Control */
#define REG_TXNCON   0x1B  /* Transmit Normal FIFO Control */
#define REG_TXSTAT   0x24  /* TX MAC Status Register */
#define REG_SOFTRST  0x2A  /* Soft Reset */
#define REG_TXSTBL   0x2E  /* TX Stabilization */
#define REG_INTSTAT  0x31  /* Interrupt Status */
#define REG_INTCON   0x32  /* Interrupt Control */
#define REG_RFCTL    0x36  /* RF Control Mode Register */
#define REG_BBREG1   0x39  /* Baseband Registers */
#define REG_BBREG2   0x3A  /* */
#define REG_BBREG6   0x3E  /* */
#define REG_CCAEDTH  0x3F  /* Energy Detection Threshold */

/* MRF24J40 Long Address Registers */
#define REG_RFCON0     0x200  /* RF Control Registers */
#define REG_RFCON1     0x201
#define REG_RFCON2     0x202
#define REG_RFCON3     0x203
#define REG_RFCON5     0x205
#define REG_RFCON6     0x206
#define REG_RFCON7     0x207
#define REG_RFCON8     0x208
#define REG_RSSI       0x210
#define REG_SLPCON0    0x211  /* Sleep Clock Control Registers */
#define REG_SLPCON1    0x220
#define REG_WAKETIMEL  0x222  /* Wake-up Time Match Value Low */
#define REG_WAKETIMEH  0x223  /* Wake-up Time Match Value High */
#define REG_RX_FIFO    0x300  /* Receive FIFO */

/* Device configuration: Only channels 11-26 on page 0 are supported. */
#define MRF24J40_CHAN_MIN 11
#define MRF24J40_CHAN_MAX 26
#define CHANNEL_MASK (((u32)1 << (MRF24J40_CHAN_MAX + 1)) \
              - ((u32)1 << MRF24J40_CHAN_MIN))

#define TX_FIFO_SIZE 128 /* From datasheet */
#define RX_FIFO_SIZE 144 /* From datasheet */
#define SET_CHANNEL_DELAY_US 192 /* From datasheet */

/* Device Private Data */
struct mrf24j40 {
    struct spi_device *spi;
    struct ieee802154_dev *dev;

    struct mutex buffer_mutex; /* only used to protect buf */
    struct completion tx_complete;
    struct work_struct irqwork;
    u8 *buf; /* 3 bytes. Used for SPI single-register transfers. */
};

/* Read/Write SPI Commands for Short and Long Address registers. */
#define MRF24J40_READSHORT(reg) ((reg) << 1)
#define MRF24J40_WRITESHORT(reg) ((reg) << 1 | 1)
#define MRF24J40_READLONG(reg) (1 << 15 | (reg) << 5)
#define MRF24J40_WRITELONG(reg) (1 << 15 | (reg) << 5 | 1 << 4)

/* Maximum speed to run the device at. TODO: Get the real max value from
 * someone at Microchip since it isn't in the datasheet. */
#define MAX_SPI_SPEED_HZ 1000000

#define printdev(X) (&X->spi->dev)

static int write_short_reg(struct mrf24j40 *devrec, u8 reg, u8 value)
{
    int ret;
    struct spi_message msg;
    struct spi_transfer xfer = {
        .len = 2,
        .tx_buf = devrec->buf,
        .rx_buf = devrec->buf,
    };

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    mutex_lock(&devrec->buffer_mutex);
    devrec->buf[0] = MRF24J40_WRITESHORT(reg);
    devrec->buf[1] = value;

    ret = spi_sync(devrec->spi, &msg);
    if (ret)
        dev_err(printdev(devrec),
            "SPI write Failed for short register 0x%hhx\n", reg);

    mutex_unlock(&devrec->buffer_mutex);
    return ret;
}

static int read_short_reg(struct mrf24j40 *devrec, u8 reg, u8 *val)
{
    int ret = -1;
    struct spi_message msg;
    struct spi_transfer xfer = {
        .len = 2,
        .tx_buf = devrec->buf,
        .rx_buf = devrec->buf,
    };

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    mutex_lock(&devrec->buffer_mutex);
    devrec->buf[0] = MRF24J40_READSHORT(reg);
    devrec->buf[1] = 0;

    ret = spi_sync(devrec->spi, &msg);
    if (ret)
        dev_err(printdev(devrec),
            "SPI read Failed for short register 0x%hhx\n", reg);
    else
        *val = devrec->buf[1];

    mutex_unlock(&devrec->buffer_mutex);
    return ret;
}

static int read_long_reg(struct mrf24j40 *devrec, u16 reg, u8 *value)
{
    int ret;
    u16 cmd;
    struct spi_message msg;
    struct spi_transfer xfer = {
        .len = 3,
        .tx_buf = devrec->buf,
        .rx_buf = devrec->buf,
    };

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    cmd = MRF24J40_READLONG(reg);
    mutex_lock(&devrec->buffer_mutex);
    devrec->buf[0] = cmd >> 8 & 0xff;
    devrec->buf[1] = cmd & 0xff;
    devrec->buf[2] = 0;

    ret = spi_sync(devrec->spi, &msg);
    if (ret)
        dev_err(printdev(devrec),
            "SPI read Failed for long register 0x%hx\n", reg);
    else
        *value = devrec->buf[2];

    mutex_unlock(&devrec->buffer_mutex);
    return ret;
}

static int write_long_reg(struct mrf24j40 *devrec, u16 reg, u8 val)
{
    int ret;
    u16 cmd;
    struct spi_message msg;
    struct spi_transfer xfer = {
        .len = 3,
        .tx_buf = devrec->buf,
        .rx_buf = devrec->buf,
    };

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    cmd = MRF24J40_WRITELONG(reg);
    mutex_lock(&devrec->buffer_mutex);
    devrec->buf[0] = cmd >> 8 & 0xff;
    devrec->buf[1] = cmd & 0xff;
    devrec->buf[2] = val;

    ret = spi_sync(devrec->spi, &msg);
    if (ret)
        dev_err(printdev(devrec),
            "SPI write Failed for long register 0x%hx\n", reg);

    mutex_unlock(&devrec->buffer_mutex);
    return ret;
}

/* This function relies on an undocumented write method. Once a write command
   and address is set, as many bytes of data as desired can be clocked into
   the device. The datasheet only shows setting one byte at a time. */
static int write_tx_buf(struct mrf24j40 *devrec, u16 reg,
            const u8 *data, size_t length)
{
    int ret;
    u16 cmd;
    u8 lengths[2];
    struct spi_message msg;
    struct spi_transfer addr_xfer = {
        .len = 2,
        .tx_buf = devrec->buf,
    };
    struct spi_transfer lengths_xfer = {
        .len = 2,
        .tx_buf = &lengths, /* TODO: Is DMA really required for SPI? */
    };
    struct spi_transfer data_xfer = {
        .len = length,
        .tx_buf = data,
    };

    /* Range check the length. 2 bytes are used for the length fields.*/
    if (length > TX_FIFO_SIZE-2) {
        dev_err(printdev(devrec), "write_tx_buf() was passed too large a buffer. Performing short write.\n");
        length = TX_FIFO_SIZE-2;
    }

    spi_message_init(&msg);
    spi_message_add_tail(&addr_xfer, &msg);
    spi_message_add_tail(&lengths_xfer, &msg);
    spi_message_add_tail(&data_xfer, &msg);

    cmd = MRF24J40_WRITELONG(reg);
    mutex_lock(&devrec->buffer_mutex);
    devrec->buf[0] = cmd >> 8 & 0xff;
    devrec->buf[1] = cmd & 0xff;
    lengths[0] = 0x0; /* Header Length. Set to 0 for now. TODO */
    lengths[1] = length; /* Total length */

    ret = spi_sync(devrec->spi, &msg);
    if (ret)
        dev_err(printdev(devrec), "SPI write Failed for TX buf\n");

    mutex_unlock(&devrec->buffer_mutex);
    return ret;
}

static int mrf24j40_read_rx_buf(struct mrf24j40 *devrec,
                u8 *data, u8 *len, u8 *lqi)
{
    u8 rx_len;
    u8 addr[2];
    u8 lqi_rssi[2];
    u16 cmd;
    int ret;
    struct spi_message msg;
    struct spi_transfer addr_xfer = {
        .len = 2,
        .tx_buf = &addr,
    };
    struct spi_transfer data_xfer = {
        .len = 0x0, /* set below */
        .rx_buf = data,
    };
    struct spi_transfer status_xfer = {
        .len = 2,
        .rx_buf = &lqi_rssi,
    };

    /* Get the length of the data in the RX FIFO. The length in this
     * register exclues the 1-byte length field at the beginning. */
    ret = read_long_reg(devrec, REG_RX_FIFO, &rx_len);
    if (ret)
        goto out;

    /* Range check the RX FIFO length, accounting for the one-byte
     * length field at the begining. */
    if (rx_len > RX_FIFO_SIZE-1) {
        dev_err(printdev(devrec), "Invalid length read from device. Performing short read.\n");
        rx_len = RX_FIFO_SIZE-1;
    }

    if (rx_len > *len) {
        /* Passed in buffer wasn't big enough. Should never happen. */
        dev_err(printdev(devrec), "Buffer not big enough. Performing short read\n");
        rx_len = *len;
    }

    /* Set up the commands to read the data. */
    cmd = MRF24J40_READLONG(REG_RX_FIFO+1);
    addr[0] = cmd >> 8 & 0xff;
    addr[1] = cmd & 0xff;
    data_xfer.len = rx_len;

    spi_message_init(&msg);
    spi_message_add_tail(&addr_xfer, &msg);
    spi_message_add_tail(&data_xfer, &msg);
    spi_message_add_tail(&status_xfer, &msg);

    ret = spi_sync(devrec->spi, &msg);
    if (ret) {
        dev_err(printdev(devrec), "SPI RX Buffer Read Failed.\n");
        goto out;
    }

    *lqi = lqi_rssi[0];
    *len = rx_len;

#ifdef DEBUG
    print_hex_dump(KERN_DEBUG, "mrf24j40 rx: ",
        DUMP_PREFIX_OFFSET, 16, 1, data, *len, 0);
    printk(KERN_DEBUG "mrf24j40 rx: lqi: %02hhx rssi: %02hhx\n",
        lqi_rssi[0], lqi_rssi[1]);
#endif

out:
    return ret;
}

static int mrf24j40_tx(struct ieee802154_dev *dev, struct sk_buff *skb)
{
    struct mrf24j40 *devrec = dev->priv;
    u8 val;
    int ret = 0;

    dev_dbg(printdev(devrec), "tx packet of %d bytes\n", skb->len);

    ret = write_tx_buf(devrec, 0x000, skb->data, skb->len);
    if (ret)
        goto err;

    /* Set TXNTRIG bit of TXNCON to send packet */
    ret = read_short_reg(devrec, REG_TXNCON, &val);
    if (ret)
        goto err;
    val |= 0x1;
    val &= ~0x4;
    write_short_reg(devrec, REG_TXNCON, val);

    INIT_COMPLETION(devrec->tx_complete);

    /* Wait for the device to send the TX complete interrupt. */
    ret = wait_for_completion_interruptible_timeout(
                        &devrec->tx_complete,
                        5 * HZ);
    if (ret == -ERESTARTSYS)
        goto err;
    if (ret == 0) {
        ret = -ETIMEDOUT;
        goto err;
    }

    /* Check for send error from the device. */
    ret = read_short_reg(devrec, REG_TXSTAT, &val);
    if (ret)
        goto err;
    if (val & 0x1) {
        dev_err(printdev(devrec), "Error Sending. Retry count exceeded\n");
        ret = -ECOMM; /* TODO: Better error code ? */
    } else
        dev_dbg(printdev(devrec), "Packet Sent\n");

err:

    return ret;
}

static int mrf24j40_ed(struct ieee802154_dev *dev, u8 *level)
{
    /* TODO: */
    printk(KERN_WARNING "mrf24j40: ed not implemented\n");
    *level = 0;
    return 0;
}

static int mrf24j40_start(struct ieee802154_dev *dev)
{
    struct mrf24j40 *devrec = dev->priv;
    u8 val;
    int ret;

    dev_dbg(printdev(devrec), "start\n");

    ret = read_short_reg(devrec, REG_INTCON, &val);
    if (ret)
        return ret;
    val &= ~(0x1|0x8); /* Clear TXNIE and RXIE. Enable interrupts */
    write_short_reg(devrec, REG_INTCON, val);

    return 0;
}

static void mrf24j40_stop(struct ieee802154_dev *dev)
{
    struct mrf24j40 *devrec = dev->priv;
    u8 val;
    int ret;
    dev_dbg(printdev(devrec), "stop\n");

    ret = read_short_reg(devrec, REG_INTCON, &val);
    if (ret)
        return;
    val |= 0x1|0x8; /* Set TXNIE and RXIE. Disable Interrupts */
    write_short_reg(devrec, REG_INTCON, val);

    return;
}

static int mrf24j40_set_channel(struct ieee802154_dev *dev,
                int page, int channel)
{
    struct mrf24j40 *devrec = dev->priv;
    u8 val;
    int ret;

    dev_dbg(printdev(devrec), "Set Channel %d\n", channel);

    WARN_ON(page != 0);
    WARN_ON(channel < MRF24J40_CHAN_MIN);
    WARN_ON(channel > MRF24J40_CHAN_MAX);

    /* Set Channel TODO */
    val = (channel-11) << 4 | 0x03;
    write_long_reg(devrec, REG_RFCON0, val);

    /* RF Reset */
    ret = read_short_reg(devrec, REG_RFCTL, &val);
    if (ret)
        return ret;
    val |= 0x04;
    write_short_reg(devrec, REG_RFCTL, val);
    val &= ~0x04;
    write_short_reg(devrec, REG_RFCTL, val);

    udelay(SET_CHANNEL_DELAY_US); /* per datasheet */

    return 0;
}

static int mrf24j40_filter(struct ieee802154_dev *dev,
               struct ieee802154_hw_addr_filt *filt,
               unsigned long changed)
{
    struct mrf24j40 *devrec = dev->priv;

    dev_dbg(printdev(devrec), "filter\n");

    if (changed & IEEE802515_AFILT_SADDR_CHANGED) {
        /* Short Addr */
        u8 addrh, addrl;
        addrh = filt->short_addr >> 8 & 0xff;
        addrl = filt->short_addr & 0xff;

        write_short_reg(devrec, REG_SADRH, addrh);
        write_short_reg(devrec, REG_SADRL, addrl);
        dev_dbg(printdev(devrec),
            "Set short addr to %04hx\n", filt->short_addr);
    }

    if (changed & IEEE802515_AFILT_IEEEADDR_CHANGED) {
        /* Device Address */
        int i;
        for (i = 0; i < 8; i++)
            write_short_reg(devrec, REG_EADR0+i,
                    filt->ieee_addr[i]);

#ifdef DEBUG
        printk(KERN_DEBUG "Set long addr to: ");
        for (i = 0; i < 8; i++)
            printk("%02hhx ", filt->ieee_addr[i]);
        printk(KERN_DEBUG "\n");
#endif
    }

    if (changed & IEEE802515_AFILT_PANID_CHANGED) {
        /* PAN ID */
        u8 panidl, panidh;
        panidh = filt->pan_id >> 8 & 0xff;
        panidl = filt->pan_id & 0xff;
        write_short_reg(devrec, REG_PANIDH, panidh);
        write_short_reg(devrec, REG_PANIDL, panidl);

        dev_dbg(printdev(devrec), "Set PANID to %04hx\n", filt->pan_id);
    }

    if (changed & IEEE802515_AFILT_PANC_CHANGED) {
        /* Pan Coordinator */
        u8 val;
        int ret;

        ret = read_short_reg(devrec, REG_RXMCR, &val);
        if (ret)
            return ret;
        if (filt->pan_coord)
            val |= 0x8;
        else
            val &= ~0x8;
        write_short_reg(devrec, REG_RXMCR, val);

        /* REG_SLOTTED is maintained as default (unslotted/CSMA-CA).
         * REG_ORDER is maintained as default (no beacon/superframe).
         */

        dev_dbg(printdev(devrec), "Set Pan Coord to %s\n",
                    filt->pan_coord ? "on" : "off");
    }

    return 0;
}

static int mrf24j40_handle_rx(struct mrf24j40 *devrec)
{
    u8 len = RX_FIFO_SIZE;
    u8 lqi = 0;
    u8 val;
    int ret = 0;
    struct sk_buff *skb;

    /* Turn off reception of packets off the air. This prevents the
     * device from overwriting the buffer while we're reading it. */
    ret = read_short_reg(devrec, REG_BBREG1, &val);
    if (ret)
        goto out;
    val |= 4; /* SET RXDECINV */
    write_short_reg(devrec, REG_BBREG1, val);

    skb = alloc_skb(len, GFP_KERNEL);
    if (!skb) {
        ret = -ENOMEM;
        goto out;
    }

    ret = mrf24j40_read_rx_buf(devrec, skb_put(skb, len), &len, &lqi);
    if (ret < 0) {
        dev_err(printdev(devrec), "Failure reading RX FIFO\n");
        kfree_skb(skb);
        ret = -EINVAL;
        goto out;
    }

    /* Cut off the checksum */
    skb_trim(skb, len-2);

    /* TODO: Other drivers call ieee20154_rx_irqsafe() here (eg: cc2040,
     * also from a workqueue).  I think irqsafe is not necessary here.
     * Can someone confirm? */
    ieee802154_rx_irqsafe(devrec->dev, skb, lqi);

    dev_dbg(printdev(devrec), "RX Handled\n");

out:
    /* Turn back on reception of packets off the air. */
    ret = read_short_reg(devrec, REG_BBREG1, &val);
    if (ret)
        return ret;
    val &= ~0x4; /* Clear RXDECINV */
    write_short_reg(devrec, REG_BBREG1, val);

    return ret;
}

static struct ieee802154_ops mrf24j40_ops = {
    .owner = THIS_MODULE,
    .xmit = mrf24j40_tx,
    .ed = mrf24j40_ed,
    .start = mrf24j40_start,
    .stop = mrf24j40_stop,
    .set_channel = mrf24j40_set_channel,
    .set_hw_addr_filt = mrf24j40_filter,
};

static irqreturn_t mrf24j40_isr(int irq, void *data)
{
    struct mrf24j40 *devrec = data;

    disable_irq_nosync(irq);

    schedule_work(&devrec->irqwork);

    return IRQ_HANDLED;
}

static void mrf24j40_isrwork(struct work_struct *work)
{
    struct mrf24j40 *devrec = container_of(work, struct mrf24j40, irqwork);
    u8 intstat;
    int ret;

    /* Read the interrupt status */
    ret = read_short_reg(devrec, REG_INTSTAT, &intstat);
    if (ret)
        goto out;

    /* Check for TX complete */
    if (intstat & 0x1)
        complete(&devrec->tx_complete);

    /* Check for Rx */
    if (intstat & 0x8)
        mrf24j40_handle_rx(devrec);

out:
    enable_irq(devrec->spi->irq);
}

static int __devinit mrf24j40_probe(struct spi_device *spi)
{
    int ret = -ENOMEM;
    u8 val;
    struct mrf24j40 *devrec;

    printk(KERN_INFO "mrf24j40: probe(). IRQ: %d\n", spi->irq);

    devrec = kzalloc(sizeof(struct mrf24j40), GFP_KERNEL);
    if (!devrec)
        goto err_devrec;
    devrec->buf = kzalloc(3, GFP_KERNEL);
    if (!devrec->buf)
        goto err_buf;

    spi->mode = SPI_MODE_0; /* TODO: Is this appropriate for right here? */
    if (spi->max_speed_hz > MAX_SPI_SPEED_HZ)
        spi->max_speed_hz = MAX_SPI_SPEED_HZ;

    mutex_init(&devrec->buffer_mutex);
    init_completion(&devrec->tx_complete);
    INIT_WORK(&devrec->irqwork, mrf24j40_isrwork);
    devrec->spi = spi;
    dev_set_drvdata(&spi->dev, devrec);

    /* Register with the 802154 subsystem */

    devrec->dev = ieee802154_alloc_device(0, &mrf24j40_ops);
    if (!devrec->dev)
        goto err_alloc_dev;

    devrec->dev->priv = devrec;
    devrec->dev->parent = &devrec->spi->dev;
    devrec->dev->phy->channels_supported[0] = CHANNEL_MASK;
    devrec->dev->flags = IEEE802154_HW_OMIT_CKSUM|IEEE802154_HW_AACK;

    dev_dbg(printdev(devrec), "registered mrf24j40\n");
    ret = ieee802154_register_device(devrec->dev);
    if (ret)
        goto err_register_device;

    /* Initialize the device.
        From datasheet section 3.2: Initialization. */
    write_short_reg(devrec, REG_SOFTRST, 0x07);
    write_short_reg(devrec, REG_PACON2, 0x98);
    write_short_reg(devrec, REG_TXSTBL, 0x95);
    write_long_reg(devrec, REG_RFCON0, 0x03);
    write_long_reg(devrec, REG_RFCON1, 0x01);
    write_long_reg(devrec, REG_RFCON2, 0x80);
    write_long_reg(devrec, REG_RFCON6, 0x90);
    write_long_reg(devrec, REG_RFCON7, 0x80);
    write_long_reg(devrec, REG_RFCON8, 0x10);
    write_long_reg(devrec, REG_SLPCON1, 0x21);
    write_short_reg(devrec, REG_BBREG2, 0x80);
    write_short_reg(devrec, REG_CCAEDTH, 0x60);
    write_short_reg(devrec, REG_BBREG6, 0x40);
    write_short_reg(devrec, REG_RFCTL, 0x04);
    write_short_reg(devrec, REG_RFCTL, 0x0);
    udelay(192);

    /* Set RX Mode. RXMCR<1:0>: 0x0 normal, 0x1 promisc, 0x2 error */
    ret = read_short_reg(devrec, REG_RXMCR, &val);
    if (ret)
        goto err_read_reg;
    val &= ~0x3; /* Clear RX mode (normal) */
    write_short_reg(devrec, REG_RXMCR, val);

    ret = request_irq(spi->irq,
              mrf24j40_isr,
              IRQF_TRIGGER_FALLING,
              dev_name(&spi->dev),
              devrec);

    if (ret) {
        dev_err(printdev(devrec), "Unable to get IRQ");
        goto err_irq;
    }

    return 0;

err_irq:
err_read_reg:
    ieee802154_unregister_device(devrec->dev);
err_register_device:
    ieee802154_free_device(devrec->dev);
err_alloc_dev:
    kfree(devrec->buf);
err_buf:
    kfree(devrec);
err_devrec:
    return ret;
}

static int __devexit mrf24j40_remove(struct spi_device *spi)
{
    struct mrf24j40 *devrec = dev_get_drvdata(&spi->dev);

    dev_dbg(printdev(devrec), "remove\n");

    free_irq(spi->irq, devrec);
    flush_work(&devrec->irqwork); /* TODO: Is this the right call? */
    ieee802154_unregister_device(devrec->dev);
    ieee802154_free_device(devrec->dev);
    /* TODO: Will ieee802154_free_device() wait until ->xmit() is
     * complete? */

    /* Clean up the SPI stuff. */
    dev_set_drvdata(&spi->dev, NULL);
    kfree(devrec->buf);
    kfree(devrec);
    return 0;
}

static const struct spi_device_id mrf24j40_ids[] = {
    { "mrf24j40", 0 },
    { "mrf24j40ma", 0 },
    { },
};
MODULE_DEVICE_TABLE(spi, mrf24j40_ids);

static struct spi_driver mrf24j40_driver = {
    .driver = {
        .name = "mrf24j40",
        .bus = &spi_bus_type,
        .owner = THIS_MODULE,
    },
    .id_table = mrf24j40_ids,
    .probe = mrf24j40_probe,
    .remove = __devexit_p(mrf24j40_remove),
};

static int __init mrf24j40_init(void)
{
    return spi_register_driver(&mrf24j40_driver);
}

static void __exit mrf24j40_exit(void)
{
    spi_unregister_driver(&mrf24j40_driver);
}

module_init(mrf24j40_init);
module_exit(mrf24j40_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alan Ott");
MODULE_DESCRIPTION("MRF24J40 SPI 802.15.4 Controller Driver");