Linux 3DS SPI functions

static int spi_write_2(struct spi_device *spi,
               u8 *tx_buf0, u8 tx_len0,
               u8 *tx_buf1, u8 tx_len1)
{
    struct spi_message msg;
    struct spi_transfer xfers[2];

    memset(xfers, 0, sizeof(xfers));

    xfers[0].tx_buf = tx_buf0;
    xfers[0].len = tx_len0;

    xfers[1].tx_buf = tx_buf1;
    xfers[1].len = tx_len1;

    spi_message_init(&msg);
    spi_message_add_tail(&xfers[0], &msg);
    spi_message_add_tail(&xfers[1], &msg);

    return spi_sync(spi, &msg);
}

static int spi_write_read(struct spi_device *spi,
              u8 *tx_buf, u8 tx_len,
              u8 *rx_buf, u8 rx_len)
{
    struct spi_message msg;
    struct spi_transfer xfers[2];

    memset(xfers, 0, sizeof(xfers));

    xfers[0].tx_buf = tx_buf;
    xfers[0].len = tx_len;

    xfers[1].rx_buf = rx_buf;
    xfers[1].len = rx_len;

    spi_message_init(&msg);

    spi_message_add_tail(&xfers[0], &msg);
    spi_message_add_tail(&xfers[1], &msg);

    return spi_sync(spi, &msg);
}

static void spi_reg_select(struct spi_device *spi, u8 reg)
{
    u8 buffer1[4];
    u8 buffer2[0x40];

    buffer1[0] = 0;
    buffer2[0] = reg;

    spi_write_2(spi, buffer1, 1, buffer2, 1);
}

static u8 spi_reg_read_offset(struct spi_device *spi, u8 offset)
{
    u8 buffer_wr[8];
    u8 buffer_rd[0x40];

    buffer_wr[0] = 1 | (offset << 1);

    spi_write_read(spi, buffer_wr, 1, buffer_rd, 1);

    return buffer_rd[0];
}

static void spi_reg_write_offset(struct spi_device *spi, u8 reg, u8 val)
{
    u8 buffer1[8];
    u8 buffer2[0x40];

    buffer1[0] = (reg << 1); // Write
    buffer2[0] = val;

    spi_write_2(spi, buffer1, 1, buffer2, 1);
}

static void spi_reg_read_buffer(struct spi_device *spi,
                   u8 offset, void *buffer, u8 size)
{
    u8 buffer_wr[0x10];

    buffer_wr[0] = 1 | (offset << 1);

    spi_write_read(spi, buffer_wr, 1, buffer, size);
}

static void spi_reg_write_buffer(struct spi_device *spi, u8 reg, void *buffer, u8 size)
{
    uint8_t buffer_reg[8];

    buffer_reg[0] = reg << 1;

    spi_write_2(spi, buffer_reg, 1, buffer, size);
}

static void spi_reg_mask_offset(struct spi_device *spi, u8 offset, u8 mask0, u8 mask1)
{
    u8 buffer1[4];
    u8 buffer2[0x40];

    buffer1[0] = 1 | (offset << 1);

    spi_write_read(spi, buffer1, 1, buffer2, 1);

    buffer1[0] = offset << 1;
    buffer2[0] = (buffer2[0] & ~mask1) | (mask0 & mask1);

    spi_write_2(spi, buffer1, 1, buffer2, 1);
}

static void spi_codec_hid_initialize(struct spi_device *spi)
{
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x24, 0x98);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x26, 0x00);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x25, 0x43);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x24, 0x18);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x17, 0x43);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x19, 0x69);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x1B, 0x80);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x27, 0x11);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x26, 0xEC);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x24, 0x18);
    spi_reg_select(spi, 0x67);
    spi_reg_write_offset(spi, 0x25, 0x53);
}

static void spi_codec_ts_initialize(struct spi_device *spi)
{
    spi_reg_select(spi, 0x67);
    spi_reg_mask_offset(spi, 0x26, 0x80, 0x80);
    spi_reg_select(spi, 0x67);
    spi_reg_mask_offset(spi, 0x24, 0x00, 0x80);
    spi_reg_select(spi, 0x67);
    spi_reg_mask_offset(spi, 0x25, 0x10, 0x3C);
}