sean static int ad714x_spi_read(struct ad714x_chip chip,
unsigned short reg, unsigned short data, size_t len)
{
struct spi_device *spi = to_spi_device(chip->dev);
struct spi_message message;
struct spi_transfer xfer[2];
int i;
int error;
spi_message_init(&message);
memset(xfer, 0, sizeof(xfer));
chip->xfer_buf[0] = cpu_to_be16(AD714x_SPI_CMD_PREFIX |
AD714x_SPI_READ | reg);
xfer[0].tx_buf = &chip->xfer_buf[0];
xfer[0].len = sizeof(chip->xfer_buf[0]);
spi_message_add_tail(&xfer[0], &message);
xfer[1].rx_buf = &chip->xfer_buf[1];
xfer[1].len = sizeof(chip->xfer_buf[1]) * len;
spi_message_add_tail(&xfer[1], &message);
error = spi_sync(spi, &message);
if (unlikely(error)) {
dev_err(chip->dev, "SPI read error: %d\n", error);
return error;
}
for (i = 0; i < len; i++)
data[i] = be16_to_cpu(chip->xfer_buf[i + 1]);
return 0;
你看到第一次add的是cmd，第二次add的是rbuf