RE: [PATCH] spi: Fix warning for Clang build

[Lh Kuo 郭力豪]

Yes. I think the function can be simplified as follows

static int sp7021_spi_slave_transfer_one(struct spi_controller *ctlr, struct spi_device *spi,
				       struct spi_transfer *xfer)
{
	struct sp7021_spi_ctlr *pspim = spi_master_get_devdata(ctlr);
	struct device *dev = pspim->dev;
	int ret;

	mode = SP7021_SPI_IDLE;
	if (xfer->tx_buf && xfer->rx_buf) {
		dev_dbg(&ctlr->dev, "%s() wrong command\n", __func__);
		return -EINVAL;
	} else if (xfer->tx_buf) {
		xfer->tx_dma = dma_map_single(dev, (void *)xfer->tx_buf,
					      xfer->len, DMA_TO_DEVICE);
		if (dma_mapping_error(dev, xfer->tx_dma))
			return -ENOMEM;
		ret = sp7021_spi_slave_tx(spi, xfer);
	} else if (xfer->rx_buf) {
		xfer->rx_dma = dma_map_single(dev, xfer->rx_buf, xfer->len,
					      DMA_FROM_DEVICE);
		if (dma_mapping_error(dev, xfer->rx_dma))
			return -ENOMEM;
		ret = sp7021_spi_slave_rx(spi, xfer);
	}

	if (xfer->tx_buf)
		dma_unmap_single(dev, xfer->tx_dma, xfer->len, DMA_TO_DEVICE);
	if (xfer->rx_buf)
		dma_unmap_single(dev, xfer->rx_dma, xfer->len, DMA_FROM_DEVICE);

	spi_finalize_current_transfer(ctlr);
	return ret;
}