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

From: Nathan Chancellor
Date: Sun Feb 13 2022 - 13:11:30 EST


On Fri, Feb 11, 2022 at 04:59:00AM +0000, Lh Kuo 郭力豪 wrote:
> 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;
> }

Clang will still warn that ret is uninitialized when the else if
branches are not taken.

How about something like:

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;

if (xfer->tx_buf && !xfer->rx_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);
dma_unmap_single(dev, xfer->tx_dma, xfer->len, DMA_TO_DEVICE);
} else if (xfer->rx_buf && !xfer->tx_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);
dma_unmap_single(dev, xfer->rx_dma, xfer->len, DMA_FROM_DEVICE);
} else {
dev_dbg(&ctlr->dev, "%s() wrong command\n", __func__);
return -EINVAL;
}

spi_finalize_current_transfer(ctlr);
return ret;
}