[PATCH 0/2] dmaengine: add helper macro dmaengine_prep_submit()

Frank Li
2026-01-30T15:21:36Z

Add helper macro dmaengine_prep_submit() to combine prep and submit to
one call.

Pervious try to use cleanup
https://lore.kernel.org/dmaengine/20251002-dma_chan_free-v1-0-4dbf116c2b19@nxp.com/

It is not simple enough and easy missing retain_and_null_ptr() at success
path.

struct dma_async_tx_descriptor *rx_cmd_desc __free(dma_async_tx_descriptor) = NULL;
...
cookie = dmaengine_submit(rx_cmd_desc);
if (dma_submit_error(cookie))
return dma_submit_error(cookie);
...
retain_and_null_ptr(rx_cmd_desc);
}

So create help macro to combine prep and submit by one call.
patch 2.

static int lpi2c_dma_rx_cmd_submit(struct lpi2c_imx_struct *lpi2c_imx)
{
- struct dma_async_tx_descriptor *rx_cmd_desc;
struct lpi2c_imx_dma *dma = lpi2c_imx->dma;
struct dma_chan *txchan = dma->chan_tx;
dma_cookie_t cookie;
@@ -761,15 +760,10 @@ static int lpi2c_dma_rx_cmd_submit(struct lpi2c_imx_struct *lpi2c_imx)
return -EINVAL;
}

- rx_cmd_desc = dmaengine_prep_slave_single(txchan, dma->dma_tx_addr,
- dma->rx_cmd_buf_len, DMA_MEM_TO_DEV,
- DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
- if (!rx_cmd_desc) {
- dev_err(&lpi2c_imx->adapter.dev, "DMA prep slave sg failed, use pio\n");
- goto desc_prepare_err_exit;
- }
-
- cookie = dmaengine_submit(rx_cmd_desc);
+ cookie = dmaengine_prep_submit(txchan, NULL, NULL, slave_single,
+ dma->dma_tx_addr,
+ dma->rx_cmd_buf_len, DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (dma_submit_error(cookie)) {
dev_err(&lpi2c_imx->adapter.dev, "submitting DMA failed, use pio\n");
goto submit_err_exit;
@@ -779,15 +773,9 @@ static int lpi2c_dma_rx_cmd_submit(struct lpi2c_imx_struct *lpi2c_imx)

return 0;

-desc_prepare_err_exit:
- dma_unmap_single(txchan->device->dev, dma->dma_tx_addr,
- dma->rx_cmd_buf_len, DMA_TO_DEVICE);
- return -EINVAL;
-
submit_err_exit:
dma_unmap_single(txchan->device->dev, dma->dma_tx_addr,
dma->rx_cmd_buf_len, DMA_TO_DEVICE);
- dmaengine_desc_free(rx_cmd_desc);
return -EINVAL;
}

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Frank Li (2):
dmaengine: Add helper macro dmaengine_prep_submit()
i2c: imx-lpi2c: use dmaengine_prep_submit() to simple code

drivers/i2c/busses/i2c-imx-lpi2c.c | 20 ++++----------------
include/linux/dmaengine.h | 16 ++++++++++++++++
2 files changed, 20 insertions(+), 16 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20260130-dma_prep_submit-cbeac742de48

Best regards,
--
Frank Li <Frank.Li@nxp.com>