Subject: [PATCH v2 0/2] dmaengine: add helper macro dmaengine_prep_submit()

From: [email-masked]
Date: Fri, 22 May 2026 16:13:30 -0400

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

Pervious try to use cleanup
https://lore.kernel.org/dmaengine/[email-masked]/

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 <[email-masked]>
---
Changes in v2:
- use API dmaengine_prep_submit_slave_single()
- Link to v1: https://lore.kernel.org/r/[email-masked]

---
Frank Li (2):
      dmaengine: Add helper dmaengine_prep_submit_slave_single()
      i2c: imx-lpi2c: use dmaengine_prep_submit() to simple code

 drivers/dma/dmaengine.c            | 28 ++++++++++++++++++++++++++++
 drivers/i2c/busses/i2c-imx-lpi2c.c | 21 +++++----------------
 include/linux/dmaengine.h          | 17 +++++++++++++++++
 3 files changed, 50 insertions(+), 16 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20260130-dma_prep_submit-cbeac742de48

Best regards,
--  
Frank Li <[email-masked]>