linux-kernel - [PATCH 0/2] dmaengine: add helper macro dmaengine_prep

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Message-Id: <20260130-dma_prep_submit-v1-0-2198f9e848fa@nxp.com>
Date: Fri, 30 Jan 2026 10:21:13 -0500
From: Frank Li <Frank.Li@....com>
To: Vinod Koul <vkoul@...nel.org>, Dong Aisheng <aisheng.dong@....com>, 
 Andi Shyti <andi.shyti@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-i2c@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, carlos.song@....com, 
 Frank Li <Frank.Li@....com>
Subject: [PATCH 0/2] dmaengine: add helper macro dmaengine_prep_submit()

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@....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@....com>