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

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

[Frank Li]

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>

[PATCH 1/2] dmaengine: Add helper macro dmaengine_prep_submit()

[Frank Li]

Previously, DMA users had to call dmaengine_prep_*() followed by
dmaengine_submit(). Many DMA consumers missed call dmaengine_desc_free()
when dmaengine_submit() returned an error.

Introduce dmaengine_prep_submit() to combine preparation and submission
into a single step and ensure the descriptor is freed on submission
failure.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 include/linux/dmaengine.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 99efe2b9b4ea9844ca6161208362ef18ef111d96..78246fd8a8294b6764d2717d73b9c49842f64696 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1249,6 +1249,22 @@ static inline dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc
 	return desc->tx_submit(desc);
 }
 
+#define dmaengine_prep_submit(chan, cb, cb_param, func, ...)	\
+({	struct dma_async_tx_descriptor *tx =			\
+		dmaengine_prep_##func(chan, __VA_ARGS__);	\
+	dma_cookie_t cookie = -ENOMEM;				\
+								\
+	if (tx) {						\
+		tx->callback = cb;				\
+		tx->callback_param = cb_param;			\
+		cookie = dmaengine_submit(tx);			\
+								\
+		if (dma_submit_error(cookie))			\
+			dmaengine_desc_free(tx);		\
+	}							\
+	cookie;							\
+})
+
 static inline bool dmaengine_check_align(enum dmaengine_alignment align,
 					 size_t off1, size_t off2, size_t len)
 {

-- 
2.34.1

[PATCH 2/2] i2c: imx-lpi2c: use dmaengine_prep_submit() to simple code

[Frank Li]

Use dmaengine_prep_submit() to simple code. No functional change.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 2a0962a0b441754577c15ef3a67a7640d41785cc..c9ad4c3a5c15e046d9e66050dcfd8a9379bf60df 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -720,7 +720,6 @@ static void lpi2c_dma_callback(void *data)
 
 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;
@@ -733,15 +732,10 @@ 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;
@@ -751,15 +745,9 @@ 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;
 }
 

-- 
2.34.1