[PATCHv2] dmaengine: st_fdma: simplify allocation

[PATCHv2] dmaengine: st_fdma: simplify allocation

[Rosen Penev]

Use a flexible array member to combine kzalloc and kcalloc to a single
allocation.

Add __counted_by for extra runtime analysis. Assign counting variable
after allocation before any array accesses.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: update description.
 drivers/dma/st_fdma.c | 27 ++++++++-------------------
 drivers/dma/st_fdma.h |  4 ++--
 2 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/drivers/dma/st_fdma.c b/drivers/dma/st_fdma.c
index d9547017f3bd..3ec0d6731b8d 100644
--- a/drivers/dma/st_fdma.c
+++ b/drivers/dma/st_fdma.c
@@ -710,16 +710,6 @@ static const struct of_device_id st_fdma_match[] = {
 };
 MODULE_DEVICE_TABLE(of, st_fdma_match);

-static int st_fdma_parse_dt(struct platform_device *pdev,
-			const struct st_fdma_driverdata *drvdata,
-			struct st_fdma_dev *fdev)
-{
-	snprintf(fdev->fw_name, FW_NAME_SIZE, "fdma_%s_%d.elf",
-		drvdata->name, drvdata->id);
-
-	return of_property_read_u32(pdev->dev.of_node, "dma-channels",
-				    &fdev->nr_channels);
-}
 #define FDMA_DMA_BUSWIDTHS	(BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) | \
 				 BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) | \
 				 BIT(DMA_SLAVE_BUSWIDTH_3_BYTES) | \
@@ -742,27 +732,26 @@ static int st_fdma_probe(struct platform_device *pdev)
 	struct st_fdma_dev *fdev;
 	struct device_node *np = pdev->dev.of_node;
 	const struct st_fdma_driverdata *drvdata;
+	u32 nr_channels;
 	int ret, i;

 	drvdata = device_get_match_data(&pdev->dev);

-	fdev = devm_kzalloc(&pdev->dev, sizeof(*fdev), GFP_KERNEL);
-	if (!fdev)
-		return -ENOMEM;
-
-	ret = st_fdma_parse_dt(pdev, drvdata, fdev);
+	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels", &nr_channels);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to find platform data\n");
-		goto err;
+		return ret;
 	}

-	fdev->chans = devm_kcalloc(&pdev->dev, fdev->nr_channels,
-				   sizeof(struct st_fdma_chan), GFP_KERNEL);
-	if (!fdev->chans)
+	fdev = devm_kzalloc(&pdev->dev, struct_size(fdev, chans, nr_channels), GFP_KERNEL);
+	if (!fdev)
 		return -ENOMEM;

+	fdev->nr_channels = nr_channels;
 	fdev->dev = &pdev->dev;
 	fdev->drvdata = drvdata;
+	snprintf(fdev->fw_name, FW_NAME_SIZE, "fdma_%s_%d.elf", drvdata->name, drvdata->id);
+
 	platform_set_drvdata(pdev, fdev);

 	fdev->irq = platform_get_irq(pdev, 0);
diff --git a/drivers/dma/st_fdma.h b/drivers/dma/st_fdma.h
index f1e746f7bc7d..27ded555879f 100644
--- a/drivers/dma/st_fdma.h
+++ b/drivers/dma/st_fdma.h
@@ -136,13 +136,13 @@ struct st_fdma_dev {

 	int irq;

-	struct st_fdma_chan *chans;
-
 	spinlock_t dreq_lock;
 	unsigned long dreq_mask;

 	u32 nr_channels;
 	char fw_name[FW_NAME_SIZE];
+
+	struct st_fdma_chan chans[] __counted_by(nr_channels);
 };

 /* Peripheral Registers*/
--
2.54.0