[PATCH] dmaengine: ti: omap-dma: turn lch_map into a flexible array

[Rosen Penev <rosenp@gmail.com>]

Convert the separately-allocated lch_map pointer array to a C99
flexible array member at the end of struct omap_dmadev and annotate it
with __counted_by(lch_count). The probe is reordered so platform_data
lookup and the lch_count determination happen before the parent
allocation, letting struct_size() size the FAM and the dedicated
devm_kcalloc() for lch_map go away.

Two allocations collapse into one and the runtime bounds checks from
__counted_by now apply to every lch_map[] access.

Assisted-by: Claude:Opus-4.7
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/dma/ti/omap-dma.c | 68 +++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 35 deletions(-)

diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
index 55ece7fd0d99..901e38b08962 100644
--- a/drivers/dma/ti/omap-dma.c
+++ b/drivers/dma/ti/omap-dma.c
@@ -57,7 +57,7 @@ struct omap_dmadev {
 	unsigned dma_requests;
 	spinlock_t irq_lock;
 	uint32_t irq_enable_mask;
-	struct omap_chan **lch_map;
+	struct omap_chan *lch_map[] __counted_by(lch_count);
 };
 
 struct omap_chan {
@@ -1656,36 +1656,53 @@ static const struct omap_dma_config default_cfg;
 static int omap_dma_probe(struct platform_device *pdev)
 {
 	const struct omap_dma_config *conf;
+	struct omap_system_dma_plat_info *plat;
 	struct omap_dmadev *od;
+	int lch_count;
 	int rc, i, irq;
 	u32 val;
 
-	od = devm_kzalloc(&pdev->dev, sizeof(*od), GFP_KERNEL);
-	if (!od)
-		return -ENOMEM;
-
-	od->base = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(od->base))
-		return PTR_ERR(od->base);
-
 	conf = of_device_get_match_data(&pdev->dev);
 	if (conf) {
-		od->cfg = conf;
-		od->plat = dev_get_platdata(&pdev->dev);
-		if (!od->plat) {
+		plat = dev_get_platdata(&pdev->dev);
+		if (!plat) {
 			dev_err(&pdev->dev, "omap_system_dma_plat_info is missing");
 			return -ENODEV;
 		}
 	} else if (IS_ENABLED(CONFIG_ARCH_OMAP1)) {
-		od->cfg = &default_cfg;
-
-		od->plat = omap_get_plat_info();
-		if (!od->plat)
+		plat = omap_get_plat_info();
+		if (!plat)
 			return -EPROBE_DEFER;
 	} else {
 		return -ENODEV;
 	}
 
+	/* Number of available logical channels */
+	if (!pdev->dev.of_node) {
+		lch_count = plat->dma_attr->lch_count;
+		if (unlikely(!lch_count))
+			lch_count = OMAP_SDMA_CHANNELS;
+	} else if (of_property_read_u32(pdev->dev.of_node, "dma-channels",
+					&lch_count)) {
+		dev_info(&pdev->dev,
+			 "Missing dma-channels property, using %u.\n",
+			 OMAP_SDMA_CHANNELS);
+		lch_count = OMAP_SDMA_CHANNELS;
+	}
+
+	od = devm_kzalloc(&pdev->dev, struct_size(od, lch_map, lch_count),
+			  GFP_KERNEL);
+	if (!od)
+		return -ENOMEM;
+
+	od->lch_count = lch_count;
+	od->plat = plat;
+	od->cfg = conf ? conf : &default_cfg;
+
+	od->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(od->base))
+		return PTR_ERR(od->base);
+
 	od->reg_map = od->plat->reg_map;
 
 	dma_cap_set(DMA_SLAVE, od->ddev.cap_mask);
@@ -1730,19 +1747,6 @@ static int omap_dma_probe(struct platform_device *pdev)
 			 OMAP_SDMA_REQUESTS);
 	}
 
-	/* Number of available logical channels */
-	if (!pdev->dev.of_node) {
-		od->lch_count = od->plat->dma_attr->lch_count;
-		if (unlikely(!od->lch_count))
-			od->lch_count = OMAP_SDMA_CHANNELS;
-	} else if (of_property_read_u32(pdev->dev.of_node, "dma-channels",
-					&od->lch_count)) {
-		dev_info(&pdev->dev,
-			 "Missing dma-channels property, using %u.\n",
-			 OMAP_SDMA_CHANNELS);
-		od->lch_count = OMAP_SDMA_CHANNELS;
-	}
-
 	/* Mask of allowed logical channels */
 	if (pdev->dev.of_node && !of_property_read_u32(pdev->dev.of_node,
 						       "dma-channel-mask",
@@ -1754,12 +1758,6 @@ static int omap_dma_probe(struct platform_device *pdev)
 	if (od->plat->dma_attr->dev_caps & HS_CHANNELS_RESERVED)
 		bitmap_set(od->lch_bitmap, 0, 2);
 
-	od->lch_map = devm_kcalloc(&pdev->dev, od->lch_count,
-				   sizeof(*od->lch_map),
-				   GFP_KERNEL);
-	if (!od->lch_map)
-		return -ENOMEM;
-
 	for (i = 0; i < od->dma_requests; i++) {
 		rc = omap_dma_chan_init(od);
 		if (rc) {
-- 
2.54.0