[PATCH v2] dmaengine: Use unique debugfs names

[Linus Walleij <linusw@kernel.org>]

DMA40 registers multiple dma_device instances for the same platform
device. The DMAengine debugfs code uses dev_name(dma_dev->dev) as the
directory name, so the second and third registrations try to create the
same directory and print duplicate-name warnings.

Keep the existing device-name directory for the first registration, but
use a dev_id-suffixed fallback when that name already exists.

Signed-off-by: Linus Walleij <linusw@kernel.org>
---
Fix duplicate direntry.
---
Changes in v2:
- Rebased on v7.4-rc1
- Link to v1: https://lore.kernel.org/r/20260918-dmaengine-fixes-v1-1-7e10da1633c1@kernel.org
---
 drivers/dma/dmaengine.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 34be53487a21..7eb8d53b4863 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -33,6 +33,7 @@
 
 #include <linux/acpi.h>
 #include <linux/acpi_dma.h>
+#include <linux/dcache.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
@@ -70,8 +71,24 @@ static struct dentry *rootdir;
 
 static void dmaengine_debug_register(struct dma_device *dma_dev)
 {
-	dma_dev->dbg_dev_root = debugfs_create_dir(dev_name(dma_dev->dev),
-						   rootdir);
+	const char *name = dev_name(dma_dev->dev);
+	struct dentry *dentry;
+	char *uniq;
+
+	dentry = debugfs_lookup(name, rootdir);
+	if (dentry) {
+		dput(dentry);
+
+		uniq = kasprintf(GFP_KERNEL, "%s.%d", name, dma_dev->dev_id);
+		if (!uniq)
+			return;
+
+		dma_dev->dbg_dev_root = debugfs_create_dir(uniq, rootdir);
+		kfree(uniq);
+	} else {
+		dma_dev->dbg_dev_root = debugfs_create_dir(name, rootdir);
+	}
+
 	if (IS_ERR(dma_dev->dbg_dev_root))
 		dma_dev->dbg_dev_root = NULL;
 }

---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20260918-dmaengine-fixes-5c893ce71049

Best regards,
-- 
Linus Walleij <linusw@kernel.org>