linux-kernel - [PATCH 09/11] dmaengine: add support for device

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Message-Id: <20250903-v6-16-topic-sdma-v1-9-ac7bab629e8b@pengutronix.de>
Date: Wed, 03 Sep 2025 15:06:17 +0200
From: Marco Felsch <m.felsch@...gutronix.de>
To: Vinod Koul <vkoul@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Jiada Wang <jiada_wang@...tor.com>
Cc: dmaengine@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Marco Felsch <m.felsch@...gutronix.de>
Subject: [PATCH 09/11] dmaengine: add support for device_link

Add support to create device_links between dmaengine suppliers and the
dma consumers. This shifts the device dep-chain teardown/bringup logic
to the driver core.

Moving this to the core allows the dmaengine drivers to simplify the
.remove() hooks and also to ensure that no dmaengine driver is ever
removed before the consumer is removed.

Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
---
 drivers/dma/dmaengine.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 758fcd0546d8bde8e8dddc6039848feeb1e24475..a50652bc70b8ce9d4edabfaa781b3432ee47d31e 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -817,6 +817,7 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
 	struct fwnode_handle *fwnode = dev_fwnode(dev);
 	struct dma_device *d, *_d;
 	struct dma_chan *chan = NULL;
+	struct device_link *dl;
 
 	if (is_of_node(fwnode))
 		chan = of_dma_request_slave_channel(to_of_node(fwnode), name);
@@ -858,6 +859,13 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
 	/* No functional issue if it fails, users are supposed to test before use */
 #endif
 
+	dl = device_link_add(dev, chan->device->dev, DL_FLAG_AUTOREMOVE_CONSUMER);
+	if (!dl) {
+		dev_err(dev, "failed to create device link to %s\n",
+			dev_name(chan->device->dev));
+		return ERR_PTR(-EINVAL);
+	}
+
 	chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
 	if (!chan->name)
 		return chan;

-- 
2.47.2