[PATCH v4 2/2] media: ipu-bridge: reuse the software nodes on rebind

["D. Manresa" <dmanresa@gmail.com>]

The software nodes are deliberately never unregistered so that a rebind
can reuse them, but ipu_bridge_init() only takes that path when the IPU
kept its secondary fwnode link. Removing and re-scanning the IPU PCI
device clears that link, so the next probe tries to register the IPU HID
node again and fails:

  sysfs: cannot create duplicate filename '/kernel/software_nodes/INT343E'
  intel-ipu6 0000:00:05.0: Failed to register the IPU HID node
  intel-ipu6: probe of 0000:00:05.0 failed with error -17

after which the cameras are unusable until reboot.

Look the registered node up instead and restore the device's secondary
fwnode.

Assisted-by: LLM
Fixes: 803abec64ef9 ("media: ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver")
Signed-off-by: D. Manresa <dmanresa@gmail.com>
---
 drivers/media/pci/intel/ipu-bridge.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/media/pci/intel/ipu-bridge.c b/drivers/media/pci/intel/ipu-bridge.c
index aea4699..a77ea60 100644
--- a/drivers/media/pci/intel/ipu-bridge.c
+++ b/drivers/media/pci/intel/ipu-bridge.c
@@ -1098,6 +1098,7 @@ static DEFINE_MUTEX(ipu_bridge_mutex);
 int ipu_bridge_init(struct device *dev,
 		    ipu_parse_sensor_fwnode_t parse_sensor_fwnode)
 {
+	const struct software_node *ipu_node;
 	struct fwnode_handle *fwnode;
 	struct ipu_bridge *bridge;
 	unsigned int i;
@@ -1108,6 +1109,22 @@ int ipu_bridge_init(struct device *dev,
 	if (!ipu_bridge_check_fwnode_graph(dev_fwnode(dev)))
 		return 0;
 
+	/*
+	 * The nodes registered by a previous bind are still there, but the
+	 * PCI remove/rescan cycle dropped the IPU's secondary fwnode link to
+	 * them. Registering them again would fail with -EEXIST, so reuse
+	 * them and restore just that link.
+	 */
+	ipu_node = software_node_find_by_name(NULL, IPU_HID);
+	if (ipu_node) {
+		fwnode = software_node_fwnode(ipu_node);
+		set_secondary_fwnode(dev, fwnode);
+		/* The node is never unregistered, no reference is needed. */
+		fwnode_handle_put(fwnode);
+		dev_dbg(dev, "Reusing the previously registered software nodes\n");
+		return 0;
+	}
+
 	if (!ipu_bridge_ivsc_is_ready())
 		return dev_err_probe(dev, -EPROBE_DEFER,
 				     "waiting for IVSC to become ready\n");
-- 
2.43.0