Claude review: drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()

Claude review: drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

**Status: Good**

This patch takes the approach of moving to `bridge.next_bridge` (the auto-put field in `struct drm_bridge`), removing the separate `next_bridge` pointer from the driver's private struct. All usages of `priv->next_bridge` are converted to `priv->bridge.next_bridge`. This is the cleanest approach for bridge drivers that store the downstream bridge pointer for their lifetime.

The `bridge.next_bridge` field is documented as "automatically put when this bridge is freed", so no explicit cleanup is needed.

---
Generated by Claude Code Patch Reviewer

[PATCH v6 00/11] drm/bridge: handle refcounting for bridge-only callers of drm_of_find_panel_or_bridge()

[Luca Ceresoli]

This series converts all the bridge-only callers of the deprecated
drm_of_find_panel_or_bridge() API to a new, simpler API that handles bridge
refcounting.

All patches acked/reviewed except patches 3 and 4.

== Series description

 * Patch 1 (new in v2) makes drm_bridge_put() ignore ERR_PTR pointers,
   not only NULL pointers
 * Patch 2 introduces of_drm_get_bridge_by_endpoint() as a replacement for
   bridge-only calls to drm_of_find_panel_or_bridge(); the new function
   refcounts the bridge and is simpler
 * The following patches convert all bridge-only users to the new API
 * The last patch forbids new bridge-only calls to
   drm_of_find_panel_or_bridge()

== Grand plan

This is part of the work to support hotplug of DRM bridges. The grand plan
was discussed in [0].

Here's the work breakdown (➜ marks the current series):

 1. ➜ add refcounting to DRM bridges struct drm_bridge,
      based on devm_drm_bridge_alloc()
    A. ✔ add new alloc API and refcounting (v6.16)
    B. ✔ convert all bridge drivers to new API (v6.17)
    C. ✔ kunit tests (v6.17)
    D. ✔ add get/put to drm_bridge_add/remove() + attach/detach()
         and warn on old allocation pattern (v6.17)
    E. ➜ add get/put on drm_bridge accessors
       1. ✔ drm_bridge_chain_get_first_bridge(), add cleanup action (v6.18)
       2. ✔ drm_bridge_get_prev_bridge() (v6.18)
       3. ✔ drm_bridge_get_next_bridge() (v6.19)
       4. ✔ drm_for_each_bridge_in_chain() (v6.19)
       5. ✔ drm_bridge_connector_init (v6.19)
       6. ✔ protect encoder bridge chain with a mutex (v7.2)
       7. ➜ of_drm_find_bridge
          a. ✔ add of_drm_get_bridge() (v7.0),
               convert basic direct users (v7.0-v7.1)
          b. ✔ convert direct of_drm_get_bridge() users, part 2 (v7.0)
          c. ✔ convert direct of_drm_get_bridge() users, part 3 (v7.0)
          d. ✔ convert direct of_drm_get_bridge() users, part 4 (v7.1-v7.2)
          e. ➜ convert bridge-only drm_of_find_panel_or_bridge() users
       8. drm_of_find_panel_or_bridge, *_of_get_bridge
       9. ✔ enforce drm_bridge_add before drm_bridge_attach (v6.19)
    F. ✔ debugfs improvements
       1. ✔ add top-level 'bridges' file (v6.16)
       2. ✔ show refcount and list lingering bridges (v6.19)
 2. … handle gracefully atomic updates during bridge removal
    A. ✔ Add drm_bridge_enter/exit() to protect device resources (v7.0)
    B. … protect private_obj removal from list
    C. ✔ Add drm_bridge_clear_and_put() (v7.1)
 3. … DSI host-device driver interaction
 4. ✔ removing the need for the "always-disconnected" connector
 5. ✔ Migrate i.MX LCDIF driver to bridge-connector (v7.2)
 6. … DRM bridge hotplug
    A. … Bridge hotplug management in the DRM core
       1. ✔ bridge-connector: attach encoder to the connector (v7.2)
    B.   Device tree description

[0] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/#t

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Changes in v6:
- Patch 2: fix warning in the no-OF case 
- Patch 3: fix too-late next_bridge assignment
- Link to v5: https://patch.msgid.link/20260507-drm-bridge-alloc-getput-panel_or_bridge-v5-0-472b913b5cb7@bootlin.com

Changes in v5:
- Patch 1: change drm_bridge_put() only
- Patches 3,10: simplify error management code flow
- Link to v4: https://patch.msgid.link/20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-0-b578c3daaf10@bootlin.com

Changes in v4:
- Fixed patches 3 and 10
- Minor fixes to patches 1 and 2
- Removed bouncing addresses yongqin.liu@linaro.org and
  xinliang.liu@linaro.org from Cc
- Link to v3: https://patch.msgid.link/20260428-drm-bridge-alloc-getput-panel_or_bridge-v3-0-a537b5567add@bootlin.com

Changes in v3:
- patch 3, 8, 10: fixed ERR_PTR deref in the -ENODEV case, and removed
  Dmitry's R-by from those patches as they are changed
- Added review trailers to the other patches
- Link to v2: https://patch.msgid.link/20260428-drm-bridge-alloc-getput-panel_or_bridge-v2-0-4300744a1c47@bootlin.com

Changes in v2:
- Added patch to ignore ERR_PTR values in drm_bridge_get/put()
- Changed API to return the bridge (or a ERR_PTR) in the return value,
  not as a double-pointer output parameter
- Adapted all patches to the new API, dropped Dmitry's review tags as the
  patches are all modified
- Removed bouncing addresses from Cc list
- Link to v1: https://patch.msgid.link/20260413-drm-bridge-alloc-getput-panel_or_bridge-v1-0-acd01cd79a1f@bootlin.com

---
Luca Ceresoli (11):
      drm/bridge: drm_bridge_put(): ignore ERR_PTR
      drm/bridge: add of_drm_get_bridge_by_endpoint()
      drm/msm/hdmi: switch to of_drm_get_bridge_by_endpoint()
      drm/hisilicon/kirin: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lontium-lt9611uxc: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lt9611: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: adv7511: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lt8713sx: switch to of_drm_get_bridge_by_endpoint()
      drm: zynqmp_dp: switch to of_drm_get_bridge_by_endpoint()
      drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

 drivers/gpu/drm/bridge/adv7511/adv7511.h     |  1 -
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 15 +++---
 drivers/gpu/drm/bridge/chrontel-ch7033.c     | 28 ++++++-----
 drivers/gpu/drm/bridge/lontium-lt8713sx.c    | 10 ++--
 drivers/gpu/drm/bridge/lontium-lt9611.c      |  9 ++--
 drivers/gpu/drm/bridge/lontium-lt9611uxc.c   |  9 ++--
 drivers/gpu/drm/drm_bridge.c                 | 45 +++++++++++++++++-
 drivers/gpu/drm/drm_of.c                     | 26 +++++------
 drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c |  9 ++--
 drivers/gpu/drm/msm/hdmi/hdmi.c              | 70 +++++++++++++++++++---------
 drivers/gpu/drm/xlnx/zynqmp_dp.c             | 19 ++++----
 include/drm/drm_bridge.h                     |  7 +++
 12 files changed, 162 insertions(+), 86 deletions(-)
---
base-commit: 7af78cfbe2b47cd9ecb61480fb74d64b584d8a94
change-id: 20260410-drm-bridge-alloc-getput-panel_or_bridge-42501b38eaad

Best regards,
--  
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[PATCH v6 01/11] drm/bridge: drm_bridge_put(): ignore ERR_PTR

[Luca Ceresoli]

Most functions returning a struct drm_bridge pointer currently return a
valid pointer or NULL, but this restricts their ability to return an error
code as an ERR_PTR describing the error kind.

In preparation to have new APIs that can return a struct drm_bridge pointer
holding an ERR_PTR (and for those which already do) make drm_bridge_put()
ignore ERR_PTR values, just like it ignores NULL pointers.

This will avoid annoying error checking in many places and the risk of
missing error checks.

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/all/20260318152533.GA633439@killaraus.ideasonboard.com/
Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/all/omlnswxukeqgnatzdvooaashgkfcacjevkvbkm6xt33itgua2k@jcmzll2w6kdq/
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Changes in v5:
- don't change drm_bridge_get(), only drm_bridge_put() has known use cases

Changes in v4:
- removed incorrect change to drm_bridge_clear_and_put() kdoc

Patch added in v2
---
 drivers/gpu/drm/drm_bridge.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index ce180f0b26b2..b46c01db8d83 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -300,7 +300,7 @@ EXPORT_SYMBOL(drm_bridge_get);
 
 /**
  * drm_bridge_put - Release a bridge reference
- * @bridge: DRM bridge; if NULL this function does nothing
+ * @bridge: DRM bridge; if NULL or an ERR_PTR this function does nothing
  *
  * This function decrements the bridge's reference count and frees the
  * object if the reference count drops to zero.
@@ -310,7 +310,7 @@ EXPORT_SYMBOL(drm_bridge_get);
  */
 void drm_bridge_put(struct drm_bridge *bridge)
 {
-	if (bridge)
+	if (!IS_ERR_OR_NULL(bridge))
 		kref_put(&bridge->refcount, __drm_bridge_free);
 }
 EXPORT_SYMBOL(drm_bridge_put);

-- 
2.54.0

[PATCH v6 02/11] drm/bridge: add of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

drm_of_find_panel_or_bridge() is widely used, but many callers pass NULL
into the @panel or the @bridge arguments, thus making a very partial usage
of this rather complex function.

Besides, the bridge returned in @bridge is not refcounted, thus making this
API unsafe when DRM bridge hotplug will be introduced.

Solve both issues for the cases of calls to drm_of_find_panel_or_bridge()
with a NULL @panel pointer by adding a new function that only looks for
bridges (and is thus much simpler) and increments the refcount of the
returned bridge.

The new function is identical to drm_of_find_panel_or_bridge() except it:

 - handles bridge refcounting: uses of_drm_find_and_get_bridge() instead of
   of_drm_find_bridge() internally to return a refcounted bridge
 - is simpler to use: just takes no @panel parameter, returns the pointer
   in the return value instead of a double pointer argument
 - has a simpler implementation: it is equal to
   drm_of_find_panel_or_bridge() after removing the code that becomes dead
   when @panel == NULL

Also add this function to drm_bridge.c and not drm_of.c because it returns
bridges only.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Changes in v5:
- add missing ERR_PTR() in return statement for no-OF inline variant

Changes in v4:
- update function declaration in non-OF case
- fix grammar in comment

Changes in v2:
- return the bridge in the return value, not a double pointer
---
 drivers/gpu/drm/drm_bridge.c | 41 +++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_bridge.h     |  7 +++++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index b46c01db8d83..687b36eea0c7 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -1582,6 +1582,47 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np)
 	return bridge;
 }
 EXPORT_SYMBOL(of_drm_find_bridge);
+
+/**
+ * of_drm_get_bridge_by_endpoint - return DRM bridge connected to a port/endpoint
+ * @np: device tree node containing output ports
+ * @port: port in the device tree node, or -1 for the first port found
+ * @endpoint: endpoint in the device tree node, or -1 for the first endpoint found
+ *
+ * Given a DT node's port and endpoint number, find the connected node and
+ * return the associated drm_bridge device.
+ *
+ * The refcount of the returned bridge is incremented. Use drm_bridge_put()
+ * when done with it.
+ *
+ * Returns a pointer to the connected drm_bridge, or a negative error on failure
+ */
+struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
+						 int port, int endpoint)
+{
+	struct drm_bridge *bridge;
+
+	/*
+	 * of_graph_get_remote_node() produces a noisy error message if port
+	 * node isn't found and the absence of the port is a legit case here,
+	 * so at first we silently check whether graph is present in the
+	 * device-tree node.
+	 */
+	if (!of_graph_is_present(np))
+		return ERR_PTR(-ENODEV);
+
+	struct device_node *remote __free(device_node) =
+		of_graph_get_remote_node(np, port, endpoint);
+	if (!remote)
+		return ERR_PTR(-ENODEV);
+
+	bridge = of_drm_find_and_get_bridge(remote);
+	if (!bridge)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	return bridge;
+}
+EXPORT_SYMBOL_GPL(of_drm_get_bridge_by_endpoint);
 #endif
 
 /**
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index fdac9a526f38..4ba3a5deef9a 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -1327,6 +1327,8 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 #ifdef CONFIG_OF
 struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np);
 struct drm_bridge *of_drm_find_bridge(struct device_node *np);
+struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
+						 int port, int endpoint);
 #else
 static inline struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np)
 {
@@ -1336,6 +1338,11 @@ static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np)
 {
 	return NULL;
 }
+static inline struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
+							       int port, int endpoint)
+{
+	return ERR_PTR(-ENODEV);
+}
 #endif
 
 static inline bool drm_bridge_is_last(struct drm_bridge *bridge)

-- 
2.54.0

[PATCH v6 03/11] drm/msm/hdmi: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

---

Changes in v6:
- move assignment of next_bridge earlier (avoid access before assignment)

Changes in v5:
- simplify error management code flow

Changes in v4:
- ensure next_bridge is put on later probe failures

Changes in v3:
- fix ERR_PTR deref when -ENODEV is returned

- move assignment of next_bridge earlier (avoid access before assignment)
---
 drivers/gpu/drm/msm/hdmi/hdmi.c | 70 +++++++++++++++++++++++++++--------------
 1 file changed, 47 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/msm/hdmi/hdmi.c b/drivers/gpu/drm/msm/hdmi/hdmi.c
index d9491aac1a89..474006084633 100644
--- a/drivers/gpu/drm/msm/hdmi/hdmi.c
+++ b/drivers/gpu/drm/msm/hdmi/hdmi.c
@@ -285,19 +285,27 @@ static int msm_hdmi_dev_probe(struct platform_device *pdev)
 	spin_lock_init(&hdmi->reg_lock);
 	mutex_init(&hdmi->state_mutex);
 
-	ret = drm_of_find_panel_or_bridge(dev_of_node(dev), 1, 0, NULL, &hdmi->next_bridge);
-	if (ret && ret != -ENODEV)
-		return ret;
+	hdmi->next_bridge = of_drm_get_bridge_by_endpoint(dev_of_node(dev), 1, 0);
+	if (IS_ERR(hdmi->next_bridge)) {
+		if (PTR_ERR(hdmi->next_bridge) != -ENODEV)
+			return PTR_ERR(hdmi->next_bridge);
+
+		hdmi->next_bridge = NULL;
+	}
 
 	hdmi->mmio = msm_ioremap(pdev, "core_physical");
-	if (IS_ERR(hdmi->mmio))
-		return PTR_ERR(hdmi->mmio);
+	if (IS_ERR(hdmi->mmio)) {
+		ret = PTR_ERR(hdmi->mmio);
+		goto err_put_bridge;
+	}
 
 	/* HDCP needs physical address of hdmi register */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
 		"core_physical");
-	if (!res)
-		return -EINVAL;
+	if (!res) {
+		ret = -EINVAL;
+		goto err_put_bridge;
+	}
 	hdmi->mmio_phy_addr = res->start;
 
 	hdmi->qfprom_mmio = msm_ioremap(pdev, "qfprom_physical");
@@ -307,45 +315,58 @@ static int msm_hdmi_dev_probe(struct platform_device *pdev)
 	}
 
 	hdmi->irq = platform_get_irq(pdev, 0);
-	if (hdmi->irq < 0)
-		return hdmi->irq;
+	if (hdmi->irq < 0) {
+		ret = hdmi->irq;
+		goto err_put_bridge;
+	}
 
 	hdmi->pwr_regs = devm_kcalloc(dev, config->pwr_reg_cnt,
 				      sizeof(hdmi->pwr_regs[0]),
 				      GFP_KERNEL);
-	if (!hdmi->pwr_regs)
-		return -ENOMEM;
+	if (!hdmi->pwr_regs) {
+		ret = -ENOMEM;
+		goto err_put_bridge;
+	}
 
 	for (i = 0; i < config->pwr_reg_cnt; i++)
 		hdmi->pwr_regs[i].supply = config->pwr_reg_names[i];
 
 	ret = devm_regulator_bulk_get(dev, config->pwr_reg_cnt, hdmi->pwr_regs);
-	if (ret)
-		return dev_err_probe(dev, ret, "failed to get pwr regulators\n");
+	if (ret) {
+		dev_err_probe(dev, ret, "failed to get pwr regulators\n");
+		goto err_put_bridge;
+	}
 
 	hdmi->pwr_clks = devm_kcalloc(dev, config->pwr_clk_cnt,
 				      sizeof(hdmi->pwr_clks[0]),
 				      GFP_KERNEL);
-	if (!hdmi->pwr_clks)
-		return -ENOMEM;
+	if (!hdmi->pwr_clks) {
+		ret = -ENOMEM;
+		goto err_put_bridge;
+	}
 
 	for (i = 0; i < config->pwr_clk_cnt; i++)
 		hdmi->pwr_clks[i].id = config->pwr_clk_names[i];
 
 	ret = devm_clk_bulk_get(dev, config->pwr_clk_cnt, hdmi->pwr_clks);
 	if (ret)
-		return ret;
+		goto err_put_bridge;
+
 
 	hdmi->extp_clk = devm_clk_get_optional(dev, "extp");
-	if (IS_ERR(hdmi->extp_clk))
-		return dev_err_probe(dev, PTR_ERR(hdmi->extp_clk),
-				     "failed to get extp clock\n");
+	if (IS_ERR(hdmi->extp_clk)) {
+		ret = dev_err_probe(dev, PTR_ERR(hdmi->extp_clk),
+				    "failed to get extp clock\n");
+		goto err_put_bridge;
+	}
 
 	hdmi->hpd_gpiod = devm_gpiod_get_optional(dev, "hpd", GPIOD_IN);
 	/* This will catch e.g. -EPROBE_DEFER */
-	if (IS_ERR(hdmi->hpd_gpiod))
-		return dev_err_probe(dev, PTR_ERR(hdmi->hpd_gpiod),
-				     "failed to get hpd gpio\n");
+	if (IS_ERR(hdmi->hpd_gpiod)) {
+		ret = dev_err_probe(dev, PTR_ERR(hdmi->hpd_gpiod),
+				    "failed to get hpd gpio\n");
+		goto err_put_bridge;
+	}
 
 	if (!hdmi->hpd_gpiod)
 		DBG("failed to get HPD gpio");
@@ -355,7 +376,7 @@ static int msm_hdmi_dev_probe(struct platform_device *pdev)
 
 	ret = msm_hdmi_get_phy(hdmi);
 	if (ret)
-		return ret;
+		goto err_put_bridge;
 
 	ret = devm_pm_runtime_enable(dev);
 	if (ret)
@@ -371,6 +392,8 @@ static int msm_hdmi_dev_probe(struct platform_device *pdev)
 
 err_put_phy:
 	msm_hdmi_put_phy(hdmi);
+err_put_bridge:
+	drm_bridge_put(hdmi->next_bridge);
 	return ret;
 }
 
@@ -381,6 +404,7 @@ static void msm_hdmi_dev_remove(struct platform_device *pdev)
 	component_del(&pdev->dev, &msm_hdmi_ops);
 
 	msm_hdmi_put_phy(hdmi);
+	drm_bridge_put(hdmi->next_bridge);
 }
 
 static int msm_hdmi_runtime_suspend(struct device *dev)

-- 
2.54.0

[PATCH v6 04/11] drm/hisilicon/kirin: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. Here the bridge pointer is
only stored in a temporary variable, so a cleanup action is enough.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c b/drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c
index e80debdc4176..ab3cd309505a 100644
--- a/drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c
+++ b/drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c
@@ -778,17 +778,16 @@ static int dsi_host_init(struct device *dev, struct dw_dsi *dsi)
 static int dsi_bridge_init(struct drm_device *dev, struct dw_dsi *dsi)
 {
 	struct drm_encoder *encoder = &dsi->encoder;
-	struct drm_bridge *bridge;
+	struct drm_bridge *bridge __free(drm_bridge_put) = NULL;
 	struct device_node *np = dsi->dev->of_node;
-	int ret;
 
 	/*
 	 * Get the endpoint node. In our case, dsi has one output port1
 	 * to which the external HDMI bridge is connected.
 	 */
-	ret = drm_of_find_panel_or_bridge(np, 1, 0, NULL, &bridge);
-	if (ret)
-		return ret;
+	bridge = of_drm_get_bridge_by_endpoint(np, 1, 0);
+	if (IS_ERR(bridge))
+		return PTR_ERR(bridge);
 
 	/* associate the bridge to dsi encoder */
 	return drm_bridge_attach(encoder, bridge, NULL, 0);

-- 
2.54.0

[PATCH v6 05/11] drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/bridge/chrontel-ch7033.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/bridge/chrontel-ch7033.c b/drivers/gpu/drm/bridge/chrontel-ch7033.c
index 54d49d4882c8..a237c65ebd69 100644
--- a/drivers/gpu/drm/bridge/chrontel-ch7033.c
+++ b/drivers/gpu/drm/bridge/chrontel-ch7033.c
@@ -199,7 +199,6 @@ enum {
 
 struct ch7033_priv {
 	struct regmap *regmap;
-	struct drm_bridge *next_bridge;
 	struct drm_bridge bridge;
 	struct drm_connector connector;
 };
@@ -215,7 +214,7 @@ static enum drm_connector_status ch7033_connector_detect(
 {
 	struct ch7033_priv *priv = conn_to_ch7033_priv(connector);
 
-	return drm_bridge_detect(priv->next_bridge, connector);
+	return drm_bridge_detect(priv->bridge.next_bridge, connector);
 }
 
 static const struct drm_connector_funcs ch7033_connector_funcs = {
@@ -233,7 +232,7 @@ static int ch7033_connector_get_modes(struct drm_connector *connector)
 	const struct drm_edid *drm_edid;
 	int ret;
 
-	drm_edid = drm_bridge_edid_read(priv->next_bridge, connector);
+	drm_edid = drm_bridge_edid_read(priv->bridge.next_bridge, connector);
 	drm_edid_connector_update(connector, drm_edid);
 	if (drm_edid) {
 		ret = drm_edid_connector_add_modes(connector);
@@ -275,7 +274,7 @@ static int ch7033_bridge_attach(struct drm_bridge *bridge,
 	struct drm_connector *connector = &priv->connector;
 	int ret;
 
-	ret = drm_bridge_attach(encoder, priv->next_bridge, bridge,
+	ret = drm_bridge_attach(encoder, priv->bridge.next_bridge, bridge,
 				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
 	if (ret)
 		return ret;
@@ -283,15 +282,15 @@ static int ch7033_bridge_attach(struct drm_bridge *bridge,
 	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
 		return 0;
 
-	if (priv->next_bridge->ops & DRM_BRIDGE_OP_DETECT) {
+	if (priv->bridge.next_bridge->ops & DRM_BRIDGE_OP_DETECT) {
 		connector->polled = DRM_CONNECTOR_POLL_HPD;
 	} else {
 		connector->polled = DRM_CONNECTOR_POLL_CONNECT |
 				    DRM_CONNECTOR_POLL_DISCONNECT;
 	}
 
-	if (priv->next_bridge->ops & DRM_BRIDGE_OP_HPD) {
-		drm_bridge_hpd_enable(priv->next_bridge, ch7033_hpd_event,
+	if (priv->bridge.next_bridge->ops & DRM_BRIDGE_OP_HPD) {
+		drm_bridge_hpd_enable(priv->bridge.next_bridge, ch7033_hpd_event,
 				      priv);
 	}
 
@@ -299,8 +298,8 @@ static int ch7033_bridge_attach(struct drm_bridge *bridge,
 				 &ch7033_connector_helper_funcs);
 	ret = drm_connector_init_with_ddc(bridge->dev, &priv->connector,
 					  &ch7033_connector_funcs,
-					  priv->next_bridge->type,
-					  priv->next_bridge->ddc);
+					  priv->bridge.next_bridge->type,
+					  priv->bridge.next_bridge->ddc);
 	if (ret) {
 		DRM_ERROR("Failed to initialize connector\n");
 		return ret;
@@ -313,8 +312,8 @@ static void ch7033_bridge_detach(struct drm_bridge *bridge)
 {
 	struct ch7033_priv *priv = bridge_to_ch7033_priv(bridge);
 
-	if (priv->next_bridge->ops & DRM_BRIDGE_OP_HPD)
-		drm_bridge_hpd_disable(priv->next_bridge);
+	if (priv->bridge.next_bridge->ops & DRM_BRIDGE_OP_HPD)
+		drm_bridge_hpd_disable(priv->bridge.next_bridge);
 	drm_connector_cleanup(&priv->connector);
 }
 
@@ -543,10 +542,9 @@ static int ch7033_probe(struct i2c_client *client)
 
 	dev_set_drvdata(dev, priv);
 
-	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1, NULL,
-					  &priv->next_bridge);
-	if (ret)
-		return ret;
+	priv->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node, 1, -1);
+	if (IS_ERR(priv->bridge.next_bridge))
+		return PTR_ERR(priv->bridge.next_bridge);
 
 	priv->regmap = devm_regmap_init_i2c(client, &ch7033_regmap_config);
 	if (IS_ERR(priv->regmap)) {

-- 
2.54.0

[PATCH v6 06/11] drm/bridge: lontium-lt9611uxc: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/bridge/lontium-lt9611uxc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
index 11aab07d88df..9427cc2358ae 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
@@ -35,7 +35,6 @@
 struct lt9611uxc {
 	struct device *dev;
 	struct drm_bridge bridge;
-	struct drm_bridge *next_bridge;
 
 	struct regmap *regmap;
 	/* Protects all accesses to registers by stopping the on-chip MCU */
@@ -284,7 +283,7 @@ static int lt9611uxc_bridge_attach(struct drm_bridge *bridge,
 {
 	struct lt9611uxc *lt9611uxc = bridge_to_lt9611uxc(bridge);
 
-	return drm_bridge_attach(encoder, lt9611uxc->next_bridge,
+	return drm_bridge_attach(encoder, lt9611uxc->bridge.next_bridge,
 				 bridge, flags);
 }
 
@@ -487,7 +486,11 @@ static int lt9611uxc_parse_dt(struct device *dev,
 
 	lt9611uxc->dsi1_node = of_graph_get_remote_node(dev->of_node, 1, -1);
 
-	return drm_of_find_panel_or_bridge(dev->of_node, 2, -1, NULL, &lt9611uxc->next_bridge);
+	lt9611uxc->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node, 2, -1);
+	if (IS_ERR(lt9611uxc->bridge.next_bridge))
+		return PTR_ERR(lt9611uxc->bridge.next_bridge);
+
+	return 0;
 }
 
 static int lt9611uxc_gpio_init(struct lt9611uxc *lt9611uxc)

-- 
2.54.0

[PATCH v6 07/11] drm/bridge: lt9611: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/bridge/lontium-lt9611.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index 0f49b13193b9..21305296e111 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -37,7 +37,6 @@
 struct lt9611 {
 	struct device *dev;
 	struct drm_bridge bridge;
-	struct drm_bridge *next_bridge;
 
 	struct regmap *regmap;
 
@@ -761,7 +760,7 @@ static int lt9611_bridge_attach(struct drm_bridge *bridge,
 {
 	struct lt9611 *lt9611 = bridge_to_lt9611(bridge);
 
-	return drm_bridge_attach(encoder, lt9611->next_bridge,
+	return drm_bridge_attach(encoder, lt9611->bridge.next_bridge,
 				 bridge, flags);
 }
 
@@ -1058,7 +1057,11 @@ static int lt9611_parse_dt(struct device *dev,
 
 	lt9611->ac_mode = of_property_read_bool(dev->of_node, "lt,ac-mode");
 
-	return drm_of_find_panel_or_bridge(dev->of_node, 2, -1, NULL, &lt9611->next_bridge);
+	lt9611->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node, 2, -1);
+	if (IS_ERR(lt9611->bridge.next_bridge))
+		return PTR_ERR(lt9611->bridge.next_bridge);
+
+	return 0;
 }
 
 static int lt9611_gpio_init(struct lt9611 *lt9611)

-- 
2.54.0

[PATCH v6 08/11] drm/bridge: adv7511: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Changes in v3:
- fix ERR_PTR deref when -ENODEV is returned
---
 drivers/gpu/drm/bridge/adv7511/adv7511.h     |  1 -
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 15 +++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511.h b/drivers/gpu/drm/bridge/adv7511/adv7511.h
index 8be7266fd4f4..12c95198d9a4 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511.h
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h
@@ -354,7 +354,6 @@ struct adv7511 {
 	enum drm_connector_status status;
 	bool powered;
 
-	struct drm_bridge *next_bridge;
 	struct drm_display_mode curr_mode;
 
 	unsigned int f_tmds;
diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 821a3008a1e7..02f8f7e78a16 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -849,8 +849,8 @@ static int adv7511_bridge_attach(struct drm_bridge *bridge,
 	struct adv7511 *adv = bridge_to_adv7511(bridge);
 	int ret = 0;
 
-	if (adv->next_bridge) {
-		ret = drm_bridge_attach(encoder, adv->next_bridge, bridge,
+	if (adv->bridge.next_bridge) {
+		ret = drm_bridge_attach(encoder, adv->bridge.next_bridge, bridge,
 					flags | DRM_BRIDGE_ATTACH_NO_CONNECTOR);
 		if (ret)
 			return ret;
@@ -1249,10 +1249,13 @@ static int adv7511_probe(struct i2c_client *i2c)
 
 	memset(&link_config, 0, sizeof(link_config));
 
-	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1, NULL,
-					  &adv7511->next_bridge);
-	if (ret && ret != -ENODEV)
-		return ret;
+	adv7511->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node, 1, -1);
+	if (IS_ERR(adv7511->bridge.next_bridge)) {
+		if (PTR_ERR(adv7511->bridge.next_bridge) == -ENODEV)
+			adv7511->bridge.next_bridge = NULL;
+		else
+			return PTR_ERR(adv7511->bridge.next_bridge);
+	}
 
 	if (adv7511->info->link_config)
 		ret = adv7511_parse_dt(dev->of_node, &link_config);

-- 
2.54.0

[PATCH v6 09/11] drm/bridge: lt8713sx: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/bridge/lontium-lt8713sx.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt8713sx.c b/drivers/gpu/drm/bridge/lontium-lt8713sx.c
index 18fac6a46db4..cee485adf5e5 100644
--- a/drivers/gpu/drm/bridge/lontium-lt8713sx.c
+++ b/drivers/gpu/drm/bridge/lontium-lt8713sx.c
@@ -32,7 +32,6 @@ DECLARE_CRC8_TABLE(lt8713sx_crc_table);
 struct lt8713sx {
 	struct device *dev;
 	struct drm_bridge bridge;
-	struct drm_bridge *next_bridge;
 
 	struct regmap *regmap;
 	/* Protects all accesses to registers by stopping the on-chip MCU */
@@ -458,7 +457,7 @@ static int lt8713sx_bridge_attach(struct drm_bridge *bridge,
 	struct lt8713sx *lt8713sx = container_of(bridge, struct lt8713sx, bridge);
 
 	return drm_bridge_attach(encoder,
-				lt8713sx->next_bridge,
+				lt8713sx->bridge.next_bridge,
 				bridge, flags);
 }
 
@@ -537,10 +536,9 @@ static int lt8713sx_probe(struct i2c_client *client)
 	if (IS_ERR(lt8713sx->regmap))
 		return dev_err_probe(dev, PTR_ERR(lt8713sx->regmap), "regmap i2c init failed\n");
 
-	ret = drm_of_find_panel_or_bridge(lt8713sx->dev->of_node, 1, -1, NULL,
-					  &lt8713sx->next_bridge);
-	if (ret < 0)
-		return ret;
+	lt8713sx->bridge.next_bridge = of_drm_get_bridge_by_endpoint(lt8713sx->dev->of_node, 1, -1);
+	if (IS_ERR(lt8713sx->bridge.next_bridge))
+		return PTR_ERR(lt8713sx->bridge.next_bridge);
 
 	ret = lt8713sx_gpio_init(lt8713sx);
 	if (ret < 0)

-- 
2.54.0

[PATCH v6 10/11] drm: zynqmp_dp: switch to of_drm_get_bridge_by_endpoint()

[Luca Ceresoli]

This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().

Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Changes in v4:
- fix missing assignment
- simplify error management code flow

Changes in v3:
- fix ERR_PTR deref when -ENODEV is returned
---
 drivers/gpu/drm/xlnx/zynqmp_dp.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 05bd31fe675b..7fb11b0a44f0 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -353,7 +353,6 @@ struct zynqmp_dp_train_set_priv {
  * @lock: Mutex protecting this struct and register access (but not AUX)
  * @irq: irq
  * @bridge: DRM bridge for the DP encoder
- * @next_bridge: The downstream bridge
  * @test: Configuration for test mode
  * @config: IP core configuration from DTS
  * @aux: aux channel
@@ -385,7 +384,6 @@ struct zynqmp_dp {
 	struct completion aux_done;
 	struct mutex lock;
 
-	struct drm_bridge *next_bridge;
 	struct device *dev;
 	struct zynqmp_dpsub *dpsub;
 	void __iomem *iomem;
@@ -1494,8 +1492,8 @@ static int zynqmp_dp_bridge_attach(struct drm_bridge *bridge,
 		return ret;
 	}
 
-	if (dp->next_bridge) {
-		ret = drm_bridge_attach(encoder, dp->next_bridge,
+	if (dp->bridge.next_bridge) {
+		ret = drm_bridge_attach(encoder, dp->bridge.next_bridge,
 					bridge, flags);
 		if (ret < 0)
 			goto error;
@@ -2461,10 +2459,15 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
 	 * Acquire the next bridge in the chain. Ignore errors caused by port@5
 	 * not being connected for backward-compatibility with older DTs.
 	 */
-	ret = drm_of_find_panel_or_bridge(dp->dev->of_node, 5, 0, NULL,
-					  &dp->next_bridge);
-	if (ret < 0 && ret != -ENODEV)
-		goto err_reset;
+	dp->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dp->dev->of_node, 5, 0);
+	if (IS_ERR(dp->bridge.next_bridge)) {
+		if (PTR_ERR(dp->bridge.next_bridge) != -ENODEV) {
+			ret = PTR_ERR(dp->bridge.next_bridge);
+			goto err_reset;
+		}
+
+		dp->bridge.next_bridge = NULL;
+	}
 
 	/* Initialize the hardware. */
 	dp->config.misc0 &= ~ZYNQMP_DP_MAIN_STREAM_MISC0_SYNC_LOCK;

-- 
2.54.0

[PATCH v6 11/11] drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

[Luca Ceresoli]

Up to now drm_of_find_panel_or_bridge() can be called with a bridge pointer
only, a panel pointer only, or both a bridge and a panel pointers. The
logic to handle all the three cases is somewhat complex to read however.

Now all bridge-only callers have been converted to
of_drm_get_bridge_by_endpoint(), which is simpler and handles bridge
refcounting. So forbid new bridge-only users by mandating a non-NULL panel
pointer in the docs and in the sanity checks along with a warning.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/drm_of.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index ef6b09316963..d03ada82eac9 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -225,15 +225,15 @@ EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
  * @np: device tree node containing encoder output ports
  * @port: port in the device tree node
  * @endpoint: endpoint in the device tree node
- * @panel: pointer to hold returned drm_panel
+ * @panel: pointer to hold returned drm_panel, must not be NULL
  * @bridge: pointer to hold returned drm_bridge
  *
  * Given a DT node's port and endpoint number, find the connected node and
- * return either the associated struct drm_panel or drm_bridge device. Either
- * @panel or @bridge must not be NULL.
+ * return either the associated struct drm_panel or drm_bridge device.
  *
  * This function is deprecated and should not be used in new drivers. Use
- * devm_drm_of_get_bridge() instead.
+ * of_drm_get_bridge_by_endpoint() instead when not looking for a panel, or
+ * devm_drm_of_get_bridge() otherwise.
  *
  * Returns zero if successful, or one of the standard error codes if it fails.
  */
@@ -245,10 +245,10 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	int ret = -EPROBE_DEFER;
 	struct device_node *remote;
 
-	if (!panel && !bridge)
+	if (WARN_ON(!panel))
 		return -EINVAL;
-	if (panel)
-		*panel = NULL;
+
+	*panel = NULL;
 
 	/*
 	 * of_graph_get_remote_node() produces a noisy error message if port
@@ -263,13 +263,11 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	if (!remote)
 		return -ENODEV;
 
-	if (panel) {
-		*panel = of_drm_find_panel(remote);
-		if (!IS_ERR(*panel))
-			ret = 0;
-		else
-			*panel = NULL;
-	}
+	*panel = of_drm_find_panel(remote);
+	if (!IS_ERR(*panel))
+		ret = 0;
+	else
+		*panel = NULL;
 
 	if (bridge) {
 		if (ret) {

-- 
2.54.0

Re: [PATCH v6 03/11] drm/msm/hdmi: switch to of_drm_get_bridge_by_endpoint()

[Dmitry Baryshkov]

On Mon, May 11, 2026 at 06:40:07PM +0200, Luca Ceresoli wrote:
> This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
> @panel parameter, thus using a reduced feature set of that function.
> Replace this call with the simpler of_drm_get_bridge_by_endpoint().
> 
> Since of_drm_get_bridge_by_endpoint() increases the refcount of the
> returned bridge, ensure it is put on removal.
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> 
> ---
> 
> Changes in v6:
> - move assignment of next_bridge earlier (avoid access before assignment)
> 
> Changes in v5:
> - simplify error management code flow
> 
> Changes in v4:
> - ensure next_bridge is put on later probe failures
> 
> Changes in v3:
> - fix ERR_PTR deref when -ENODEV is returned
> 
> - move assignment of next_bridge earlier (avoid access before assignment)
> ---
>  drivers/gpu/drm/msm/hdmi/hdmi.c | 70 +++++++++++++++++++++++++++--------------
>  1 file changed, 47 insertions(+), 23 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Ack to merge this through the drm-misc tree

-- 
With best wishes
Dmitry

Claude review: drm/bridge: handle refcounting for bridge-only callers of drm_of_find_panel_or_bridge()

[Claude Code Review Bot]

Overall Series Review

Subject: drm/bridge: handle refcounting for bridge-only callers of drm_of_find_panel_or_bridge()
Author: Luca Ceresoli <luca.ceresoli@bootlin.com>
Patches: 13
Reviewed: 2026-05-16T15:02:22.126708

---

This is a well-structured, incremental series that continues Luca Ceresoli's long-running work to add proper refcounting to DRM bridges. The series introduces `of_drm_get_bridge_by_endpoint()` as a refcount-aware replacement for bridge-only calls to the deprecated `drm_of_find_panel_or_bridge()`, converts all bridge-only callers, and then forbids that usage pattern going forward.

The approach is sound: the new API is simpler (returns the bridge directly instead of via double-pointer), safer (refcounted), and each driver conversion correctly handles the lifecycle of the returned bridge — either via the auto-put `bridge.next_bridge` field, explicit `drm_bridge_put()`, or the `__free(drm_bridge_put)` cleanup annotation.

All patches are already reviewed/acked except patches 3 and 4. The series is at v6, with the main changes across versions being error handling improvements. The code quality is high and the pattern is consistent.

**No blocking issues found.** A couple of very minor nits below.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: drm_bridge_put(): ignore ERR_PTR

[Claude Code Review Bot]

Patch Review

Clean one-liner. The change from `if (bridge)` to `if (!IS_ERR_OR_NULL(bridge))` follows the standard kernel pattern (e.g. `kfree()` ignoring NULL). This is essential prep work since `of_drm_get_bridge_by_endpoint()` returns ERR_PTR values, and callers should be able to safely call `drm_bridge_put()` without checking first.

Already has R-by from Dmitry and Laurent. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: add of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

The new function is a clean wrapper around `of_drm_find_and_get_bridge()` with OF graph resolution. Key details look correct:

```c
bridge = of_drm_find_and_get_bridge(remote);
if (!bridge)
    return ERR_PTR(-EPROBE_DEFER);
```

This correctly converts the NULL return from `of_drm_find_and_get_bridge()` (bridge registered but not yet available) into `-EPROBE_DEFER`, matching the semantics of the old `drm_of_find_panel_or_bridge()`.

The non-OF inline stub correctly returns `ERR_PTR(-ENODEV)` rather than NULL, consistent with the new API contract.

**Very minor nit:** The kdoc return description is missing a trailing period:
```
 * Returns a pointer to the connected drm_bridge, or a negative error on failure
```

Already has R-by from Dmitry and Laurent. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/msm/hdmi: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

This is the most involved conversion because the MSM HDMI driver's bridge is in a separate `hdmi_bridge` struct (allocated in `hdmi_bridge.c`), not embedded in the `hdmi` struct. So unlike later patches, this one can't use the auto-put `bridge.next_bridge` field and must manage the refcount explicitly.

The conversion correctly:
- Handles the `-ENODEV` case by setting `hdmi->next_bridge = NULL` (preserving old behavior)
- Changes all early-return paths after the bridge lookup to `goto err_put_bridge`
- Adds `drm_bridge_put(hdmi->next_bridge)` in both `err_put_bridge` and `msm_hdmi_dev_remove()`

The `drm_bridge_put()` in the remove function is safe even if `next_bridge` is NULL (patch 1 ensures this).

**Minor nit:** There's a double blank line introduced at the `devm_clk_bulk_get` error path:
```c
 	if (ret)
-		return ret;
+		goto err_put_bridge;
+
 
 	hdmi->extp_clk = devm_clk_get_optional(dev, "extp");
```

No functional issues. This patch needs review/ack from MSM maintainers.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/hisilicon/kirin: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Clever use of `__free(drm_bridge_put)` on the local bridge variable. The bridge is only needed to pass to `drm_bridge_attach()`, which (since v6.17) takes its own reference. So dropping the `of_drm_get_bridge_by_endpoint()` reference via the cleanup annotation when the variable goes out of scope is correct.

```c
struct drm_bridge *bridge __free(drm_bridge_put) = NULL;
```

This is the cleanest conversion pattern for drivers that don't store the next_bridge pointer. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Good conversion. Removes the separate `next_bridge` field and migrates to `bridge.next_bridge`, which is auto-put when the bridge is freed (verified in the kernel tree — `__drm_bridge_free()` calls `drm_bridge_put(bridge->next_bridge)`). All references consistently updated:

```c
-	return drm_bridge_detect(priv->next_bridge, connector);
+	return drm_bridge_detect(priv->bridge.next_bridge, connector);
```

No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: lontium-lt9611uxc: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Same pattern as patch 5 — removes `next_bridge` field, uses `bridge.next_bridge`. Clean and correct. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: lt9611: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Same pattern as patches 5-6. Clean and correct. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: adv7511: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Same migration pattern. Also correctly handles the optional `-ENODEV` case (no downstream bridge connected):

```c
if (IS_ERR(adv7511->bridge.next_bridge)) {
    if (PTR_ERR(adv7511->bridge.next_bridge) == -ENODEV)
        adv7511->bridge.next_bridge = NULL;
    else
        return PTR_ERR(adv7511->bridge.next_bridge);
}
```

The existing `if (adv->bridge.next_bridge)` guard in `adv7511_bridge_attach()` correctly handles the NULL case. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/bridge: lt8713sx: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Same pattern as patches 5-7 (no optional bridge, so no -ENODEV handling needed). Clean and correct. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm: zynqmp_dp: switch to of_drm_get_bridge_by_endpoint()

[Claude Code Review Bot]

Patch Review

Same migration pattern with -ENODEV handling (the comment explains backward-compatibility with older DTs that don't have port@5). Removes the `next_bridge` field and the associated kdoc entry. The existing `if (dp->bridge.next_bridge)` guard in `zynqmp_dp_bridge_attach()` handles the NULL case. No issues.

---
Generated by Claude Code Patch Reviewer

Claude review: drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

[Claude Code Review Bot]

Patch Review

Good final cleanup. The `WARN_ON(!panel)` serves as both a runtime check and documentation that bridge-only callers must use `of_drm_get_bridge_by_endpoint()` instead:

```c
-	if (!panel && !bridge)
+	if (WARN_ON(!panel))
 		return -EINVAL;
```

The code simplification that follows (removing `if (panel)` guards) is a clean consequence. The function still correctly handles the `bridge == NULL` case for panel-only callers, and the `panel != NULL, bridge != NULL` case for dual-use callers.

The updated kdoc correctly points developers to the right replacement APIs. No issues.

---
Generated by Claude Code Patch Reviewer