[PATCH v3 0/3] drm/display: simplify support for transparent DRM bridges

[PATCH v3 0/3] drm/display: simplify support for transparent DRM bridges

[Dmitry Baryshkov]

Supporting DP/USB-C can result in a chain of several transparent
bridges (PHY, redrivers, mux, etc). This results in drivers having
similar boilerplate code for such bridges.

Next, these drivers are susceptible to -EPROBE_DEFER loops: the next
bridge can either be probed from the bridge->attach callback, when it is
too late to return -EPROBE_DEFER, or from the probe() callback, when the
next bridge might not yet be available, because it depends on the
resources provided by the probing device.

Last, but not least, this results in the the internal knowledge of DRM
subsystem slowly diffusing into other subsystems, like PHY or USB/TYPEC.

To solve all these issues, define a separate DRM helper, which creates
separate aux device just for the bridge. During probe such aux device
doesn't result in the EPROBE_DEFER loops. Instead it allows the device
drivers to probe properly, according to the actual resource
dependencies. The bridge auxdevs are then probed when the next bridge
becomes available, sparing drivers from drm_bridge_attach() returning
-EPROBE_DEFER.

Proposed merge strategy: immutable branch with the drm commit, which is
then merged into PHY and USB subsystems together with the corresponding
patch.

Changes since v2:
 - ifdef'ed bridge->of_node access (LKP)

Changes since v1:
 - Added EXPORT_SYMBOL_GPL / MODULE_LICENSE / etc. to drm_simple_bridge

Dmitry Baryshkov (3):
  drm/display: add transparent bridge helper
  phy: qcom: qmp-combo: switch to DRM_SIMPLE_BRIDGE
  usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE

 drivers/gpu/drm/display/Kconfig             |   9 ++
 drivers/gpu/drm/display/Makefile            |   2 +
 drivers/gpu/drm/display/drm_simple_bridge.c | 127 ++++++++++++++++++++
 drivers/phy/qualcomm/Kconfig                |   2 +-
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c   |  44 +------
 drivers/usb/typec/mux/Kconfig               |   2 +-
 drivers/usb/typec/mux/nb7vpq904m.c          |  44 +------
 include/drm/display/drm_simple_bridge.h     |  19 +++
 8 files changed, 163 insertions(+), 86 deletions(-)
 create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c
 create mode 100644 include/drm/display/drm_simple_bridge.h

-- 
2.39.2

[PATCH v3 1/3] drm/display: add transparent bridge helper

[Dmitry Baryshkov]

Define a helper for creating simple transparent bridges which serve the
only purpose of linking devices into the bridge chain up to the last
bridge representing the connector. This is especially useful for
DP/USB-C bridge chains, which can span across several devices, but do
not require any additional functionality from the intermediate bridges.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/display/Kconfig             |   9 ++
 drivers/gpu/drm/display/Makefile            |   2 +
 drivers/gpu/drm/display/drm_simple_bridge.c | 127 ++++++++++++++++++++
 include/drm/display/drm_simple_bridge.h     |  19 +++
 4 files changed, 157 insertions(+)
 create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c
 create mode 100644 include/drm/display/drm_simple_bridge.h

diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
index 09712b88a5b8..a6132984b9e3 100644
--- a/drivers/gpu/drm/display/Kconfig
+++ b/drivers/gpu/drm/display/Kconfig
@@ -49,3 +49,12 @@ config DRM_DP_CEC
 
 	  Note: not all adapters support this feature, and even for those
 	  that do support this they often do not hook up the CEC pin.
+
+config DRM_SIMPLE_BRIDGE
+	tristate
+	depends on DRM
+	select AUXILIARY_BUS
+	select DRM_PANEL_BRIDGE
+	help
+	  Simple transparent bridge that is used by several drivers to build
+	  bridges chain.
diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
index 17ac4a1006a8..6e2b0d7f24b3 100644
--- a/drivers/gpu/drm/display/Makefile
+++ b/drivers/gpu/drm/display/Makefile
@@ -16,3 +16,5 @@ drm_display_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
 drm_display_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
 
 obj-$(CONFIG_DRM_DISPLAY_HELPER) += drm_display_helper.o
+
+obj-$(CONFIG_DRM_SIMPLE_BRIDGE) += drm_simple_bridge.o
diff --git a/drivers/gpu/drm/display/drm_simple_bridge.c b/drivers/gpu/drm/display/drm_simple_bridge.c
new file mode 100644
index 000000000000..9e80efe67b93
--- /dev/null
+++ b/drivers/gpu/drm/display/drm_simple_bridge.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Linaro Ltd.
+ *
+ * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
+ */
+#include <linux/auxiliary_bus.h>
+#include <linux/module.h>
+
+#include <drm/drm_bridge.h>
+#include <drm/display/drm_simple_bridge.h>
+
+static DEFINE_IDA(simple_bridge_ida);
+
+static void drm_simple_bridge_release(struct device *dev)
+{
+	struct auxiliary_device *adev = to_auxiliary_dev(dev);
+
+	kfree(adev);
+}
+
+static void drm_simple_bridge_unregister_adev(void *_adev)
+{
+	struct auxiliary_device *adev = _adev;
+
+	auxiliary_device_delete(adev);
+	auxiliary_device_uninit(adev);
+}
+
+int drm_simple_bridge_register(struct device *parent)
+{
+	struct auxiliary_device *adev;
+	int ret;
+
+	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
+	if (!adev)
+		return -ENOMEM;
+
+	ret = ida_alloc(&simple_bridge_ida, GFP_KERNEL);
+	if (ret < 0)
+		return ret;
+
+	adev->id = ret;
+	adev->name = "simple_bridge";
+	adev->dev.parent = parent;
+	adev->dev.of_node = parent->of_node;
+	adev->dev.release = drm_simple_bridge_release;
+
+	ret = auxiliary_device_init(adev);
+	if (ret) {
+		kfree(adev);
+		return ret;
+	}
+
+	ret = auxiliary_device_add(adev);
+	if (ret) {
+		auxiliary_device_uninit(adev);
+		return ret;
+	}
+
+	return devm_add_action_or_reset(parent, drm_simple_bridge_unregister_adev, adev);
+}
+EXPORT_SYMBOL_GPL(drm_simple_bridge_register);
+
+struct drm_simple_bridge_data {
+	struct drm_bridge bridge;
+	struct drm_bridge *next_bridge;
+	struct device *dev;
+};
+
+static int drm_simple_bridge_attach(struct drm_bridge *bridge,
+				    enum drm_bridge_attach_flags flags)
+{
+	struct drm_simple_bridge_data *data;
+
+	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
+		return -EINVAL;
+
+	data = container_of(bridge, struct drm_simple_bridge_data, bridge);
+
+	return drm_bridge_attach(bridge->encoder, data->next_bridge, bridge,
+				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+}
+
+static const struct drm_bridge_funcs drm_simple_bridge_funcs = {
+	.attach	= drm_simple_bridge_attach,
+};
+
+static int drm_simple_bridge_probe(struct auxiliary_device *auxdev,
+				   const struct auxiliary_device_id *id)
+{
+	struct drm_simple_bridge_data *data;
+
+	data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->dev = &auxdev->dev;
+	data->next_bridge = devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0);
+	if (IS_ERR(data->next_bridge))
+		return dev_err_probe(&auxdev->dev, PTR_ERR(data->next_bridge),
+				     "failed to acquire drm_bridge\n");
+
+	data->bridge.funcs = &drm_simple_bridge_funcs;
+#ifdef CONFIG_OF
+	data->bridge.of_node = data->dev->of_node;
+#endif
+
+	return devm_drm_bridge_add(data->dev, &data->bridge);
+}
+
+static const struct auxiliary_device_id drm_simple_bridge_table[] = {
+	{ .name = KBUILD_MODNAME ".simple_bridge" },
+	{},
+};
+MODULE_DEVICE_TABLE(auxiliary, drm_simple_bridge_table);
+
+struct auxiliary_driver drm_simple_bridge_drv = {
+	.name = "simple_bridge",
+	.id_table = drm_simple_bridge_table,
+	.probe = drm_simple_bridge_probe,
+};
+module_auxiliary_driver(drm_simple_bridge_drv);
+
+MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
+MODULE_DESCRIPTION("DRM simple bridge helper");
+MODULE_LICENSE("GPL");
diff --git a/include/drm/display/drm_simple_bridge.h b/include/drm/display/drm_simple_bridge.h
new file mode 100644
index 000000000000..3da8e1fb1137
--- /dev/null
+++ b/include/drm/display/drm_simple_bridge.h
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Linaro Ltd.
+ *
+ * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
+ */
+#ifndef DRM_SIMPLE_BRIDGE_H
+#define DRM_SIMPLE_BRIDGE_H
+
+#if IS_ENABLED(CONFIG_DRM_SIMPLE_BRIDGE)
+int drm_simple_bridge_register(struct device *parent);
+#else
+static inline int drm_simple_bridge_register(struct device *parent)
+{
+	return 0;
+}
+#endif
+
+#endif
-- 
2.39.2

[PATCH v3 2/3] phy: qcom: qmp-combo: switch to DRM_SIMPLE_BRIDGE

[Dmitry Baryshkov]

Switch to using the new DRM_SIMPLE_BRIDGE helper to create the
transparent DRM bridge device instead of handcoding corresponding
functionality.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/phy/qualcomm/Kconfig              |  2 +-
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 44 ++---------------------
 2 files changed, 3 insertions(+), 43 deletions(-)

diff --git a/drivers/phy/qualcomm/Kconfig b/drivers/phy/qualcomm/Kconfig
index ced603806375..fb03e3b3f637 100644
--- a/drivers/phy/qualcomm/Kconfig
+++ b/drivers/phy/qualcomm/Kconfig
@@ -63,7 +63,7 @@ config PHY_QCOM_QMP_COMBO
 	depends on DRM || DRM=n
 	select GENERIC_PHY
 	select MFD_SYSCON
-	select DRM_PANEL_BRIDGE if DRM
+	select DRM_SIMPLE_BRIDGE if DRM
 	help
 	  Enable this to support the QMP Combo PHY transceiver that is used
 	  with USB3 and DisplayPort controllers on Qualcomm chips.
diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
index 9c3de41ecedb..5c7615edb161 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
@@ -21,7 +21,7 @@
 #include <linux/usb/typec.h>
 #include <linux/usb/typec_mux.h>
 
-#include <drm/drm_bridge.h>
+#include <drm/display/drm_simple_bridge.h>
 
 #include <dt-bindings/phy/phy-qcom-qmp.h>
 
@@ -1419,8 +1419,6 @@ struct qmp_combo {
 	struct clk_hw dp_link_hw;
 	struct clk_hw dp_pixel_hw;
 
-	struct drm_bridge bridge;
-
 	struct typec_switch_dev *sw;
 	enum typec_orientation orientation;
 };
@@ -3193,44 +3191,6 @@ static int qmp_combo_typec_switch_register(struct qmp_combo *qmp)
 }
 #endif
 
-#if IS_ENABLED(CONFIG_DRM)
-static int qmp_combo_bridge_attach(struct drm_bridge *bridge,
-				   enum drm_bridge_attach_flags flags)
-{
-	struct qmp_combo *qmp = container_of(bridge, struct qmp_combo, bridge);
-	struct drm_bridge *next_bridge;
-
-	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
-		return -EINVAL;
-
-	next_bridge = devm_drm_of_get_bridge(qmp->dev, qmp->dev->of_node, 0, 0);
-	if (IS_ERR(next_bridge)) {
-		dev_err(qmp->dev, "failed to acquire drm_bridge: %pe\n", next_bridge);
-		return PTR_ERR(next_bridge);
-	}
-
-	return drm_bridge_attach(bridge->encoder, next_bridge, bridge,
-				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
-}
-
-static const struct drm_bridge_funcs qmp_combo_bridge_funcs = {
-	.attach	= qmp_combo_bridge_attach,
-};
-
-static int qmp_combo_dp_register_bridge(struct qmp_combo *qmp)
-{
-	qmp->bridge.funcs = &qmp_combo_bridge_funcs;
-	qmp->bridge.of_node = qmp->dev->of_node;
-
-	return devm_drm_bridge_add(qmp->dev, &qmp->bridge);
-}
-#else
-static int qmp_combo_dp_register_bridge(struct qmp_combo *qmp)
-{
-	return 0;
-}
-#endif
-
 static int qmp_combo_parse_dt_lecacy_dp(struct qmp_combo *qmp, struct device_node *np)
 {
 	struct device *dev = qmp->dev;
@@ -3436,7 +3396,7 @@ static int qmp_combo_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	ret = qmp_combo_dp_register_bridge(qmp);
+	ret = drm_simple_bridge_register(dev);
 	if (ret)
 		return ret;
 
-- 
2.39.2

[PATCH v3 3/3] usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE

[Dmitry Baryshkov]

Switch to using the new DRM_SIMPLE_BRIDGE helper to create the
transparent DRM bridge device instead of handcoding corresponding
functionality.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/usb/typec/mux/Kconfig      |  2 +-
 drivers/usb/typec/mux/nb7vpq904m.c | 44 ++----------------------------
 2 files changed, 3 insertions(+), 43 deletions(-)

diff --git a/drivers/usb/typec/mux/Kconfig b/drivers/usb/typec/mux/Kconfig
index 784b9d8107e9..350a7ffce67e 100644
--- a/drivers/usb/typec/mux/Kconfig
+++ b/drivers/usb/typec/mux/Kconfig
@@ -39,7 +39,7 @@ config TYPEC_MUX_NB7VPQ904M
 	tristate "On Semiconductor NB7VPQ904M Type-C redriver driver"
 	depends on I2C
 	depends on DRM || DRM=n
-	select DRM_PANEL_BRIDGE if DRM
+	select DRM_SIMPLE_BRIDGE if DRM
 	select REGMAP_I2C
 	help
 	  Say Y or M if your system has a On Semiconductor NB7VPQ904M Type-C
diff --git a/drivers/usb/typec/mux/nb7vpq904m.c b/drivers/usb/typec/mux/nb7vpq904m.c
index 9360b65e8b06..c89a956412ea 100644
--- a/drivers/usb/typec/mux/nb7vpq904m.c
+++ b/drivers/usb/typec/mux/nb7vpq904m.c
@@ -11,7 +11,7 @@
 #include <linux/regmap.h>
 #include <linux/bitfield.h>
 #include <linux/of_graph.h>
-#include <drm/drm_bridge.h>
+#include <drm/display/drm_simple_bridge.h>
 #include <linux/usb/typec_dp.h>
 #include <linux/usb/typec_mux.h>
 #include <linux/usb/typec_retimer.h>
@@ -70,8 +70,6 @@ struct nb7vpq904m {
 	bool swap_data_lanes;
 	struct typec_switch *typec_switch;
 
-	struct drm_bridge bridge;
-
 	struct mutex lock; /* protect non-concurrent retimer & switch */
 
 	enum typec_orientation orientation;
@@ -297,44 +295,6 @@ static int nb7vpq904m_retimer_set(struct typec_retimer *retimer, struct typec_re
 	return ret;
 }
 
-#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_DRM_PANEL_BRIDGE)
-static int nb7vpq904m_bridge_attach(struct drm_bridge *bridge,
-				    enum drm_bridge_attach_flags flags)
-{
-	struct nb7vpq904m *nb7 = container_of(bridge, struct nb7vpq904m, bridge);
-	struct drm_bridge *next_bridge;
-
-	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
-		return -EINVAL;
-
-	next_bridge = devm_drm_of_get_bridge(&nb7->client->dev, nb7->client->dev.of_node, 0, 0);
-	if (IS_ERR(next_bridge)) {
-		dev_err(&nb7->client->dev, "failed to acquire drm_bridge: %pe\n", next_bridge);
-		return PTR_ERR(next_bridge);
-	}
-
-	return drm_bridge_attach(bridge->encoder, next_bridge, bridge,
-				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
-}
-
-static const struct drm_bridge_funcs nb7vpq904m_bridge_funcs = {
-	.attach	= nb7vpq904m_bridge_attach,
-};
-
-static int nb7vpq904m_register_bridge(struct nb7vpq904m *nb7)
-{
-	nb7->bridge.funcs = &nb7vpq904m_bridge_funcs;
-	nb7->bridge.of_node = nb7->client->dev.of_node;
-
-	return devm_drm_bridge_add(&nb7->client->dev, &nb7->bridge);
-}
-#else
-static int nb7vpq904m_register_bridge(struct nb7vpq904m *nb7)
-{
-	return 0;
-}
-#endif
-
 static const struct regmap_config nb7_regmap = {
 	.max_register = 0x1f,
 	.reg_bits = 8,
@@ -461,7 +421,7 @@ static int nb7vpq904m_probe(struct i2c_client *client)
 
 	gpiod_set_value(nb7->enable_gpio, 1);
 
-	ret = nb7vpq904m_register_bridge(nb7);
+	ret = drm_simple_bridge_register(dev);
 	if (ret)
 		return ret;
 
-- 
2.39.2

Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[Neil Armstrong]

Hi Dmitry,

On 02/08/2023 03:18, Dmitry Baryshkov wrote:
> Define a helper for creating simple transparent bridges which serve the
> only purpose of linking devices into the bridge chain up to the last
> bridge representing the connector. This is especially useful for
> DP/USB-C bridge chains, which can span across several devices, but do
> not require any additional functionality from the intermediate bridges.

Can you CC me on the whole patchset ?

Thanks,
Neil


<snip>

Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[Neil Armstrong]

On 02/08/2023 10:08, Neil Armstrong wrote:
> Hi Dmitry,
> 
> On 02/08/2023 03:18, Dmitry Baryshkov wrote:
>> Define a helper for creating simple transparent bridges which serve the
>> only purpose of linking devices into the bridge chain up to the last
>> bridge representing the connector. This is especially useful for
>> DP/USB-C bridge chains, which can span across several devices, but do
>> not require any additional functionality from the intermediate bridges.
> 
> Can you CC me on the whole patchset ?

Oops I am... sorry for the noise...

> 
> Thanks,
> Neil
> 
> 
> <snip>
> 

Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[Neil Armstrong]

Hi,

On 02/08/2023 03:18, Dmitry Baryshkov wrote:
> Define a helper for creating simple transparent bridges which serve the
> only purpose of linking devices into the bridge chain up to the last
> bridge representing the connector. This is especially useful for
> DP/USB-C bridge chains, which can span across several devices, but do
> not require any additional functionality from the intermediate bridges.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>   drivers/gpu/drm/display/Kconfig             |   9 ++
>   drivers/gpu/drm/display/Makefile            |   2 +
>   drivers/gpu/drm/display/drm_simple_bridge.c | 127 ++++++++++++++++++++

I wonder why drm/display/ and not drm/bridge ?

It's an helper, but it's mainly a bridge.

>   include/drm/display/drm_simple_bridge.h     |  19 +++
>   4 files changed, 157 insertions(+)
>   create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c
>   create mode 100644 include/drm/display/drm_simple_bridge.h
> 
> diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
> index 09712b88a5b8..a6132984b9e3 100644
> --- a/drivers/gpu/drm/display/Kconfig
> +++ b/drivers/gpu/drm/display/Kconfig
> @@ -49,3 +49,12 @@ config DRM_DP_CEC
>   
>   	  Note: not all adapters support this feature, and even for those
>   	  that do support this they often do not hook up the CEC pin.
> +
> +config DRM_SIMPLE_BRIDGE
> +	tristate
> +	depends on DRM
> +	select AUXILIARY_BUS
> +	select DRM_PANEL_BRIDGE
> +	help
> +	  Simple transparent bridge that is used by several drivers to build
> +	  bridges chain.
> diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
> index 17ac4a1006a8..6e2b0d7f24b3 100644
> --- a/drivers/gpu/drm/display/Makefile
> +++ b/drivers/gpu/drm/display/Makefile
> @@ -16,3 +16,5 @@ drm_display_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
>   drm_display_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
>   
>   obj-$(CONFIG_DRM_DISPLAY_HELPER) += drm_display_helper.o
> +
> +obj-$(CONFIG_DRM_SIMPLE_BRIDGE) += drm_simple_bridge.o
> diff --git a/drivers/gpu/drm/display/drm_simple_bridge.c b/drivers/gpu/drm/display/drm_simple_bridge.c
> new file mode 100644
> index 000000000000..9e80efe67b93
> --- /dev/null
> +++ b/drivers/gpu/drm/display/drm_simple_bridge.c
> @@ -0,0 +1,127 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> + */
> +#include <linux/auxiliary_bus.h>
> +#include <linux/module.h>
> +
> +#include <drm/drm_bridge.h>
> +#include <drm/display/drm_simple_bridge.h>
> +
> +static DEFINE_IDA(simple_bridge_ida);
> +
> +static void drm_simple_bridge_release(struct device *dev)
> +{
> +	struct auxiliary_device *adev = to_auxiliary_dev(dev);
> +
> +	kfree(adev);
> +}
> +
> +static void drm_simple_bridge_unregister_adev(void *_adev)
> +{
> +	struct auxiliary_device *adev = _adev;
> +
> +	auxiliary_device_delete(adev);
> +	auxiliary_device_uninit(adev);
> +}
> +
> +int drm_simple_bridge_register(struct device *parent)
> +{
> +	struct auxiliary_device *adev;
> +	int ret;
> +
> +	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
> +	if (!adev)
> +		return -ENOMEM;
> +
> +	ret = ida_alloc(&simple_bridge_ida, GFP_KERNEL);
> +	if (ret < 0)
> +		return ret;
> +
> +	adev->id = ret;
> +	adev->name = "simple_bridge";
> +	adev->dev.parent = parent;
> +	adev->dev.of_node = parent->of_node;
> +	adev->dev.release = drm_simple_bridge_release;
> +
> +	ret = auxiliary_device_init(adev);
> +	if (ret) {
> +		kfree(adev);
> +		return ret;
> +	}
> +
> +	ret = auxiliary_device_add(adev);
> +	if (ret) {
> +		auxiliary_device_uninit(adev);
> +		return ret;
> +	}
> +
> +	return devm_add_action_or_reset(parent, drm_simple_bridge_unregister_adev, adev);
> +}
> +EXPORT_SYMBOL_GPL(drm_simple_bridge_register);
> +
> +struct drm_simple_bridge_data {
> +	struct drm_bridge bridge;
> +	struct drm_bridge *next_bridge;
> +	struct device *dev;
> +};
> +
> +static int drm_simple_bridge_attach(struct drm_bridge *bridge,
> +				    enum drm_bridge_attach_flags flags)
> +{
> +	struct drm_simple_bridge_data *data;
> +
> +	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> +		return -EINVAL;
> +
> +	data = container_of(bridge, struct drm_simple_bridge_data, bridge);
> +
> +	return drm_bridge_attach(bridge->encoder, data->next_bridge, bridge,
> +				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +}
> +
> +static const struct drm_bridge_funcs drm_simple_bridge_funcs = {
> +	.attach	= drm_simple_bridge_attach,
> +};
> +
> +static int drm_simple_bridge_probe(struct auxiliary_device *auxdev,
> +				   const struct auxiliary_device_id *id)
> +{
> +	struct drm_simple_bridge_data *data;
> +
> +	data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->dev = &auxdev->dev;
> +	data->next_bridge = devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0);
> +	if (IS_ERR(data->next_bridge))
> +		return dev_err_probe(&auxdev->dev, PTR_ERR(data->next_bridge),
> +				     "failed to acquire drm_bridge\n");
> +
> +	data->bridge.funcs = &drm_simple_bridge_funcs;
> +#ifdef CONFIG_OF
> +	data->bridge.of_node = data->dev->of_node;
> +#endif

I think the whole stuff should depend on OF since devm_drm_of_get_bridge() is a no-op when !OF

> +
> +	return devm_drm_bridge_add(data->dev, &data->bridge);
> +}
> +
> +static const struct auxiliary_device_id drm_simple_bridge_table[] = {
> +	{ .name = KBUILD_MODNAME ".simple_bridge" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(auxiliary, drm_simple_bridge_table);
> +
> +struct auxiliary_driver drm_simple_bridge_drv = {
> +	.name = "simple_bridge",
> +	.id_table = drm_simple_bridge_table,
> +	.probe = drm_simple_bridge_probe,
> +};
> +module_auxiliary_driver(drm_simple_bridge_drv);
> +
> +MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
> +MODULE_DESCRIPTION("DRM simple bridge helper");
> +MODULE_LICENSE("GPL");
> diff --git a/include/drm/display/drm_simple_bridge.h b/include/drm/display/drm_simple_bridge.h
> new file mode 100644
> index 000000000000..3da8e1fb1137
> --- /dev/null
> +++ b/include/drm/display/drm_simple_bridge.h
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> + */
> +#ifndef DRM_SIMPLE_BRIDGE_H
> +#define DRM_SIMPLE_BRIDGE_H
> +
> +#if IS_ENABLED(CONFIG_DRM_SIMPLE_BRIDGE)
> +int drm_simple_bridge_register(struct device *parent);
> +#else
> +static inline int drm_simple_bridge_register(struct device *parent)
> +{
> +	return 0;
> +}
> +#endif
> +
> +#endif

The design looks fine, but I'll need another review.

Thanks,
Neil

Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[Dmitry Baryshkov]

On Wed, 2 Aug 2023 at 11:15, Neil Armstrong <neil.armstrong@linaro.org> wrote:
>
> Hi,
>
> On 02/08/2023 03:18, Dmitry Baryshkov wrote:
> > Define a helper for creating simple transparent bridges which serve the
> > only purpose of linking devices into the bridge chain up to the last
> > bridge representing the connector. This is especially useful for
> > DP/USB-C bridge chains, which can span across several devices, but do
> > not require any additional functionality from the intermediate bridges.
> >
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > ---
> >   drivers/gpu/drm/display/Kconfig             |   9 ++
> >   drivers/gpu/drm/display/Makefile            |   2 +
> >   drivers/gpu/drm/display/drm_simple_bridge.c | 127 ++++++++++++++++++++
>
> I wonder why drm/display/ and not drm/bridge ?
>
> It's an helper, but it's mainly a bridge.

Why not? I'm open to any suggestions.

>
> >   include/drm/display/drm_simple_bridge.h     |  19 +++
> >   4 files changed, 157 insertions(+)
> >   create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c
> >   create mode 100644 include/drm/display/drm_simple_bridge.h
> >
> > diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
> > index 09712b88a5b8..a6132984b9e3 100644
> > --- a/drivers/gpu/drm/display/Kconfig
> > +++ b/drivers/gpu/drm/display/Kconfig
> > @@ -49,3 +49,12 @@ config DRM_DP_CEC
> >
> >         Note: not all adapters support this feature, and even for those
> >         that do support this they often do not hook up the CEC pin.
> > +
> > +config DRM_SIMPLE_BRIDGE
> > +     tristate
> > +     depends on DRM
> > +     select AUXILIARY_BUS
> > +     select DRM_PANEL_BRIDGE
> > +     help
> > +       Simple transparent bridge that is used by several drivers to build
> > +       bridges chain.
> > diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
> > index 17ac4a1006a8..6e2b0d7f24b3 100644
> > --- a/drivers/gpu/drm/display/Makefile
> > +++ b/drivers/gpu/drm/display/Makefile
> > @@ -16,3 +16,5 @@ drm_display_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
> >   drm_display_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
> >
> >   obj-$(CONFIG_DRM_DISPLAY_HELPER) += drm_display_helper.o
> > +
> > +obj-$(CONFIG_DRM_SIMPLE_BRIDGE) += drm_simple_bridge.o
> > diff --git a/drivers/gpu/drm/display/drm_simple_bridge.c b/drivers/gpu/drm/display/drm_simple_bridge.c
> > new file mode 100644
> > index 000000000000..9e80efe67b93
> > --- /dev/null
> > +++ b/drivers/gpu/drm/display/drm_simple_bridge.c
> > @@ -0,0 +1,127 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2023 Linaro Ltd.
> > + *
> > + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > + */
> > +#include <linux/auxiliary_bus.h>
> > +#include <linux/module.h>
> > +
> > +#include <drm/drm_bridge.h>
> > +#include <drm/display/drm_simple_bridge.h>
> > +
> > +static DEFINE_IDA(simple_bridge_ida);
> > +
> > +static void drm_simple_bridge_release(struct device *dev)
> > +{
> > +     struct auxiliary_device *adev = to_auxiliary_dev(dev);
> > +
> > +     kfree(adev);
> > +}
> > +
> > +static void drm_simple_bridge_unregister_adev(void *_adev)
> > +{
> > +     struct auxiliary_device *adev = _adev;
> > +
> > +     auxiliary_device_delete(adev);
> > +     auxiliary_device_uninit(adev);
> > +}
> > +
> > +int drm_simple_bridge_register(struct device *parent)
> > +{
> > +     struct auxiliary_device *adev;
> > +     int ret;
> > +
> > +     adev = kzalloc(sizeof(*adev), GFP_KERNEL);
> > +     if (!adev)
> > +             return -ENOMEM;
> > +
> > +     ret = ida_alloc(&simple_bridge_ida, GFP_KERNEL);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     adev->id = ret;
> > +     adev->name = "simple_bridge";
> > +     adev->dev.parent = parent;
> > +     adev->dev.of_node = parent->of_node;
> > +     adev->dev.release = drm_simple_bridge_release;
> > +
> > +     ret = auxiliary_device_init(adev);
> > +     if (ret) {
> > +             kfree(adev);
> > +             return ret;
> > +     }
> > +
> > +     ret = auxiliary_device_add(adev);
> > +     if (ret) {
> > +             auxiliary_device_uninit(adev);
> > +             return ret;
> > +     }
> > +
> > +     return devm_add_action_or_reset(parent, drm_simple_bridge_unregister_adev, adev);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_simple_bridge_register);
> > +
> > +struct drm_simple_bridge_data {
> > +     struct drm_bridge bridge;
> > +     struct drm_bridge *next_bridge;
> > +     struct device *dev;
> > +};
> > +
> > +static int drm_simple_bridge_attach(struct drm_bridge *bridge,
> > +                                 enum drm_bridge_attach_flags flags)
> > +{
> > +     struct drm_simple_bridge_data *data;
> > +
> > +     if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> > +             return -EINVAL;
> > +
> > +     data = container_of(bridge, struct drm_simple_bridge_data, bridge);
> > +
> > +     return drm_bridge_attach(bridge->encoder, data->next_bridge, bridge,
> > +                              DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> > +}
> > +
> > +static const struct drm_bridge_funcs drm_simple_bridge_funcs = {
> > +     .attach = drm_simple_bridge_attach,
> > +};
> > +
> > +static int drm_simple_bridge_probe(struct auxiliary_device *auxdev,
> > +                                const struct auxiliary_device_id *id)
> > +{
> > +     struct drm_simple_bridge_data *data;
> > +
> > +     data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
> > +     if (!data)
> > +             return -ENOMEM;
> > +
> > +     data->dev = &auxdev->dev;
> > +     data->next_bridge = devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0);
> > +     if (IS_ERR(data->next_bridge))
> > +             return dev_err_probe(&auxdev->dev, PTR_ERR(data->next_bridge),
> > +                                  "failed to acquire drm_bridge\n");
> > +
> > +     data->bridge.funcs = &drm_simple_bridge_funcs;
> > +#ifdef CONFIG_OF
> > +     data->bridge.of_node = data->dev->of_node;
> > +#endif
>
> I think the whole stuff should depend on OF since devm_drm_of_get_bridge() is a no-op when !OF

Hmm, true. Probably we should rework bridges to use fwnode at some point.

>
> > +
> > +     return devm_drm_bridge_add(data->dev, &data->bridge);
> > +}
> > +
> > +static const struct auxiliary_device_id drm_simple_bridge_table[] = {
> > +     { .name = KBUILD_MODNAME ".simple_bridge" },
> > +     {},
> > +};
> > +MODULE_DEVICE_TABLE(auxiliary, drm_simple_bridge_table);
> > +
> > +struct auxiliary_driver drm_simple_bridge_drv = {
> > +     .name = "simple_bridge",
> > +     .id_table = drm_simple_bridge_table,
> > +     .probe = drm_simple_bridge_probe,
> > +};
> > +module_auxiliary_driver(drm_simple_bridge_drv);
> > +
> > +MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
> > +MODULE_DESCRIPTION("DRM simple bridge helper");
> > +MODULE_LICENSE("GPL");
> > diff --git a/include/drm/display/drm_simple_bridge.h b/include/drm/display/drm_simple_bridge.h
> > new file mode 100644
> > index 000000000000..3da8e1fb1137
> > --- /dev/null
> > +++ b/include/drm/display/drm_simple_bridge.h
> > @@ -0,0 +1,19 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2023 Linaro Ltd.
> > + *
> > + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > + */
> > +#ifndef DRM_SIMPLE_BRIDGE_H
> > +#define DRM_SIMPLE_BRIDGE_H
> > +
> > +#if IS_ENABLED(CONFIG_DRM_SIMPLE_BRIDGE)
> > +int drm_simple_bridge_register(struct device *parent);
> > +#else
> > +static inline int drm_simple_bridge_register(struct device *parent)
> > +{
> > +     return 0;
> > +}
> > +#endif
> > +
> > +#endif
>
> The design looks fine, but I'll need another review.
>
> Thanks,
> Neil
>


-- 
With best wishes
Dmitry

Re: [PATCH v3 3/3] usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE

[Heikki Krogerus]

On Wed, Aug 02, 2023 at 04:18:45AM +0300, Dmitry Baryshkov wrote:
> Switch to using the new DRM_SIMPLE_BRIDGE helper to create the
> transparent DRM bridge device instead of handcoding corresponding
> functionality.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/mux/Kconfig      |  2 +-
>  drivers/usb/typec/mux/nb7vpq904m.c | 44 ++----------------------------
>  2 files changed, 3 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/usb/typec/mux/Kconfig b/drivers/usb/typec/mux/Kconfig
> index 784b9d8107e9..350a7ffce67e 100644
> --- a/drivers/usb/typec/mux/Kconfig
> +++ b/drivers/usb/typec/mux/Kconfig
> @@ -39,7 +39,7 @@ config TYPEC_MUX_NB7VPQ904M
>  	tristate "On Semiconductor NB7VPQ904M Type-C redriver driver"
>  	depends on I2C
>  	depends on DRM || DRM=n
> -	select DRM_PANEL_BRIDGE if DRM
> +	select DRM_SIMPLE_BRIDGE if DRM
>  	select REGMAP_I2C
>  	help
>  	  Say Y or M if your system has a On Semiconductor NB7VPQ904M Type-C
> diff --git a/drivers/usb/typec/mux/nb7vpq904m.c b/drivers/usb/typec/mux/nb7vpq904m.c
> index 9360b65e8b06..c89a956412ea 100644
> --- a/drivers/usb/typec/mux/nb7vpq904m.c
> +++ b/drivers/usb/typec/mux/nb7vpq904m.c
> @@ -11,7 +11,7 @@
>  #include <linux/regmap.h>
>  #include <linux/bitfield.h>
>  #include <linux/of_graph.h>
> -#include <drm/drm_bridge.h>
> +#include <drm/display/drm_simple_bridge.h>
>  #include <linux/usb/typec_dp.h>
>  #include <linux/usb/typec_mux.h>
>  #include <linux/usb/typec_retimer.h>
> @@ -70,8 +70,6 @@ struct nb7vpq904m {
>  	bool swap_data_lanes;
>  	struct typec_switch *typec_switch;
>  
> -	struct drm_bridge bridge;
> -
>  	struct mutex lock; /* protect non-concurrent retimer & switch */
>  
>  	enum typec_orientation orientation;
> @@ -297,44 +295,6 @@ static int nb7vpq904m_retimer_set(struct typec_retimer *retimer, struct typec_re
>  	return ret;
>  }
>  
> -#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_DRM_PANEL_BRIDGE)
> -static int nb7vpq904m_bridge_attach(struct drm_bridge *bridge,
> -				    enum drm_bridge_attach_flags flags)
> -{
> -	struct nb7vpq904m *nb7 = container_of(bridge, struct nb7vpq904m, bridge);
> -	struct drm_bridge *next_bridge;
> -
> -	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> -		return -EINVAL;
> -
> -	next_bridge = devm_drm_of_get_bridge(&nb7->client->dev, nb7->client->dev.of_node, 0, 0);
> -	if (IS_ERR(next_bridge)) {
> -		dev_err(&nb7->client->dev, "failed to acquire drm_bridge: %pe\n", next_bridge);
> -		return PTR_ERR(next_bridge);
> -	}
> -
> -	return drm_bridge_attach(bridge->encoder, next_bridge, bridge,
> -				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> -}
> -
> -static const struct drm_bridge_funcs nb7vpq904m_bridge_funcs = {
> -	.attach	= nb7vpq904m_bridge_attach,
> -};
> -
> -static int nb7vpq904m_register_bridge(struct nb7vpq904m *nb7)
> -{
> -	nb7->bridge.funcs = &nb7vpq904m_bridge_funcs;
> -	nb7->bridge.of_node = nb7->client->dev.of_node;
> -
> -	return devm_drm_bridge_add(&nb7->client->dev, &nb7->bridge);
> -}
> -#else
> -static int nb7vpq904m_register_bridge(struct nb7vpq904m *nb7)
> -{
> -	return 0;
> -}
> -#endif
> -
>  static const struct regmap_config nb7_regmap = {
>  	.max_register = 0x1f,
>  	.reg_bits = 8,
> @@ -461,7 +421,7 @@ static int nb7vpq904m_probe(struct i2c_client *client)
>  
>  	gpiod_set_value(nb7->enable_gpio, 1);
>  
> -	ret = nb7vpq904m_register_bridge(nb7);
> +	ret = drm_simple_bridge_register(dev);
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.39.2

-- 
heikki

Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[kernel test robot]

Hi Dmitry,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on usb/usb-testing usb/usb-next usb/usb-linus drm-intel/for-linux-next drm-intel/for-linux-next-fixes drm-tip/drm-tip linus/master v6.5-rc4 next-20230804]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Baryshkov/drm-display-add-transparent-bridge-helper/20230802-091932
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230802011845.4176631-2-dmitry.baryshkov%40linaro.org
patch subject: [PATCH v3 1/3] drm/display: add transparent bridge helper
config: i386-randconfig-r072-20230806 (https://download.01.org/0day-ci/archive/20230806/202308062017.iKU92hML-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230806/202308062017.iKU92hML-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308062017.iKU92hML-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/gpu/drm/display/drm_simple_bridge.c:118:25: sparse: sparse: symbol 'drm_simple_bridge_drv' was not declared. Should it be static?

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v3 3/3] usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE

[kernel test robot]

Hi Dmitry,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on usb/usb-testing usb/usb-next usb/usb-linus drm-intel/for-linux-next drm-intel/for-linux-next-fixes drm-tip/drm-tip linus/master v6.5-rc5 next-20230808]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Baryshkov/drm-display-add-transparent-bridge-helper/20230802-091932
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230802011845.4176631-4-dmitry.baryshkov%40linaro.org
patch subject: [PATCH v3 3/3] usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE
config: s390-randconfig-r033-20230808 (https://download.01.org/0day-ci/archive/20230809/202308090347.sZtwmCUB-lkp@intel.com/config)
compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project.git 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
reproduce: (https://download.01.org/0day-ci/archive/20230809/202308090347.sZtwmCUB-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308090347.sZtwmCUB-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/gpu/drm/bridge/simple-bridge.c:212:18: error: no member named 'of_node' in 'struct drm_bridge'
           sbridge->bridge.of_node = pdev->dev.of_node;
           ~~~~~~~~~~~~~~~ ^
   1 error generated.


vim +212 drivers/gpu/drm/bridge/simple-bridge.c

56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  168  
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  169  static int simple_bridge_probe(struct platform_device *pdev)
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  170  {
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  171  	struct simple_bridge *sbridge;
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  172  	struct device_node *remote;
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  173  
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  174  	sbridge = devm_kzalloc(&pdev->dev, sizeof(*sbridge), GFP_KERNEL);
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  175  	if (!sbridge)
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  176  		return -ENOMEM;
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  177  	platform_set_drvdata(pdev, sbridge);
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  178  
272378ec0eb972 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  179  	sbridge->info = of_device_get_match_data(&pdev->dev);
272378ec0eb972 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  180  
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  181  	/* Get the next bridge in the pipeline. */
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  182  	remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  183  	if (!remote)
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  184  		return -EINVAL;
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  185  
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  186  	sbridge->next_bridge = of_drm_find_bridge(remote);
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  187  	of_node_put(remote);
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  188  
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  189  	if (!sbridge->next_bridge) {
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  190  		dev_dbg(&pdev->dev, "Next bridge not found, deferring probe\n");
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  191  		return -EPROBE_DEFER;
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  192  	}
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  193  
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  194  	/* Get the regulator and GPIO resources. */
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  195  	sbridge->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  196  	if (IS_ERR(sbridge->vdd)) {
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  197  		int ret = PTR_ERR(sbridge->vdd);
af948a25ecb214 drivers/gpu/drm/bridge/dumb-vga-dac.c  Chen-Yu Tsai     2016-11-16  198  		if (ret == -EPROBE_DEFER)
af948a25ecb214 drivers/gpu/drm/bridge/dumb-vga-dac.c  Chen-Yu Tsai     2016-11-16  199  			return -EPROBE_DEFER;
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  200  		sbridge->vdd = NULL;
af948a25ecb214 drivers/gpu/drm/bridge/dumb-vga-dac.c  Chen-Yu Tsai     2016-11-16  201  		dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
af948a25ecb214 drivers/gpu/drm/bridge/dumb-vga-dac.c  Chen-Yu Tsai     2016-11-16  202  	}
af948a25ecb214 drivers/gpu/drm/bridge/dumb-vga-dac.c  Chen-Yu Tsai     2016-11-16  203  
2df6428e290a61 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  204  	sbridge->enable = devm_gpiod_get_optional(&pdev->dev, "enable",
2df6428e290a61 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  205  						  GPIOD_OUT_LOW);
db8496d0b50519 drivers/gpu/drm/bridge/simple-bridge.c Ye Xingchen      2023-03-22  206  	if (IS_ERR(sbridge->enable))
db8496d0b50519 drivers/gpu/drm/bridge/simple-bridge.c Ye Xingchen      2023-03-22  207  		return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->enable),
db8496d0b50519 drivers/gpu/drm/bridge/simple-bridge.c Ye Xingchen      2023-03-22  208  				     "Unable to retrieve enable GPIO\n");
2df6428e290a61 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  209  
00686ac55d0a21 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-05-26  210  	/* Register the bridge. */
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  211  	sbridge->bridge.funcs = &simple_bridge_bridge_funcs;
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26 @212  	sbridge->bridge.of_node = pdev->dev.of_node;
272378ec0eb972 drivers/gpu/drm/bridge/simple-bridge.c Laurent Pinchart 2020-02-26  213  	sbridge->bridge.timings = sbridge->info->timings;
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  214  
94ded532ffdb42 drivers/gpu/drm/bridge/dumb-vga-dac.c  Laurent Pinchart 2020-02-26  215  	drm_bridge_add(&sbridge->bridge);
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  216  
47e34278549ca4 drivers/gpu/drm/bridge/dumb-vga-dac.c  Inki Dae         2017-07-03  217  	return 0;
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  218  }
56fe8b6f499167 drivers/gpu/drm/bridge/dumb-vga-dac.c  Maxime Ripard    2016-09-30  219  

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Re: [PATCH v3 1/3] drm/display: add transparent bridge helper

[Dan Carpenter]

Hi Dmitry,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Baryshkov/drm-display-add-transparent-bridge-helper/20230802-091932
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20230802011845.4176631-2-dmitry.baryshkov%40linaro.org
patch subject: [PATCH v3 1/3] drm/display: add transparent bridge helper
config: x86_64-randconfig-m001-20230808 (https://download.01.org/0day-ci/archive/20230809/202308090559.RMlH2Dl6-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230809/202308090559.RMlH2Dl6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202308090559.RMlH2Dl6-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/display/drm_simple_bridge.c:41 drm_simple_bridge_register() warn: possible memory leak of 'adev'

vim +/adev +41 drivers/gpu/drm/display/drm_simple_bridge.c

abf701043719cd Dmitry Baryshkov 2023-08-02  30  int drm_simple_bridge_register(struct device *parent)
abf701043719cd Dmitry Baryshkov 2023-08-02  31  {
abf701043719cd Dmitry Baryshkov 2023-08-02  32  	struct auxiliary_device *adev;
abf701043719cd Dmitry Baryshkov 2023-08-02  33  	int ret;
abf701043719cd Dmitry Baryshkov 2023-08-02  34  
abf701043719cd Dmitry Baryshkov 2023-08-02  35  	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
abf701043719cd Dmitry Baryshkov 2023-08-02  36  	if (!adev)
abf701043719cd Dmitry Baryshkov 2023-08-02  37  		return -ENOMEM;
abf701043719cd Dmitry Baryshkov 2023-08-02  38  
abf701043719cd Dmitry Baryshkov 2023-08-02  39  	ret = ida_alloc(&simple_bridge_ida, GFP_KERNEL);
abf701043719cd Dmitry Baryshkov 2023-08-02  40  	if (ret < 0)
abf701043719cd Dmitry Baryshkov 2023-08-02 @41  		return ret;

kfree(adev);

abf701043719cd Dmitry Baryshkov 2023-08-02  42  
abf701043719cd Dmitry Baryshkov 2023-08-02  43  	adev->id = ret;
abf701043719cd Dmitry Baryshkov 2023-08-02  44  	adev->name = "simple_bridge";
abf701043719cd Dmitry Baryshkov 2023-08-02  45  	adev->dev.parent = parent;
abf701043719cd Dmitry Baryshkov 2023-08-02  46  	adev->dev.of_node = parent->of_node;
abf701043719cd Dmitry Baryshkov 2023-08-02  47  	adev->dev.release = drm_simple_bridge_release;
abf701043719cd Dmitry Baryshkov 2023-08-02  48  
abf701043719cd Dmitry Baryshkov 2023-08-02  49  	ret = auxiliary_device_init(adev);
abf701043719cd Dmitry Baryshkov 2023-08-02  50  	if (ret) {
abf701043719cd Dmitry Baryshkov 2023-08-02  51  		kfree(adev);

This needs to ida_free(&simple_bridge_ida, adev->id) as well.  There is
a smatch check for this (check_unwind.c) but I guess I plan to re-write
it a bit before I turn that on.

abf701043719cd Dmitry Baryshkov 2023-08-02  52  		return ret;
abf701043719cd Dmitry Baryshkov 2023-08-02  53  	}
abf701043719cd Dmitry Baryshkov 2023-08-02  54  
abf701043719cd Dmitry Baryshkov 2023-08-02  55  	ret = auxiliary_device_add(adev);
abf701043719cd Dmitry Baryshkov 2023-08-02  56  	if (ret) {
abf701043719cd Dmitry Baryshkov 2023-08-02  57  		auxiliary_device_uninit(adev);
abf701043719cd Dmitry Baryshkov 2023-08-02  58  		return ret;
abf701043719cd Dmitry Baryshkov 2023-08-02  59  	}
abf701043719cd Dmitry Baryshkov 2023-08-02  60  
abf701043719cd Dmitry Baryshkov 2023-08-02  61  	return devm_add_action_or_reset(parent, drm_simple_bridge_unregister_adev, adev);
abf701043719cd Dmitry Baryshkov 2023-08-02  62  }

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