[PATCH v5 0/3] serdev: handle devices without an ACPI or device tree node

[PATCH v5 0/3] serdev: handle devices without an ACPI or device tree node

[ChunAn Wu]

Driver-created serdev clients without an ACPI companion or device tree
node currently have no modalias and cannot be matched to a driver:
their modalias sysfs read returns -ENODEV and their creators force a
bind with device_driver_attach().

Backlight function on dell-uart-backlight is not affected: that class
device is registered independently and gets its own add uevent. The
user-visible breakage is the failing modalias read on an existing
serdev child -- Checkbox dkms_info_attachment aborts with
"OSError: [Errno 19] No such device".

Resolve the two long-standing serdev-core TODOs by letting the creator
pass a modalias to serdev_device_add() and giving the serdev driver an
id_table, modelled on the SPI bus. ACPI and OF match first and are
unchanged. Convert dell-uart-backlight and the Lenovo Yoga Tab 2 Pro
fastcharger to this path and drop their force-attach workarounds.

Changes in v5:
- Patch 1: restore is_serdev_device() guard at the top of
  serdev_device_match(). Dropping it was correct when match only
  called acpi/of helpers, but Patch 1 also adds
  serdev_match_id(sdrv->id_table, serdev->modalias), which
  dereferences serdev_device-only memory. Since serdev_controller
  shares serdev_bus_type, the driver core calls .match on controllers
  too; without the guard, serdev->modalias on a controller reads bytes
  from inside host/nr/serdev/ops, and strcmp() can walk past the end of
  the controller struct. Reported by sashiko-bot on 2/3 and 3/3.

Changes in v4:
- Patch 1: drop the dead is_serdev_device() guard from the match
  callback, and dereference serdev once at the top
- Patch 1: drop the "large enough" comment on SERDEV_NAME_SIZE
- Patch 1: in struct serdev_device_driver, place id_table right under
  driver, next to driver->of_match_table and driver->acpi_match_table
- Patch 1: merge serdev_device_set_modalias() into serdev_device_add()
  so the modalias is set at the only point where forgetting it would
  matter; internal firmware callers pass NULL
- All three patches: tightened commit messages and moved the v2/v3
  changelog narrative out of Patch 1 into this cover letter

Changes in v3:
- Rename struct serdev_device::name to ::modalias; dev_name() is
  unchanged
- Model matching on the SPI bus: add struct serdev_device_id and
  id_table; drop driver->name matching
- Add serdev_device_set_modalias() helper and SERDEV_MODULE_PREFIX
- No MODULE_DEVICE_TABLE(serdev, ...) support: both in-tree
  firmware-less clients are created by the same module that provides
  their driver, so udev has nothing to autoload

Changes in v2:
- Instead of silently returning success with no modalias, use a
  creator-supplied name as a "serial:<name>" modalias fallback and as
  the matching key, so clients can bind through normal serdev matching

v4: https://lore.kernel.org/lkml/20261024022930.2704030-1-an.wu@canonical.com/
v3: https://lore.kernel.org/lkml/20261023052717.2577234-1-an.wu@canonical.com/
v2: https://lore.kernel.org/lkml/20261022032842.2492572-1-an.wu@canonical.com/
v1: https://lore.kernel.org/lkml/20261021092124.2306053-1-an.wu@canonical.com/

ChunAn Wu (3):
  serdev: handle devices without an ACPI or device tree node
  platform/x86: dell-uart-backlight: Bind through normal serdev matching
  platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: Bind through
    normal serdev matching

 MAINTAINERS                                   |  1 +
 .../platform/x86/dell/dell-uart-backlight.c   | 18 +++---
 .../lenovo/yoga-tab2-pro-1380-fastcharger.c   | 25 +++-----
 .../platform/x86/x86-android-tablets/core.c   |  2 +-
 drivers/power/sequencing/pwrseq-pcie-m2.c     |  2 +-
 drivers/tty/serdev/core.c                     | 62 ++++++++++++++++---
 include/linux/device-id/serdev.h              | 19 ++++++
 include/linux/serdev.h                        | 12 +++-
 8 files changed, 102 insertions(+), 39 deletions(-)
 create mode 100644 include/linux/device-id/serdev.h


base-commit: 9e947d96915af63e28896caae85a81b74855621b
--
2.34.1

[PATCH v5 1/3] serdev: handle devices without an ACPI or device tree node

[ChunAn Wu]

Serdev clients instantiated by a driver have no ACPI companion and no
device tree node. Their modalias read returns -ENODEV, their add uevent
is suppressed, and they cannot be driver-matched, so creators force a
bind with device_driver_attach().

Resolve both TODOs in the serdev core by modelling matching on the SPI
bus: let the creator pass a modalias to serdev_device_add() and give
struct serdev_device_driver an id_table. ACPI and OF are still tried
first; clients without their own modalias keep returning -ENODEV. The
device name, derived from the controller, is unchanged.

Split struct serdev_device_id and its defines into a new
include/linux/device-id/serdev.h, following the pattern already used by
the SPI and I2C buses.

Signed-off-by: ChunAn Wu <an.wu@canonical.com>
---
 MAINTAINERS                                   |  1 +
 .../platform/x86/x86-android-tablets/core.c   |  2 +-
 drivers/power/sequencing/pwrseq-pcie-m2.c     |  2 +-
 drivers/tty/serdev/core.c                     | 62 ++++++++++++++++---
 include/linux/device-id/serdev.h              | 19 ++++++
 include/linux/serdev.h                        | 12 +++-
 6 files changed, 86 insertions(+), 12 deletions(-)
 create mode 100644 include/linux/device-id/serdev.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 917f3f72e31b..06e67aa5d9b0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -24905,6 +24905,7 @@ L:	linux-serial@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/serial/serial.yaml
 F:	drivers/tty/serdev/
+F:	include/linux/device-id/serdev.h
 F:	include/linux/serdev.h
 F:	rust/helpers/serdev.c
 F:	rust/kernel/serdev.rs
diff --git a/drivers/platform/x86/x86-android-tablets/core.c b/drivers/platform/x86/x86-android-tablets/core.c
index cfff7f5eac5d..853aa6ff5d50 100644
--- a/drivers/platform/x86/x86-android-tablets/core.c
+++ b/drivers/platform/x86/x86-android-tablets/core.c
@@ -317,7 +317,7 @@ static __init int x86_instantiate_serdev(const struct x86_dev_info *dev_info, in
 	ACPI_COMPANION_SET(&serdev->dev, serdev_adev);
 	acpi_device_set_enumerated(serdev_adev);
 
-	ret = serdev_device_add(serdev);
+	ret = serdev_device_add(serdev, NULL);
 	if (ret) {
 		dev_err(&serdev->dev, "error %d adding serdev\n", ret);
 		serdev_device_put(serdev);
diff --git a/drivers/power/sequencing/pwrseq-pcie-m2.c b/drivers/power/sequencing/pwrseq-pcie-m2.c
index e42e85f47629..e0482f2ef39f 100644
--- a/drivers/power/sequencing/pwrseq-pcie-m2.c
+++ b/drivers/power/sequencing/pwrseq-pcie-m2.c
@@ -309,7 +309,7 @@ static int pwrseq_pcie_m2_create_serdev_one(struct pwrseq_pcie_m2_ctx *ctx,
 	if (ret)
 		goto err_free_serdev;
 
-	ret = serdev_device_add(pci_dev->serdev);
+	ret = serdev_device_add(pci_dev->serdev, NULL);
 	if (ret) {
 		dev_err(dev, "Failed to add serdev for PCI device (%s): %d\n",
 			pci_name(pdev), ret);
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 7500efcdfc21..e0517d5a48da 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -29,13 +29,21 @@ static DEFINE_IDA(ctrl_ida);
 static ssize_t modalias_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
+	const struct serdev_device *serdev = to_serdev_device(dev);
 	int len;
 
 	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
 	if (len != -ENODEV)
 		return len;
 
-	return of_device_modalias(dev, buf, PAGE_SIZE);
+	len = of_device_modalias(dev, buf, PAGE_SIZE);
+	if (len != -ENODEV)
+		return len;
+
+	if (!serdev->modalias[0])
+		return -ENODEV;
+
+	return sysfs_emit(buf, "%s%s\n", SERDEV_MODULE_PREFIX, serdev->modalias);
 }
 static DEVICE_ATTR_RO(modalias);
 
@@ -47,15 +55,22 @@ ATTRIBUTE_GROUPS(serdev_device);
 
 static int serdev_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
 {
+	const struct serdev_device *serdev = to_serdev_device(dev);
 	int rc;
 
-	/* TODO: platform modalias */
-
 	rc = acpi_device_uevent_modalias(dev, env);
 	if (rc != -ENODEV)
 		return rc;
 
-	return of_device_uevent_modalias(dev, env);
+	rc = of_device_uevent_modalias(dev, env);
+	if (rc != -ENODEV)
+		return rc;
+
+	if (!serdev->modalias[0])
+		return -ENODEV;
+
+	return add_uevent_var(env, "MODALIAS=%s%s", SERDEV_MODULE_PREFIX,
+			      serdev->modalias);
 }
 
 static void serdev_device_release(struct device *dev)
@@ -86,28 +101,57 @@ static const struct device_type serdev_ctrl_type = {
 	.release	= serdev_ctrl_release,
 };
 
+static const struct serdev_device_id *serdev_match_id(const struct serdev_device_id *id,
+						      const char *modalias)
+{
+	if (!id || !modalias[0])
+		return NULL;
+
+	while (id->name[0]) {
+		if (!strcmp(modalias, id->name))
+			return id;
+		id++;
+	}
+
+	return NULL;
+}
+
 static int serdev_device_match(struct device *dev, const struct device_driver *drv)
 {
+	const struct serdev_device *serdev;
+	const struct serdev_device_driver *sdrv;
+
 	if (!is_serdev_device(dev))
 		return 0;
 
-	/* TODO: platform matching */
+	serdev = to_serdev_device(dev);
+	sdrv = to_serdev_device_driver(drv);
+
 	if (acpi_driver_match_device(dev, drv))
 		return 1;
 
-	return of_driver_match_device(dev, drv);
+	if (of_driver_match_device(dev, drv))
+		return 1;
+
+	return !!serdev_match_id(sdrv->id_table, serdev->modalias);
 }
 
 /**
  * serdev_device_add() - add a device previously constructed via serdev_device_alloc()
  * @serdev:	serdev_device to be added
+ * @modalias:	Driver name or alias, used to match devices which have neither
+ *		an ACPI companion nor a device tree node. NULL for devices
+ *		enumerated from firmware.
  */
-int serdev_device_add(struct serdev_device *serdev)
+int serdev_device_add(struct serdev_device *serdev, const char *modalias)
 {
 	struct serdev_controller *ctrl = serdev->ctrl;
 	struct device *parent = serdev->dev.parent;
 	int err;
 
+	if (modalias)
+		strscpy(serdev->modalias, modalias);
+
 	dev_set_name(&serdev->dev, "%s-%d", dev_name(parent), serdev->nr);
 
 	/* Only a single slave device is currently supported. */
@@ -553,7 +597,7 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
 
 		device_set_node(&serdev->dev, of_fwnode_handle(node));
 
-		err = serdev_device_add(serdev);
+		err = serdev_device_add(serdev, NULL);
 		if (err) {
 			dev_err(&serdev->dev,
 				"failure adding device. status %pe\n",
@@ -707,7 +751,7 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
 	ACPI_COMPANION_SET(&serdev->dev, adev);
 	acpi_device_set_enumerated(adev);
 
-	err = serdev_device_add(serdev);
+	err = serdev_device_add(serdev, NULL);
 	if (err) {
 		dev_err(&serdev->dev,
 			"failure adding ACPI serdev device. status %pe\n",
diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
new file mode 100644
index 000000000000..96644953cece
--- /dev/null
+++ b/include/linux/device-id/serdev.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_DEVICE_ID_SERDEV_H
+#define LINUX_DEVICE_ID_SERDEV_H
+
+#ifdef __KERNEL__
+typedef unsigned long kernel_ulong_t;
+#endif
+
+/* serdev */
+
+#define SERDEV_NAME_SIZE	40
+#define SERDEV_MODULE_PREFIX	"serial:"
+
+struct serdev_device_id {
+	char name[SERDEV_NAME_SIZE];
+	kernel_ulong_t driver_data;	/* Data private to the driver */
+};
+
+#endif /* ifndef LINUX_DEVICE_ID_SERDEV_H */
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index b6c3d957ec15..96a441abc1ac 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -7,7 +7,9 @@
 
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/device-id/serdev.h>
 #include <linux/iopoll.h>
+#include <linux/string.h>
 #include <linux/uaccess.h>
 #include <linux/termios.h>
 #include <linux/delay.h>
@@ -35,6 +37,10 @@ struct serdev_device_ops {
  * struct serdev_device - Basic representation of an serdev device
  * @dev:	Driver model representation of the device.
  * @nr:		Device number on serdev bus.
+ * @modalias:	Name of the driver to use with this device, or the alias
+ *		for it. Empty for devices enumerated from firmware, which
+ *		are identified through their ACPI companion or their device
+ *		tree node instead. See serdev_device_add().
  * @ctrl:	serdev controller managing this device.
  * @ops:	Device operations.
  * @write_comp:	Completion used by serdev_device_write() internally
@@ -43,6 +49,7 @@ struct serdev_device_ops {
 struct serdev_device {
 	struct device dev;
 	int nr;
+	char modalias[SERDEV_NAME_SIZE];
 	struct serdev_controller *ctrl;
 	const struct serdev_device_ops *ops;
 	struct completion write_comp;
@@ -55,12 +62,15 @@ struct serdev_device {
  * struct serdev_device_driver - serdev slave device driver
  * @driver:	serdev device drivers should initialize name field of this
  *		structure.
+ * @id_table:	List of serdev devices supported by this driver, used to
+ *		match devices which are not enumerated from firmware.
  * @probe:	binds this driver to a serdev device.
  * @remove:	unbinds this driver from the serdev device.
  * @shutdown:	shut down this serdev device.
  */
 struct serdev_device_driver {
 	struct device_driver driver;
+	const struct serdev_device_id *id_table;
 	int	(*probe)(struct serdev_device *);
 	void	(*remove)(struct serdev_device *);
 	void	(*shutdown)(struct serdev_device *);
@@ -158,7 +168,7 @@ static inline void serdev_controller_put(struct serdev_controller *ctrl)
 }
 
 struct serdev_device *serdev_device_alloc(struct serdev_controller *);
-int serdev_device_add(struct serdev_device *);
+int serdev_device_add(struct serdev_device *serdev, const char *modalias);
 void serdev_device_remove(struct serdev_device *);
 
 struct serdev_controller *serdev_controller_alloc(struct device *host,
-- 
2.34.1

Re: [PATCH v5 1/3] serdev: handle devices without an ACPI or device tree node

[Markus Probst]

[-- Attachment #1: Type: text/plain, Size: 11051 bytes --]

On Sat, 2026-10-24 at 20:04 +0800, ChunAn Wu wrote:
> Serdev clients instantiated by a driver have no ACPI companion and no
> device tree node. Their modalias read returns -ENODEV, their add uevent
> is suppressed, and they cannot be driver-matched, so creators force a
> bind with device_driver_attach().
> 
> Resolve both TODOs in the serdev core by modelling matching on the SPI
> bus: let the creator pass a modalias to serdev_device_add() and give
> struct serdev_device_driver an id_table. ACPI and OF are still tried
> first; clients without their own modalias keep returning -ENODEV. The
> device name, derived from the controller, is unchanged.
> 
> Split struct serdev_device_id and its defines into a new
> include/linux/device-id/serdev.h, following the pattern already used by
> the SPI and I2C buses.
> 
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
>  MAINTAINERS                                   |  1 +
>  .../platform/x86/x86-android-tablets/core.c   |  2 +-
>  drivers/power/sequencing/pwrseq-pcie-m2.c     |  2 +-
>  drivers/tty/serdev/core.c                     | 62 ++++++++++++++++---
>  include/linux/device-id/serdev.h              | 19 ++++++
>  include/linux/serdev.h                        | 12 +++-
>  6 files changed, 86 insertions(+), 12 deletions(-)
>  create mode 100644 include/linux/device-id/serdev.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 917f3f72e31b..06e67aa5d9b0 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -24905,6 +24905,7 @@ L:	linux-serial@vger.kernel.org
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/serial/serial.yaml
>  F:	drivers/tty/serdev/
> +F:	include/linux/device-id/serdev.h
>  F:	include/linux/serdev.h
>  F:	rust/helpers/serdev.c
>  F:	rust/kernel/serdev.rs
> diff --git a/drivers/platform/x86/x86-android-tablets/core.c b/drivers/platform/x86/x86-android-tablets/core.c
> index cfff7f5eac5d..853aa6ff5d50 100644
> --- a/drivers/platform/x86/x86-android-tablets/core.c
> +++ b/drivers/platform/x86/x86-android-tablets/core.c
> @@ -317,7 +317,7 @@ static __init int x86_instantiate_serdev(const struct x86_dev_info *dev_info, in
>  	ACPI_COMPANION_SET(&serdev->dev, serdev_adev);
>  	acpi_device_set_enumerated(serdev_adev);
>  
> -	ret = serdev_device_add(serdev);
> +	ret = serdev_device_add(serdev, NULL);
>  	if (ret) {
>  		dev_err(&serdev->dev, "error %d adding serdev\n", ret);
>  		serdev_device_put(serdev);
> diff --git a/drivers/power/sequencing/pwrseq-pcie-m2.c b/drivers/power/sequencing/pwrseq-pcie-m2.c
> index e42e85f47629..e0482f2ef39f 100644
> --- a/drivers/power/sequencing/pwrseq-pcie-m2.c
> +++ b/drivers/power/sequencing/pwrseq-pcie-m2.c
> @@ -309,7 +309,7 @@ static int pwrseq_pcie_m2_create_serdev_one(struct pwrseq_pcie_m2_ctx *ctx,
>  	if (ret)
>  		goto err_free_serdev;
>  
> -	ret = serdev_device_add(pci_dev->serdev);
> +	ret = serdev_device_add(pci_dev->serdev, NULL);
>  	if (ret) {
>  		dev_err(dev, "Failed to add serdev for PCI device (%s): %d\n",
>  			pci_name(pdev), ret);
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index 7500efcdfc21..e0517d5a48da 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -29,13 +29,21 @@ static DEFINE_IDA(ctrl_ida);
>  static ssize_t modalias_show(struct device *dev,
>  			     struct device_attribute *attr, char *buf)
>  {
> +	const struct serdev_device *serdev = to_serdev_device(dev);
>  	int len;
>  
>  	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
>  	if (len != -ENODEV)
>  		return len;
>  
> -	return of_device_modalias(dev, buf, PAGE_SIZE);
> +	len = of_device_modalias(dev, buf, PAGE_SIZE);
> +	if (len != -ENODEV)
> +		return len;
> +
> +	if (!serdev->modalias[0])
> +		return -ENODEV;
> +
> +	return sysfs_emit(buf, "%s%s\n", SERDEV_MODULE_PREFIX, serdev->modalias);
>  }
>  static DEVICE_ATTR_RO(modalias);
>  
> @@ -47,15 +55,22 @@ ATTRIBUTE_GROUPS(serdev_device);
>  
>  static int serdev_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
>  {
> +	const struct serdev_device *serdev = to_serdev_device(dev);
>  	int rc;
>  
> -	/* TODO: platform modalias */
> -
>  	rc = acpi_device_uevent_modalias(dev, env);
>  	if (rc != -ENODEV)
>  		return rc;
>  
> -	return of_device_uevent_modalias(dev, env);
> +	rc = of_device_uevent_modalias(dev, env);
> +	if (rc != -ENODEV)
> +		return rc;
> +
> +	if (!serdev->modalias[0])
> +		return -ENODEV;
> +
> +	return add_uevent_var(env, "MODALIAS=%s%s", SERDEV_MODULE_PREFIX,
> +			      serdev->modalias);
>  }
>  
>  static void serdev_device_release(struct device *dev)
> @@ -86,28 +101,57 @@ static const struct device_type serdev_ctrl_type = {
>  	.release	= serdev_ctrl_release,
>  };
>  
> +static const struct serdev_device_id *serdev_match_id(const struct serdev_device_id *id,
> +						      const char *modalias)
> +{
> +	if (!id || !modalias[0])
> +		return NULL;
> +
> +	while (id->name[0]) {
> +		if (!strcmp(modalias, id->name))
> +			return id;
> +		id++;
> +	}
> +
> +	return NULL;
> +}
> +
>  static int serdev_device_match(struct device *dev, const struct device_driver *drv)
>  {
> +	const struct serdev_device *serdev;
> +	const struct serdev_device_driver *sdrv;
> +
>  	if (!is_serdev_device(dev))
>  		return 0;
>  
> -	/* TODO: platform matching */
> +	serdev = to_serdev_device(dev);
> +	sdrv = to_serdev_device_driver(drv);
> +
>  	if (acpi_driver_match_device(dev, drv))
>  		return 1;
>  
> -	return of_driver_match_device(dev, drv);
> +	if (of_driver_match_device(dev, drv))
> +		return 1;
> +
> +	return !!serdev_match_id(sdrv->id_table, serdev->modalias);
>  }
>  
>  /**
>   * serdev_device_add() - add a device previously constructed via serdev_device_alloc()
>   * @serdev:	serdev_device to be added
> + * @modalias:	Driver name or alias, used to match devices which have neither
> + *		an ACPI companion nor a device tree node. NULL for devices
> + *		enumerated from firmware.
>   */
> -int serdev_device_add(struct serdev_device *serdev)
> +int serdev_device_add(struct serdev_device *serdev, const char *modalias)
>  {
>  	struct serdev_controller *ctrl = serdev->ctrl;
>  	struct device *parent = serdev->dev.parent;
>  	int err;
>  
> +	if (modalias)
> +		strscpy(serdev->modalias, modalias);
> +
>  	dev_set_name(&serdev->dev, "%s-%d", dev_name(parent), serdev->nr);
>  
>  	/* Only a single slave device is currently supported. */
> @@ -553,7 +597,7 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
>  
>  		device_set_node(&serdev->dev, of_fwnode_handle(node));
>  
> -		err = serdev_device_add(serdev);
> +		err = serdev_device_add(serdev, NULL);
>  		if (err) {
>  			dev_err(&serdev->dev,
>  				"failure adding device. status %pe\n",
> @@ -707,7 +751,7 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>  	ACPI_COMPANION_SET(&serdev->dev, adev);
>  	acpi_device_set_enumerated(adev);
>  
> -	err = serdev_device_add(serdev);
> +	err = serdev_device_add(serdev, NULL);
>  	if (err) {
>  		dev_err(&serdev->dev,
>  			"failure adding ACPI serdev device. status %pe\n",
> diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
> new file mode 100644
> index 000000000000..96644953cece
> --- /dev/null
> +++ b/include/linux/device-id/serdev.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef LINUX_DEVICE_ID_SERDEV_H
> +#define LINUX_DEVICE_ID_SERDEV_H
> +
> +#ifdef __KERNEL__
> +typedef unsigned long kernel_ulong_t;
> +#endif
> +
> +/* serdev */
> +
> +#define SERDEV_NAME_SIZE	40
> +#define SERDEV_MODULE_PREFIX	"serial:"
> +
> +struct serdev_device_id {
> +	char name[SERDEV_NAME_SIZE];
> +	kernel_ulong_t driver_data;	/* Data private to the driver */
> +};
> +
> +#endif /* ifndef LINUX_DEVICE_ID_SERDEV_H */
> diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> index b6c3d957ec15..96a441abc1ac 100644
> --- a/include/linux/serdev.h
> +++ b/include/linux/serdev.h
> @@ -7,7 +7,9 @@
>  
>  #include <linux/types.h>
>  #include <linux/device.h>
> +#include <linux/device-id/serdev.h>
>  #include <linux/iopoll.h>
> +#include <linux/string.h>
Unused include.

>  #include <linux/uaccess.h>
>  #include <linux/termios.h>
>  #include <linux/delay.h>
> @@ -35,6 +37,10 @@ struct serdev_device_ops {
>   * struct serdev_device - Basic representation of an serdev device
>   * @dev:	Driver model representation of the device.
>   * @nr:		Device number on serdev bus.
> + * @modalias:	Name of the driver to use with this device, or the alias
> + *		for it. Empty for devices enumerated from firmware, which
> + *		are identified through their ACPI companion or their device
> + *		tree node instead. See serdev_device_add().
>   * @ctrl:	serdev controller managing this device.
>   * @ops:	Device operations.
>   * @write_comp:	Completion used by serdev_device_write() internally
> @@ -43,6 +49,7 @@ struct serdev_device_ops {
>  struct serdev_device {
>  	struct device dev;
>  	int nr;
> +	char modalias[SERDEV_NAME_SIZE];
>  	struct serdev_controller *ctrl;
>  	const struct serdev_device_ops *ops;
>  	struct completion write_comp;
> @@ -55,12 +62,15 @@ struct serdev_device {
>   * struct serdev_device_driver - serdev slave device driver
>   * @driver:	serdev device drivers should initialize name field of this
>   *		structure.
> + * @id_table:	List of serdev devices supported by this driver, used to
> + *		match devices which are not enumerated from firmware.
>   * @probe:	binds this driver to a serdev device.
>   * @remove:	unbinds this driver from the serdev device.
>   * @shutdown:	shut down this serdev device.
>   */
>  struct serdev_device_driver {
>  	struct device_driver driver;
> +	const struct serdev_device_id *id_table;
>  	int	(*probe)(struct serdev_device *);
>  	void	(*remove)(struct serdev_device *);
>  	void	(*shutdown)(struct serdev_device *);
> @@ -158,7 +168,7 @@ static inline void serdev_controller_put(struct serdev_controller *ctrl)
>  }
>  
>  struct serdev_device *serdev_device_alloc(struct serdev_controller *);
> -int serdev_device_add(struct serdev_device *);
> +int serdev_device_add(struct serdev_device *serdev, const char *modalias);
>  void serdev_device_remove(struct serdev_device *);
>  
>  struct serdev_controller *serdev_controller_alloc(struct device *host,

You will need to address the sashiko report (both are true positives).

In the scripts/mod/file2alias.c file, you can copy the spi entry.
scripts/mod/devicetable-offsets.{h,c,s} and
include/linux/mod_devicetable.h are also relevant for this.
(Didn't know myself those files existed, so thx Sashiko)

Also add serdev_device_id to scripts/coccinelle/misc/of_table.cocci .


With that fixed,

Reviewed-by: Markus Probst <markus.probst@posteo.de>


Thanks
- Markus Probst

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 870 bytes --]

Re: [PATCH v5 1/3] serdev: handle devices without an ACPI or device tree node

[An Wu]

Hi Markus
    Working on it,
Thank you~

BR
    An

On Sat, Oct 24, 2026 at 8:58 PM Markus Probst <markus.probst@posteo.de> wrote:
>
> On Sat, 2026-10-24 at 20:04 +0800, ChunAn Wu wrote:
> > Serdev clients instantiated by a driver have no ACPI companion and no
> > device tree node. Their modalias read returns -ENODEV, their add uevent
> > is suppressed, and they cannot be driver-matched, so creators force a
> > bind with device_driver_attach().
> >
> > Resolve both TODOs in the serdev core by modelling matching on the SPI
> > bus: let the creator pass a modalias to serdev_device_add() and give
> > struct serdev_device_driver an id_table. ACPI and OF are still tried
> > first; clients without their own modalias keep returning -ENODEV. The
> > device name, derived from the controller, is unchanged.
> >
> > Split struct serdev_device_id and its defines into a new
> > include/linux/device-id/serdev.h, following the pattern already used by
> > the SPI and I2C buses.
> >
> > Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> > ---
> >  MAINTAINERS                                   |  1 +
> >  .../platform/x86/x86-android-tablets/core.c   |  2 +-
> >  drivers/power/sequencing/pwrseq-pcie-m2.c     |  2 +-
> >  drivers/tty/serdev/core.c                     | 62 ++++++++++++++++---
> >  include/linux/device-id/serdev.h              | 19 ++++++
> >  include/linux/serdev.h                        | 12 +++-
> >  6 files changed, 86 insertions(+), 12 deletions(-)
> >  create mode 100644 include/linux/device-id/serdev.h
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 917f3f72e31b..06e67aa5d9b0 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -24905,6 +24905,7 @@ L:    linux-serial@vger.kernel.org
> >  S:   Maintained
> >  F:   Documentation/devicetree/bindings/serial/serial.yaml
> >  F:   drivers/tty/serdev/
> > +F:   include/linux/device-id/serdev.h
> >  F:   include/linux/serdev.h
> >  F:   rust/helpers/serdev.c
> >  F:   rust/kernel/serdev.rs
> > diff --git a/drivers/platform/x86/x86-android-tablets/core.c b/drivers/platform/x86/x86-android-tablets/core.c
> > index cfff7f5eac5d..853aa6ff5d50 100644
> > --- a/drivers/platform/x86/x86-android-tablets/core.c
> > +++ b/drivers/platform/x86/x86-android-tablets/core.c
> > @@ -317,7 +317,7 @@ static __init int x86_instantiate_serdev(const struct x86_dev_info *dev_info, in
> >       ACPI_COMPANION_SET(&serdev->dev, serdev_adev);
> >       acpi_device_set_enumerated(serdev_adev);
> >
> > -     ret = serdev_device_add(serdev);
> > +     ret = serdev_device_add(serdev, NULL);
> >       if (ret) {
> >               dev_err(&serdev->dev, "error %d adding serdev\n", ret);
> >               serdev_device_put(serdev);
> > diff --git a/drivers/power/sequencing/pwrseq-pcie-m2.c b/drivers/power/sequencing/pwrseq-pcie-m2.c
> > index e42e85f47629..e0482f2ef39f 100644
> > --- a/drivers/power/sequencing/pwrseq-pcie-m2.c
> > +++ b/drivers/power/sequencing/pwrseq-pcie-m2.c
> > @@ -309,7 +309,7 @@ static int pwrseq_pcie_m2_create_serdev_one(struct pwrseq_pcie_m2_ctx *ctx,
> >       if (ret)
> >               goto err_free_serdev;
> >
> > -     ret = serdev_device_add(pci_dev->serdev);
> > +     ret = serdev_device_add(pci_dev->serdev, NULL);
> >       if (ret) {
> >               dev_err(dev, "Failed to add serdev for PCI device (%s): %d\n",
> >                       pci_name(pdev), ret);
> > diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> > index 7500efcdfc21..e0517d5a48da 100644
> > --- a/drivers/tty/serdev/core.c
> > +++ b/drivers/tty/serdev/core.c
> > @@ -29,13 +29,21 @@ static DEFINE_IDA(ctrl_ida);
> >  static ssize_t modalias_show(struct device *dev,
> >                            struct device_attribute *attr, char *buf)
> >  {
> > +     const struct serdev_device *serdev = to_serdev_device(dev);
> >       int len;
> >
> >       len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
> >       if (len != -ENODEV)
> >               return len;
> >
> > -     return of_device_modalias(dev, buf, PAGE_SIZE);
> > +     len = of_device_modalias(dev, buf, PAGE_SIZE);
> > +     if (len != -ENODEV)
> > +             return len;
> > +
> > +     if (!serdev->modalias[0])
> > +             return -ENODEV;
> > +
> > +     return sysfs_emit(buf, "%s%s\n", SERDEV_MODULE_PREFIX, serdev->modalias);
> >  }
> >  static DEVICE_ATTR_RO(modalias);
> >
> > @@ -47,15 +55,22 @@ ATTRIBUTE_GROUPS(serdev_device);
> >
> >  static int serdev_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
> >  {
> > +     const struct serdev_device *serdev = to_serdev_device(dev);
> >       int rc;
> >
> > -     /* TODO: platform modalias */
> > -
> >       rc = acpi_device_uevent_modalias(dev, env);
> >       if (rc != -ENODEV)
> >               return rc;
> >
> > -     return of_device_uevent_modalias(dev, env);
> > +     rc = of_device_uevent_modalias(dev, env);
> > +     if (rc != -ENODEV)
> > +             return rc;
> > +
> > +     if (!serdev->modalias[0])
> > +             return -ENODEV;
> > +
> > +     return add_uevent_var(env, "MODALIAS=%s%s", SERDEV_MODULE_PREFIX,
> > +                           serdev->modalias);
> >  }
> >
> >  static void serdev_device_release(struct device *dev)
> > @@ -86,28 +101,57 @@ static const struct device_type serdev_ctrl_type = {
> >       .release        = serdev_ctrl_release,
> >  };
> >
> > +static const struct serdev_device_id *serdev_match_id(const struct serdev_device_id *id,
> > +                                                   const char *modalias)
> > +{
> > +     if (!id || !modalias[0])
> > +             return NULL;
> > +
> > +     while (id->name[0]) {
> > +             if (!strcmp(modalias, id->name))
> > +                     return id;
> > +             id++;
> > +     }
> > +
> > +     return NULL;
> > +}
> > +
> >  static int serdev_device_match(struct device *dev, const struct device_driver *drv)
> >  {
> > +     const struct serdev_device *serdev;
> > +     const struct serdev_device_driver *sdrv;
> > +
> >       if (!is_serdev_device(dev))
> >               return 0;
> >
> > -     /* TODO: platform matching */
> > +     serdev = to_serdev_device(dev);
> > +     sdrv = to_serdev_device_driver(drv);
> > +
> >       if (acpi_driver_match_device(dev, drv))
> >               return 1;
> >
> > -     return of_driver_match_device(dev, drv);
> > +     if (of_driver_match_device(dev, drv))
> > +             return 1;
> > +
> > +     return !!serdev_match_id(sdrv->id_table, serdev->modalias);
> >  }
> >
> >  /**
> >   * serdev_device_add() - add a device previously constructed via serdev_device_alloc()
> >   * @serdev:  serdev_device to be added
> > + * @modalias:        Driver name or alias, used to match devices which have neither
> > + *           an ACPI companion nor a device tree node. NULL for devices
> > + *           enumerated from firmware.
> >   */
> > -int serdev_device_add(struct serdev_device *serdev)
> > +int serdev_device_add(struct serdev_device *serdev, const char *modalias)
> >  {
> >       struct serdev_controller *ctrl = serdev->ctrl;
> >       struct device *parent = serdev->dev.parent;
> >       int err;
> >
> > +     if (modalias)
> > +             strscpy(serdev->modalias, modalias);
> > +
> >       dev_set_name(&serdev->dev, "%s-%d", dev_name(parent), serdev->nr);
> >
> >       /* Only a single slave device is currently supported. */
> > @@ -553,7 +597,7 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
> >
> >               device_set_node(&serdev->dev, of_fwnode_handle(node));
> >
> > -             err = serdev_device_add(serdev);
> > +             err = serdev_device_add(serdev, NULL);
> >               if (err) {
> >                       dev_err(&serdev->dev,
> >                               "failure adding device. status %pe\n",
> > @@ -707,7 +751,7 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
> >       ACPI_COMPANION_SET(&serdev->dev, adev);
> >       acpi_device_set_enumerated(adev);
> >
> > -     err = serdev_device_add(serdev);
> > +     err = serdev_device_add(serdev, NULL);
> >       if (err) {
> >               dev_err(&serdev->dev,
> >                       "failure adding ACPI serdev device. status %pe\n",
> > diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
> > new file mode 100644
> > index 000000000000..96644953cece
> > --- /dev/null
> > +++ b/include/linux/device-id/serdev.h
> > @@ -0,0 +1,19 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef LINUX_DEVICE_ID_SERDEV_H
> > +#define LINUX_DEVICE_ID_SERDEV_H
> > +
> > +#ifdef __KERNEL__
> > +typedef unsigned long kernel_ulong_t;
> > +#endif
> > +
> > +/* serdev */
> > +
> > +#define SERDEV_NAME_SIZE     40
> > +#define SERDEV_MODULE_PREFIX "serial:"
> > +
> > +struct serdev_device_id {
> > +     char name[SERDEV_NAME_SIZE];
> > +     kernel_ulong_t driver_data;     /* Data private to the driver */
> > +};
> > +
> > +#endif /* ifndef LINUX_DEVICE_ID_SERDEV_H */
> > diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> > index b6c3d957ec15..96a441abc1ac 100644
> > --- a/include/linux/serdev.h
> > +++ b/include/linux/serdev.h
> > @@ -7,7 +7,9 @@
> >
> >  #include <linux/types.h>
> >  #include <linux/device.h>
> > +#include <linux/device-id/serdev.h>
> >  #include <linux/iopoll.h>
> > +#include <linux/string.h>
> Unused include.
>
> >  #include <linux/uaccess.h>
> >  #include <linux/termios.h>
> >  #include <linux/delay.h>
> > @@ -35,6 +37,10 @@ struct serdev_device_ops {
> >   * struct serdev_device - Basic representation of an serdev device
> >   * @dev:     Driver model representation of the device.
> >   * @nr:              Device number on serdev bus.
> > + * @modalias:        Name of the driver to use with this device, or the alias
> > + *           for it. Empty for devices enumerated from firmware, which
> > + *           are identified through their ACPI companion or their device
> > + *           tree node instead. See serdev_device_add().
> >   * @ctrl:    serdev controller managing this device.
> >   * @ops:     Device operations.
> >   * @write_comp:      Completion used by serdev_device_write() internally
> > @@ -43,6 +49,7 @@ struct serdev_device_ops {
> >  struct serdev_device {
> >       struct device dev;
> >       int nr;
> > +     char modalias[SERDEV_NAME_SIZE];
> >       struct serdev_controller *ctrl;
> >       const struct serdev_device_ops *ops;
> >       struct completion write_comp;
> > @@ -55,12 +62,15 @@ struct serdev_device {
> >   * struct serdev_device_driver - serdev slave device driver
> >   * @driver:  serdev device drivers should initialize name field of this
> >   *           structure.
> > + * @id_table:        List of serdev devices supported by this driver, used to
> > + *           match devices which are not enumerated from firmware.
> >   * @probe:   binds this driver to a serdev device.
> >   * @remove:  unbinds this driver from the serdev device.
> >   * @shutdown:        shut down this serdev device.
> >   */
> >  struct serdev_device_driver {
> >       struct device_driver driver;
> > +     const struct serdev_device_id *id_table;
> >       int     (*probe)(struct serdev_device *);
> >       void    (*remove)(struct serdev_device *);
> >       void    (*shutdown)(struct serdev_device *);
> > @@ -158,7 +168,7 @@ static inline void serdev_controller_put(struct serdev_controller *ctrl)
> >  }
> >
> >  struct serdev_device *serdev_device_alloc(struct serdev_controller *);
> > -int serdev_device_add(struct serdev_device *);
> > +int serdev_device_add(struct serdev_device *serdev, const char *modalias);
> >  void serdev_device_remove(struct serdev_device *);
> >
> >  struct serdev_controller *serdev_controller_alloc(struct device *host,
>
> You will need to address the sashiko report (both are true positives).
>
> In the scripts/mod/file2alias.c file, you can copy the spi entry.
> scripts/mod/devicetable-offsets.{h,c,s} and
> include/linux/mod_devicetable.h are also relevant for this.
> (Didn't know myself those files existed, so thx Sashiko)
>
> Also add serdev_device_id to scripts/coccinelle/misc/of_table.cocci .
>
>
> With that fixed,
>
> Reviewed-by: Markus Probst <markus.probst@posteo.de>
>
>
> Thanks
> - Markus Probst

[PATCH v5 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching

[ChunAn Wu]

The driver creates a serdev client without firmware metadata and
force-attaches its driver to it.

Pass the modalias to serdev_device_add() and give the serdev driver a
matching id_table, so that the serdev core binds the two through normal
matching, then drop the manual attachment.

The client now also reports a "serial:dell_uart_backlight" modalias to
userspace instead of failing with -ENODEV. A failing serdev probe no
longer propagates out of the platform probe; as for any other bus, the
client is simply left unbound.

Signed-off-by: ChunAn Wu <an.wu@canonical.com>
---
 .../platform/x86/dell/dell-uart-backlight.c    | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
index f323a667dc2d..9b8ef91bb0a2 100644
--- a/drivers/platform/x86/dell/dell-uart-backlight.c
+++ b/drivers/platform/x86/dell/dell-uart-backlight.c
@@ -325,11 +325,17 @@ static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
 	return PTR_ERR_OR_ZERO(dell_bl->bl);
 }
 
+static const struct serdev_device_id dell_uart_bl_serdev_id[] = {
+	{ KBUILD_MODNAME },
+	{ }
+};
+
 static struct serdev_device_driver dell_uart_bl_serdev_driver = {
 	.probe = dell_uart_bl_serdev_probe,
 	.driver = {
 		.name = KBUILD_MODNAME,
 	},
+	.id_table = dell_uart_bl_serdev_id,
 };
 
 static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
@@ -354,7 +360,7 @@ static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
 	if (!serdev)
 		return -ENOMEM;
 
-	ret = serdev_device_add(serdev);
+	ret = serdev_device_add(serdev, KBUILD_MODNAME);
 	if (ret) {
 		dev_err(&pdev->dev, "error %d adding serdev\n", ret);
 		serdev_device_put(serdev);
@@ -365,20 +371,10 @@ static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_remove_serdev;
 
-	/*
-	 * serdev device <-> driver matching relies on OF or ACPI matches and
-	 * neither is available here, manually bind the driver.
-	 */
-	ret = device_driver_attach(&dell_uart_bl_serdev_driver.driver, &serdev->dev);
-	if (ret)
-		goto err_unregister_serdev_driver;
-
 	/* So that dell_uart_bl_pdev_remove() can remove the serdev */
 	platform_set_drvdata(pdev, serdev);
 	return 0;
 
-err_unregister_serdev_driver:
-	serdev_device_driver_unregister(&dell_uart_bl_serdev_driver);
 err_remove_serdev:
 	serdev_device_remove(serdev);
 	return ret;
-- 
2.34.1

Re: [PATCH v5 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching

[Markus Probst]

[-- Attachment #1: Type: text/plain, Size: 2783 bytes --]

On Sat, 2026-10-24 at 20:04 +0800, ChunAn Wu wrote:
> The driver creates a serdev client without firmware metadata and
> force-attaches its driver to it.
> 
> Pass the modalias to serdev_device_add() and give the serdev driver a
> matching id_table, so that the serdev core binds the two through normal
> matching, then drop the manual attachment.
> 
> The client now also reports a "serial:dell_uart_backlight" modalias to
> userspace instead of failing with -ENODEV. A failing serdev probe no
> longer propagates out of the platform probe; as for any other bus, the
> client is simply left unbound.
> 
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
>  .../platform/x86/dell/dell-uart-backlight.c    | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
> index f323a667dc2d..9b8ef91bb0a2 100644
> --- a/drivers/platform/x86/dell/dell-uart-backlight.c
> +++ b/drivers/platform/x86/dell/dell-uart-backlight.c
> @@ -325,11 +325,17 @@ static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
>  	return PTR_ERR_OR_ZERO(dell_bl->bl);
>  }
>  
> +static const struct serdev_device_id dell_uart_bl_serdev_id[] = {
> +	{ KBUILD_MODNAME },
> +	{ }
> +};
> +
>  static struct serdev_device_driver dell_uart_bl_serdev_driver = {
>  	.probe = dell_uart_bl_serdev_probe,
>  	.driver = {
>  		.name = KBUILD_MODNAME,
>  	},
> +	.id_table = dell_uart_bl_serdev_id,
>  };
>  
>  static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
> @@ -354,7 +360,7 @@ static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
>  	if (!serdev)
>  		return -ENOMEM;
>  
> -	ret = serdev_device_add(serdev);
> +	ret = serdev_device_add(serdev, KBUILD_MODNAME);
>  	if (ret) {
>  		dev_err(&pdev->dev, "error %d adding serdev\n", ret);
>  		serdev_device_put(serdev);
> @@ -365,20 +371,10 @@ static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_remove_serdev;
>  
> -	/*
> -	 * serdev device <-> driver matching relies on OF or ACPI matches and
> -	 * neither is available here, manually bind the driver.
> -	 */
> -	ret = device_driver_attach(&dell_uart_bl_serdev_driver.driver, &serdev->dev);
> -	if (ret)
> -		goto err_unregister_serdev_driver;
> -
>  	/* So that dell_uart_bl_pdev_remove() can remove the serdev */
>  	platform_set_drvdata(pdev, serdev);
>  	return 0;
>  
> -err_unregister_serdev_driver:
> -	serdev_device_driver_unregister(&dell_uart_bl_serdev_driver);
>  err_remove_serdev:
>  	serdev_device_remove(serdev);
>  	return ret;

Reviewed-by: Markus Probst <markus.probst@posteo.de>

Thanks
- Markus Probst

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[PATCH v5 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: Bind through normal serdev matching

[ChunAn Wu]

The software-node-backed serdev client cannot be matched through ACPI or
device tree and is force-attached to its driver.

Pass the modalias to serdev_device_add() and give the serdev driver a
matching id_table, so that the serdev core binds the two through normal
matching. Deferred probing is then handled by the driver core, so the
-EAGAIN translation is no longer needed.

A failing serdev probe no longer propagates out of the platform probe;
as for any other bus, the client is simply left unbound.

Signed-off-by: ChunAn Wu <an.wu@canonical.com>
---
 .../lenovo/yoga-tab2-pro-1380-fastcharger.c   | 25 +++++++------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c b/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
index 8551ab4d2c7d..d0bd9d4e3137 100644
--- a/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
+++ b/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
@@ -219,11 +219,17 @@ static int yt2_1380_fc_serdev_probe(struct serdev_device *serdev)
 	return 0;
 }
 
+static const struct serdev_device_id yt2_1380_fc_serdev_id[] = {
+	{ KBUILD_MODNAME },
+	{ }
+};
+
 static struct serdev_device_driver yt2_1380_fc_serdev_driver = {
 	.probe = yt2_1380_fc_serdev_probe,
 	.driver = {
 		.name = KBUILD_MODNAME,
 	},
+	.id_table = yt2_1380_fc_serdev_id,
 };
 
 static const struct pinctrl_map yt2_1380_fc_pinctrl_map[] = {
@@ -260,25 +266,12 @@ static int yt2_1380_fc_pdev_probe(struct platform_device *pdev)
 	/* The fwnode is a managed node, so it will be auto-put on serdev_device_put() */
 	fwnode_handle_get(dev_fwnode(&serdev->dev));
 
-	ret = serdev_device_add(serdev);
+	ret = serdev_device_add(serdev, KBUILD_MODNAME);
 	if (ret) {
 		serdev_device_put(serdev);
 		return dev_err_probe(&pdev->dev, ret, "adding serdev\n");
 	}
 
-	/*
-	 * serdev device <-> driver matching relies on OF or ACPI matches and
-	 * neither is available here, manually bind the driver.
-	 */
-	ret = device_driver_attach(&yt2_1380_fc_serdev_driver.driver, &serdev->dev);
-	if (ret) {
-		/* device_driver_attach() maps EPROBE_DEFER to EAGAIN, map it back */
-		serdev_device_remove(serdev);
-		return dev_err_probe(&pdev->dev,
-				     (ret == -EAGAIN) ? -EPROBE_DEFER : ret,
-				     "attaching serdev driver\n");
-	}
-
 	/* So that yt2_1380_fc_pdev_remove() can remove the serdev */
 	platform_set_drvdata(pdev, serdev);
 	return 0;
@@ -305,8 +298,8 @@ static int __init yt2_1380_fc_module_init(void)
 	int ret;
 
 	/*
-	 * serdev driver MUST be registered first because pdev driver calls
-	 * device_driver_attach() on the serdev, serdev-driver pair.
+	 * serdev driver MUST be registered first so that the serdev device
+	 * created by the pdev probe binds to it via the id_table match.
 	 */
 	ret = serdev_device_driver_register(&yt2_1380_fc_serdev_driver);
 	if (ret)
-- 
2.34.1

Re: [PATCH v5 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: Bind through normal serdev matching

[Markus Probst]

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On Sat, 2026-10-24 at 20:04 +0800, ChunAn Wu wrote:
> The software-node-backed serdev client cannot be matched through ACPI or
> device tree and is force-attached to its driver.
> 
> Pass the modalias to serdev_device_add() and give the serdev driver a
> matching id_table, so that the serdev core binds the two through normal
> matching. Deferred probing is then handled by the driver core, so the
> -EAGAIN translation is no longer needed.
> 
> A failing serdev probe no longer propagates out of the platform probe;
> as for any other bus, the client is simply left unbound.
> 
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
>  .../lenovo/yoga-tab2-pro-1380-fastcharger.c   | 25 +++++++------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c b/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
> index 8551ab4d2c7d..d0bd9d4e3137 100644
> --- a/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
> +++ b/drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c
> @@ -219,11 +219,17 @@ static int yt2_1380_fc_serdev_probe(struct serdev_device *serdev)
>  	return 0;
>  }
>  
> +static const struct serdev_device_id yt2_1380_fc_serdev_id[] = {
> +	{ KBUILD_MODNAME },
> +	{ }
> +};
> +
>  static struct serdev_device_driver yt2_1380_fc_serdev_driver = {
>  	.probe = yt2_1380_fc_serdev_probe,
>  	.driver = {
>  		.name = KBUILD_MODNAME,
>  	},
> +	.id_table = yt2_1380_fc_serdev_id,
>  };
>  
>  static const struct pinctrl_map yt2_1380_fc_pinctrl_map[] = {
> @@ -260,25 +266,12 @@ static int yt2_1380_fc_pdev_probe(struct platform_device *pdev)
>  	/* The fwnode is a managed node, so it will be auto-put on serdev_device_put() */
>  	fwnode_handle_get(dev_fwnode(&serdev->dev));
>  
> -	ret = serdev_device_add(serdev);
> +	ret = serdev_device_add(serdev, KBUILD_MODNAME);
>  	if (ret) {
>  		serdev_device_put(serdev);
>  		return dev_err_probe(&pdev->dev, ret, "adding serdev\n");
>  	}
>  
> -	/*
> -	 * serdev device <-> driver matching relies on OF or ACPI matches and
> -	 * neither is available here, manually bind the driver.
> -	 */
> -	ret = device_driver_attach(&yt2_1380_fc_serdev_driver.driver, &serdev->dev);
> -	if (ret) {
> -		/* device_driver_attach() maps EPROBE_DEFER to EAGAIN, map it back */
> -		serdev_device_remove(serdev);
> -		return dev_err_probe(&pdev->dev,
> -				     (ret == -EAGAIN) ? -EPROBE_DEFER : ret,
> -				     "attaching serdev driver\n");
> -	}
> -
>  	/* So that yt2_1380_fc_pdev_remove() can remove the serdev */
>  	platform_set_drvdata(pdev, serdev);
>  	return 0;
> @@ -305,8 +298,8 @@ static int __init yt2_1380_fc_module_init(void)
>  	int ret;
>  
>  	/*
> -	 * serdev driver MUST be registered first because pdev driver calls
> -	 * device_driver_attach() on the serdev, serdev-driver pair.
> +	 * serdev driver MUST be registered first so that the serdev device
> +	 * created by the pdev probe binds to it via the id_table match.
>  	 */
NIT: I think the order doesn't matter anymore, since it will bind
regardless whether driver or device is registered/added first. I think
you can remove the comment.

Reviewed-by: Markus Probst <markus.probst@posteo.de>

Thanks
- Markus Probst



>  	ret = serdev_device_driver_register(&yt2_1380_fc_serdev_driver);
>  	if (ret)



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