* [PATCH v3 0/3] serdev: handle devices without an ACPI or device tree
@ 2026-10-23 5:27 ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node ChunAn Wu
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: ChunAn Wu @ 2026-10-23 5:27 UTC (permalink / raw)
To: linux-serial, platform-driver-x86
Cc: linux-kernel, markus.probst, gregkh, jirislaby, hansg,
ilpo.jarvinen, mpearson-lenovo, derekjohn.clark
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 adding a creator-set
modalias and 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.
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 | 27 +++++-----
drivers/tty/serdev/core.c | 54 ++++++++++++++++---
include/linux/device-id/serdev.h | 16 ++++++
include/linux/serdev.h | 34 ++++++++++++
6 files changed, 119 insertions(+), 31 deletions(-)
create mode 100644 include/linux/device-id/serdev.h
base-commit: 9e947d96915af63e28896caae85a81b74855621b
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node
2026-10-23 5:27 [PATCH v3 0/3] serdev: handle devices without an ACPI or device tree ChunAn Wu
@ 2026-10-23 5:27 ` ChunAn Wu
2026-10-23 12:26 ` Markus Probst
2026-10-23 5:27 ` [PATCH v3 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: " ChunAn Wu
2 siblings, 1 reply; 6+ messages in thread
From: ChunAn Wu @ 2026-10-23 5:27 UTC (permalink / raw)
To: linux-serial, platform-driver-x86
Cc: linux-kernel, markus.probst, gregkh, jirislaby, hansg,
ilpo.jarvinen, mpearson-lenovo, derekjohn.clark
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: add a creator-set modalias to struct serdev_device and an id_table
to struct serdev_device_driver. ACPI and OF are still tried first;
clients without their own modalias keep returning -ENODEV. The device
name, derived from the controller, is unchanged.
Signed-off-by: ChunAn Wu <an.wu@canonical.com>
---
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
MAINTAINERS | 1 +
drivers/tty/serdev/core.c | 54 ++++++++++++++++++++++++++++----
include/linux/device-id/serdev.h | 16 ++++++++++
include/linux/serdev.h | 34 ++++++++++++++++++++
4 files changed, 99 insertions(+), 6 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/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 7500efcdfc21..e178dc57d31b 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)
@@ -86,16 +101,43 @@ 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;
+
if (!is_serdev_device(dev))
return 0;
- /* TODO: platform matching */
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;
+
+ /*
+ * Devices which are instantiated by a driver instead of by firmware
+ * have no ACPI companion and no device tree node, match them by the
+ * modalias their creator gave them.
+ */
+ serdev = to_serdev_device(dev);
+
+ return !!serdev_match_id(to_serdev_device_driver(drv)->id_table,
+ serdev->modalias);
}
/**
diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
new file mode 100644
index 000000000000..1c3b03b7d501
--- /dev/null
+++ b/include/linux/device-id/serdev.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_DEVICE_ID_SERDEV_H
+#define LINUX_DEVICE_ID_SERDEV_H
+
+/* serdev */
+
+/* Large enough to hold the KBUILD_MODNAME of any serdev client driver */
+#define SERDEV_NAME_SIZE 40
+#define SERDEV_MODULE_PREFIX "serial:"
+
+struct serdev_device_id {
+ char name[SERDEV_NAME_SIZE];
+ unsigned long 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..9f91aa3e875d 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_set_modalias().
* @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;
@@ -58,12 +65,15 @@ struct serdev_device {
* @probe: binds this driver to a serdev device.
* @remove: unbinds this driver from the serdev device.
* @shutdown: shut down this serdev device.
+ * @id_table: List of serdev devices supported by this driver, used to
+ * match devices which are not enumerated from firmware.
*/
struct serdev_device_driver {
struct device_driver driver;
int (*probe)(struct serdev_device *);
void (*remove)(struct serdev_device *);
void (*shutdown)(struct serdev_device *);
+ const struct serdev_device_id *id_table;
};
#define to_serdev_device_driver(d) container_of_const(d, struct serdev_device_driver, driver)
@@ -135,6 +145,30 @@ static inline void serdev_device_set_client_ops(struct serdev_device *serdev,
serdev->ops = ops;
}
+/**
+ * serdev_device_set_modalias() - set the modalias of a serdev device
+ * @serdev: serdev device.
+ * @modalias: non-empty modalias to use, typically KBUILD_MODNAME of the
+ * client driver.
+ *
+ * A serdev device is identified by its ACPI companion, by its device tree
+ * node, or by a modalias set by its creator. Serdev devices which are
+ * instantiated by a driver rather than by firmware have neither of the
+ * former, so they must set a modalias before serdev_device_add() to be
+ * identifiable. Doing so reports a SERDEV_MODULE_PREFIX modalias to
+ * userspace and makes the device match an id_table entry of a serdev
+ * device driver.
+ *
+ * Devices enumerated from firmware have no modalias of their own and keep
+ * deriving their modalias and their driver match from firmware only. The
+ * device name is not affected either way.
+ */
+static inline void serdev_device_set_modalias(struct serdev_device *serdev,
+ const char *modalias)
+{
+ strscpy(serdev->modalias, modalias);
+}
+
static inline
void *serdev_controller_get_drvdata(const struct serdev_controller *ctrl)
{
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching
2026-10-23 5:27 [PATCH v3 0/3] serdev: handle devices without an ACPI or device tree ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node ChunAn Wu
@ 2026-10-23 5:27 ` ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: " ChunAn Wu
2 siblings, 0 replies; 6+ messages in thread
From: ChunAn Wu @ 2026-10-23 5:27 UTC (permalink / raw)
To: linux-serial, platform-driver-x86
Cc: linux-kernel, markus.probst, gregkh, jirislaby, hansg,
ilpo.jarvinen, mpearson-lenovo, derekjohn.clark
The driver creates a serdev client without firmware metadata and
force-attaches its driver to it.
Set the modalias of the client before adding it 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>
---
Changes in v3:
- Use serdev_device_set_modalias() instead of ::name; add an id_table
to the serdev driver
Changes in v2:
- New in v2
.../platform/x86/dell/dell-uart-backlight.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
index f323a667dc2d..13515ebda3dc 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_table[] = {
+ { 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_table,
};
static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
@@ -354,6 +360,8 @@ static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
if (!serdev)
return -ENOMEM;
+ serdev_device_set_modalias(serdev, KBUILD_MODNAME);
+
ret = serdev_device_add(serdev);
if (ret) {
dev_err(&pdev->dev, "error %d adding serdev\n", ret);
@@ -365,20 +373,10 @@ 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
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: Bind through normal serdev matching
2026-10-23 5:27 [PATCH v3 0/3] serdev: handle devices without an ACPI or device tree ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching ChunAn Wu
@ 2026-10-23 5:27 ` ChunAn Wu
2 siblings, 0 replies; 6+ messages in thread
From: ChunAn Wu @ 2026-10-23 5:27 UTC (permalink / raw)
To: linux-serial, platform-driver-x86
Cc: linux-kernel, markus.probst, gregkh, jirislaby, hansg,
ilpo.jarvinen, mpearson-lenovo, derekjohn.clark
The software-node-backed serdev client cannot be matched through ACPI or
device tree and is force-attached to its driver.
Set the modalias of the client before adding it 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>
---
Changes in v3:
- Use serdev_device_set_modalias() instead of ::name; add an id_table
to the serdev driver
Changes in v2:
- New in v2
.../lenovo/yoga-tab2-pro-1380-fastcharger.c | 27 +++++++++----------
1 file changed, 12 insertions(+), 15 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..31780c4aebe0 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_table[] = {
+ { 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_table,
};
static const struct pinctrl_map yt2_1380_fc_pinctrl_map[] = {
@@ -260,25 +266,14 @@ 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));
+ serdev_device_set_modalias(serdev, KBUILD_MODNAME);
+
ret = serdev_device_add(serdev);
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 +300,10 @@ 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.
+ * Register the serdev driver first, so that the serdev device which
+ * the pdev driver's probe() adds is matched as soon as it is added.
+ * Registering it afterwards would work as well, since driver_register()
+ * also walks the devices which are already on the bus.
*/
ret = serdev_device_driver_register(&yt2_1380_fc_serdev_driver);
if (ret)
--
2.34.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node
2026-10-23 5:27 ` [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node ChunAn Wu
@ 2026-10-23 12:26 ` Markus Probst
2026-10-23 13:02 ` An Wu
0 siblings, 1 reply; 6+ messages in thread
From: Markus Probst @ 2026-10-23 12:26 UTC (permalink / raw)
To: ChunAn Wu, linux-serial, platform-driver-x86
Cc: linux-kernel, gregkh, jirislaby, hansg, ilpo.jarvinen,
mpearson-lenovo, derekjohn.clark
[-- Attachment #1: Type: text/plain, Size: 10865 bytes --]
On Fri, 2026-10-23 at 13:27 +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: add a creator-set modalias to struct serdev_device and an id_table
> to struct serdev_device_driver. ACPI and OF are still tried first;
> clients without their own modalias keep returning -ENODEV. The device
> name, derived from the controller, is unchanged.
>
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
> 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
>
Thats something I would expect on the cover letter.
> MAINTAINERS | 1 +
> drivers/tty/serdev/core.c | 54 ++++++++++++++++++++++++++++----
> include/linux/device-id/serdev.h | 16 ++++++++++
> include/linux/serdev.h | 34 ++++++++++++++++++++
> 4 files changed, 99 insertions(+), 6 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/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index 7500efcdfc21..e178dc57d31b 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)
> @@ -86,16 +101,43 @@ 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;
> +
> if (!is_serdev_device(dev))
> return 0;
>
> - /* TODO: platform matching */
> 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;
> +
> + /*
> + * Devices which are instantiated by a driver instead of by firmware
> + * have no ACPI companion and no device tree node, match them by the
> + * modalias their creator gave them.
> + */
Drop comment.
> + serdev = to_serdev_device(dev);
> +
> + return !!serdev_match_id(to_serdev_device_driver(drv)->id_table,
> + serdev->modalias);
I think you can drop the `is_serdev_device` check and use
```
const struct serdev_device *serdev = to_serdev_device(dev);
const struct serdev_device_driver *sdrv = to_serdev_device_driver(drv);
```
in the top.
The function `serdev_device_match` is only used inside the match
callback on the bus type definition. Other bus devices also do not have
this check. It should be safe.
Alternatively `to_serdev_device` in the same expression as the function
call (like with `to_serdev_device_driver`). It should be consistent
(either both as variables or none).
> }
>
> /**
> diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
> new file mode 100644
> index 000000000000..1c3b03b7d501
> --- /dev/null
> +++ b/include/linux/device-id/serdev.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef LINUX_DEVICE_ID_SERDEV_H
> +#define LINUX_DEVICE_ID_SERDEV_H
> +
> +/* serdev */
> +
> +/* Large enough to hold the KBUILD_MODNAME of any serdev client driver */
Is this relevant for anyone reading the code? If not, drop the comment.
> +#define SERDEV_NAME_SIZE 40
> +#define SERDEV_MODULE_PREFIX "serial:"
> +
> +struct serdev_device_id {
> + char name[SERDEV_NAME_SIZE];
> + unsigned long driver_data; /* Data private to the driver */
> +};
In almost any other include/linux/device-id/*.h file, there is a
```
#ifdef __KERNEL__
#include <linux/types.h>
typedef unsigned long kernel_ulong_t;
#endif
```
statement and `kernel_ulong_t` is used.
I don't know why, but there is likely a reason for it. Thus do it the
same way, unless you can explain why this isn't needed here.
> +
> +#endif /* ifndef LINUX_DEVICE_ID_SERDEV_H */
> diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> index b6c3d957ec15..9f91aa3e875d 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_set_modalias().
> * @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;
> @@ -58,12 +65,15 @@ struct serdev_device {
> * @probe: binds this driver to a serdev device.
> * @remove: unbinds this driver from the serdev device.
> * @shutdown: shut down this serdev device.
> + * @id_table: List of serdev devices supported by this driver, used to
> + * match devices which are not enumerated from firmware.
> */
> struct serdev_device_driver {
> struct device_driver driver;
> int (*probe)(struct serdev_device *);
> void (*remove)(struct serdev_device *);
> void (*shutdown)(struct serdev_device *);
> + const struct serdev_device_id *id_table;
Just a suggestion:
Move it directly under driver, so the fields (driver->of_match_table,
driver->acpi_match_table, id_table) are next to each other. It has no
real runtime difference, so I won't complain if you leave it there.
> };
>
> #define to_serdev_device_driver(d) container_of_const(d, struct serdev_device_driver, driver)
> @@ -135,6 +145,30 @@ static inline void serdev_device_set_client_ops(struct serdev_device *serdev,
> serdev->ops = ops;
> }
>
> +/**
> + * serdev_device_set_modalias() - set the modalias of a serdev device
> + * @serdev: serdev device.
> + * @modalias: non-empty modalias to use, typically KBUILD_MODNAME of the
> + * client driver.
> + *
> + * A serdev device is identified by its ACPI companion, by its device tree
> + * node, or by a modalias set by its creator. Serdev devices which are
> + * instantiated by a driver rather than by firmware have neither of the
> + * former, so they must set a modalias before serdev_device_add() to be
> + * identifiable. Doing so reports a SERDEV_MODULE_PREFIX modalias to
> + * userspace and makes the device match an id_table entry of a serdev
> + * device driver.
> + *
> + * Devices enumerated from firmware have no modalias of their own and keep
> + * deriving their modalias and their driver match from firmware only. The
> + * device name is not affected either way.
> + */
> +static inline void serdev_device_set_modalias(struct serdev_device *serdev,
> + const char *modalias)
> +{
> + strscpy(serdev->modalias, modalias);
> +}
Drop the function.
Add `const char *modalias` as parameter to `serdev_device_add`. It
should be clear that any driver calling this function manually should
provide a modalias. Also, keep documentation simple (unless there is
need).
Either you add `__serdev_device_add` for internal use (of or acpi), or
it will use NULL. Your choice.
Overall, looks pretty good so far.
Thanks
- Markus Probst
> +
> static inline
> void *serdev_controller_get_drvdata(const struct serdev_controller *ctrl)
> {
[-- Attachment #2: This is a digitally signed message part --]
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node
2026-10-23 12:26 ` Markus Probst
@ 2026-10-23 13:02 ` An Wu
0 siblings, 0 replies; 6+ messages in thread
From: An Wu @ 2026-10-23 13:02 UTC (permalink / raw)
To: Markus Probst
Cc: linux-serial, platform-driver-x86, linux-kernel, gregkh,
jirislaby, hansg, ilpo.jarvinen, mpearson-lenovo,
derekjohn.clark
Hi Markus
Thank you for your review.
For this,
```
#ifdef __KERNEL__
#include <linux/types.h>
typedef unsigned long kernel_ulong_t;
#endif
```
I originally implemented it this way, but checkpatch.pl reported a warning.
Since it's only a warning, I'll go ahead and update it accordingly.
I really appreciate your patience and guidance. Thank you!
BR
An
On Fri, Oct 23, 2026 at 8:26 PM Markus Probst <markus.probst@posteo.de> wrote:
>
> On Fri, 2026-10-23 at 13:27 +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: add a creator-set modalias to struct serdev_device and an id_table
> > to struct serdev_device_driver. ACPI and OF are still tried first;
> > clients without their own modalias keep returning -ENODEV. The device
> > name, derived from the controller, is unchanged.
> >
> > Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> > ---
> > 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
> >
> Thats something I would expect on the cover letter.
> > MAINTAINERS | 1 +
> > drivers/tty/serdev/core.c | 54 ++++++++++++++++++++++++++++----
> > include/linux/device-id/serdev.h | 16 ++++++++++
> > include/linux/serdev.h | 34 ++++++++++++++++++++
> > 4 files changed, 99 insertions(+), 6 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/tty/serdev/core.c b/drivers/tty/serdev/core.c
> > index 7500efcdfc21..e178dc57d31b 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)
> > @@ -86,16 +101,43 @@ 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;
> > +
> > if (!is_serdev_device(dev))
> > return 0;
> >
> > - /* TODO: platform matching */
> > 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;
> > +
> > + /*
> > + * Devices which are instantiated by a driver instead of by firmware
> > + * have no ACPI companion and no device tree node, match them by the
> > + * modalias their creator gave them.
> > + */
> Drop comment.
>
> > + serdev = to_serdev_device(dev);
> > +
> > + return !!serdev_match_id(to_serdev_device_driver(drv)->id_table,
> > + serdev->modalias);
> I think you can drop the `is_serdev_device` check and use
>
> ```
> const struct serdev_device *serdev = to_serdev_device(dev);
> const struct serdev_device_driver *sdrv = to_serdev_device_driver(drv);
> ```
>
> in the top.
>
> The function `serdev_device_match` is only used inside the match
> callback on the bus type definition. Other bus devices also do not have
> this check. It should be safe.
>
> Alternatively `to_serdev_device` in the same expression as the function
> call (like with `to_serdev_device_driver`). It should be consistent
> (either both as variables or none).
>
> > }
> >
> > /**
> > diff --git a/include/linux/device-id/serdev.h b/include/linux/device-id/serdev.h
> > new file mode 100644
> > index 000000000000..1c3b03b7d501
> > --- /dev/null
> > +++ b/include/linux/device-id/serdev.h
> > @@ -0,0 +1,16 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef LINUX_DEVICE_ID_SERDEV_H
> > +#define LINUX_DEVICE_ID_SERDEV_H
> > +
> > +/* serdev */
> > +
> > +/* Large enough to hold the KBUILD_MODNAME of any serdev client driver */
> Is this relevant for anyone reading the code? If not, drop the comment.
>
> > +#define SERDEV_NAME_SIZE 40
> > +#define SERDEV_MODULE_PREFIX "serial:"
> > +
> > +struct serdev_device_id {
> > + char name[SERDEV_NAME_SIZE];
> > + unsigned long driver_data; /* Data private to the driver */
> > +};
> In almost any other include/linux/device-id/*.h file, there is a
>
> ```
> #ifdef __KERNEL__
> #include <linux/types.h>
> typedef unsigned long kernel_ulong_t;
> #endif
> ```
>
> statement and `kernel_ulong_t` is used.
>
> I don't know why, but there is likely a reason for it. Thus do it the
> same way, unless you can explain why this isn't needed here.
>
> > +
> > +#endif /* ifndef LINUX_DEVICE_ID_SERDEV_H */
> > diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> > index b6c3d957ec15..9f91aa3e875d 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_set_modalias().
> > * @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;
> > @@ -58,12 +65,15 @@ struct serdev_device {
> > * @probe: binds this driver to a serdev device.
> > * @remove: unbinds this driver from the serdev device.
> > * @shutdown: shut down this serdev device.
> > + * @id_table: List of serdev devices supported by this driver, used to
> > + * match devices which are not enumerated from firmware.
> > */
> > struct serdev_device_driver {
> > struct device_driver driver;
> > int (*probe)(struct serdev_device *);
> > void (*remove)(struct serdev_device *);
> > void (*shutdown)(struct serdev_device *);
> > + const struct serdev_device_id *id_table;
> Just a suggestion:
> Move it directly under driver, so the fields (driver->of_match_table,
> driver->acpi_match_table, id_table) are next to each other. It has no
> real runtime difference, so I won't complain if you leave it there.
>
> > };
> >
> > #define to_serdev_device_driver(d) container_of_const(d, struct serdev_device_driver, driver)
> > @@ -135,6 +145,30 @@ static inline void serdev_device_set_client_ops(struct serdev_device *serdev,
> > serdev->ops = ops;
> > }
> >
> > +/**
> > + * serdev_device_set_modalias() - set the modalias of a serdev device
> > + * @serdev: serdev device.
> > + * @modalias: non-empty modalias to use, typically KBUILD_MODNAME of the
> > + * client driver.
> > + *
> > + * A serdev device is identified by its ACPI companion, by its device tree
> > + * node, or by a modalias set by its creator. Serdev devices which are
> > + * instantiated by a driver rather than by firmware have neither of the
> > + * former, so they must set a modalias before serdev_device_add() to be
> > + * identifiable. Doing so reports a SERDEV_MODULE_PREFIX modalias to
> > + * userspace and makes the device match an id_table entry of a serdev
> > + * device driver.
> > + *
> > + * Devices enumerated from firmware have no modalias of their own and keep
> > + * deriving their modalias and their driver match from firmware only. The
> > + * device name is not affected either way.
> > + */
> > +static inline void serdev_device_set_modalias(struct serdev_device *serdev,
> > + const char *modalias)
> > +{
> > + strscpy(serdev->modalias, modalias);
> > +}
> Drop the function.
> Add `const char *modalias` as parameter to `serdev_device_add`. It
> should be clear that any driver calling this function manually should
> provide a modalias. Also, keep documentation simple (unless there is
> need).
>
> Either you add `__serdev_device_add` for internal use (of or acpi), or
> it will use NULL. Your choice.
>
>
> Overall, looks pretty good so far.
>
> Thanks
> - Markus Probst
>
> > +
> > static inline
> > void *serdev_controller_get_drvdata(const struct serdev_controller *ctrl)
> > {
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-10-23 13:02 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-10-23 5:27 [PATCH v3 0/3] serdev: handle devices without an ACPI or device tree ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 1/3] serdev: handle devices without an ACPI or device tree node ChunAn Wu
2026-10-23 12:26 ` Markus Probst
2026-10-23 13:02 ` An Wu
2026-10-23 5:27 ` [PATCH v3 2/3] platform/x86: dell-uart-backlight: Bind through normal serdev matching ChunAn Wu
2026-10-23 5:27 ` [PATCH v3 3/3] platform/x86: lenovo-yoga-tab2-pro-1380-fastcharger: " ChunAn Wu
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