serdev: handle devices without an ACPI or device tree node

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, and wire the new ID struct up in file2alias and the of_table coccinelle check.

Update the existing serdev_device_add() callers to pass NULL. The two in-tree firmware-less clients (dell-uart-backlight, yoga-tab2-pro-1380 fastcharger) also pass NULL here so the tree keeps building across the series; the two following patches switch them to a real modalias and drop their force_attach workarounds.

Signed-off-by ChunAn Wu <[email protected]>

---
 MAINTAINERS                                   |  1 +
 .../platform/x86/dell/dell-uart-backlight.c   |  2 +-
 .../lenovo/yoga-tab2-pro-1380-fastcharger.c   |  2 +-
 .../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/mod_devicetable.h               |  1 +
 include/linux/serdev.h                        | 11 +++-
 scripts/coccinelle/misc/of_table.cocci        | 16 ++---
 scripts/mod/devicetable-offsets.c             |  3 +
 scripts/mod/file2alias.c                      |  9 +++
 12 files changed, 108 insertions(+), 22 deletions(-)
 create mode 100644 include/linux/device-id/serdev.h

MAINTAINERS +1 -0

index 917f3f72e31b..06e67aa5d9b0 100644
@@ -24905,6 +24905,7 @@ L:	[email protected]
 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

drivers/platform/x86/dell/dell-uart-backlight.c +1 -1

index f323a667dc2d..f076cfac2bc5 100644
@@ -354,7 +354,7 @@ 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, NULL);
 	if (ret) {
 		dev_err(&pdev->dev, "error %d adding serdev\n", ret);
 		serdev_device_put(serdev);

drivers/platform/x86/lenovo/yoga-tab2-pro-1380-fastcharger.c +1 -1

index 8551ab4d2c7d..5e568fe1162d 100644
@@ -260,7 +260,7 @@ 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, NULL);
 	if (ret) {
 		serdev_device_put(serdev);
 		return dev_err_probe(&pdev->dev, ret, "adding serdev\n");

drivers/platform/x86/x86-android-tablets/core.c +1 -1

index cfff7f5eac5d..853aa6ff5d50 100644
@@ -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);

drivers/power/sequencing/pwrseq-pcie-m2.c +1 -1

index e42e85f47629..e0482f2ef39f 100644
@@ -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);

drivers/tty/serdev/core.c +53 -9

index 7500efcdfc21..e0517d5a48da 100644
@@ -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",

include/linux/device-id/serdev.h new file +19 -0

new file mode 100644
index 000000000000..96644953cece
@@ -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 */

include/linux/mod_devicetable.h +1 -0

index 318c4b5c3451..4cb18c41254a 100644
@@ -52,6 +52,7 @@
 #include "device-id/rpmsg.h"
 #include "device-id/sdio.h"
 #include "device-id/sdw.h"
+#include "device-id/serdev.h"
 #include "device-id/serio.h"
 #include "device-id/slim.h"
 #include "device-id/spi.h"

include/linux/serdev.h +10 -1

index b6c3d957ec15..81528c69456a 100644
@@ -7,6 +7,7 @@
 
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/device-id/serdev.h>
 #include <linux/iopoll.h>
 #include <linux/uaccess.h>
 #include <linux/termios.h>

@@ -35,6 +36,10 @@ 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 +48,7 @@ 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 +61,15 @@ 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 +167,7 @@ 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,

scripts/coccinelle/misc/of_table.cocci +8 -8

index 17881cb0884b..3b6dc2c13703 100644
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
-/// Make sure (of/i2c/platform/spi)_device_id tables are NULL terminated
+/// Make sure (of/i2c/platform/serdev/spi)_device_id tables are NULL terminated
 //
-// Keywords: of_table i2c_table platform_table
+// Keywords: of_table i2c_table platform_table serdev_table
 // Confidence: Medium
 // Options: --include-headers
 

@@ -15,14 +15,14 @@ identifier var, arr;
 expression E;
 @@
 (
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 	{
 	.var = E,
 *	}
 };
 |
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 *	{ ..., E, ... },
 };

@@ -33,7 +33,7 @@ identifier var, arr;
 expression E;
 @@
 (
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 	{
 	.var = E,

@@ -42,7 +42,7 @@ struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\)
 +	{ }
 };
 |
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 	{ ..., E, ... },
 +	{ },

@@ -55,7 +55,7 @@ identifier var, arr;
 expression E;
 @@
 (
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 	{
 	.var = E,

@@ -63,7 +63,7 @@ struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\)
 	@p1
 };
 |
-struct \(of_device_id \| i2c_device_id \| platform_device_id \| spi_device_id\) arr[] = {
+struct \(of_device_id \| i2c_device_id \| platform_device_id \| serdev_device_id \| spi_device_id\) arr[] = {
 	...,
 	{ ..., E, ... }
 	@p1

scripts/mod/devicetable-offsets.c +3 -0

index 1492e9fdc7cb..522bea285c7a 100644
@@ -158,6 +158,9 @@ int main(void)
 	DEVID_FIELD(slim_device_id, manf_id);
 	DEVID_FIELD(slim_device_id, prod_code);
 
+	DEVID(serdev_device_id);
+	DEVID_FIELD(serdev_device_id, name);
+
 	DEVID(spi_device_id);
 	DEVID_FIELD(spi_device_id, name);
 

scripts/mod/file2alias.c +8 -0

index 980d7da456bb..552847deab94 100644
@@ -886,6 +886,14 @@ static void do_slim_entry(struct module *mod, void *symval)
 	module_alias_printf(mod, false, "slim:%x:%x:*", manf_id, prod_code);
 }
 
+/* Looks like: serial:S */
+static void do_serdev_entry(struct module *mod, void *symval)
+{
+	DEF_FIELD_ADDR(symval, serdev_device_id, name);
+
+	module_alias_printf(mod, false, SERDEV_MODULE_PREFIX "%s", *name);
+}
+
 /* Looks like: spi:S */
 static void do_spi_entry(struct module *mod, void *symval)
 {

Reviewed-by Markus Probst <[email protected]>

You should add the maintainers for the modpost scripts to To/Cc.

$ ./scripts/get_maintainer.pl scripts/coccinelle/misc/of_table.cocci
scripts/mod/file2alias.c scripts/mod/devicetable-offsets.c
include/linux/mod_devicetable.h

Quoted 7 lines · Markus Probst

Reviewed-by Markus Probst <[email protected]>

You should add the maintainers for the modpost scripts to To/Cc.

$ ./scripts/get_maintainer.pl scripts/coccinelle/misc/of_table.cocci
scripts/mod/file2alias.c scripts/mod/devicetable-offsets.c
include/linux/mod_devicetable.h

Hi Markus,

Thank you for the reminder. Adding the Coccinelle and modpost maintainers to Cc now.

BR
An