[PATCH v4 0/4] Enable sysfs module symlink for more built-in drivers

[PATCH v4 0/4] Enable sysfs module symlink for more built-in drivers

[Shashank Balaji]

struct device_driver's mod_name is not set by a number of bus' driver registration
functions. Without that, built-in drivers don't have the module symlink in sysfs.
We want this to go from unbound driver name -> module name -> kernel config name.
This is useful on embedded platforms to minimize kernel config, reduce kernel size,
and reduce boot time.

In order to achieve this, mod_name has to be set to KBUILD_MODNAME, and this has
to be done for all buses which don't yet do this.

Here are some treewide stats:
- 110 registration functions across all bus types
- 20 of them set mod_name
- Remaining 90 do not set mod_name:
    1. 36 functions under pattern 1:
        They have a __register function + register macro. KBUILD_MODNAME needs to
        be passed and the function needs to take mod_name as input.
    2. 42 functions under pattern 2:
        These have no macro wrapper. They need a double-underscore rename + macro
        wrapper to make them similar to pattern 1.
    3. Remaining 12 do not have such a clean registration interface. More analysis
       is required.

We plan to start with pattern 1, since it's the easiest category of changes.
Within that, for now we're only sending the platform patch. If we get the go-ahead
on that, we'll send the remaining ones.

Patch 3 depends on patches 1 and 2.

Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
---
Changes in v4:
- Initialize module_kset in do_basic_setup() before do_initcalls() (Gary)
- Add commit body to the documentation patch (Greg)
- Link to v3: https://patch.msgid.link/20260422-acpi_mod_name-v3-0-a184eff9ff6f@sony.com

Changes in v3:
- Initialize module_kset on-demand (Greg)
- Make coresight driver registration happen through a macro (Greg)
- Split up the patch adding mod_name to platform driver registrations (Greg)
- Link to v2: https://patch.msgid.link/20260421-acpi_mod_name-v2-0-e73f9310dad3@sony.com

Changes in v2:
- Drop acpi patch, send platform instead (Rafael)
- Link to v1: https://patch.msgid.link/20260416-acpi_mod_name-v1-0-1a4d96fd86c9@sony.com

To: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Mike Leach <mike.leach@linaro.org>
To: James Clark <james.clark@linaro.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Maxime Coquelin <mcoquelin.stm32@gmail.com>
To: Alexandre Torgue <alexandre.torgue@foss.st.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
To: Danilo Krummrich <dakr@kernel.org>
To: Miguel Ojeda <ojeda@kernel.org>
To: Boqun Feng <boqun@kernel.org>
To: Gary Guo <gary@garyguo.net>
To: Björn Roy Baron <bjorn3_gh@protonmail.com>
To: Benno Lossin <lossin@kernel.org>
To: Andreas Hindborg <a.hindborg@kernel.org>
To: Alice Ryhl <aliceryhl@google.com>
To: Trevor Gross <tmgross@umich.edu>
To: Richard Cochran <richardcochran@gmail.com>
To: Jonathan Corbet <corbet@lwn.net>
To: Shuah Khan <skhan@linuxfoundation.org>
To: Luis Chamberlain <mcgrof@kernel.org>
To: Petr Pavlu <petr.pavlu@suse.com>
To: Daniel Gomez <da.gomez@kernel.org>
To: Sami Tolvanen <samitolvanen@google.com>
To: Aaron Tomlin <atomlin@atomlin.com>
To: Mike Leach <mike.leach@arm.com>
To: Leo Yan <leo.yan@arm.com>
Cc: linux-kernel@vger.kernel.org
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: driver-core@lists.linux.dev
Cc: rust-for-linux@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: Shashank Balaji <shashank.mahadasyam@sony.com>
Cc: Rahul Bukte <rahul.bukte@sony.com>
Cc: Daniel Palmer <daniel.palmer@sony.com>
Cc: Tim Bird <tim.bird@sony.com>
Cc: linux-modules@vger.kernel.org

---
Shashank Balaji (4):
      kernel: param: initialize module_kset before do_initcalls()
      coresight: pass THIS_MODULE implicitly through a macro
      driver core: platform: set mod_name in driver registration
      docs: driver-api: add mod_name argument to __platform_register_drivers()

 Documentation/driver-api/driver-model/platform.rst |  3 ++-
 drivers/base/platform.c                            | 21 ++++++++++++++-------
 drivers/hwtracing/coresight/coresight-catu.c       |  2 +-
 drivers/hwtracing/coresight/coresight-core.c       |  9 +++++----
 drivers/hwtracing/coresight/coresight-cpu-debug.c  |  3 +--
 drivers/hwtracing/coresight/coresight-funnel.c     |  3 +--
 drivers/hwtracing/coresight/coresight-replicator.c |  3 +--
 drivers/hwtracing/coresight/coresight-stm.c        |  2 +-
 drivers/hwtracing/coresight/coresight-tmc-core.c   |  2 +-
 drivers/hwtracing/coresight/coresight-tnoc.c       |  2 +-
 drivers/hwtracing/coresight/coresight-tpdm.c       |  3 +--
 drivers/hwtracing/coresight/coresight-tpiu.c       |  2 +-
 include/linux/coresight.h                          |  7 +++++--
 include/linux/module.h                             |  4 ++++
 include/linux/platform_device.h                    | 17 +++++++++--------
 init/main.c                                        |  1 +
 kernel/params.c                                    | 21 +++++++++------------
 rust/kernel/platform.rs                            |  4 +++-
 18 files changed, 61 insertions(+), 48 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260416-acpi_mod_name-f645a76e337b

Best regards,
--  
Shashank Balaji <shashank.mahadasyam@sony.com>

[PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

[Shashank Balaji]

module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
of platform drivers register themselves prior to subsys_initcalls
(tegra194_cbb_driver registers in a pure_initcall, for example). With an
upcoming patch ("driver core: platform: set mod_name in driver registration")
that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
This causes a null deref because module_kset isn't alive yet.

Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
Modernize the pr_warn while we're at it.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
---
 include/linux/module.h |  4 ++++
 init/main.c            |  1 +
 kernel/params.c        | 21 +++++++++------------
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 7566815fabbe..6478596e8f9f 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -886,6 +886,10 @@ static inline void module_for_each_mod(int(*func)(struct module *mod, void *data
 #ifdef CONFIG_SYSFS
 extern struct kset *module_kset;
 extern const struct kobj_type module_ktype;
+
+void param_sysfs_init(void);
+#else
+static inline void param_sysfs_init(void) {}
 #endif /* CONFIG_SYSFS */
 
 #define symbol_request(x) try_then_request_module(symbol_get(x), "symbol:" #x)
diff --git a/init/main.c b/init/main.c
index 96f93bb06c49..01552c6b62ff 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1486,6 +1486,7 @@ static void __init do_basic_setup(void)
 	ksysfs_init();
 	driver_init();
 	init_irq_proc();
+	param_sysfs_init();
 	do_ctors();
 	do_initcalls();
 }
diff --git a/kernel/params.c b/kernel/params.c
index 74d620bc2521..d1e3934fb3a7 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -942,22 +942,19 @@ const struct kobj_type module_ktype = {
 /*
  * param_sysfs_init - create "module" kset
  *
- * This must be done before the initramfs is unpacked and
- * request_module() thus becomes possible, because otherwise the
- * module load would fail in mod_sysfs_init.
+ * Must run before:
+ * - do_initcalls(): some drivers register during initcalls and rely on
+ *   module_kset existing for their sysfs module symlink.
+ * - rootfs_initcall (initramfs unpack): request_module() becomes possible.
+ *   But if module_kset is null, module load would fail in mod_sysfs_init(),
+ *   causing request_module() to fail.
  */
-static int __init param_sysfs_init(void)
+void __init param_sysfs_init(void)
 {
 	module_kset = kset_create_and_add("module", &module_uevent_ops, NULL);
-	if (!module_kset) {
-		printk(KERN_WARNING "%s (%d): error creating kset\n",
-			__FILE__, __LINE__);
-		return -ENOMEM;
-	}
-
-	return 0;
+	if (!module_kset)
+		pr_warn("Error creating module kset\n");
 }
-subsys_initcall(param_sysfs_init);
 
 /*
  * param_sysfs_builtin_init - add sysfs version and parameter

-- 
2.43.0

[PATCH v4 2/4] coresight: pass THIS_MODULE implicitly through a macro

[Shashank Balaji]

Rename coresight_init_driver() to __coresight_init_driver() and replace
it with a macro wrapper that passes THIS_MODULE implicitly. This is in line with
what other buses do.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
---
 drivers/hwtracing/coresight/coresight-catu.c       | 2 +-
 drivers/hwtracing/coresight/coresight-core.c       | 4 ++--
 drivers/hwtracing/coresight/coresight-cpu-debug.c  | 3 +--
 drivers/hwtracing/coresight/coresight-funnel.c     | 3 +--
 drivers/hwtracing/coresight/coresight-replicator.c | 3 +--
 drivers/hwtracing/coresight/coresight-stm.c        | 2 +-
 drivers/hwtracing/coresight/coresight-tmc-core.c   | 2 +-
 drivers/hwtracing/coresight/coresight-tnoc.c       | 2 +-
 drivers/hwtracing/coresight/coresight-tpdm.c       | 3 +--
 drivers/hwtracing/coresight/coresight-tpiu.c       | 2 +-
 include/linux/coresight.h                          | 4 +++-
 11 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-catu.c b/drivers/hwtracing/coresight/coresight-catu.c
index ce71dcddfca2..0c8698c8fc5e 100644
--- a/drivers/hwtracing/coresight/coresight-catu.c
+++ b/drivers/hwtracing/coresight/coresight-catu.c
@@ -706,7 +706,7 @@ static int __init catu_init(void)
 {
 	int ret;
 
-	ret = coresight_init_driver("catu", &catu_driver, &catu_platform_driver, THIS_MODULE);
+	ret = coresight_init_driver("catu", &catu_driver, &catu_platform_driver);
 	tmc_etr_set_catu_ops(&etr_catu_buf_ops);
 	return ret;
 }
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 46f247f73cf6..4ebcbd95b7fb 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1694,7 +1694,7 @@ static void __exit coresight_exit(void)
 module_init(coresight_init);
 module_exit(coresight_exit);
 
-int coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
+int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
 			  struct platform_driver *pdev_drv, struct module *owner)
 {
 	int ret;
@@ -1713,7 +1713,7 @@ int coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
 	amba_driver_unregister(amba_drv);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(coresight_init_driver);
+EXPORT_SYMBOL_GPL(__coresight_init_driver);
 
 void coresight_remove_driver(struct amba_driver *amba_drv,
 			     struct platform_driver *pdev_drv)
diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
index 629614278e46..3a806c1d50ea 100644
--- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
+++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
@@ -757,8 +757,7 @@ static struct platform_driver debug_platform_driver = {
 
 static int __init debug_init(void)
 {
-	return coresight_init_driver("debug", &debug_driver, &debug_platform_driver,
-				     THIS_MODULE);
+	return coresight_init_driver("debug", &debug_driver, &debug_platform_driver);
 }
 
 static void __exit debug_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
index 3f56ceccd8c9..0abc11f0690c 100644
--- a/drivers/hwtracing/coresight/coresight-funnel.c
+++ b/drivers/hwtracing/coresight/coresight-funnel.c
@@ -412,8 +412,7 @@ static struct amba_driver dynamic_funnel_driver = {
 
 static int __init funnel_init(void)
 {
-	return coresight_init_driver("funnel", &dynamic_funnel_driver, &funnel_driver,
-				     THIS_MODULE);
+	return coresight_init_driver("funnel", &dynamic_funnel_driver, &funnel_driver);
 }
 
 static void __exit funnel_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c
index 07fc04f53b88..2f382de357ee 100644
--- a/drivers/hwtracing/coresight/coresight-replicator.c
+++ b/drivers/hwtracing/coresight/coresight-replicator.c
@@ -418,8 +418,7 @@ static struct amba_driver dynamic_replicator_driver = {
 
 static int __init replicator_init(void)
 {
-	return coresight_init_driver("replicator", &dynamic_replicator_driver, &replicator_driver,
-				     THIS_MODULE);
+	return coresight_init_driver("replicator", &dynamic_replicator_driver, &replicator_driver);
 }
 
 static void __exit replicator_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c
index aca6cec7885a..4e860519a73f 100644
--- a/drivers/hwtracing/coresight/coresight-stm.c
+++ b/drivers/hwtracing/coresight/coresight-stm.c
@@ -1050,7 +1050,7 @@ static struct platform_driver stm_platform_driver = {
 
 static int __init stm_init(void)
 {
-	return coresight_init_driver("stm", &stm_driver, &stm_platform_driver, THIS_MODULE);
+	return coresight_init_driver("stm", &stm_driver, &stm_platform_driver);
 }
 
 static void __exit stm_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index c89fe996af23..bc5a133ada3e 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -1046,7 +1046,7 @@ static struct platform_driver tmc_platform_driver = {
 
 static int __init tmc_init(void)
 {
-	return coresight_init_driver("tmc", &tmc_driver, &tmc_platform_driver, THIS_MODULE);
+	return coresight_init_driver("tmc", &tmc_driver, &tmc_platform_driver);
 }
 
 static void __exit tmc_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-tnoc.c b/drivers/hwtracing/coresight/coresight-tnoc.c
index 96a25877b824..9e8de4323d28 100644
--- a/drivers/hwtracing/coresight/coresight-tnoc.c
+++ b/drivers/hwtracing/coresight/coresight-tnoc.c
@@ -344,7 +344,7 @@ static struct platform_driver itnoc_driver = {
 
 static int __init tnoc_init(void)
 {
-	return coresight_init_driver("tnoc", &trace_noc_driver, &itnoc_driver, THIS_MODULE);
+	return coresight_init_driver("tnoc", &trace_noc_driver, &itnoc_driver);
 }
 
 static void __exit tnoc_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
index eaf7210af648..8464edbba2d4 100644
--- a/drivers/hwtracing/coresight/coresight-tpdm.c
+++ b/drivers/hwtracing/coresight/coresight-tpdm.c
@@ -1563,8 +1563,7 @@ static struct platform_driver static_tpdm_driver = {
 
 static int __init tpdm_init(void)
 {
-	return coresight_init_driver("tpdm", &dynamic_tpdm_driver, &static_tpdm_driver,
-				     THIS_MODULE);
+	return coresight_init_driver("tpdm", &dynamic_tpdm_driver, &static_tpdm_driver);
 }
 
 static void __exit tpdm_exit(void)
diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c
index b8560b140e0f..7b029d2eb389 100644
--- a/drivers/hwtracing/coresight/coresight-tpiu.c
+++ b/drivers/hwtracing/coresight/coresight-tpiu.c
@@ -310,7 +310,7 @@ static struct platform_driver tpiu_platform_driver = {
 
 static int __init tpiu_init(void)
 {
-	return coresight_init_driver("tpiu", &tpiu_driver, &tpiu_platform_driver, THIS_MODULE);
+	return coresight_init_driver("tpiu", &tpiu_driver, &tpiu_platform_driver);
 }
 
 static void __exit tpiu_exit(void)
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 2131febebee9..b9ec5f195907 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -691,7 +691,9 @@ coresight_find_output_type(struct coresight_platform_data *pdata,
 			   enum coresight_dev_type type,
 			   union coresight_dev_subtype subtype);
 
-int coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
+#define coresight_init_driver(drv, amba_drv, pdev_drv) \
+	__coresight_init_driver(drv, amba_drv, pdev_drv, THIS_MODULE)
+int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
 			  struct platform_driver *pdev_drv, struct module *owner);
 
 void coresight_remove_driver(struct amba_driver *amba_drv,

-- 
2.43.0

[PATCH v4 3/4] driver core: platform: set mod_name in driver registration

[Shashank Balaji]

Pass KBUILD_MODNAME through the driver registration macro so that
the driver core can create the module symlink in sysfs for built-in
drivers, and fixup all callers.

The Rust platform adapter is updated to pass the module name through to the new
parameter.

Tested on qemu with:
- x86 defconfig + CONFIG_RUST
- arm64 defconfig + CONFIG_RUST + CONFIG_CORESIGHT stuff

Examples after this patch:

    /sys/bus/platform/drivers/...
        coresight-itnoc/module		-> coresight_tnoc
        coresight-static-tpdm/module	-> coresight_tpdm
        coresight-catu-platform/module	-> coresight_catu
        serial8250/module		-> 8250
        acpi-ged/module			-> acpi
        vmclock/module			-> ptp_vmclock

Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>

---

This patch depends on patches 1 and 2.
---
 drivers/base/platform.c                      | 21 ++++++++++++++-------
 drivers/hwtracing/coresight/coresight-core.c |  5 +++--
 include/linux/coresight.h                    |  5 +++--
 include/linux/platform_device.h              | 17 +++++++++--------
 rust/kernel/platform.rs                      |  4 +++-
 5 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 75b4698d0e58..2b0cc0889386 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -901,11 +901,14 @@ EXPORT_SYMBOL_GPL(platform_device_register_full);
  * __platform_driver_register - register a driver for platform-level devices
  * @drv: platform driver structure
  * @owner: owning module/driver
+ * @mod_name: module name string
  */
-int __platform_driver_register(struct platform_driver *drv, struct module *owner)
+int __platform_driver_register(struct platform_driver *drv, struct module *owner,
+			       const char *mod_name)
 {
 	drv->driver.owner = owner;
 	drv->driver.bus = &platform_bus_type;
+	drv->driver.mod_name = mod_name;
 
 	return driver_register(&drv->driver);
 }
@@ -938,6 +941,7 @@ static int is_bound_to_driver(struct device *dev, void *driver)
  * @drv: platform driver structure
  * @probe: the driver probe routine, probably from an __init section
  * @module: module which will be the owner of the driver
+ * @mod_name: module name string
  *
  * Use this instead of platform_driver_register() when you know the device
  * is not hotpluggable and has already been registered, and you want to
@@ -955,7 +959,8 @@ static int is_bound_to_driver(struct device *dev, void *driver)
  */
 int __init_or_module __platform_driver_probe(struct platform_driver *drv,
 					     int (*probe)(struct platform_device *),
-					     struct module *module)
+					     struct module *module,
+					     const char *mod_name)
 {
 	int retval;
 
@@ -983,7 +988,7 @@ int __init_or_module __platform_driver_probe(struct platform_driver *drv,
 
 	/* temporary section violation during probe() */
 	drv->probe = probe;
-	retval = __platform_driver_register(drv, module);
+	retval = __platform_driver_register(drv, module, mod_name);
 	if (retval)
 		return retval;
 
@@ -1011,6 +1016,7 @@ EXPORT_SYMBOL_GPL(__platform_driver_probe);
  * @data: platform specific data for this platform device
  * @size: size of platform specific data
  * @module: module which will be the owner of the driver
+ * @mod_name: module name string
  *
  * Use this in legacy-style modules that probe hardware directly and
  * register a single platform device and corresponding platform driver.
@@ -1021,7 +1027,7 @@ struct platform_device * __init_or_module
 __platform_create_bundle(struct platform_driver *driver,
 			 int (*probe)(struct platform_device *),
 			 struct resource *res, unsigned int n_res,
-			 const void *data, size_t size, struct module *module)
+			 const void *data, size_t size, struct module *module, const char *mod_name)
 {
 	struct platform_device *pdev;
 	int error;
@@ -1044,7 +1050,7 @@ __platform_create_bundle(struct platform_driver *driver,
 	if (error)
 		goto err_pdev_put;
 
-	error = __platform_driver_probe(driver, probe, module);
+	error = __platform_driver_probe(driver, probe, module, mod_name);
 	if (error)
 		goto err_pdev_del;
 
@@ -1064,6 +1070,7 @@ EXPORT_SYMBOL_GPL(__platform_create_bundle);
  * @drivers: an array of drivers to register
  * @count: the number of drivers to register
  * @owner: module owning the drivers
+ * @mod_name: module name string
  *
  * Registers platform drivers specified by an array. On failure to register a
  * driver, all previously registered drivers will be unregistered. Callers of
@@ -1073,7 +1080,7 @@ EXPORT_SYMBOL_GPL(__platform_create_bundle);
  * Returns: 0 on success or a negative error code on failure.
  */
 int __platform_register_drivers(struct platform_driver * const *drivers,
-				unsigned int count, struct module *owner)
+				unsigned int count, struct module *owner, const char *mod_name)
 {
 	unsigned int i;
 	int err;
@@ -1081,7 +1088,7 @@ int __platform_register_drivers(struct platform_driver * const *drivers,
 	for (i = 0; i < count; i++) {
 		pr_debug("registering platform driver %ps\n", drivers[i]);
 
-		err = __platform_driver_register(drivers[i], owner);
+		err = __platform_driver_register(drivers[i], owner, mod_name);
 		if (err < 0) {
 			pr_err("failed to register platform driver %ps: %d\n",
 			       drivers[i], err);
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 4ebcbd95b7fb..9c4fdef76833 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1695,7 +1695,8 @@ module_init(coresight_init);
 module_exit(coresight_exit);
 
 int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
-			  struct platform_driver *pdev_drv, struct module *owner)
+			  struct platform_driver *pdev_drv, struct module *owner,
+			  const char *mod_name)
 {
 	int ret;
 
@@ -1705,7 +1706,7 @@ int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
 		return ret;
 	}
 
-	ret = __platform_driver_register(pdev_drv, owner);
+	ret = __platform_driver_register(pdev_drv, owner, mod_name);
 	if (!ret)
 		return 0;
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index b9ec5f195907..d7ae0527d039 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -692,9 +692,10 @@ coresight_find_output_type(struct coresight_platform_data *pdata,
 			   union coresight_dev_subtype subtype);
 
 #define coresight_init_driver(drv, amba_drv, pdev_drv) \
-	__coresight_init_driver(drv, amba_drv, pdev_drv, THIS_MODULE)
+	__coresight_init_driver(drv, amba_drv, pdev_drv, THIS_MODULE, KBUILD_MODNAME)
 int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
-			  struct platform_driver *pdev_drv, struct module *owner);
+			  struct platform_driver *pdev_drv, struct module *owner,
+			  const char *mod_name);
 
 void coresight_remove_driver(struct amba_driver *amba_drv,
 			     struct platform_driver *pdev_drv);
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 975400a472e3..26e6a43358e2 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -293,18 +293,19 @@ struct platform_driver {
  * use a macro to avoid include chaining to get THIS_MODULE
  */
 #define platform_driver_register(drv) \
-	__platform_driver_register(drv, THIS_MODULE)
+	__platform_driver_register(drv, THIS_MODULE, KBUILD_MODNAME)
 extern int __platform_driver_register(struct platform_driver *,
-					struct module *);
+					struct module *, const char *mod_name);
 extern void platform_driver_unregister(struct platform_driver *);
 
 /* non-hotpluggable platform devices may use this so that probe() and
  * its support may live in __init sections, conserving runtime memory.
  */
 #define platform_driver_probe(drv, probe) \
-	__platform_driver_probe(drv, probe, THIS_MODULE)
+	__platform_driver_probe(drv, probe, THIS_MODULE, KBUILD_MODNAME)
 extern int __platform_driver_probe(struct platform_driver *driver,
-		int (*probe)(struct platform_device *), struct module *module);
+		int (*probe)(struct platform_device *), struct module *module,
+		const char *mod_name);
 
 static inline void *platform_get_drvdata(const struct platform_device *pdev)
 {
@@ -368,19 +369,19 @@ static int __init __platform_driver##_init(void) \
 device_initcall(__platform_driver##_init); \
 
 #define platform_create_bundle(driver, probe, res, n_res, data, size) \
-	__platform_create_bundle(driver, probe, res, n_res, data, size, THIS_MODULE)
+	__platform_create_bundle(driver, probe, res, n_res, data, size, THIS_MODULE, KBUILD_MODNAME)
 extern struct platform_device *__platform_create_bundle(
 	struct platform_driver *driver, int (*probe)(struct platform_device *),
 	struct resource *res, unsigned int n_res,
-	const void *data, size_t size, struct module *module);
+	const void *data, size_t size, struct module *module, const char *mod_name);
 
 int __platform_register_drivers(struct platform_driver * const *drivers,
-				unsigned int count, struct module *owner);
+				unsigned int count, struct module *owner, const char *mod_name);
 void platform_unregister_drivers(struct platform_driver * const *drivers,
 				 unsigned int count);
 
 #define platform_register_drivers(drivers, count) \
-	__platform_register_drivers(drivers, count, THIS_MODULE)
+	__platform_register_drivers(drivers, count, THIS_MODULE, KBUILD_MODNAME)
 
 #ifdef CONFIG_SUSPEND
 extern int platform_pm_suspend(struct device *dev);
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 8917d4ee499f..2d626eecc450 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -82,7 +82,9 @@ unsafe fn register(
         }
 
         // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
-        to_result(unsafe { bindings::__platform_driver_register(pdrv.get(), module.0) })
+        to_result(unsafe {
+            bindings::__platform_driver_register(pdrv.get(), module.0, name.as_char_ptr())
+        })
     }
 
     unsafe fn unregister(pdrv: &Opaque<Self::DriverType>) {

-- 
2.43.0

[PATCH v4 4/4] docs: driver-api: add mod_name argument to __platform_register_drivers()

[Shashank Balaji]

Sync the function signature of __platform_register_driver() between the code and
the doc.

Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
---
 Documentation/driver-api/driver-model/platform.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/driver-api/driver-model/platform.rst b/Documentation/driver-api/driver-model/platform.rst
index cf5ff48d3115..9673470bded2 100644
--- a/Documentation/driver-api/driver-model/platform.rst
+++ b/Documentation/driver-api/driver-model/platform.rst
@@ -70,7 +70,8 @@ Kernel modules can be composed of several platform drivers. The platform core
 provides helpers to register and unregister an array of drivers::
 
 	int __platform_register_drivers(struct platform_driver * const *drivers,
-				      unsigned int count, struct module *owner);
+				      unsigned int count, struct module *owner,
+				      const char *mod_name);
 	void platform_unregister_drivers(struct platform_driver * const *drivers,
 					 unsigned int count);
 

-- 
2.43.0

Re: [PATCH v4 2/4] coresight: pass THIS_MODULE implicitly through a macro

[Leo Yan]

Hi Shashank,

On Mon, Apr 27, 2026 at 11:41:22AM +0900, Shashank Balaji wrote:

[...]

> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -1694,7 +1694,7 @@ static void __exit coresight_exit(void)
>  module_init(coresight_init);
>  module_exit(coresight_exit);
>  
> -int coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
> +int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
>  			  struct platform_driver *pdev_drv, struct module *owner)
>  {
>  	int ret;
> @@ -1713,7 +1713,7 @@ int coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
>  	amba_driver_unregister(amba_drv);
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(coresight_init_driver);
> +EXPORT_SYMBOL_GPL(__coresight_init_driver);

For consistency, we usually use prefix "__" for internal functions.

Could you rename this function as:

  int coresight_init_driver_with_owner(..., struct module *owner);

> +#define coresight_init_driver(drv, amba_drv, pdev_drv) \
> +	__coresight_init_driver(drv, amba_drv, pdev_drv, THIS_MODULE)
> +int __coresight_init_driver(const char *drv, struct amba_driver *amba_drv,
>  			  struct platform_driver *pdev_drv, struct module *owner);

Please first function declaration, then followed by the macro to
define coresight_init_driver().

With above changes:

Reviewed-by: Leo Yan <leo.yan@arm.com>

Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

[Gary Guo]

On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote:
> module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
> of platform drivers register themselves prior to subsys_initcalls
> (tegra194_cbb_driver registers in a pure_initcall, for example). With an
> upcoming patch ("driver core: platform: set mod_name in driver registration")
> that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
> will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
> This causes a null deref because module_kset isn't alive yet.
>
> Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
> Modernize the pr_warn while we're at it.
>
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Suggested-by: Gary Guo <gary@garyguo.net>

I didn't suggest this change :)

I suggested `pure_initcall`, which is just a one line change.

diff --git a/kernel/params.c b/kernel/params.c
index 74d620bc2521..ac088d4b09a9 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
 
 	return 0;
 }
-subsys_initcall(param_sysfs_init);
+pure_initcall(param_sysfs_init);
 
 /*
  * param_sysfs_builtin_init - add sysfs version and parameter

pure_initcall is level 0 so it happens before all other init calls. Does it not
work?

Best,
Gary

> Co-developed-by: Rahul Bukte <rahul.bukte@sony.com>
> Signed-off-by: Rahul Bukte <rahul.bukte@sony.com>
> Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
> ---
>  include/linux/module.h |  4 ++++
>  init/main.c            |  1 +
>  kernel/params.c        | 21 +++++++++------------
>  3 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 7566815fabbe..6478596e8f9f 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -886,6 +886,10 @@ static inline void module_for_each_mod(int(*func)(struct module *mod, void *data
>  #ifdef CONFIG_SYSFS
>  extern struct kset *module_kset;
>  extern const struct kobj_type module_ktype;
> +
> +void param_sysfs_init(void);
> +#else
> +static inline void param_sysfs_init(void) {}
>  #endif /* CONFIG_SYSFS */
>  
>  #define symbol_request(x) try_then_request_module(symbol_get(x), "symbol:" #x)
> diff --git a/init/main.c b/init/main.c
> index 96f93bb06c49..01552c6b62ff 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1486,6 +1486,7 @@ static void __init do_basic_setup(void)
>  	ksysfs_init();
>  	driver_init();
>  	init_irq_proc();
> +	param_sysfs_init();
>  	do_ctors();
>  	do_initcalls();
>  }
> diff --git a/kernel/params.c b/kernel/params.c
> index 74d620bc2521..d1e3934fb3a7 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -942,22 +942,19 @@ const struct kobj_type module_ktype = {
>  /*
>   * param_sysfs_init - create "module" kset
>   *
> - * This must be done before the initramfs is unpacked and
> - * request_module() thus becomes possible, because otherwise the
> - * module load would fail in mod_sysfs_init.
> + * Must run before:
> + * - do_initcalls(): some drivers register during initcalls and rely on
> + *   module_kset existing for their sysfs module symlink.
> + * - rootfs_initcall (initramfs unpack): request_module() becomes possible.
> + *   But if module_kset is null, module load would fail in mod_sysfs_init(),
> + *   causing request_module() to fail.
>   */
> -static int __init param_sysfs_init(void)
> +void __init param_sysfs_init(void)
>  {
>  	module_kset = kset_create_and_add("module", &module_uevent_ops, NULL);
> -	if (!module_kset) {
> -		printk(KERN_WARNING "%s (%d): error creating kset\n",
> -			__FILE__, __LINE__);
> -		return -ENOMEM;
> -	}
> -
> -	return 0;
> +	if (!module_kset)
> +		pr_warn("Error creating module kset\n");
>  }
> -subsys_initcall(param_sysfs_init);
>  
>  /*
>   * param_sysfs_builtin_init - add sysfs version and parameter

Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

[Shashank Balaji]

Hi Gary,

On Mon, Apr 27, 2026 at 02:29:55PM +0100, Gary Guo wrote:
> On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote:
> > module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
> > of platform drivers register themselves prior to subsys_initcalls
> > (tegra194_cbb_driver registers in a pure_initcall, for example). With an
> > upcoming patch ("driver core: platform: set mod_name in driver registration")
> > that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
> > will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
> > This causes a null deref because module_kset isn't alive yet.
> >
> > Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
> > Modernize the pr_warn while we're at it.
> >
> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Suggested-by: Gary Guo <gary@garyguo.net>
> 
> I didn't suggest this change :)
> 
> I suggested `pure_initcall`, which is just a one line change.

Oops, sorry about the misattribution.

> diff --git a/kernel/params.c b/kernel/params.c
> index 74d620bc2521..ac088d4b09a9 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
>  
>  	return 0;
>  }
> -subsys_initcall(param_sysfs_init);
> +pure_initcall(param_sysfs_init);
>  
>  /*
>   * param_sysfs_builtin_init - add sysfs version and parameter
> 
> pure_initcall is level 0 so it happens before all other init calls. Does it not
> work?

tegra194_cbb_driver registers itself in a pure_initcall too. We wouldn't
want the ordering of its registration and module_kset init to be link order
dependent.

Thanks,
Shashank

Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

[Gary Guo]

On Tue Apr 28, 2026 at 1:37 AM BST, Shashank Balaji wrote:
> Hi Gary,
>
> On Mon, Apr 27, 2026 at 02:29:55PM +0100, Gary Guo wrote:
>> On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote:
>> > module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
>> > of platform drivers register themselves prior to subsys_initcalls
>> > (tegra194_cbb_driver registers in a pure_initcall, for example). With an
>> > upcoming patch ("driver core: platform: set mod_name in driver registration")
>> > that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
>> > will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
>> > This causes a null deref because module_kset isn't alive yet.
>> >
>> > Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
>> > Modernize the pr_warn while we're at it.
>> >
>> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> > Suggested-by: Gary Guo <gary@garyguo.net>
>> 
>> I didn't suggest this change :)
>> 
>> I suggested `pure_initcall`, which is just a one line change.
>
> Oops, sorry about the misattribution.
>
>> diff --git a/kernel/params.c b/kernel/params.c
>> index 74d620bc2521..ac088d4b09a9 100644
>> --- a/kernel/params.c
>> +++ b/kernel/params.c
>> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
>>  
>>  	return 0;
>>  }
>> -subsys_initcall(param_sysfs_init);
>> +pure_initcall(param_sysfs_init);
>>  
>>  /*
>>   * param_sysfs_builtin_init - add sysfs version and parameter
>> 
>> pure_initcall is level 0 so it happens before all other init calls. Does it not
>> work?
>
> tegra194_cbb_driver registers itself in a pure_initcall too. We wouldn't
> want the ordering of its registration and module_kset init to be link order
> dependent.

It's the only device driver that does this. And I don't think it's supposed to.

From documentation:

> A "pure" initcall has no dependencies on anything else, and purely
> initializes variables that couldn't be statically initialized.

I understand that given large amount of drivers registering themselves during
core/arch_initcall that there might be regressions if all of them are moved, but
surely we can demote these two specific tegra driver to core/postcore_initcall?
This will still be called earlier than init_machine call which happens during
arch_initcall.

Looks like the tegra CBB driver is just doing error logging anyway.

Best,
Gary

Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

[Shashank Balaji]

Adding Tegra maintainers.

On Tue, Apr 28, 2026 at 12:10:50PM +0100, Gary Guo wrote:
> On Tue Apr 28, 2026 at 1:37 AM BST, Shashank Balaji wrote:
> > Hi Gary,
> >
> > On Mon, Apr 27, 2026 at 02:29:55PM +0100, Gary Guo wrote:
> >> On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote:
> >> > module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
> >> > of platform drivers register themselves prior to subsys_initcalls
> >> > (tegra194_cbb_driver registers in a pure_initcall, for example). With an
> >> > upcoming patch ("driver core: platform: set mod_name in driver registration")
> >> > that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
> >> > will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
> >> > This causes a null deref because module_kset isn't alive yet.
> >> >
> >> > Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
> >> > Modernize the pr_warn while we're at it.
> >> >
> >> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >> > Suggested-by: Gary Guo <gary@garyguo.net>
> >> 
> >> I didn't suggest this change :)
> >> 
> >> I suggested `pure_initcall`, which is just a one line change.
> >
> > Oops, sorry about the misattribution.
> >
> >> diff --git a/kernel/params.c b/kernel/params.c
> >> index 74d620bc2521..ac088d4b09a9 100644
> >> --- a/kernel/params.c
> >> +++ b/kernel/params.c
> >> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
> >>  
> >>  	return 0;
> >>  }
> >> -subsys_initcall(param_sysfs_init);
> >> +pure_initcall(param_sysfs_init);
> >>  
> >>  /*
> >>   * param_sysfs_builtin_init - add sysfs version and parameter
> >> 
> >> pure_initcall is level 0 so it happens before all other init calls. Does it not
> >> work?
> >
> > tegra194_cbb_driver registers itself in a pure_initcall too. We wouldn't
> > want the ordering of its registration and module_kset init to be link order
> > dependent.
> 
> It's the only device driver that does this. And I don't think it's supposed to.
> 
> >From documentation:
> 
> > A "pure" initcall has no dependencies on anything else, and purely
> > initializes variables that couldn't be statically initialized.
> 
> I understand that given large amount of drivers registering themselves during
> core/arch_initcall that there might be regressions if all of them are moved, but
> surely we can demote these two specific tegra driver to core/postcore_initcall?
> This will still be called earlier than init_machine call which happens during
> arch_initcall.
> 
> Looks like the tegra CBB driver is just doing error logging anyway.

That's a good point, Gary. Thanks!

Hi Thierry and Jonathan,

You can find the context for this email in this patch:
https://lore.kernel.org/all/20260427-acpi_mod_name-v4-1-22b42240c9bf@sony.com/

TL;DR: tegra194_cbb_driver and tegra234_cbb_driver are the only drivers
registering themselves as early as in a pure_initcall. This is a problem
on two fronts:
1. Philosophical: As Gary pointed out, pure_initcalls are intended to purely
initialize variables that couldn't be statically initialized. But these
are doing driver registrations.
2. module_kset not initialized at pure_initcall stage: This is needed to
set the module sysfs symlink. Since module_kset is not alive yet during
pure_initcalls, registering these drivers panics the kernel.

We would like to do the tegra cbb driver registration in a core_initcall
(or some later initcall works too), and move module_kset initialization
to a pure_initcall. Like this:

diff --git a/drivers/soc/tegra/cbb/tegra194-cbb.c b/drivers/soc/tegra/cbb/tegra194-cbb.c
index ab75d50cc85c..2f69e104c838 100644
--- a/drivers/soc/tegra/cbb/tegra194-cbb.c
+++ b/drivers/soc/tegra/cbb/tegra194-cbb.c
@@ -2342,7 +2342,7 @@ static int __init tegra194_cbb_init(void)
 {
        return platform_driver_register(&tegra194_cbb_driver);
 }
-pure_initcall(tegra194_cbb_init);
+core_initcall(tegra194_cbb_init);

 static void __exit tegra194_cbb_exit(void)
 {
diff --git a/drivers/soc/tegra/cbb/tegra234-cbb.c b/drivers/soc/tegra/cbb/tegra234-cbb.c
index fb26f085f691..785072fa4e85 100644
--- a/drivers/soc/tegra/cbb/tegra234-cbb.c
+++ b/drivers/soc/tegra/cbb/tegra234-cbb.c
@@ -1774,7 +1774,7 @@ static int __init tegra234_cbb_init(void)
 {
        return platform_driver_register(&tegra234_cbb_driver);
 }
-pure_initcall(tegra234_cbb_init);
+core_initcall(tegra234_cbb_init);

 static void __exit tegra234_cbb_exit(void)
 {

Would this work?

Thanks,
Shashank