[PATCH 0/5] driver core: Allow the constification of device attributes

[PATCH 0/5] driver core: Allow the constification of device attributes

[Thomas Weißschuh]

Allow device attribute to reside in read-only memory.
Both const and non-const attributes are handled by the utility macros
and attributes can be migrated one-by-one.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Thomas Weißschuh (5):
      driver core: Delete DEVICE_ATTR_PREALLOC()
      driver core: Add low-level macros for device attributes
      driver core: stop using generic sysfs macros for device attributes
      driver core: Allow the constification of device attributes
      driver core: Constify core device attributes

 drivers/base/core.c    |  50 ++++++++++----------
 include/linux/device.h | 122 +++++++++++++++++++++++++++++++++++++------------
 2 files changed, 121 insertions(+), 51 deletions(-)
---
base-commit: 6c8dfb0362732bf1e4829867a2a5239fedc592d0
change-id: 20260408-sysfs-const-attr-device_attr-prep-9971fb4439da

Best regards,
--  
Thomas Weißschuh <linux@weissschuh.net>

[PATCH 1/5] driver core: Delete DEVICE_ATTR_PREALLOC()

[Thomas Weißschuh]

This macro is unused and would create extra work during the upcoming
constification of device attributes. Remove it.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 include/linux/device.h | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index f0d52e1a6e07..8ba3168180e5 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -157,19 +157,6 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
 #define DEVICE_ATTR(_name, _mode, _show, _store) \
 	struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show, _store)
 
-/**
- * DEVICE_ATTR_PREALLOC - Define a preallocated device attribute.
- * @_name: Attribute name.
- * @_mode: File mode.
- * @_show: Show handler. Optional, but mandatory if attribute is readable.
- * @_store: Store handler. Optional, but mandatory if attribute is writable.
- *
- * Like DEVICE_ATTR(), but ``SYSFS_PREALLOC`` is set on @_mode.
- */
-#define DEVICE_ATTR_PREALLOC(_name, _mode, _show, _store) \
-	struct device_attribute dev_attr_##_name = \
-		__ATTR_PREALLOC(_name, _mode, _show, _store)
-
 /**
  * DEVICE_ATTR_RW - Define a read-write device attribute.
  * @_name: Attribute name.

-- 
2.53.0

[PATCH 2/5] driver core: Add low-level macros for device attributes

[Thomas Weißschuh]

For the upcoming constification of device attributes the generic
__ATTR() macros are insufficient.

Prepare for a split by introducing new low-level macros specific to
device attributes.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 include/linux/device.h | 43 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index 8ba3168180e5..a0384dac06ee 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -135,6 +135,27 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
 ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
 			   char *buf);
 
+#define __DEVICE_ATTR(_name, _mode, _show, _store) \
+	__ATTR(_name, _mode, _show, _store)
+
+#define __DEVICE_ATTR_RO_MODE(_name, _mode) \
+	__ATTR_RO_MODE(_name, _mode)
+
+#define __DEVICE_ATTR_RO(_name) \
+	__ATTR_RO(_name)
+
+#define __DEVICE_ATTR_WO(_name) \
+	__ATTR_WO(_name)
+
+#define __DEVICE_ATTR_RW_MODE(_name, _mode) \
+	__ATTR_RW_MODE(_name, _mode)
+
+#define __DEVICE_ATTR_RW(_name) \
+	__ATTR_RW(_name)
+
+#define __DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
+	__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
+
 /**
  * DEVICE_ATTR - Define a device attribute.
  * @_name: Attribute name.
@@ -155,7 +176,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  *	};
  */
 #define DEVICE_ATTR(_name, _mode, _show, _store) \
-	struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show, _store)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR(_name, _mode, _show, _store)
 
 /**
  * DEVICE_ATTR_RW - Define a read-write device attribute.
@@ -165,7 +186,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  * and @_store is <_name>_store.
  */
 #define DEVICE_ATTR_RW(_name) \
-	struct device_attribute dev_attr_##_name = __ATTR_RW(_name)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR_RW(_name)
 
 /**
  * DEVICE_ATTR_ADMIN_RW - Define an admin-only read-write device attribute.
@@ -174,7 +195,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  * Like DEVICE_ATTR_RW(), but @_mode is 0600.
  */
 #define DEVICE_ATTR_ADMIN_RW(_name) \
-	struct device_attribute dev_attr_##_name = __ATTR_RW_MODE(_name, 0600)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR_RW_MODE(_name, 0600)
 
 /**
  * DEVICE_ATTR_RO - Define a readable device attribute.
@@ -183,7 +204,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  * Like DEVICE_ATTR(), but @_mode is 0444 and @_show is <_name>_show.
  */
 #define DEVICE_ATTR_RO(_name) \
-	struct device_attribute dev_attr_##_name = __ATTR_RO(_name)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR_RO(_name)
 
 /**
  * DEVICE_ATTR_ADMIN_RO - Define an admin-only readable device attribute.
@@ -192,7 +213,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  * Like DEVICE_ATTR_RO(), but @_mode is 0400.
  */
 #define DEVICE_ATTR_ADMIN_RO(_name) \
-	struct device_attribute dev_attr_##_name = __ATTR_RO_MODE(_name, 0400)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR_RO_MODE(_name, 0400)
 
 /**
  * DEVICE_ATTR_WO - Define an admin-only writable device attribute.
@@ -201,7 +222,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  * Like DEVICE_ATTR(), but @_mode is 0200 and @_store is <_name>_store.
  */
 #define DEVICE_ATTR_WO(_name) \
-	struct device_attribute dev_attr_##_name = __ATTR_WO(_name)
+	struct device_attribute dev_attr_##_name = __DEVICE_ATTR_WO(_name)
 
 /**
  * DEVICE_ULONG_ATTR - Define a device attribute backed by an unsigned long.
@@ -214,7 +235,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  */
 #define DEVICE_ULONG_ATTR(_name, _mode, _var) \
 	struct dev_ext_attribute dev_attr_##_name = \
-		{ __ATTR(_name, _mode, device_show_ulong, device_store_ulong), &(_var) }
+		{ __DEVICE_ATTR(_name, _mode, device_show_ulong, device_store_ulong), &(_var) }
 
 /**
  * DEVICE_INT_ATTR - Define a device attribute backed by an int.
@@ -226,7 +247,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  */
 #define DEVICE_INT_ATTR(_name, _mode, _var) \
 	struct dev_ext_attribute dev_attr_##_name = \
-		{ __ATTR(_name, _mode, device_show_int, device_store_int), &(_var) }
+		{ __DEVICE_ATTR(_name, _mode, device_show_int, device_store_int), &(_var) }
 
 /**
  * DEVICE_BOOL_ATTR - Define a device attribute backed by a bool.
@@ -238,7 +259,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  */
 #define DEVICE_BOOL_ATTR(_name, _mode, _var) \
 	struct dev_ext_attribute dev_attr_##_name = \
-		{ __ATTR(_name, _mode, device_show_bool, device_store_bool), &(_var) }
+		{ __DEVICE_ATTR(_name, _mode, device_show_bool, device_store_bool), &(_var) }
 
 /**
  * DEVICE_STRING_ATTR_RO - Define a device attribute backed by a r/o string.
@@ -251,11 +272,11 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
  */
 #define DEVICE_STRING_ATTR_RO(_name, _mode, _var) \
 	struct dev_ext_attribute dev_attr_##_name = \
-		{ __ATTR(_name, (_mode) & ~0222, device_show_string, NULL), (_var) }
+		{ __DEVICE_ATTR(_name, (_mode) & ~0222, device_show_string, NULL), (_var) }
 
 #define DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
 	struct device_attribute dev_attr_##_name =		\
-		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
+		__DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
 
 int device_create_file(struct device *device,
 		       const struct device_attribute *entry);

-- 
2.53.0

[PATCH 3/5] driver core: stop using generic sysfs macros for device attributes

[Thomas Weißschuh]

The constification of device attributes will require a transition phase,
where 'struct device_attribute' contains a classic non-const and a new
const variant of the 'show' and 'store' callbacks.

As __ATTR() and friends can not handle this duplication stop using them.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 include/linux/device.h | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index a0384dac06ee..714e36d610e3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -135,26 +135,38 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
 ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
 			   char *buf);
 
-#define __DEVICE_ATTR(_name, _mode, _show, _store) \
-	__ATTR(_name, _mode, _show, _store)
+#define __DEVICE_ATTR(_name, _mode, _show, _store) {			\
+	.attr = {.name = __stringify(_name),				\
+		 .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
+	.show	= _show,						\
+	.store	= _store,						\
+}
 
 #define __DEVICE_ATTR_RO_MODE(_name, _mode) \
-	__ATTR_RO_MODE(_name, _mode)
+	__DEVICE_ATTR(_name, _mode, _name##_show, NULL)
 
 #define __DEVICE_ATTR_RO(_name) \
-	__ATTR_RO(_name)
+	__DEVICE_ATTR_RO_MODE(_name, 0444)
 
 #define __DEVICE_ATTR_WO(_name) \
-	__ATTR_WO(_name)
+	__DEVICE_ATTR(_name, 0200, NULL, _name##_store)
 
 #define __DEVICE_ATTR_RW_MODE(_name, _mode) \
-	__ATTR_RW_MODE(_name, _mode)
+	__DEVICE_ATTR(_name, _mode, _name##_show, _name##_store)
 
 #define __DEVICE_ATTR_RW(_name) \
-	__ATTR_RW(_name)
-
-#define __DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
-	__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
+	__DEVICE_ATTR_RW_MODE(_name, 0644)
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define __DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) {	\
+	.attr = {.name = __stringify(_name), .mode = _mode,		\
+			.ignore_lockdep = true },			\
+	.show		= _show,					\
+	.store		= _store,					\
+}
+#else
+#define __DEVICE_ATTR_IGNORE_LOCKDEP	__DEVICE_ATTR
+#endif
 
 /**
  * DEVICE_ATTR - Define a device attribute.

-- 
2.53.0

[PATCH 4/5] driver core: Allow the constification of device attributes

[Thomas Weißschuh]

Allow device attribute to reside in read-only memory.
Both const and non-const attributes are handled by the utility macros
and attributes can be migrated one-by-one.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/base/core.c    | 12 ++++++----
 include/linux/device.h | 62 +++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 62 insertions(+), 12 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 763e17e9f148..8a48cb2137ae 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2419,9 +2419,11 @@ static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr,
 
 	if (dev_attr->show)
 		ret = dev_attr->show(dev, dev_attr, buf);
+	else if (dev_attr->show_const)
+		ret = dev_attr->show_const(dev, dev_attr, buf);
 	if (ret >= (ssize_t)PAGE_SIZE) {
-		printk("dev_attr_show: %pS returned bad count\n",
-				dev_attr->show);
+		printk("dev_attr_show: %pS/%pS returned bad count\n",
+				dev_attr->show, dev_attr->show_const);
 	}
 	return ret;
 }
@@ -2435,6 +2437,8 @@ static ssize_t dev_attr_store(struct kobject *kobj, struct attribute *attr,
 
 	if (dev_attr->store)
 		ret = dev_attr->store(dev, dev_attr, buf, count);
+	else if (dev_attr->store_const)
+		ret = dev_attr->store_const(dev, dev_attr, buf, count);
 	return ret;
 }
 
@@ -3048,10 +3052,10 @@ int device_create_file(struct device *dev,
 	int error = 0;
 
 	if (dev) {
-		WARN(((attr->attr.mode & S_IWUGO) && !attr->store),
+		WARN(((attr->attr.mode & S_IWUGO) && !(attr->store || attr->store_const)),
 			"Attribute %s: write permission without 'store'\n",
 			attr->attr.name);
-		WARN(((attr->attr.mode & S_IRUGO) && !attr->show),
+		WARN(((attr->attr.mode & S_IRUGO) && !(attr->show || attr->show_const)),
 			"Attribute %s: read permission without 'show'\n",
 			attr->attr.name);
 		error = sysfs_create_file(&dev->kobj, &attr->attr);
diff --git a/include/linux/device.h b/include/linux/device.h
index 714e36d610e3..a529a8eaaa9a 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -104,10 +104,18 @@ struct device_type {
  */
 struct device_attribute {
 	struct attribute	attr;
-	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
-			char *buf);
-	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
-			 const char *buf, size_t count);
+	__SYSFS_FUNCTION_ALTERNATIVE(
+		ssize_t (*show)(struct device *dev, struct device_attribute *attr,
+				char *buf);
+		ssize_t (*show_const)(struct device *dev, const struct device_attribute *attr,
+				      char *buf);
+	);
+	__SYSFS_FUNCTION_ALTERNATIVE(
+		ssize_t (*store)(struct device *dev, struct device_attribute *attr,
+				 const char *buf, size_t count);
+		ssize_t (*store_const)(struct device *dev, const struct device_attribute *attr,
+				       const char *buf, size_t count);
+	);
 };
 
 /**
@@ -135,11 +143,50 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
 ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
 			   char *buf);
 
+typedef ssize_t __device_show_handler_const(struct device *dev, const struct device_attribute *attr,
+					    char *buf);
+typedef ssize_t __device_store_handler_const(struct device *dev, const struct device_attribute *attr,
+					     const char *buf, size_t count);
+
+#ifdef CONFIG_CFI
+
+#define __DEVICE_ATTR_SHOW_STORE(_show, _store)						\
+	.show		= _Generic(_show,						\
+			  __device_show_handler_const * : NULL,				\
+			  default : _show						\
+	),										\
+	.show_const	= _Generic(_show,						\
+			  __device_show_handler_const * : _show,			\
+			  default : NULL						\
+	),										\
+	.store		= _Generic(_store,						\
+			  __device_store_handler_const * : NULL,			\
+			  default : _store						\
+	),										\
+	.store_const	= _Generic(_store,						\
+			  __device_store_handler_const * : _store,			\
+			  default : NULL \
+	),
+
+#else
+
+#define __DEVICE_ATTR_SHOW_STORE(_show, _store)						\
+	.show		= _Generic(_show,						\
+			  __device_show_handler_const * : (void *)_show,		\
+			  default : _show						\
+	),										\
+	.store		= _Generic(_store,						\
+			  __device_store_handler_const * : (void *)_store,		\
+			  default : _store						\
+	),										\
+
+#endif
+
+
 #define __DEVICE_ATTR(_name, _mode, _show, _store) {			\
 	.attr = {.name = __stringify(_name),				\
 		 .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
-	.show	= _show,						\
-	.store	= _store,						\
+	__DEVICE_ATTR_SHOW_STORE(_show, _store)				\
 }
 
 #define __DEVICE_ATTR_RO_MODE(_name, _mode) \
@@ -161,8 +208,7 @@ ssize_t device_show_string(struct device *dev, struct device_attribute *attr,
 #define __DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) {	\
 	.attr = {.name = __stringify(_name), .mode = _mode,		\
 			.ignore_lockdep = true },			\
-	.show		= _show,					\
-	.store		= _store,					\
+	__DEVICE_ATTR_SHOW_STORE(_show, _store)				\
 }
 #else
 #define __DEVICE_ATTR_IGNORE_LOCKDEP	__DEVICE_ATTR

-- 
2.53.0

[PATCH 5/5] driver core: Constify core device attributes

[Thomas Weißschuh]

To make sure these attributes are not modified by accident or by an
attacker, move them to read-only memory.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/base/core.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 8a48cb2137ae..0f314c83eb9d 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -422,7 +422,7 @@ void device_pm_move_to_tail(struct device *dev)
 #define to_devlink(dev)	container_of((dev), struct device_link, link_dev)
 
 static ssize_t status_show(struct device *dev,
-			   struct device_attribute *attr, char *buf)
+			   const struct device_attribute *attr, char *buf)
 {
 	const char *output;
 
@@ -452,10 +452,10 @@ static ssize_t status_show(struct device *dev,
 
 	return sysfs_emit(buf, "%s\n", output);
 }
-static DEVICE_ATTR_RO(status);
+static const DEVICE_ATTR_RO(status);
 
 static ssize_t auto_remove_on_show(struct device *dev,
-				   struct device_attribute *attr, char *buf)
+				   const struct device_attribute *attr, char *buf)
 {
 	struct device_link *link = to_devlink(dev);
 	const char *output;
@@ -469,27 +469,27 @@ static ssize_t auto_remove_on_show(struct device *dev,
 
 	return sysfs_emit(buf, "%s\n", output);
 }
-static DEVICE_ATTR_RO(auto_remove_on);
+static const DEVICE_ATTR_RO(auto_remove_on);
 
 static ssize_t runtime_pm_show(struct device *dev,
-			       struct device_attribute *attr, char *buf)
+			       const struct device_attribute *attr, char *buf)
 {
 	struct device_link *link = to_devlink(dev);
 
 	return sysfs_emit(buf, "%d\n", device_link_test(link, DL_FLAG_PM_RUNTIME));
 }
-static DEVICE_ATTR_RO(runtime_pm);
+static const DEVICE_ATTR_RO(runtime_pm);
 
 static ssize_t sync_state_only_show(struct device *dev,
-				    struct device_attribute *attr, char *buf)
+				    const struct device_attribute *attr, char *buf)
 {
 	struct device_link *link = to_devlink(dev);
 
 	return sysfs_emit(buf, "%d\n", device_link_test(link, DL_FLAG_SYNC_STATE_ONLY));
 }
-static DEVICE_ATTR_RO(sync_state_only);
+static const DEVICE_ATTR_RO(sync_state_only);
 
-static struct attribute *devlink_attrs[] = {
+static const struct attribute *const devlink_attrs[] = {
 	&dev_attr_status.attr,
 	&dev_attr_auto_remove_on.attr,
 	&dev_attr_runtime_pm.attr,
@@ -1233,7 +1233,7 @@ static void device_link_drop_managed(struct device_link *link)
 }
 
 static ssize_t waiting_for_supplier_show(struct device *dev,
-					 struct device_attribute *attr,
+					 const struct device_attribute *attr,
 					 char *buf)
 {
 	bool val;
@@ -1244,7 +1244,7 @@ static ssize_t waiting_for_supplier_show(struct device *dev,
 	device_unlock(dev);
 	return sysfs_emit(buf, "%u\n", val);
 }
-static DEVICE_ATTR_RO(waiting_for_supplier);
+static const DEVICE_ATTR_RO(waiting_for_supplier);
 
 /**
  * device_links_force_bind - Prepares device to be force bound
@@ -2727,7 +2727,7 @@ static const struct kset_uevent_ops device_uevent_ops = {
 	.uevent =	dev_uevent,
 };
 
-static ssize_t uevent_show(struct device *dev, struct device_attribute *attr,
+static ssize_t uevent_show(struct device *dev, const struct device_attribute *attr,
 			   char *buf)
 {
 	struct kobject *top_kobj;
@@ -2770,7 +2770,7 @@ static ssize_t uevent_show(struct device *dev, struct device_attribute *attr,
 	return len;
 }
 
-static ssize_t uevent_store(struct device *dev, struct device_attribute *attr,
+static ssize_t uevent_store(struct device *dev, const struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
 	int rc;
@@ -2784,9 +2784,9 @@ static ssize_t uevent_store(struct device *dev, struct device_attribute *attr,
 
 	return count;
 }
-static DEVICE_ATTR_RW(uevent);
+static const DEVICE_ATTR_RW(uevent);
 
-static ssize_t online_show(struct device *dev, struct device_attribute *attr,
+static ssize_t online_show(struct device *dev, const struct device_attribute *attr,
 			   char *buf)
 {
 	bool val;
@@ -2797,7 +2797,7 @@ static ssize_t online_show(struct device *dev, struct device_attribute *attr,
 	return sysfs_emit(buf, "%u\n", val);
 }
 
-static ssize_t online_store(struct device *dev, struct device_attribute *attr,
+static ssize_t online_store(struct device *dev, const struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
 	bool val;
@@ -2815,9 +2815,9 @@ static ssize_t online_store(struct device *dev, struct device_attribute *attr,
 	unlock_device_hotplug();
 	return ret < 0 ? ret : count;
 }
-static DEVICE_ATTR_RW(online);
+static const DEVICE_ATTR_RW(online);
 
-static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
+static ssize_t removable_show(struct device *dev, const struct device_attribute *attr,
 			      char *buf)
 {
 	const char *loc;
@@ -2834,7 +2834,7 @@ static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
 	}
 	return sysfs_emit(buf, "%s\n", loc);
 }
-static DEVICE_ATTR_RO(removable);
+static const DEVICE_ATTR_RO(removable);
 
 int device_add_groups(struct device *dev,
 		      const struct attribute_group *const *groups)

-- 
2.53.0

Re: [PATCH 0/5] driver core: Allow the constification of device attributes

[Greg Kroah-Hartman]

On Wed, Apr 08, 2026 at 09:30:46PM +0200, Thomas Weißschuh wrote:
> Allow device attribute to reside in read-only memory.
> Both const and non-const attributes are handled by the utility macros
> and attributes can be migrated one-by-one.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
> Thomas Weißschuh (5):
>       driver core: Delete DEVICE_ATTR_PREALLOC()
>       driver core: Add low-level macros for device attributes
>       driver core: stop using generic sysfs macros for device attributes
>       driver core: Allow the constification of device attributes
>       driver core: Constify core device attributes
> 
>  drivers/base/core.c    |  50 ++++++++++----------
>  include/linux/device.h | 122 +++++++++++++++++++++++++++++++++++++------------
>  2 files changed, 121 insertions(+), 51 deletions(-)
> ---
> base-commit: 6c8dfb0362732bf1e4829867a2a5239fedc592d0
> change-id: 20260408-sysfs-const-attr-device_attr-prep-9971fb4439da
> 
> Best regards,
> --  
> Thomas Weißschuh <linux@weissschuh.net>
> 
> 

We still have the is_visible_const() stuff not finished yet, why not fix
that up first?

And this makes me worry, how many changes are going to be needed to move
everything over?  thousands?

thanks,

greg k-h

Re: [PATCH 0/5] driver core: Allow the constification of device attributes

[Thomas Weißschuh]

On 2026-04-09 07:36:09+0200, Greg Kroah-Hartman wrote:
> On Wed, Apr 08, 2026 at 09:30:46PM +0200, Thomas Weißschuh wrote:
> > Allow device attribute to reside in read-only memory.
> > Both const and non-const attributes are handled by the utility macros
> > and attributes can be migrated one-by-one.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> > ---
> > Thomas Weißschuh (5):
> >       driver core: Delete DEVICE_ATTR_PREALLOC()
> >       driver core: Add low-level macros for device attributes
> >       driver core: stop using generic sysfs macros for device attributes
> >       driver core: Allow the constification of device attributes
> >       driver core: Constify core device attributes
> > 
> >  drivers/base/core.c    |  50 ++++++++++----------
> >  include/linux/device.h | 122 +++++++++++++++++++++++++++++++++++++------------
> >  2 files changed, 121 insertions(+), 51 deletions(-)
> > ---
> > base-commit: 6c8dfb0362732bf1e4829867a2a5239fedc592d0
> > change-id: 20260408-sysfs-const-attr-device_attr-prep-9971fb4439da
> > 
> > Best regards,
> > --  
> > Thomas Weißschuh <linux@weissschuh.net>
> > 
> > 
> 
> We still have the is_visible_const() stuff not finished yet, why not fix
> that up first?

Because I want to touch each file or subsystem as few times as
possible. So before a subsystem is migrated, the prerequisites for
all of their used features need to be there.

Currently only the prerequisites for 'struct device_attribute' and
'struct kobj_attribute' are missing. So with this series in we can start
migrating everything that is *not* using 'struct kobj_attribute'.

> And this makes me worry, how many changes are going to be needed to move
> everything over?  thousands?

Depends on the granularity of the patches. I want to do as few as
possible, but still expect a few hundred patches.


Thomas