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Message-Id: <20260205-next-15nov_expose_sysfs-v23-2-b0c5bdcc9f94@oss.qualcomm.com>
Date: Thu, 05 Feb 2026 22:47:14 +0530
From: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
To: Sebastian Reichel <sre@...nel.org>,
Bartosz Golaszewski <bgolasze@...cinc.com>,
Bjorn Andersson <andersson@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-pm@...r.kernel.org, Bartosz Golaszewski <brgl@...ev.pl>,
Shivendra Pratap <shivendra.pratap@....qualcomm.com>
Subject: [PATCH v23 2/2] power: reset: reboot-mode: Expose sysfs for
registered reboot_modes
Currently, there is no standardized mechanism for userspace to discover
supported reboot modes on a platform. This limits userspace scripts, to
rely on hardcoded assumptions about the available reboot-modes.
Create a class 'reboot-mode' and a device under it. Use the name of the
registering driver as device name. Expose a sysfs interface under this
device to show available reboot mode arguments.
This results in the creation of:
/sys/class/reboot-mode/<driver>/reboot_modes
This read-only sysfs file will exposes the supported reboot mode
arguments provided by the registering driver, enabling userspace to
query the list of arguments.
Signed-off-by: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
---
drivers/power/reset/reboot-mode.c | 151 +++++++++++++++++++++++++++++++++++++-
1 file changed, 148 insertions(+), 3 deletions(-)
diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
index fba53f638da04655e756b5f8b7d2d666d1379535..7fdb788c8cc85f26bdd381e1cea7a936b052e8ab 100644
--- a/drivers/power/reset/reboot-mode.c
+++ b/drivers/power/reset/reboot-mode.c
@@ -4,12 +4,16 @@
*/
#include <linux/device.h>
+#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/reboot.h>
#include <linux/reboot-mode.h>
+#include <linux/slab.h>
+#include <linux/string.h>
#define PREFIX "mode-"
@@ -19,6 +23,54 @@ struct mode_info {
struct list_head list;
};
+struct reboot_mode_sysfs_data {
+ struct device *reboot_mode_device;
+ struct list_head head;
+};
+
+static inline void reboot_mode_release_list(struct list_head *head)
+{
+ struct mode_info *info;
+ struct mode_info *next;
+
+ list_for_each_entry_safe(info, next, head, list) {
+ list_del(&info->list);
+ kfree_const(info->mode);
+ kfree(info);
+ }
+}
+
+static ssize_t reboot_modes_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ struct reboot_mode_sysfs_data *priv;
+ struct mode_info *sysfs_info;
+ ssize_t size = 0;
+
+ priv = dev_get_drvdata(dev);
+ if (!priv)
+ return -ENODATA;
+
+ list_for_each_entry(sysfs_info, &priv->head, list)
+ size += sysfs_emit_at(buf, size, "%s ", sysfs_info->mode);
+
+ if (!size)
+ return -ENODATA;
+
+ return size + sysfs_emit_at(buf, size - 1, "\n");
+}
+static DEVICE_ATTR_RO(reboot_modes);
+
+static struct attribute *reboot_mode_attrs[] = {
+ &dev_attr_reboot_modes.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(reboot_mode);
+
+static const struct class reboot_mode_class = {
+ .name = "reboot-mode",
+ .dev_groups = reboot_mode_groups,
+};
+
static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
const char *cmd)
{
@@ -62,6 +114,52 @@ static int reboot_mode_notify(struct notifier_block *this,
return NOTIFY_DONE;
}
+static int reboot_mode_create_device(struct reboot_mode_driver *reboot)
+{
+ struct reboot_mode_sysfs_data *priv;
+ struct mode_info *sysfs_info;
+ struct mode_info *info;
+ int ret;
+
+ priv = kzalloc_obj(*priv, GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&priv->head);
+
+ list_for_each_entry(info, &reboot->head, list) {
+ sysfs_info = kzalloc_obj(*sysfs_info, GFP_KERNEL);
+ if (!sysfs_info) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ sysfs_info->mode = kstrdup_const(info->mode, GFP_KERNEL);
+ if (!sysfs_info->mode) {
+ kfree(sysfs_info);
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ list_add_tail(&sysfs_info->list, &priv->head);
+ }
+
+ priv->reboot_mode_device = device_create(&reboot_mode_class, NULL, 0,
+ (void *)priv, reboot->dev->driver->name);
+
+ if (IS_ERR(priv->reboot_mode_device)) {
+ ret = PTR_ERR(priv->reboot_mode_device);
+ goto error;
+ }
+
+ return 0;
+
+error:
+ reboot_mode_release_list(&priv->head);
+ kfree(priv);
+ return ret;
+}
+
/**
* reboot_mode_register - register a reboot mode driver
* @reboot: reboot mode driver
@@ -113,16 +211,49 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
reboot->reboot_notifier.notifier_call = reboot_mode_notify;
register_reboot_notifier(&reboot->reboot_notifier);
+ ret = reboot_mode_create_device(reboot);
+ if (ret)
+ goto error;
+
return 0;
error:
- list_for_each_entry(info, &reboot->head, list)
- kfree_const(info->mode);
-
+ reboot_mode_unregister(reboot);
return ret;
}
EXPORT_SYMBOL_GPL(reboot_mode_register);
+static int reboot_mode_match_by_name(struct device *dev, const void *data)
+{
+ const char *name = data;
+
+ if (!dev || !data)
+ return 0;
+
+ return dev_name(dev) && strcmp(dev_name(dev), name) == 0;
+}
+
+static inline void reboot_mode_unregister_device(struct reboot_mode_driver *reboot)
+{
+ struct reboot_mode_sysfs_data *priv;
+ struct device *reboot_mode_device;
+
+ reboot_mode_device = class_find_device(&reboot_mode_class, NULL, reboot->dev->driver->name,
+ reboot_mode_match_by_name);
+
+ if (!reboot_mode_device)
+ return;
+
+ priv = dev_get_drvdata(reboot_mode_device);
+ device_unregister(reboot_mode_device);
+
+ if (!priv)
+ return;
+
+ reboot_mode_release_list(&priv->head);
+ kfree(priv);
+}
+
/**
* reboot_mode_unregister - unregister a reboot mode driver
* @reboot: reboot mode driver
@@ -132,6 +263,7 @@ int reboot_mode_unregister(struct reboot_mode_driver *reboot)
struct mode_info *info;
unregister_reboot_notifier(&reboot->reboot_notifier);
+ reboot_mode_unregister_device(reboot);
list_for_each_entry(info, &reboot->head, list)
kfree_const(info->mode);
@@ -199,6 +331,19 @@ void devm_reboot_mode_unregister(struct device *dev,
}
EXPORT_SYMBOL_GPL(devm_reboot_mode_unregister);
+static int __init reboot_mode_init(void)
+{
+ return class_register(&reboot_mode_class);
+}
+
+static void __exit reboot_mode_exit(void)
+{
+ class_unregister(&reboot_mode_class);
+}
+
+subsys_initcall(reboot_mode_init);
+module_exit(reboot_mode_exit);
+
MODULE_AUTHOR("Andy Yan <andy.yan@...k-chips.com>");
MODULE_DESCRIPTION("System reboot mode core library");
MODULE_LICENSE("GPL v2");
--
2.34.1
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