[PATCH v11 1/8] power: reset: reboot-mode: Add device tree node-based registration

[Dmitry Baryshkov]

On Sat, Jul 19, 2025 at 09:05:16PM +0530, Shivendra Pratap wrote:
> 
> 
> On 7/19/2025 12:07 AM, Dmitry Baryshkov wrote:
> > On Thu, Jul 17, 2025 at 06:16:47PM +0530, Shivendra Pratap wrote:
> >> The reboot-mode driver does not have a strict requirement for
> >> device-based registration. It primarily uses the device's of_node
> >> to read mode-<cmd> properties and the device pointer for logging.
> >>
> >> Remove the dependency on struct device and introduce support for
> >> Device Tree (DT) node-based registration. This enables drivers
> >> that are not associated with a struct device to leverage the
> >> reboot-mode framework.
> >>
> >> Signed-off-by: Shivendra Pratap <shivendra.pratap at oss.qualcomm.com>
> >> ---
> >>  drivers/power/reset/reboot-mode.c | 29 +++++++++++++++++++----------
> >>  include/linux/reboot-mode.h       |  2 +-
> >>  2 files changed, 20 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
> >> index fba53f638da04655e756b5f8b7d2d666d1379535..0269ec55106472cf2f2b12bd65704dd0114bf4a3 100644
> >> --- a/drivers/power/reset/reboot-mode.c
> >> +++ b/drivers/power/reset/reboot-mode.c
> >> @@ -3,13 +3,17 @@
> >>   * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
> >>   */
> >>  
> >> +#define pr_fmt(fmt)	"reboot-mode: " fmt
> >> +
> >>  #include <linux/device.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>
> >>  
> >>  #define PREFIX "mode-"
> >>  
> >> @@ -65,33 +69,35 @@ static int reboot_mode_notify(struct notifier_block *this,
> >>  /**
> >>   * reboot_mode_register - register a reboot mode driver
> >>   * @reboot: reboot mode driver
> >> + * @np: Pointer to device tree node
> >>   *
> >>   * Returns: 0 on success or a negative error code on failure.
> >>   */
> >> -int reboot_mode_register(struct reboot_mode_driver *reboot)
> >> +int reboot_mode_register(struct reboot_mode_driver *reboot, struct device_node *np)
> >>  {
> >>  	struct mode_info *info;
> >>  	struct property *prop;
> >> -	struct device_node *np = reboot->dev->of_node;
> >>  	size_t len = strlen(PREFIX);
> >>  	int ret;
> >>  
> >> +	if (!np)
> >> +		return -EINVAL;
> >> +
> >>  	INIT_LIST_HEAD(&reboot->head);
> >>  
> >>  	for_each_property_of_node(np, prop) {
> >>  		if (strncmp(prop->name, PREFIX, len))
> >>  			continue;
> >>  
> >> -		info = devm_kzalloc(reboot->dev, sizeof(*info), GFP_KERNEL);
> >> +		info = kzalloc(sizeof(*info), GFP_KERNEL);
> >>  		if (!info) {
> >>  			ret = -ENOMEM;
> >>  			goto error;
> >>  		}
> >>  
> >>  		if (of_property_read_u32(np, prop->name, &info->magic)) {
> >> -			dev_err(reboot->dev, "reboot mode %s without magic number\n",
> >> -				info->mode);
> >> -			devm_kfree(reboot->dev, info);
> >> +			pr_err("reboot mode %s without magic number\n", info->mode);
> >> +			kfree(info);
> >>  			continue;
> >>  		}
> >>  
> >> @@ -102,8 +108,7 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
> >>  		} else if (info->mode[0] == '\0') {
> >>  			kfree_const(info->mode);
> >>  			ret = -EINVAL;
> >> -			dev_err(reboot->dev, "invalid mode name(%s): too short!\n",
> >> -				prop->name);
> >> +			pr_err("invalid mode name(%s): too short!\n", prop->name);
> >>  			goto error;
> >>  		}
> >>  
> >> @@ -130,11 +135,15 @@ EXPORT_SYMBOL_GPL(reboot_mode_register);
> >>  int reboot_mode_unregister(struct reboot_mode_driver *reboot)
> >>  {
> >>  	struct mode_info *info;
> >> +	struct mode_info *next;
> >>  
> >>  	unregister_reboot_notifier(&reboot->reboot_notifier);
> >>  
> >> -	list_for_each_entry(info, &reboot->head, list)
> >> +	list_for_each_entry_safe(info, next, &reboot->head, list) {
> > 
> > This feels liks a missing lock.
> Should we add a lock here? The list will mostly be fully created only
> once at the time of registration.

Does it matter? The code should be correct. List traversal should be
protected by the lock in all the cases.

> - thanks.
> > 
> >>  		kfree_const(info->mode);
> >> +		list_del(&info->list);
> > 
> > list_del should come before kfree, otherwise it's possible to access
> > freed memory while traversing the list.
> sure. will make it list_del(&info->list) and then kfree_const(info->mode).
> - thanks.
> > 
> >> +		kfree(info);
> >> +	}
> >>  
> >>  	return 0;
> >>  }
> >> @@ -162,7 +171,7 @@ int devm_reboot_mode_register(struct device *dev,
> >>  	if (!dr)
> >>  		return -ENOMEM;
> >>  
> >> -	rc = reboot_mode_register(reboot);
> >> +	rc = reboot_mode_register(reboot, reboot->dev->of_node);
> >>  	if (rc) {
> >>  		devres_free(dr);
> >>  		return rc;
> >> diff --git a/include/linux/reboot-mode.h b/include/linux/reboot-mode.h
> >> index 4a2abb38d1d612ec0fdf05eb18c98b210f631b7f..36f071f4b82e1fc255d8dd679a18e537655c3179 100644
> >> --- a/include/linux/reboot-mode.h
> >> +++ b/include/linux/reboot-mode.h
> >> @@ -9,7 +9,7 @@ struct reboot_mode_driver {
> >>  	struct notifier_block reboot_notifier;
> >>  };
> >>  
> >> -int reboot_mode_register(struct reboot_mode_driver *reboot);
> >> +int reboot_mode_register(struct reboot_mode_driver *reboot, struct device_node *np);
> >>  int reboot_mode_unregister(struct reboot_mode_driver *reboot);
> >>  int devm_reboot_mode_register(struct device *dev,
> >>  			      struct reboot_mode_driver *reboot);
> >>
> >> -- 
> >> 2.34.1
> >>
> > 

-- 
With best wishes
Dmitry