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Message-ID: <32d8329f-0d73-fb16-f12d-308e6ee6b45d@oss.qualcomm.com>
Date: Wed, 17 Sep 2025 08:26:38 +0530
From: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
Sudeep Holla <sudeep.holla@....com>,
Souvik Chakravarty <Souvik.Chakravarty@....com>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley
<conor+dt@...nel.org>,
Andy Yan <andy.yan@...k-chips.com>,
Mark Rutland <mark.rutland@....com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Konrad Dybcio <konradybcio@...nel.org>,
cros-qcom-dts-watchers@...omium.org, Vinod Koul <vkoul@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Florian Fainelli <florian.fainelli@...adcom.com>,
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
Mukesh Ojha <mukesh.ojha@....qualcomm.com>,
Stephen Boyd <swboyd@...omium.org>,
Andre Draszik
<andre.draszik@...aro.org>, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
Elliot Berman <quic_eberman@...cinc.com>,
Srinivas Kandagatla <srini@...nel.org>
Subject: Re: [PATCH v14 05/10] power: reset: reboot-mode: Expose sysfs for
registered reboot_modes
On 9/17/2025 12:32 AM, Sebastian Reichel wrote:
> Hi,
>
> On Fri, Aug 15, 2025 at 08:05:10PM +0530, Shivendra Pratap wrote:
>> Currently, there is no standardized mechanism for userspace to
>> discover which reboot-modes are supported on a given platform.
>> This limitation forces tools and scripts to rely on hardcoded
>> assumptions about the supported reboot-modes.
>>
>> Create a class 'reboot-mode' and a device under it to expose a
>> sysfs interface to show the available reboot mode arguments to
>> userspace.
>>
>> Provision the register function with an additional parameter to
>> get an explicit driver_name. Create the device using this
>> driver_name. For platform drivers, use the driver_name configured
>> in dev node.
>>
>> This results in the creation of:
>> /sys/class/reboot-mode/<driver>/reboot_modes
>>
>> This read-only sysfs file will exposes the list of supported
>> reboot modes arguments provided by the driver, enabling userspace
>> to query the list of arguments.
>>
>> Align the clean up path to maintain backward compatibility for
>> existing reboot-mode based drivers.
>>
>> Signed-off-by: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
>> ---
>> drivers/power/reset/reboot-mode.c | 131 +++++++++++++++++++++++++++++++-------
>> include/linux/reboot-mode.h | 4 +-
>> 2 files changed, 110 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
>> index ac81b8b0a9b7fc31f8ef21024333a050087ce90f..7ecab050e496af3e1cc01c1a4614787707cb74b4 100644
>> --- a/drivers/power/reset/reboot-mode.c
>> +++ b/drivers/power/reset/reboot-mode.c
>> @@ -6,6 +6,7 @@
>> #define pr_fmt(fmt) "reboot-mode: " fmt
>>
>> #include <linux/device.h>
>> +#include <linux/err.h>
>> #include <linux/init.h>
>> #include <linux/kernel.h>
>> #include <linux/list.h>
>> @@ -23,6 +24,8 @@ struct mode_info {
>> struct list_head list;
>> };
>>
>> +static struct class *rb_class;
>> +
>> static u64 get_reboot_mode_magic(struct reboot_mode_driver *reboot, const char *cmd)
>> {
>> const char *normal = "normal";
>> @@ -75,26 +78,121 @@ static int reboot_mode_notify(struct notifier_block *this,
>> return NOTIFY_DONE;
>> }
>>
>> +static void release_reboot_mode_device(struct device *dev, void *res);
>> +
>> +static ssize_t reboot_modes_show(struct device *dev, struct device_attribute *attr, char *buf)
>> +{
>> + struct reboot_mode_driver **devres_reboot;
>> + struct reboot_mode_driver *reboot;
>> + struct mode_info *info;
>> + ssize_t size = 0;
>> +
>> + devres_reboot = devres_find(dev, release_reboot_mode_device, NULL, NULL);
>> + if (!devres_reboot || !(*devres_reboot))
>> + return -ENODATA;
>> +
>> + reboot = *devres_reboot;
>> + mutex_lock(&reboot->rb_lock);
>> + list_for_each_entry(info, &reboot->head, list) {
>> + size += sprintf(buf + size, "%s ", info->mode);
>
> sysfs_emit_at
ACK. will update.
>
>> + }
>> + mutex_unlock(&reboot->rb_lock);
>> +
>> + if (size) {
>> + size += sprintf(buf + size - 1, "\n");
>
> sysfs_emit_at
ACK. will update.
>
>> + return size;
>> + }
>> +
>> + return -ENODATA;
>> +}
>> +static DEVICE_ATTR_RO(reboot_modes);
>> +
>> +static void release_reboot_mode_device(struct device *dev, void *res)
>> +{
>> + struct reboot_mode_driver *reboot = *(struct reboot_mode_driver **)res;
>> + struct mode_info *info;
>> + struct mode_info *next;
>> +
>> + unregister_reboot_notifier(&reboot->reboot_notifier);
>> +
>> + mutex_lock(&reboot->rb_lock);
>> + list_for_each_entry_safe(info, next, &reboot->head, list) {
>> + list_del(&info->list);
>> + kfree_const(info->mode);
>> + kfree(info);
>> + }
>> + mutex_unlock(&reboot->rb_lock);
>> +
>> + device_remove_file(reboot->reboot_dev, &dev_attr_reboot_modes);
>> +}
>> +
>> +static int create_reboot_mode_device(struct reboot_mode_driver *reboot,
>> + const char *dev_name)
>
> Instead of adding more and more arguments to this, just add a name
> field to struct reboot_mode_driver.
ACK. will update.
thanks,
Shivendra
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