linux-kernel - Re: [PATCH 1/2] Documentation: ABI: Add sysfs-class-reboot-mode-reboot

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Message-ID: <t3hfhlp27numfxurtmtcwrovvlgwdvnujain46kwmi37zehdak@xt3vngtkxpsm>
Date: Sun, 16 Nov 2025 19:44:24 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
Cc: Sebastian Reichel <sre@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        Sebastian Reichel <sebastian.reichel@...labora.com>
Subject: Re: [PATCH 1/2] Documentation: ABI: Add
 sysfs-class-reboot-mode-reboot_modes

On Sun, Nov 16, 2025 at 08:49:47PM +0530, Shivendra Pratap wrote:
> Add ABI documentation for /sys/class/reboot-mode/*/reboot_modes, a
> read-only sysfs attribute exposing the list of supported reboot-mode
> arguments. This file is created by reboot-mode framework and provides a
> user-readable interface to query available reboot-mode arguments.
> 
> Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> Signed-off-by: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
> ---
>  .../testing/sysfs-class-reboot-mode-reboot_modes   | 39 ++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes b/Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes
> new file mode 100644
> index 0000000000000000000000000000000000000000..28280ffe9bf962ef9d2136ea5d7c6aef77c4bd34
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes
> @@ -0,0 +1,39 @@
> +What:		/sys/class/reboot-mode/<driver>/reboot_modes
> +Date:		November 2025
> +KernelVersion:	6.18.0-rc5
> +Contact:	linux-pm@...r.kernel.org
> +		Description:
> +		This interface exposes the reboot-mode arguments
> +		registered with the reboot-mode framework. It is
> +		a read-only interface and provides a space
> +		separated list of reboot-mode arguments supported
> +		on the current platform.
> +		Example:
> +		 recovery fastboot bootloader
> +
> +		The exact sysfs path may vary depending on the
> +		name of the driver that registers the arguments.
> +		Example:
> +		 /sys/class/reboot-mode/nvmem-reboot-mode/reboot_modes
> +		 /sys/class/reboot-mode/syscon-reboot-mode/reboot_modes
> +		 /sys/class/reboot-mode/qcom-pon/reboot_modes

This part is obvious, isn't it?

> +
> +		The supported arguments can be used by userspace
> +		to invoke device reset using the reboot() system
> +		call, with the "argument" as string to "*arg"
> +		parameter along with LINUX_REBOOT_CMD_RESTART2.
> +		Example:
> +		 reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
> +		        LINUX_REBOOT_CMD_RESTART2, "bootloader");

So, does one need to write a tool for invoking reboot with the corerct
set of args? If we are adding a sysfs interface, wouldn't it be logical
to also add another sysfs file, setting the argument?

> +
> +		A driver can expose the supported arguments by
> +		registering them with the reboot-mode framework
> +		using the property names that follow the
> +		mode-<argument> format.
> +		Example:
> +		 mode-bootloader, mode-recovery.
> +
> +		This attribute is useful for scripts or initramfs
> +		logic that need to programmatically determine
> +		which reboot-mode arguments are valid before
> +		triggering a reboot.
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry