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    SubjectRe: [PATCH v4] reboot: allow to specify reboot mode via sysfs
    On Mon, Feb 22, 2021 at 11:03 AM Pavel Machek <pavel@ucw.cz> wrote:
    >
    > On Tue 2020-11-10 21:27:46, Matteo Croce wrote:
    > > From: Matteo Croce <mcroce@microsoft.com>
    > >
    > > The kernel cmdline reboot= option offers some sort of control
    > > on how the reboot is issued.
    > > Add handles in sysfs to allow setting these reboot options, so they
    > > can be changed when the system is booted, other than at boot time.
    >
    > We already have a reboot syscall, do we need sysfs interface, too?
    >
    >
    > > +What: /sys/kernel/reboot/mode
    > > +Date: November 2020
    > > +KernelVersion: 5.11
    > > +Contact: Matteo Croce <mcroce@microsoft.com>
    > > +Description: Reboot mode. Valid values are: cold warm hard soft gpio
    >
    >
    > > +What: /sys/kernel/reboot/type
    > > +Date: November 2020
    > > +KernelVersion: 5.11
    > > +Contact: Matteo Croce <mcroce@microsoft.com>
    > > +Description: Reboot type. Valid values are: bios acpi kbd triple efi pci
    >
    > what is difference between mode and type? What is difference between
    > cold and hard for example? WTF is gpio?
    >
    > > +What: /sys/kernel/reboot/cpu
    > > +Date: November 2020
    > > +KernelVersion: 5.11
    > > +Contact: Matteo Croce <mcroce@microsoft.com>
    > > +Description: CPU number to use to reboot.
    >
    > Why should user care about this?
    >

    Mode is the reboot mode (soft, warm, cold, gpio), and type is an x86
    specific type, (bios, acpi, uefi, etc.).
    I never used GPIO reboot but it's used by some ARM devices.

    I didn't invent anything from scratch, I just transposed the settings
    available from the kernel command line (see
    Documentation/admin-guide/kernel-parameters.txt) to sysfs.
    Everithing was already tunable before, like the CPU used during reboot.

    --
    per aspera ad upstream

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