On Mon, 13 Jan 2025 17:25:25 +0100 Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: > We currently leave the decision of whether to shutdown or reboot to > protect hardware in an emergency situation to the individual drivers. > > This works out in some cases, where the driver detecting the critical > failure has inside knowledge: It binds to the system management controller > for example or is guided by hardware description that defines what to do. > > This is inadequate in the general case though as a driver reporting e.g. > an imminent power failure can't know whether a shutdown or a reboot would > be more appropriate for a given hardware platform. > > To address this, this series adds a hw_protection kernel parameter and > sysfs toggle that can be used to change the action from the shutdown > default to reboot. A new hw_protection_trigger API then makes use of > this default action. > > My particular use case is unattended embedded systems that don't > have support for shutdown and that power on automatically when power is > supplied: > > - A brief power cycle gets detected by the driver > - The kernel powers down the system and SoC goes into shutdown mode > - Power is restored > - The system remains oblivious to the restored power > - System needs to be manually power cycled for a duration long enough > to drain the capacitors > > With this series, such systems can configure the kernel with > hw_protection=reboot to have the boot firmware worry about critical > conditions. This seems useful. > Documentation/ABI/testing/sysfs-kernel-reboot | 8 ++ > Documentation/admin-guide/kernel-parameters.txt | 6 + > .../devicetree/bindings/thermal/thermal-zones.yaml | 5 +- > Documentation/driver-api/thermal/sysfs-api.rst | 25 ++-- > drivers/platform/chrome/cros_ec_lpc.c | 2 +- > drivers/regulator/core.c | 4 +- > drivers/regulator/irq_helpers.c | 16 +-- > drivers/thermal/thermal_core.c | 17 +-- > drivers/thermal/thermal_core.h | 1 + > drivers/thermal/thermal_of.c | 7 +- > include/linux/reboot.h | 36 ++++-- > include/uapi/linux/capability.h | 1 + > kernel/reboot.c | 140 ++++++++++++++++----- > 13 files changed, 195 insertions(+), 73 deletions(-) I'm not sure what the merge path is. Maybe the drivers tree, maybe mm.git's mm-nonmm branches. We're at -rc7 so I'll save this away and shall revisit after -rc1 with a view to gathering acks (please) and adding the series to mm-nonmm, thanks.
