Introduce a generic platform driver for the QEMU 'virt-ctrl' device [1]
and transitions the m68k 'virt' machine to use it, replacing
architecture-specific hooks.

The new driver ('qemu-virt-ctrl') registers a restart handler and
populates the global 'pm_power_off' callback.

On the m68k side, the platform initialization is updated to register
the 'qemu-virt-ctrl' platform device. Additionally, the 'mach_reset'
hook is bridged to 'do_kernel_restart()' to ensure the kernel's restart
handler chain is correctly invoked.

Verified on QEMU m68k virt. Both system reset and power-off were
confirmed functional by invoking 'reboot(LINUX_REBOOT_CMD_RESTART)',
'reboot(LINUX_REBOOT_CMD_POWER_OFF)', and
'reboot(LINUX_REBOOT_CMD_HALT)' from userspace.

Link: https://gitlab.com/qemu-project/qemu/-/blob/v10.2.0/hw/misc/virt_ctrl.c [1]
---
Changes in v4:
- Fix sparse warning caught by kernel test robot.
- Pass the struct qemu_virt_ctrl context to sys-off handlers instead of
  the __iomem pointer.

Changes in v3:
- Add a reboot notifier in the driver to handle LINUX_REBOOT_CMD_HALT.
- Handle native endianness in the driver instead of hardcoding
  big-endian I/O writes.
- Select POWER_RESET and POWER_RESET_QEMU_VIRT_CTRL in m68k
  Kconfig.machine.

Changes in v2:
- Use devm_register_sys_off_handler() instead of register_restart_handler()
  and global pm_power_off.
- Switch Kconfig to tristate to support modular build.
- Add .id_table to platform_driver and use MODULE_DEVICE_TABLE() to correct
  module auto-loading.

v2: https://lore.kernel.org/lkml/20260203170824.2968045-1-visitorckw@gmail.com/
v1: https://lore.kernel.org/lkml/20260112182258.1851769-1-visitorckw@gmail.com/

Kuan-Wei Chiu (2):
  power: reset: Add QEMU virt-ctrl driver
  m68k: virt: Switch to qemu-virt-ctrl driver

 MAINTAINERS                          |   6 ++
 arch/m68k/Kconfig.machine            |   2 +
 arch/m68k/virt/config.c              |  42 +--------
 arch/m68k/virt/platform.c            |  20 ++++-
 drivers/power/reset/Kconfig          |  10 +++
 drivers/power/reset/Makefile         |   1 +
 drivers/power/reset/qemu-virt-ctrl.c | 122 +++++++++++++++++++++++++++
 7 files changed, 159 insertions(+), 44 deletions(-)
 create mode 100644 drivers/power/reset/qemu-virt-ctrl.c

-- 
2.53.0.1213.gd9a14994de-goog

Hi Kuan-Wei,

On Sun, 12 Apr 2026 at 23:20, Kuan-Wei Chiu <visitorckw@gmail.com> wrote:
> Introduce a generic platform driver for the QEMU 'virt-ctrl' device [1]
> and transitions the m68k 'virt' machine to use it, replacing
> architecture-specific hooks.
>
> The new driver ('qemu-virt-ctrl') registers a restart handler and
> populates the global 'pm_power_off' callback.
>
> On the m68k side, the platform initialization is updated to register
> the 'qemu-virt-ctrl' platform device. Additionally, the 'mach_reset'
> hook is bridged to 'do_kernel_restart()' to ensure the kernel's restart
> handler chain is correctly invoked.
>
> Verified on QEMU m68k virt. Both system reset and power-off were
> confirmed functional by invoking 'reboot(LINUX_REBOOT_CMD_RESTART)',
> 'reboot(LINUX_REBOOT_CMD_POWER_OFF)', and
> 'reboot(LINUX_REBOOT_CMD_HALT)' from userspace.
>
> Link: https://gitlab.com/qemu-project/qemu/-/blob/v10.2.0/hw/misc/virt_ctrl.c [1]
> ---
> Changes in v4:
> - Fix sparse warning caught by kernel test robot.
> - Pass the struct qemu_virt_ctrl context to sys-off handlers instead of
>   the __iomem pointer.

Thanks I replaced v3 with v4 in my queue in the m68k tree for v7.1,
and will postpone my PR by a few days to give it some coverage in
linux-next.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds