asmc: Prevent module unload to avoid kernel panic

[guest-seuros]

Summary

Prevent asmc driver from being detached/unloaded to avoid kernel
panics during device reprobing. When asmc.ko is unloaded and then
reloaded, acpi_driver_added() attempts to reprobe the detached
device but accesses freed driver structures in the devclass,
causing a page fault in kobj_init().

Return EBUSY from asmc_detach() to prevent unloading while the
device is attached, similar to acpi_hpet and other critical
ACPI drivers.

Crash backtrace from testing:

kobj_init+0xe
device_set_driver+0xa3
device_probe_child+0xe4
device_probe+0x8b
device_probe_and_attach+0x2e
acpi_driver_added+0x99

[markj]

Can you provide more details about the panic, e.g., the panic string and gdb backtrace? You might also try testing with a GENERIC-KASAN kernel. The stack trace you pasted is odd and it'd be nice to understand what's actually going on.

[guest-seuros]

This module load only in apple hardware. Spparently the hardware is not build to have it driver hot reloaded.

System boot -> unload driver -> ok -> load it again -> panic (resources were not freed) (need a full reboot)

[markj]

In D54615#1248205, @guest-seuros wrote:

This module load only in apple hardware. Spparently the hardware is not build to have it driver hot reloaded.

System boot -> unload driver -> ok -> load it again -> panic (resources were not freed) (need a full reboot)

Ok, but what exactly is the panic string? This sounds like a driver bug and it'd be better to understand what's actually going on.