platform: arm64: thinkpad-t14s-ec: fix IRQ race condition

Fix a race condition, that an input key related interrupt might be
triggered before the input handler has been registered, which results
in a NULL pointer dereference. This can happen if the user enables
the keyboard backlight shortly before the driver is being probed.

This fixes the following backtrace visible in dmesg:

Unable to handle kernel NULL pointer dereference at virtual address 00000000000000e0
...
Call trace:
 sparse_keymap_report_event+0x2c/0x978 [sparse_keymap] (P)
 t14s_ec_irq_handler+0x190/0x3e8 [lenovo_thinkpad_t14s]
 irq_thread_fn+0x30/0xb8
 irq_thread+0x18c/0x3b0
 kthread+0x148/0x228
 ret_from_fork+0x10/0x20

Fixes: 60b7ab6ce030 ("platform: arm64: thinkpad-t14s-ec: new driver")
Signed-off-by: Sebastian Reichel <sre@kernel.org>
1 file changed